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Loughborough Antennas & Propagation Conference (LAPC 2017)

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  • Location: Loughborough, UK
  • Conference date: 13-14 Nov. 2017
  • ISBN: 978-1-78561-699-0
  • Conference number: CP732
  • The following topics are dealt with: antennas and propagation; RF circuits; and advanced materials.
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  • Session: 1a - Antennas and Propagation Best Paper
    • A Low-cost Vector Network Analyzer: Design and Realization
      • Author(s): J. Verhaevert  and  P. Van Torre
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      • p. (5 pp.)
        In this paper, a low-cost Vector Network Analyzer (VNA) design is presented: from an initial study of network analysis fundamentals to a working design. In a first part of this paper, the architecture and functionality of a VNA are handled. The hardware components and their specifications are described. The design in this paper uses a Direct Digital Synthesizer (DDS) to generate signals. To measure phase and magnitude differences, integrated detectors are used. The design needs to be able to run embedded software in order to work. The programs, written in C code on an ARM processor, give the user the opportunity to set up the measurements using an LCD display, showing the results in a magnitude and phase plot or a Smith chart with a marker indication for reading out characteristics.
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      Portable and Low Cost Channel Sounding Platform for VHF / UHF IoT Propagation Research
      • Author(s): E.A. Ball
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      • p. (5 pp.)
        This paper presents work into realising a cost-effective and portable platform to support Internet of Things (IoT) propagation research at VHF and UHF. The sounding receiver uses a low cost RTL-SDR, Raspberry Pi and touchscreen. The platform runs dedicated channel sounding DSP algorithms written in Python. The resulting platform is a portable and convenient propagation measurement tool, covering 27MHz to 1.7GHz. Initial results from a city measurement campaign at 71MHz and 869.525MHz are presented, showing channel response and interference.
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      Metal Lens for Collimation of Orbital Angular Momentum Radio Modes
      • Author(s): T.D. Drysdale  and  B. Allen
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      • p. (4 pp.)
        We investigate the feasibility of using a metal lens for collimating Orbital Angular Momentum (OAM) radio modes. In the microwave regime, metal lenses are an attractive alternative to dielectric lenses because of their low weight and low cost. However, it is not immediately clear whether an OAM mode would successfully propagate through a metal lens due to the presence of parallel metal plates that block the transfer of energy in the plane transverse to propagation. We explore by simulation the coupling of an OAM mode from a uniform circular dipole array of diameter 180mm to a planoconvex lens of plate spacing 50 mm, focal length 1100mm and maximum thickness 800 mm, and then its re-radiation into free-space. A multi-level fast multiple method was used for the calculation. Our results indicate metal lenses can be used with OAM modes with minimal loss of mode purity.
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      Reliable EM-Driven Size Reduction of Antennas Using Feasible Region Boundary Search
      • Author(s): D.O. Johannesson  and  S. Koziel
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      • p. (5 pp.)
        An improved procedure for EM-driven reduction of antenna size has been presented. Our approach exploits explicit formulation of a miniaturization problem with the footprint area minimization as a primary objective. An iterative algorithm for exploring boundary of the feasible region is developed, allowing for efficient identification of a constrained optimum that ensures satisfaction of the prescribed matching requirements for the structure at hand. As demonstrated using three examples of UWB antennas, the proposed methodology leads to smaller footprints and better control of the in-band matching compared to the benchmark algorithm, i.e., gradient-based search with implicit reflection response control through a penalty function approach.
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      Concepts for Radar Target Simulation
      • Author(s): A.R. Diewald  and  C. Culotta-Lopez
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      • p. (5 pp.)
        With increasing radar activities in the automotive, industrial and private sector there is a need to test radar sensors in their environment. A radar target simulator can help to test radar systems repeatably. In this paper the authors present two concepts of low-cost hardware for radar target simulation. The theoretical foundations are derived and analyzed. A schematic for implementation is given.
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      Laboratory testing of a SVD-based approach to recover the nonredundant bi-polar NF data from the positioning error affected ones
      • Author(s): F. D'Agostino ; F. Ferrara ; C. Gennarelli ; R. Guerriero ; M. Migliozzi
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      • p. (5 pp.)
        An effective procedure to correct known positioning errors of the measurement probe in a bi-polar near to far-field (NFTFF) transformation for quasi-planar antennas, requiring a minimum number of NF data, is developed and experimentally assessed. The NFTFF transformation exploits a nonredundant sampling representation of the probe measured voltage got by assuming the antenna as enclosed in a surface made by two circular bowls with the same aperture (double bowl). The uniform bi-polar samples, i.e. the voltages at the points fixed by the representation, are precisely recovered from the not correctly spaced ones via a singular value decomposition based approach. Then, a 2-D optimal sampling interpolation formula is used to accurately reconstruct the NF data necessary for the plane-rectangular NFTFF transformation from the retrieved nonredundant uniform samples.
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      Multiband hybrid loop-notch antennas
      Wireless power transfer in the presence of a conducting interface: an analytical solution
      • Author(s): A. Vallecchi ; C. Stevens ; E. Shamonina
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      • p. (5 pp.)
        A combined electromagnetic-circuit model of wireless power transfer (WPT) between a pair of inductively coupled loop resonators in the presence of a conducting slab is developed. The model takes into account all electromagnetic interactions occurring between the coils and the slab. The proposed analytical model is particularly relevant to applications in the field of wireless charging of electric vehicles and WPT to feed implanted medical devices and body sensor networks for health-care and medical research, where it can be instrumental for optimizing transfer efficiency, power regulation, and assessment of compliance of WPT systems to human electromagnetic exposure limits.
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  • Session: 1c - Array Antennas 1
    • SatCom on-the-move Antenna With Mechanically Switchable Circular Polarization
      • Author(s): M. Ferrando-Rocher ; J.I. Herranz-Herruzo ; A. Valero-Nogueira ; B. Bernardo-Clemente
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      • p. (4 pp.)
        This paper discusses on some of the design challenges of Ka-band Circularly-Polarized antenna arrays for Satcom on-the-move. The antenna put forward is composed by two transmit and two receive apertures providing Right-Hand and Left-Hand circular polarization. The antennas combine a series of novel contributions, from the use of Gap Waveguide technology to ensure good assembly between layers preventing leakage, to a thin broadband polarizer achieving the circular polarization required. Experimental results of reduced-size prototypes are presented.
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      Comparative Study on the Diversity Performance between Different Microstrip Antenna Arrays
      • Author(s): A.H. Radhi ; R. Nilavalan ; H.S. Al-Raweshidy ; N. Ab Aziz
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      • p. (5 pp.)
        In this paper, a unique systematic comparative study between different microstrip antennas array types is presented. The study includes a comparison based on the mutual coupling (S21) and the envelope correlation coefficient between four different antennas array types: (a) PIFA antenna, (b) patch antenna, (c) monopole antenna, (d) slot antenna. All these different microstrip antennas have been designed and printed on a thin 1.6 mm FR-4 substrate with dielectric constant (ɛr = 4.4), suitable for wireless PCS applications (1.9 GHz). Numerical simulations are carried out using HFSS ver 17.0 software. The mutual coupling and envelope correlation coefficient between these different microstrip antennas are studied for various antenna separations. Also, another brief comparison is presented which based on the obtained results particularly in inputs return and radiation characteristics loss at fixed antenna separation, by determining the primarily associated parameters such as the bandwidth, gain, directivity, radiation efficiency. However; it is found that separation between multiple antenna elements is the most critical and crucial parameter affecting on the antenna diversity performance such as both the mutual coupling and the envelope correlation coefficient (primarily it will decrease linearly with the distance increment). This comparative study would be very helpful for RF design engineers to select suitable microstrip antenna type while designing antenna arrays at frequency 1.9 GHz for wireless PCS applications.
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      Beam Steering Antenna Arrays for 28-GHz Applications
      • Author(s): M.A. Nassar ; H.Y. Soliman ; A. Ghoneim ; S. Abuelenin
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      • p. (4 pp.)
        New 28 GHz 2×3 and 2×4 patch antenna arrays with beam steering capability are designed. For the 2×4 arrays, good impedance matching with a beam steering range of ±15° is achieved using only one phase shifter on a single port. For the 2×3 array, a new design with nonuniform amplitude excitation is presented to reduce number of elements. Better radiation directivity and less Side lobe levels are reached with the same beam steering range. The simulated results and discussions are presented.
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      Compact and Planar Slot Antenna Array for X-band Applications
      • Author(s): S. Alkaraki  and  Yue Gao
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      • p. (3 pp.)
        This paper presents a design of wide band, high gain and compact slot antenna array for X-band applications. The array consists of two thin metallic layers, where 9 radiation slots are perforated in the top layer and excited through coupling the electromagnetic energy into a cavity between both layers via standard X-band waveguide. Simulation result shows that the proposed antenna has high gain, high radiation efficiency and high aperture efficiency. The proposed antenna is compact and small so that its peak aperture efficiency is 51% at 11 GHz, with total thickness of 8.5 mm.
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      Dual-Band Compact-Size Antenna Array for Angle of Arrival Estimation
      • Author(s): M.A.G. Al-Sadoon ; I.M. Danjuma ; F.M. Abdussalam ; I.T.E. Elfergani ; J. Rodriguez ; R.A. Abd-Alhameed ; S.M.R. Jones
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      • p. (5 pp.)
        A dual-band compact-size ring antenna array is integrated with a proposed angle of arrival (AOA) algorithm to estimate directions of arrival sources. The impact of mutual coupling on the direction estimation accuracy is investigated based on the computed coupling matrices for both spectrum frequency bands. The mathematical model of direction of arrival (DOA) is illustrated and an appropriate decoupling method is integrated to eliminate the mutual coupling effects. A MATLAB code is developed to simulate various experimental scenarios. The results before and after compensation of coupling matrix are compared and discussed for several test examples.
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  • Session: 1d - Advance Materials 2
    • 3D Printed Periodic Structures in a Horn Antenna for Side-lobe Reduction using Direct Metal Laser Sintering
      • Author(s): D. Shamvedi ; C. Danilenkoff ; S. Karam ; P. O'Leary ; R. Raghavendra
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      • p. (4 pp.)
        The research presents a 3D metal printed X-band (8.2-12.4 GHz) horn antenna with side-lobe reduction, achieved by printing pyramidal periodic structures on the inner faces of the antenna's E-plane. The 3D pyramidal periodic structures result in the suppression of the surface current and hence reduce the side-lobes of the horn antenna. The placement of the periodic structures has been optimized using commercially available electromagnetic simulation software, CST (Computer Simulation Technology), not only for reducing side-lobes, but also for successful 3D metal printing. The beam efficiency of the proposed antenna was measured to be 98.5% at the selected frequency of 12.4 GHz, with an improvement of 8% over the 90.4% simulated beam efficiency of the conventional horn antenna without any periodic structures. The antenna is fabricated using the Direct Metal Laser Sintering (DMLS) technique using Maraging Steel, MS1, on an EOSINT M280 system.
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      Vanadium Dioxide Switches for a Reconfigurable Bandwidth Antenna
      • Author(s): D.E. Anagnostou ; D. Torres ; N. Sepulveda
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      • p. (2 pp.)
        An antenna with reconfigurable bandwidth is conceived and presented. It is a slot antenna that maintains its resonant frequency, and has two modes of operation, a wideband and a narrowband mode. The modes are activated by the state of the vanadium dioxide thin film that acts as a switch and varies the size of two metallic islands on the antenna aperture. The antenna was designed, simulated, and fabricated. The measurements validated the simulated results. Such antennas can find uses in weak signal applications, while this particular configuration is not easily achievable using traditional off-the-shelf components such as PIN diodes, MEMS or FET transistors.
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      A 2.4 GHz to 27 MHz non-Linear RFID Topology in Flexible Electronics
      • Author(s): G. Gentile  and  R. Ishihara
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      • p. (5 pp.)
        A non-linear commercial topology of passive RFID tag is transported onto a low-cost flexible substrate by means of antenna embedded distributed decoupling capacitors, which allow to embed both a far-field antenna, operating at 2.4 GHz, and a near-field antenna, operating at 27 MHz, into a compact low-cost layout. The sensor is based on two co-designed planar antennas and a demodulating diode, which receives a two-tone gigahertz signal and radiates back their frequency difference. Filtering elements are embedded directly into the antennas to decouple the near-field and far-field section. The layout transport is realized using silver ink printing on a flexible plastic substrate and can be used for instance as soil moisture sensor when a simple planar capacitance is added to the design. Two-tone measurements of the sensor show the amplitude of the 2nd order intermodulation product at 27 MHz to be only 9 dB lower than the 3rd intermodulation product at 2.400 GHz - 27 MHz, thanks to the high non-linearity of the sensor and the decoupling effect of the distributed capacitors in the metal traces of the folded-slot antenna topology.
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      Analytical formulation for the capacitance of 3D square split ring resonators
      • Author(s): A. Vallecchi ; C. Stevens ; E. Shamonina
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      • p. (3 pp.)
        An approximate analytical expression is derived for the equivalent capacitance of three-dimensional (3D) singly split ring resonators (SRRs) with square cross section. The total capacitance is expressed as the sum of the usual gap capacitance and the surface capacitance associated with the charges on the ring's surfaces. The surface capacitance is determined from analytical expressions for the electric field of a split square cylinder which are derived by conformal mapping. The proposed model can be used for the preliminary assessment of the resonant properties of square SRRs at any frequency. The validity of the developed formulas is assessed by comparing the resonant frequency of sample SRR configurations found analytically with the corresponding values obtained by numerical simulations.
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      Equivalent Circuit Analysis for 3D Metamaterials with Fringing Field Correction Factor
      • Author(s): T. Whittaker ; W. Whittow ; Y. Vardaxoglou
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      • p. (2 pp.)
        This paper presents a fringing field correction factor for circuit modelling techniques of metasurfaces and metamaterials. The theory is then applied to periodic three dimensional metamaterial meta-atoms. Equivalent circuits have been validated using CST Microwave Studio.
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      High gain flat antennas for Ka band SATCOM
      • Author(s): F. Caminita ; G. Minatti ; E. Martini ; S. Maci
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      • p. (2 pp.)
        This work presents the design and realization of high gain planar VSAT antennas operating in Ka band based on modulated metasurfaces (MTSs). In these antennas, a surface wave excited by a central coplanar feed is transformed into a radiative leaky wave through the interaction with a modulated impedance boundary condition implemented by a MTS. A receiving and a transmitting aperture, with directivities higher than 31dB and 39dB, respectively, are designed, realized and experimentally characterized.
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      A Reconfigurable Capacitive Impedance Surface for 1.5T Magnetic Resonance Imaging Applications
      • Author(s): I. Issa ; K.L. Ford ; M. Rao ; J. Wild
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      • p. (4 pp.)
        This paper presents a reconfigurable capacitive impedance surface (CIS) combined with a radio frequency loop coil to improve the radio frequency (RF) magnetic flux density, B1, for 1.5T magnetic resonance imaging applications. The proposed technique offers advantages of being able to tune performance in-situ as compared to passive solutions which may suffer from issues associated with manufacturing tolerances. The proposed structure is based on a periodic array of metallic patches loaded by variable capacitors. Full field simulations employing a surface with a dielectric phantom, represented the human body, show the tuneable capacitive property of the surface can be used to maximise B1+, which is advantageous for reducing transmitted power, and B1- which is important for receiver sensitivity.
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      Fully 3D printed GPS Antenna using a Low-cost Open-source 3D Printer
      • Author(s): A. Elibiary ; W. Oakey ; S. Jun ; B. Sanz-Izquierdo ; D. Bird ; A. McClelland
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      • p. (4 pp.)
        The fabrication of a circularly polarized antenna using a low-cost open-source 3D printer is described. The process comprises the combination of two popular additive manufacturing (AM) techniques into one single machine. In order to do this, a fused deposition modelling (FDM) printer has been adapted to accommodate a pneumatic dispenser. Both the FDM extruder and the dispenser are controlled using the same software. The FDM technique is the most common 3D printing process available to print plastics. This process is used to fabricate the substrate, while the connected dispenser prints out the metallic layers that form the top patch of the GPS antenna. The aim of the project is to demonstrate that inexpensive open-source machines can be used as an alternative for the 3D printing of antennas.
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  • Session: 2a - Biomedical Applications and Wearable Antennas
    • Miniature on skin passive UHF RFID antenna sticker
      • Author(s): V. Makarovaite ; A. Hillier ; S.J. Holder ; C.W. Gourlay ; J.C. Batchelor
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      • p. (2 pp.)
        Passive Radio Frequency Identification (RFID) in recent years has been more widely suggested for medical use with different types of wearable antenna designs. However, wearable passive RFID technology has always been limited by a few key constraints (primarily size) when trying to overcome the variable human body's dielectric properties to produce a high read range antenna design. Here we present an on skin passive RFID antenna design, three centimetres in diameter with a read range near two meters on the human body. With slight adjustments to the polyutherane thickness, the original sticker design can negate the difference between the variable human body dielectric properties within subject groups with only slight loses in antenna read range. It was more cost effective to vary the thickness of the breathable polyutherane used as the tag substrate to achieve a resonance within the European UHF RFID frequency range (as well as to increase the read range capability) than to redesign the antenna. Most variability was seen in subjects with high muscle to fat ratio; if the subject was highly muscular then the antenna polyutherane layer was increased to accommodate the increase in the subject's dielectric properties. This has led to a single passive RFID antenna design (two different polyutherane thicknesses) that can accommodate most people as a wearable design with numerous possible applications.
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      Design and characterization of a three material anatomical bone phantom for implanted antenna applications
      • Author(s): S. Symeonidis ; W.G. Whittow ; C. Panagamuwa
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      • p. (5 pp.)
        This work presents the development and testing of a three layer anatomical human body phantom suitable for microwave applications. The proposed phantom consisted of bone marrow, bone cortical and muscle layers. The ingredients used for each tissue along with the calculation of the mean square error of the dielectric properties showed good agreement with the dielectric properties of real life tissues and the IEEE SAR measurement standard for tissue mimicking phantoms. The geometrical characteristics of the bone layer can be adjusted to fit the geometry of any desired bone in the human body. The suitability of the phantom has been tested using an implanted antennas application, which has yielded comparable simulation and measurement results.
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      Design of a miniaturized bone implantable antenna for a wireless implant monitoring device
      • Author(s): R.P. Khokle ; K.P. Esselle ; M. Heimlich ; D. Bokor
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      • p. (2 pp.)
        In this paper, we present a spiral loop type antenna, implanted in the tibial bone. The antenna has been designed for fabrication on commercially available RT Duroid 6010 (ɛr=10.2) substrate and encapsulated in biologically compatible Polydimethylsiloxane (PDMS) material (ɛr=2.6). The antenna has a footprint of 2.6 mm × 2.6 mm and a height of 1.94 mm. The antenna operates at the 2.4 GHz ISM band with the peak gain of -36.2 dBi.
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      Effect of small wearable device antenna location on its impedance, bandwidth potential and radiation efficiency
      • Author(s): J. Chen ; M. Berg ; H.Y. Amin ; A. Pärssinen
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      • p. (5 pp.)
        In this paper, a simulation study of the effect of antenna locations on antenna matching, bandwidth potential and radiation efficiency performance operating in 3GPP Long Term Evolution (LTE) Band 3 (1710-1880 MHz), Band 20 UL (832-862 MHz) and 2.4 GHz WLAN band (2.4-2.5 GHz), in free space and with phantom, is presented. An inverted F antenna (IFA) is utilized in this study and mounted on a small cellular wrist device. The results indicate that for each band, with efficient excitation of its fundamental mode, an antenna whose electrical field maxima located at short edge of the chassis always has higher bandwidth potential and its radiation efficiency will have less reduction when introducing phantom. Moreover, changes in matching characteristic of different antenna positions vary from each band, indicating the optimal antenna placement to obtain robust matching feature. Therefore, by comparing the variations on antenna behaviors, it provides useful insights into how to select the optimal antenna locations on the device with reduced a user effect for a specific operation band.
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      Robustness of 7T-MRI Flexible Array Coil Behaviour
      • Author(s): A. Melis ; S. Casu ; C. Puddu ; A. Fanti ; N. Djuric ; G. Mazzarella ; F. Maggiorelli ; A. Retico ; G. Tiberi
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      • p. (4 pp.)
        Magnetic resonance imaging (MRI) strongly relies on signal-to-noise ratio (SNR) parameter that must be as high as possible. The electrical performance of the RF coil is critical to achieve this purpose. Using higher magnetic fields is the most common way to increase the amount of detectable nuclear magnetization, but this generates more complex interactions between the RF field and the subject. This, forces to find the best coil design to obtain an optimal RF signal, for example using a device that fits the very variable anatomies in dimension and shape, leading to the develop of coils that are geometrically adjustable to the subject to analyse. Moreover, the need to have a bigger field of view (FOV) without losing significant SNR, is usually reached increasing the number of coils for the signal detection. The main challenges of designing a flexible array coil is to develop geometry-achieved decoupling for the coil elements. In fact, mutual inductance among coil elements varies with the coil size, thus the flexibility of the coil creates even more complicated decoupling issues. Furthermore, to fit high-density receiver arrays for MRI closely around individual target anatomies, there is a need to provide a high degree of geometric adjustability with ease of handling and patient comfort. In this work is first performed an electrical characterization of the coil to evaluate the RF sensitivity of these flexible devices. Then, this work focuses on the advantages of an array of two smaller coils over a single larger coil, on the decoupling issues performing an MRI simulation over a saline and body-like phantom, measuring the magnetic field penetration with a high frequency (7T) experiment.
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  • Session: 2b - Communication and Sensing
    • Tilt and Tamper Sensing UHF RFID Security Tag
      • Author(s): M.A. Ziai  and  J.C. Batchelor
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      • p. (5 pp.)
        A passive tag is proposed for indicting mishandling of items in the supply chain. The tag signals excessive tilting by varying its read range and as a measure against counterfeiting, it is deactivated should it be removed from its original platform.
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      Antenna characterisation and channel effects on digital systems
      • Author(s): M.A. Almoteriy ; M.I. Sobhy ; J.C. Batchelor
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      • p. (5 pp.)
        This paper investigates the characterisation of a Vivaldi antenna and the effects of various channel environments on a digital communication system (DCS). Antenna characterisation involves obtaining the reflection coefficient (S11) in both amplitude and phase using a three-dimensional electromagnetic (EM) simulator and conducting experimental verification using a network analyser. Initially, the Vivaldi antenna was characterised using three techniques: (i) applying the Hilbert transform to the measurement, (ii) deriving an equivalent circuit model and (iii) processing the measurements between two identical antennas in an anechoic chamber. These techniques were then used to ascertain the transfer function (S21) of the antenna. The S21 values obtained through these techniques were compared to verify their validity. The S21 measurements were also extended using two identical antennas in two different indoor office environments. Moreover, to evaluate the effect of these indoor channels, two different path lengths were considered. Finally, these three channels with the two identical antennas were simulated and analysed in a DCS to investigate the effects of the antenna and various channel conditions on the system.
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      Recognising People Using Smart Phone Antennas: A Fuzzy Biometric
      • Author(s): S.R. Heyes  and  R.M. Edwards
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      • p. (6 pp.)
        Many calls are made to mobile phones by machines and for nuisance avoidance it would be useful to know if the caller was human or not. Also for convenience it would also be useful to know if the person using a mobile was the same as the one normally using it and if that person was an adult or a child. A wrong result could be used to trigger a request for a key code. Using the hand and four mobile frequency band antennas this paper has investigated the effects of different people on the input impedance of mobile phone antennas with the aim of establishing whether the effect is distinct enough to allow a fuzzy biometric to be achieved. Hands were placed at a range of distances from the antenna, using a test rig designed specifically for this experiment. The frequencies of operation were 900 MHz, 1800 MHz, 1900 MHz and 2.4 GHz. Results showed that the effect of each volunteer on the antenna's input impedance varied significantly when their hand was 30 mm or less from the antenna and that below 10mm they were distinct between volunteers.
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      A passive UHF RFID pH sensor (smart polymers for wireless medical sensing devices)
      • Author(s): A. Hillier ; V. Makarovaite ; S.J. Holder ; C.W. Gourlay ; J.C. Batchelor
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      • p. (2 pp.)
        A functionalised variant of polydimethylsiloxane (PDMS) was applicated atop an RFMicron RFM2100-AER UHF RFID tag and used in a series of depositions of pH buffer solutions, to observe changes in a sensor code generated by the tag. Averaged values of the sensor code data were used between 800-860MHz from 8-20dBm to compare pH buffers between 8.8 and 7.2 which consistently showed a significant degree of change in averaged sensor intensity readout. pH buffers outside the effective buffering range did not show a significant difference in averaged sensor code intensity.
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      Printed Yagi-Helix Antennas
      • Author(s): W. Alshrafi ; A. Al-Bassam ; C. Culotta-Lopez ; D. Heberling
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      • p. (4 pp.)
        This work presents the design and comparison of three different types of printed helix antennas. Using multiple directors, the printed helix antennas radiate in the backfire direction resulting in Yagi-Helix antennas. This is a further step toward the Yagi-Helix antenna design, where the printed helix is used instead of the conventional one for more mechanical stability and reproducibility. The full wave simulation results of the three designs are presented and compared. Finally, the phase centre of each of the three antennas is presented to show the possibility of using these antennas as feeders for centre-fed paraboloid reflector antennas.
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  • Session: 2c - Antennas and RF Circuits
    • Antennas that Support Multi-Mode Excitation
      • Author(s): C. Min ; N. Howland ; N.R. Potts
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      • p. (4 pp.)
        Antennas that support excitation of multiple input signals with various amplitudes and phases to allow more input power is proposed. Design and analysis of a nominated antenna design are given in conjunction with the establishment of feeding techniques to implement the function. Prototypes are fabricated and tested to prove the validity of the proposed technique.
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      MATLAB-based Multi-objective Optimization of Broadband Circularly Polarized Antennas
      • Author(s): D. Warmowska ; M. Marek ; Z. Raida
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      • p. (5 pp.)
        Since requirements on axial ratio and impedance matching of a circularly polarized antenna are conflicting objectives, a MATLAB-based multi-objective optimization was used to design the feeding system of a two-layer broadband antenna array. Whereas optimum values of state variables were computed by the Non-Dominated Sorting Genetic Algorithm in MATLAB, objective functions were evaluated in CST Microwave Studio using the time-domain solver. Optimizing the antenna array in frequency range from 19 GHz to 21 GHz, the axial-ratio bandwidth 1.44 GHz, and the gain 14.9 dB were achieved. The problem of design sensitivity on fabrication tolerances has not been satisfactorily solved yet.
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      Combined energy harvester integrated into car
      • Author(s): M. Kokolia ; J. Lacik ; Z. Raida
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      • p. (5 pp.)
        Design, fabrication and measurement of a dual-band wearable rectenna operating in 900 MHz GSM and 2.45 GHz ISM band is described in the paper. The rectenna, playing the role of the radio-frequency harvester, is completed by additional mechanical and thermal-energy harvesters to increase the amount of harvested energy. The combined harvester was designed to be integrated into the seat of a car exploiting a multi-layer textile cover as a microwave substrate. The designed harvester has been implemented and measured.
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      A CAD-Oriented Technique to Design an Optimum Load Impedance with Multi-Coupler Network for Class-F Power Amplifier
      • Author(s): B.A. Mohammed ; R.A. Abd-Alhameed ; N.A. Abduljabbar ; I.M. Danjuma ; I.T.E. Elfergani ; A.S. Hussaini ; J. Rodriguez
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      • p. (5 pp.)
        In this paper, a Load-pull technique to design a class-F power amplifier with multi-coupler network is presented. The fundamental load impedance and matching networks are separately integrated for class-F RF power amplifier high efficiency operation. The output used a transmitting type active integrated antenna. A Cree GaN FET CGH40006F transistor device at 3.50 GHz operating frequency was used in the design. The performance of the network has improved by 79.4% power added efficiency at 30.1dBm output power. This technique has been considered a useful for improving performance in mobile communication applications.
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      Engineered group delay transmission lines based on novel negative group delay networks
      • Author(s): T. Thatapudi ; P. Gardner ; A. Feresidis
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      • p. (2 pp.)
        Zero group delay performance over wide frequency bands is a prominent issue in wireless communication systems. Negative Group Delay (NGD) networks with the ability to produce positive phase variation with frequency, are proposed here as a promising solution. The principle and procedure for achieving -1O flat phase over 1.5-2.5GHz band using NGD network in combination with transmission line is presented in this paper.
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      An Investigation on Frequency Selective Antenna Interface Based on Optimization Approach
      • Author(s): H.Y. Amin ; Jiangcheng Chen ; M. Berg ; A. Pärssinen
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      • p. (5 pp.)
        New long range wireless standards, such as LTE-NB, for Internet-of-Things (IoT) devices have very challenging requirements for power consumption, however, relax, somewhat, linearity requirements of the receiver. Efforts to make low power, low cost and compact devices rise new challenges in the whole level of design including antenna interface which is the entry block of each transceiver chain. High system efficiency and selectivity as close as possible to antenna interface are key design criteria. This issue, demands the designer to ensure the optimality of the antenna interface. This paper presents a precise method for designing two-port impedance matching filters loaded by arbitrary frequency dependent loads. Above mentioned strict constraints favour using fewer number of elements and thus reduce potential losses. A design technique to quickly evaluate all possible topologies from a limited set of elements is presented. The idea is implemented in MATLAB and verified by a design example including lossy elements and practical terminations.
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      LTCC-based millimetre-wave microstrip grid array antennas
      • Author(s): Y.P. Zhang
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      • p. (2 pp.)
        This paper presents our LTCC-based microstrip grid array antennas for millimetre-wave applications.at 60 GHz and 94 GHz. It is shown that microstrip grid array antennas have all the usual benefits of conventional patch type radiators with good bandwidth and adequate cross polarization control. It is found that microstrip grid array antennas are particularly suitable for LTCC fabrication, due to their mesh structure, which helps to reduce the stress mismatch between the dielectric and metallic layers and avoid the structure warpage.
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  • Session: 2d - Propagation 1
    • Implementation of a quasioptical system for free-space measurements: applications to radio astronomy
      • Author(s): O. García-Pérez ; F. Tercero ; S. López-Ruiz ; B. Vaquero ; J.M. Serna
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      • p. (5 pp.)
        This paper presents the design and application of a free-space measurement system operating at W-band (75-110 GHz). The setup consists of two horn antennas connected to a network analyser, and two dielectric lenses that are used to obtain a collimated beam at the measurement plane. The potential applications are multiple, including characterisation of dielectric materials, and measurement of the transmission and reflection parameters of quasioptical components.
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      HF urban noise level in variable channels of 3-24 kHz: a preliminary experimental approach
      • Author(s): P. Bechet ; A.C. Bechet ; S. Miclaus
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      • p. (5 pp.)
        Lately, there has been a particular interest in increasing the bandwidth of the ionospheric channel in the high frequency (HF) range. Tests on the use of bandwidths of up to 24kHz have shown that under certain conditions a substantial increase in the data transfer rate in the HF range could be achieved. But the bandwidth increase is limited mainly due to the noise level. This paper approaches a preliminary experimental analysis of the noise power levels in variable bandwidth ionospheric channels under Near Vertical Incidence Skywave (NVIS) operating conditions in the 3-9 MHz band. The results show that the mean noise power increases by an average of 3.5 dB at doubling the bandwidth of the ionospheric channel, while the dispersion of noise is maintained (at maximum 9.5 dB) regardless of the bandwidth of the ionospheric channel.
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      Testing of low-power wide-area technologies in controlled propagation environments
      • Author(s): I. Rodriguez ; M. Lauridsen ; K. Arvidsson ; J. Kvarnstrand ; M. Andersson ; P. Mogensen
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      • p. (2 pp.)
        In this study, the uplink performance of Sigfox and LoRa is evaluated in a controlled propagation environment (reverberation chamber). This evaluation is performed in terms of packet error rate as a function of calibrated path loss, which allows a direct comparison of the performance of both systems under the exact same propagation conditions. The analysis of the results show that the proposed setup and testing methodology can be useful for comparing the many new wireless IoT technologies in a practical setting.
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      High Dynamic Range Frequency Converters for HF and VHF Propagation Measurements
      • Author(s): S.M. Feeney
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      • p. (5 pp.)
        This paper describes the development of high dynamic range HF and VHF frequency converters for use in propagation measurements. These frequency converters are used to provide variable frequency signal translation from the HF/VHF bands to a digitiser operating at a fixed frequency to perform signal recovery. The frequency converters are required to provide signal translation in the presence of many high level signals from other band users. The range of signal levels that can be accommodated is determined by the noise floor of the system and the maximum level of the unwanted input signals which can be supported without degrading the noise figure due to both third-order distortion products and reciprocal noise mixing between high level signals and the local oscillator phase noise. For this equipment synthesised signal sources with very low close to carrier noise have been developed which should allow high dynamic range to be maintained with small frequency offsets in the presence of high level signals.
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      Channel characterisation for wearable LoRaWAN monitors
      • Author(s): P.A. Catherwood ; S. McComb ; M. Little ; J.A.D. McLaughlin
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      • p. (4 pp.)
        This paper presents the results of a campaign to investigate the empirical characterisation and mathematic modelling of the radio channel for a body-centric LoRaWAN transceiver for various operating distances across various environments including urban, suburban, and rural. The radio channel for a wearable LoRa transceiver device was explored, as well as anechoic measurements to understand the effects of body-shadowing for this technology. Results indicate that the best fit model for all recorded received signal strength measurements (using the Akaike information criterion) is the Nakagami distribution with mu = 0.52 and Ω = 662.13. Anechoic measurements indicated typical additional effects regarding the orientation of the user with respect to the gateway location. This work highlights LoRaWAN as a credible wearable wireless technology.
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      An empirical study of link quality assessment in wireless sensor networks applicable to transmission power control protocols
      • Author(s): J.B. Hughes ; P. Lazaridis ; I. Glover ; A. Ball
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      • p. (5 pp.)
        Transmission Power Control (TPC) protocols are poised for wide spread adoption in Wireless Sensor Networks (WSNs) to address energy constraints. Identifying the optimum transmission power is a significant challenge due to the complex and dynamic nature of the wireless transmission medium and this has resulted in several previous TPC protocols reporting poor reliability and energy efficiency in certain scenarios. In line with current studies, this study presents an empirical characterisation of the transmission medium in typical WSN environments. Through this, the sources of link quality degradation are identified and extensive empirical evidence of their effects are presented. The results highlight that low power wireless links are significantly affected by spatio-temporal factors with the severity of these factors being heavily dependent on environment.
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      Millimetre-wave propagation in urban clutter for 5G systems
      • Author(s): R.F. Rudd  and  M. Nekovee
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      • p. (2 pp.)
        This paper describes path loss measurements carried out at 27 GHz in London and Brighton. The primary purpose of the measurement campaign was to provide empirical support for the development of clutter loss models for use at millimetre wave frequencies, being undertaken separately. Particular attention has been paid to characterising the role of reflections in coupling energy on interference paths.
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  • Session: 3a - Antenna measurements and design
    • Examination of the effect of common CATR quiet zone specifications on antenna pattern measurement uncertainties
      • Author(s): S.F. Gregson  and  C.G. Parini
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      • p. (5 pp.)
        The use of uniformity of the quiet-zone (QZ) in determining the maximum size of test antenna that can be measured in a given point-source compact antenna test range (CATR) has been the accepted method since its inception [1]. Furthermore, the definition of a quiet zone (QZ) having amplitude taper of less than 1 dB, amplitude ripple of less than ±0.5 dB in amplitude and ±5° in phase has become a near universal standard both in academia and industry [1]. However, this almost omnipresent usage belies the fact that surprisingly few workers are familiar with what this implies for an actual antenna pattern measurement. The recent development of a novel computational electromagnetic (CEM) simulation tool that permits the simulation of "measured" far-field pattern data for a known CATR and test antenna combination [2] permits the careful examination of the behaviour of these three conventional CATR QZ specifications on "measured" far-field patterns for a given test antenna. Results are presented and discussed.
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      Cost/Performance Trade-Off of Domain Segmentation for EM-Driven Surrogate-Assisted Multi-Objective Antenna Design
      • Author(s): A. Bekasiewicz  and  S. Koziel
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      • p. (4 pp.)
        EM-driven multi-objective design of modern antenna structures is a challenging task which involves seeking for trade-offs between various electrical/field performance figures and geometrical requirements. Conventional approach for solving these problems, i.e., utilization of population-based metaheuristics, is numerically prohibitive as such methods require thousands of EM simulations to complete the optimization run. Design cost can be reduced by executing a metaheuristic algorithm on a fast data-driven model constructed from coarsely-discretized EM simulation data. One of the most recent methods exploiting such a concept, allows for low cost determination of the Pareto set by dividing the search space into a set of adjacent compartments (each of which is represented by a separate data-driven model) located along the Pareto front. In this work, the effect of setup segmentation on performance and computational cost of the design process is investigated. Our considerations are illustrated using a planar monopole antenna. A discussion on the obtained numerical results is also provided.
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      Antenna Design Explorer: A GUI Software Tool for Efficient Antenna Design Optimization
      • Author(s): M.O. Akinsolu ; F.M. Abdussalam ; O. Arabi ; Bo Liu ; R.A. Abd-Alhameed ; N. Ali ; G. Ibrahim ; T. Rashid
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      • p. (5 pp.)
        Due to stringent specifications, antennas for IoT devices are very complex to design. Thus, the need for antenna design exploration/optimization to achieve desired antenna performance in IoT applications. This paper presents a GUI software tool, called Antenna Design Explorer (ADE), for the design exploration/optimization of microwave antennas. Compared to available popular antenna design explorers, (e.g., CST Microwave Studio Optimizers, MATLAB optimizers), the advantages of ADE include: (1) 5-10 times efficiency improvement for full-wave EM simulation driven antenna optimization; (2) largely improved optimization capacity for high-performance antenna synthesis; (3) substantially improved usability considering the background of antenna engineers; and (4) general and no ad-hoc initial design is needed. Three real-world antenna design cases verify the above advantages.
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      Parametric Analysis and Bandwidth Optimisation of Hybrid Linear-exponential Tapered Slot Vivaldi Antennas
      • Author(s): I.K. Ukaegbu  and  K.A.A. Gamage
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      • p. (5 pp.)
        This work presents an analysis of the effects of a hybrid linear-exponential tapered slot on the key properties of both the antipodal and co-planar Vivaldi antennas at low frequencies using parametric analysis and Nonlinear Sequential Programming optimisation. It was observed that the hybrid tapered slot can extend the lower frequency limit of the antipodal Vivaldi antenna however with slight deterioration of the gain and E-plane radiation pattern. On the other hand, the optimisation of the hybrid and conventional tapered slot co-planar Vivaldi antennas converged to antennas with the same performance results.
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      Nonredundant Spiral NFTFF Transformation for a Long Antenna Mounted with an Offset with respect to the Scan Sphere
      • Author(s): F. D'Agostino ; F. Ferrara ; C. Gennarelli ; R. Guerriero ; M. Migliozzi
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      • p. (5 pp.)
        A fast and accurate near-field to far-field (NFTFF) transformation technique with spherical spiral scanning for an offset mounted long antenna, which requires practically the same number of NF data both in its onset and offset mounting, is proposed in this work. It relies on the nonredundant sampling representations of electromagnetic fields and is developed by properly applying the unified theory of spiral scans for nonvolumetric antennas, when the antenna under test is modelled by a prolate ellipsoid. Some numerical results assessing the accuracy of the proposed technique and its robustness with respect to random errors affecting the NF data are shown.
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  • Session: 3b - Millimetre and Sub-millimetre Antennas
    • Study of mm-wave microstrip patch array on curved substrate
      • Author(s): Z. Ahmed ; Kansheng Yang ; P. McEvoy ; M.J. Ammann
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      • p. (4 pp.)
        A millimetre wave rectangular microstrip patch antenna array for fifth generation communications (5G) applications is presented. With the increase in demand for high data rates and capacity, there is a need to include mm-Wave frequencies for 5G. The 4×2 patch array is simulated and fabricated on a Rogers RT/Duroid 5880 substrate with a thickness of 0.25 mm. The effects of bending the substrate on the antenna performance are also presented. The experimental results show a fractional bandwidth and gain of more than 3% and 16.1 dBi, respectively.
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      Millimetre wave reflectarray antenna unit cell measurements
      • Author(s): G. Ahmad ; T.W.C. Brown ; C.I. Underwood ; T.H. Loh
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      • p. (5 pp.)
        Reflectarray antennas are a potential candidate solution to realize high gains at millimetre waves (mm-waves). A reflectarray contains a large number of spatially illuminated unit cells. The performance of a good reflectarray design is manifested by the behaviour of its comprising unit cells. An established technique to characterise a unit cell is by placing it inside a waveguide to achieve periodic boundary conditions. This usually requires custom waveguide products; making the tests difficult and expensive. Additionally, when the unit cells are reconfigurable as in a smart reflectarray it is hard to take the DC bias lines out of the waveguide without using custom made waveguide parts. This contribution address the issue of unit cell placement inside the waveguide and proposes simple unit cell structures to avoid custom made waveguide parts. The idea was verified by measuring a series of unit cells at mm-waves in various configurations and a practically acceptable agreement was found. The proposed structures greatly simplify the reconfigurable unit cell testing.
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      A New THz Corrugated-Ground Antenna
      • Author(s): D. Kampouridou  and  A. Feresidis
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      • p. (2 pp.)
        In this summary, an improved Bull's Eye antenna is proposed, designed for optimum response at 300 GHz. The metallic plate is composed of 11 corrugated concentric rings. A novel feeding technique is proposed, by using a tapered aperture at the middle of the plate. The antenna performance is significantly enhanced in terms of bandwidth and gain. The structure has been simulated with CST Microwave Studio package, and the simulated results demonstrate a maximum gain of 22.8 dBi and a 3-dB bandwidth of 4%. A prototype has been fabricated and the measured results will be presented.
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      Superdirective meta-arrays at telecommunication wavelengths
      • Author(s): A. Vallecchi ; C. Stevens ; E. Shamonina
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      • p. (4 pp.)
        The objective of this work is to develop superdirective nanoantennas (NAs) with the capability of concentrating radiated light into a narrow angular region that can serve for the realization of point-to-point wireless links and efficient optical nanocouplers for application in photonic integrated circuits (PICs). The proposed NAs consist of a superdirective meta-array of nanoscale plasmonic split ring resonators (SRRs) operating at the optical telecommunication wavelength of 1500 nm. These NAs have a substantially planar architecture and can be fabricated using standard CMOS technology for realization of multi-layered PICs. The performance of sample configurations of the proposed superdirective meta-arrays is verified with numerical fullwave simulations.
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      Characterisation of a quasi-optical transmissometer for precise measurement of a sub-THz multenna
      • Author(s): A.S. Andy ; P. Alizadeh ; O. Sushko ; M.M. Torrico ; T. Kreouzis ; R. Donnan ; C. Parini ; R. Dubrovka
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      • p. (4 pp.)
        Analysis on estimating the input power of a non-linear multiplier, positioned at the focal point of a quasi-optical (QO) transmissometer driven by a vector network analyser (VNA), has been carried out. The multenna, or an integrated antenna with a multiplier, has the functionality of generating the second harmonic (300 GHz) of an antenna element resonating at 100 GHz. The output power from the mm-wave multiplier head, operating in the WR-10 waveguide band, was estimated using the QO transmissometer. The input power at 100 GHz to the multenna was critically measured using the R&S Spectrum Analyser and a WR-10 mixer. Additionally, the beam waist at the focal point of the QO transmissometer was estimated in the WR-10 waveguide band (75 - 110 GHz).
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      Role of Surface Waves in the Reflection Properties of a Millimetre Wave Reflectarray Unit Cell
      • Author(s): G. Ahmad ; C.I. Underwood ; T.W.C. Brown ; T.H. Loh
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      • p. (5 pp.)
        A steady increasing trend towards millimetre waves (mmwaves) for next generation communication has initiated an intensive research in the field of mm-wave antenna technologies. Reflectarray antennas being one of the potential candidates offer significant advantages over parabolic and phased array antennas at mm-wave bands. In a well-designed reflectarray, the overall performance is mainly determined by its comprising unit cell(s). Most of the recent reflectarray designs are based on printed microstrip technology. It is well known that surface waves get generated in printed microstrip technology and contribute to loss in the radiated signal power in the intended direction. This paper analyses the effect of surface waves in the reflection properties of a printed microstrip millimetre wave reflectarray unit cell. The analytical results are compared with measured data at 32 GHz and an excellent agreement was observed. It was observed that surface waves, though generally considered to have malign effects in antennas, play a significant positive role in the reduction of reflection loss magnitude at unit cell level.
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      Design of Ultra Wideband Vivaldi Nanoantenna for Solar Energy Collection
      • Author(s): W. Amara ; N. Eltresy ; A. Yahyaoui ; H. Rmili ; T. Aguili ; J.M. Floch
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      • p. (4 pp.)
        This paper describes a Vivaldi nano-antenna with high performances designed to operate over the frequency band 5 - 30 THz, with maximum localized electric field intensity across its gap. The proposed nano-antenna has advantage of focusing the electromagnetic energy into small localized area around the antenna slot. Linear polarized incident plane wave is used to excite the structure and then concentrate the electric field in its gap. The obtained maximum electric field is equal to 81.47 V/m at 6.67 THz.
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  • Session: 3c - Array Antennas 2
    • A cost-effective technique for concurrent IQ stream capture for prototyping phased arrays
      • Author(s): A. Vasileiadis  and  E.A. Ball
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      • p. (4 pp.)
        This paper introduces a new and affordable method of realising 10 IQ Software Defined receivers, and how to synchronise them. We first discuss the need for multiple IQ and the available techniques. We then introduce the RTL-SDR and Matlab as a very low cost prototype implementation of 10 IQ streams. This leads to the design and manufacture of a PCB to distribute a single clock to multiple RTL-SDRs. The required modifications to the RTL-SDRs to receive the distributed clock and other modifications to improve the overall performance are presented. We then describe how to attain raw IQ data and synchronise the receivers. Finally, we prove all 10 can maintain a phase lock over a frame of 7 seconds.
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      Single shot DoA estimation for large-array base station systems in multi-user environments
      • Author(s): T.A.H. Bressner ; U. Johannsen ; A.B. Smolders
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      • p. (4 pp.)
        The next generation of wireless communications has to deal with the demand for higher data rates and the increase of subscribers. A feasible approach to cope with these challenges is to utilize millimeter waves (mmWaves). To provide at these high frequencies a sufficient high signal to noise ratio (SNR) narrow beam antenna systems can be used. These systems require knowledge about the direction of arrival (DoA) to steer their beams towards the optimal direction. The determination of the DoA can become time consuming for large areas where a single narrow beam can cover only a small spot. Dealing with this challenge, the single shot DoA enables to find the optimal direction within an instant of time for multiple users. This paper introduces the single shot DoA method and shows its functionality based on conducted simulations.
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      Dual-Element Antenna System for Hexa-band Smartphone MIMO Applications
      • Author(s): S.S. Alja'afreh ; Yi Huang ; Qian Xu ; Lei Xing ; O.A. Saraereh
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      • p. (5 pp.)
        A new low-profile dual-element antenna is proposed for hexa-band Smartphone MIMO applications. It consists of two antenna structures in which, each one excite orthogonal characteristic mode to achieve isolation very easily below 1 GHz. Both elements (the metal frame antennas and the internal PILA antenna) are is analyzed and optimized in terms of the reflection coefficient and the current distribution. The final design (dual-element) is made and tested in terms of S-parameters, envelope correlation coefficient, mean effective gain and the diversity gain. The results show that this design is a good candidate for hexaband MIMO applications and in particularly suitable for such as GSM850/DCS1800/PCS1900/UMTS2100/LTE2500/LTE3600 mobile applications.
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      Image transmission using OSTBC-encoded 16-QAM over MIMO time-selective fading channels
      • Author(s): M. Lodro ; S. Greedy ; A. Vukovic ; C. Smart ; D.W.P. Thomas
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      • p. (5 pp.)
        In this work we have studied the performance analysis of OSTBC-encoded 16-QAM by transmitting digital image over fading channels.The performance of 2×2 MIMO fading channels is compared with SISO fading channel with no OSTBC encoding at signal-to-noise ratio (SNR) of 20 dB. Multipath MIMO channels under-discussion are time-selective in nature and have flat channel response in frequency. Hence, we specify only Doppler shift which in our case is modelled by Jakes Doppler spectrum. The performance of 2×2 communication system over MIMO time-selective fading channels has been studied. The key performance indicative parameters of OSTBC-encoded 16-QAM over 1×1 single-input single-output (SISO), 2×1 multiple-input single-output (MISO) and 2×2 MIMO wireless communication have been recorded appropriately.
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      Comparative study of “Phoenix” reflectarray phase-shifting cells
      • Author(s): T. Makdissy  and  R. Gillard
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      • p. (4 pp.)
        This paper presents a fair comparison between four different “Phoenix” phase-shifting cells that can be found in the literature. This comparison is mainly based on the frequency dispersion and on the bandwidth where the maximum differential phase shift is less than 90°. Then, an alternative “Phoenix” unit-cell of reduced size offering an enhanced bandwidth is proposed.
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  • Session: 3d - Advanced Materials 2
    • The ultra-thin reconfigurable meta-surface
      • Author(s): Xin Liu  and  Ai Xin Chen
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      • p. (4 pp.)
        This paper proposes a novel ultrathin reconfigurable meta-surface with the function of dual-frequency multi-pattern. By switching the PIN diodes loaded on the meta-surface, it can work at 2.4GHz or at 5.63GHz with the different radiation patterns.
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      High Gain Circularly Polarized Meta-Surface Antenna
      • Author(s): Aixin Chen  and  Xin Liu
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      • p. (4 pp.)
        A novel circularly polarized antenna with meta-surface is proposed and studied in this paper. The meta-surface consisting 16 radiating elements, which are 4×4 periodically arranged under the Rogers 5880 substrate, can converse the linear polarized wave radiated by the micro-strip antenna into circularly polarized electromagnetic wave with the total radiation gain of 10.13dB. The proposal antenna prototype operating at 2.4GHZ is analysed, and the fabricated model is measured.
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      Optimisation of the Q Factor of a Complementary Frequency Selective Surface
      • Author(s): C.K. Lee ; S.S. Bukhari ; J.C. Vardaxoglou ; W.G. Whittow
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      • p. (4 pp.)
        The complementary frequency selective surface (CFSS) consists of an array of dipoles and slots either side of a thin dielectric and exhibits a sharp passband. The conductors layer adds capacitance to the apertures layer which in turn miniaturises the FSS. In this paper, the CFSS is placed in a waveguide and the Q factor is maximised by varying the electric properties and physical parameters. The fabricated CFSS structure shows good agreement with the simulations.
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      Artificially anisotropic cylinder to convert omnidirectional linear polarization into circular polarization
      • Author(s): E. Kaivanto ; E. Salonen ; M. Berg
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      • p. (4 pp.)
        Circular polarization and omnidirectional radiation are desired characteristics in various mobile communication systems. This paper studies possibilities to convert linear polarization into circular polarization by designing an artificially anisotropic cylinder around the antenna. The design process and simulated results for the cylinder with a half wave dipole antenna at the centre frequency of 2.3 GHz are presented. It is shown that the cylinder has minor effect on the return loss and gain of the antenna and that axial ratio remains below 5dB over the frequency range of 900MHz.
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      Demonstrating a low temperature organic dense dielectric patch antenna
      • Author(s): R.J. Espley-Jones ; F. Tong ; J.E.J. Dalley ; D.S. Langley
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      • p. (2 pp.)
        This paper demonstrates the possible implementation of a low temperature organic dense dielectric patch antenna (DDPA). Instead of using deionised water for the patch material, a mixture of ethanol and methanol was the material of choice as it remains liquid below 0°C. The freezing points of ethanol and methanol are -114.1°C and -97.6°C respectively. The mixture was 80% ethanol, 20% methanol. Reasonable reflection coefficients, efficiencies and gains can be achieved. The maximum gain over the band of interest is 5.62 dB at 1.31 GHz.
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      Metasurface synthesis using susceptibility tensors and holographic technique
      • Author(s): M. Cerveny ; K.L. Ford ; A. Tennant
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      • p. (4 pp.)
        For a conventional, conducting surface, Snell's law applies such that the incident and reflected waves have the same angle to the surface normal. Two methods are studied in this paper that allow the design of planar metasurfaces which reflect wavefronts to prescribed directions. Two techniques are investigated; the first is based on the calculation of electric and magnetic susceptibility tensors and the second uses a holographic technique.
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      Analysis and Design of Metasurface Antennas
      • Author(s): G. Minatti ; F. Caminita ; E. Martini ; S. Maci
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      • p. (2 pp.)
        Modulated metasurface antennas are leaky wave antennas which allow for a tailoring of the radiative field through the control of the interaction of a cylindrical surface wave with a modulated impedance surface. In this paper, we briefly describe an efficient pseudo-analytical method for the accurate analysis of such antennas. This method can be used as a basis to set up a design procedure which provides the MTS required to obtain a target aperture field distribution. Full wave simulations are provided to demonstrate the accuracy of the proposed approach.
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      Properties of antennas made with sprayed selective silver metallization
      • Author(s): A. Jammes ; M. Petisme ; K. Staelens
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      • p. (4 pp.)
        This paper starts with the description of a new direct chemical plating method for silver, called the JET METAL (JMT) process and of the JET SELECTIVE process, which allows to obtain a selective metallization on any substrate which can be metallized with the JET METAL process. This technology is based on spraying separately an aqueous solution containing silver metallic ions together with a CMR free, aqueous based reducing agent. This process allows to plate chemical silver at twelve microm/hour at room temperature and at ambient pressure and is already used in industrial processes for metallizing plastics, composites and non-conductive materials in general and this in different formats (3D pieces, 2D foils, ...). In the second part, results obtained with metallized antenna patch realized with the process described above are shown and discussed.
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      On the introduction of lumped inductors for optimizing UHF band AMCs in terms of size and angular stability
      • Author(s): H.F. Alvarez ; M.E. de Cos ; F. Las-Heras
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      • p. (5 pp.)
        This work has analysed the potential enhancements concerning the angular stabilization and the size reduction of a hexagonal loop-based artificial magnetic conductor (AMC), through a novel approach entailing the use of lumped inductances. As a reward from the lumped inductances' introduction, unit-cell size reduction is achieved while preserving the angular stability and AMC operating bandwidth. A simple design methodology and insight to calculate the optimum lumped inductor value is presented. This work has been focused on UHF-band AMCs due to the size reduction and suitable bandwidth challenges. However the methodology can be also applied not only for lower frequency bands, but also to higher ones, provided that the resulting unit-cell size makes sense in terms of the manufacturing constraints and the lumped inductor's size vs. the metallization one.
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  • Session: 4A - Biomedical Applications and Electrically Small Antennas
    • Assembly conformal antenna array for wearable microwave breast imaging application
      • Author(s): F. Wang
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      • p. (5 pp.)
        In this paper, a novel assembly of the conformal antenna array for microwave breast imaging (MWI) is proposed. A pair of 6-element hemispherical antenna arrays is proposed using an optimised author-designed thin-film UWB antenna integrated into the dielectric spacer. A single 6-element array allows detection of the tumour using a rough version of the monostatic radar-based method. Also, a larger element array such as a 12-element array can be assembled with the 8-element array as the block unit to improve the accuracy of imaging results. The performance of the proposed configuration of the conformal array is validated in the CST Microwave Studio (MWS) and Design Studio (DS) software. In the simulation work, a realistic voxel-based phantom is introduced and exported from an MRI-scanned human breast. During the imaging stage, an effective estimation algorithm such as Delay-and-Sum (DAS) is implemented to create an energy distribution map by processing the scattered microwave signal received at different receiving antenna located around the breast area. Results show that a small tumour of 5 mm in diameter can be successfully detected in a 2-D image and localised using the proposed antenna array.
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      Microwave apparatus for testing breast integrity based on Huygens principle: clinical validation on 16 subjects
      • Author(s): L. Sani ; M. Paoli ; G. Raspa ; A. Vispa ; N. Ghavami ; G. Tiberi ; A. Saracini ; S. Ercolani ; E. Vannini ; M. Duranti
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      • p. (5 pp.)
        In this study, we present the initial results of the clinical validation of a microwave apparatus for testing breast integrity. The microwave apparatus does not emit ionizing radiation; thus, it is completely safe for the patients. Moreover, no matching liquid is required. Huygens Principle is used to process microwave signals and construct a correspondent image. We compare microwave images with respect to echography and/or mammogram diagnosis. From the microwave images obtained from the first 16 subjects, it is possible to conclude that microwave images of non-healthy subjects have a maximum to average ratio, which is approximately 10% greater than that of the healthy subjects. Maximum to average ratio has been also used to classify the microwave images, obtaining a sensitivity of 91%.
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      Miniaturization of a broadband monopole antenna using low loss magneto-dielectric materials in VHF band
      • Author(s): A. Kabalan ; A.-C. Tarot ; A. Sharaiha
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      • p. (4 pp.)
        This paper presents the miniaturization of a broadband monopole antenna covering the VHF band through the use of low loss Magneto-Dielectric Materials (MDM). After a parametrical study to determine the impact of the thickness, the width and the height of the MDM, we show that a partial recovering of the antenna by the MDM provides an optimum miniaturization rate. The measurement of the prototypes, realized with a MDM of 3 mm of thickness, is confronted with the simulations and confirm the size miniaturization rate and a good agreement between simulation and measurement.
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  • Session: 4B - Propagation 2
    • A Wideband Circularly Polarised Cross-Slot Antenna with an L-Shaped Feed-Line
      • Author(s): M.G. Aly  and  Yi Wang
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      • p. (4 pp.)
        This paper presents a new wideband and circularly polarised (CP) slot antenna realised by using an L-shaped feed underneath the cross-slot antenna, and tapered to the conventional microstrip feed-line. The proposed antenna is fabricated with an area of 75 × 80 mm2. The simulated results showed that the antenna had an impedance matching bandwidth of 34% from 1.3 to 1.83 GHz, and an axial ratio (AR) bandwidth of 20% from 1.36 to 1.66 GHz. A maximum gain value of 3.4 - 3.8 dBi has been achieved within the operating band. The proposed antenna is of a simple and single-substrate structure, suitable for the Global Navigation Satellite Systems (GNSS) application. The impedance bandwidth and radiation patterns have been confirmed by measurement.
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      A feasibility study on the extension of the point scatterer formulation to include wind induced dynamics
      • Author(s): N. Leonor ; R. Caldeirinha ; M. Sanchez ; T. Fernandes ; S. Morgadinho
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      • p. (5 pp.)
        This paper presents a feasibility study on the extension of the point scatterer formulation to include time-varying effects caused by wind induced channel dynamics. This modeling approach, which is based on a ray-tracing algorithm, employs various point scatterers with specific radiation characteristics, distributed within a computational volume, to characterize the electromagnetic behavior in the presence of trees and vegetation volumes. This propagation model has now been extended to include the time-varying received signal level, caused by the swaying motion of branches, twigs and leafs. To this extent, a statistical model is used to characterize the time-varying attenuation of each multipath component. The performance of the proposed model is assessed against measurements intended to record the dynamic re-radiation pattern of a tree in various windy conditions, which included four wind directions and two wind speeds.
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      A channel model for the propagation of X-band radio waves through the solar corona
      • Author(s): A.J. Stocker ; D.R. Siddle ; E.M. Warrington ; G. Mariotti ; D. Silvestri ; A. Zeqai ; P. Tortora ; A. Argyriou ; J. De Vicente ; R. Abello ; M. Mercolino
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      • p. (2 pp.)
        Spacecraft communication systems operating at X-band are strongly affected when the propagation path passes close to the sun (characterised by the Sun-Earth-Probe, SEP, angle). In this paper, a channel model that can generate a time-series of signal amplitude and phase is presented. The channel model reproduces the observations well for SEP>2° and, with some caveats, works at smaller values of SEP.
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  • Session: 4C - Multiband and Wideband Antennas
    • High Aperture Efficient Corrugated Plate Antenna at X-band
      • Author(s): S. Alkaraki  and  Yue Gao
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      • p. (3 pp.)
        This paper presents a compact and high aperture efficient corrugated plate antenna for X-band applications. The proposed antenna consists of two metallic thin plates stacked on top of each other, where the electromagnetic energy is launched into a cavity between both plates through a standard rectangular x-band waveguide and coupled to the top plate surface via three slots. Furthermore, the three slots in the top plate are surrounded by periodic corrugations and rectangular cavity that dramatically improve the gain of the antenna, hence improving its aperture efficiency. The proposed antenna has high performance in terms of bandwidth, gain, aperture efficiency and radiation efficiency. The peak gain of the proposed antenna is 18.5 dBi with a peak of aperture efficiency of 63.2% and radiation efficiency of more than 94% over its entire bandwidth.
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      Optimization of log-periodic dipole antenna with LTE band-rejection
      • Author(s): K.K. Mistry ; P.I. Lazaridis ; Z.D. Zaharis ; T.D. Xenos ; I.A. Glover
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      • p. (5 pp.)
        This study presents an optimized design of a 10-dipole log-periodic antenna for UHF TV reception with LTE band rejection. The simulation of the antenna was performed in CST simulation software followed by optimization of the design using TRF (Trusted Region Framework) algorithm in the frequency range of 450 MHz-900 MHz. The parameters optimized are S11, realized gain and front-to-back ratio of the antenna. TV reception passband is 450 MHz-790 MHz and LTE band is 810 MHz-900 MHz. The proposed antenna design provides a good matching with a low S11 in the passband (470 MHz-790 MHz) and a high S11 in the stopband (i.e. LTE region of 810 MHz-900 MHz). The antenna provides a realized gain between 7 dBi and 8 dBi whereas front-to-back ratio above 14 dB in the passband.
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      Size Reduction of Multi-Band Antennas Using Feature-Based Optimization
      • Author(s): S. Koziel  and  A. Bekasiewicz
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      • p. (4 pp.)
        Explicit size reduction of multi-band antennas using EM-driven design optimization is presented. The major challenge of multi-band antenna miniaturization is the necessity of independent control of frequency allocation and depths of several resonances while attempting to reduce physical dimensions of the structure at hand at the same time. In this work, we exploit feature-based optimization (FBO) framework which is well suited for handling multi-band antenna responses. The primary objective of the optimization process is the footprint area of the antenna, whereas design specifications imposed on reflection characteristics are handled by means of a penalty function approach. Owing to the general properties of FBO (i.e., “flattening” of the functional landscape) the design optimization costs can be kept at an acceptable levels of a few dozen of evaluation of the EM simulation model of the antenna. The proposed methodology is demonstrated using two structures, a dual-band patch antenna, and a triple-band dipole antenna.
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      A Compact Multiband Antenna for Mobile Handset Using Characteristic Modes Optimization
      • Author(s): H. Jaafar ; S. Collardey ; A. Sharaiha
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      • p. (4 pp.)
        In this paper we present the design of a compact multiband antenna using the theory of characteristic modes. By properly loading the antenna at specified positions, the characteristic currents are manipulated in order to match the antenna in the desired frequency bands. The optimal load values are calculated by combining the characteristic modes with an optimization algorithm. The loaded antenna covers the GSM-850/900 and Bluetooth bands with an efficiency higher than 90%.
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      Characterisation of Flexible, Thermal Transfer Printed UWB Antenna Under Static Bending
      • Author(s): M. Kgwadi  and  T.D. Drysdale
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      • p. (5 pp.)
        We present low-cost, flexible thermal transfer printed (TTP) ultra-wideband printed monopole antenna in the IEEE 802.15.3a band ideal for low-power, short-range and high-data-rate communications. The performance of the antenna was characterised under various static bending conditions. The antenna retained ultra-wideband characteristics under static flexing covering 100% under no bending, 85% under 40 mm radius bend, and 70% under 19 mm radius bend of the total IEEE 802.15.3a band. The radiation characteristics of the antenna remained omnidirectional throughout the entire band and closely follows simulated characteristics.
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      A Printed Monopole UWB Antenna Design with Single and Dual Band-Suppression Characteristics
      • Author(s): I.T.E. Elfergani ; P. Lopes ; J. Rodriguez ; A.S. Hussaini ; R.A. Abd-Alhameed
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      • p. (5 pp.)
        This paper addresses an approach to synchronise with the UWB spectrum, as well as elaborating on the phenomena of frequency interference within UWB antennas. The proposed design occupies a compact volume of 30x30x0.8mm3. The antenna consists of a hexagonal shaped structure printed over FR4 substrate. For bandwidth improvement, a defected ground structure (DGS) was first introduced and secondly a stub was added over the feeding strip to accomplish a larger bandwidth. To achieve the frequency band notched characteristics, a half hexagon slot was etched onto the radiator, that creates a notch at 5.2 GHz, then by introducing a full hexagon slot, another rejected band was created at 10 GHz. The proposed antennas show a stable performance in the UWB spectrum as well as achieving superior dual band-notch features at desired frequency bands.
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  • Session: 4D - Reconfigurable Antennas
    • Evidence of mainbeam steering capability of a patch antenna with an anisotropic dielectric realised using a transmission line model
      • Author(s): W. Kuhirun ; P. Boonek ; W. Silabut
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      • p. (5 pp.)
        A mainbeam steerable patch antenna element ideally steered by adjusting the permittivity in between the patch and ground has been previously investigated. Later, it was found that the ideal mainbeam steerable antenna element is realisable using a transmission line model. As a result, mainbeam steerable antenna elements using a transmission line model have recently been proposed. It was originally assumed that the dielectric in between the patch and ground was isotropic and double positive. Later, it was found that the dielectric can possibly be either isotropic or anisotropic. This paper briefly discusses a mainbeam steerable patch antenna element realised using a transmission line model and provides evidence that the mainbeam of a patch antenna element with an anisotropic dielectric realised using a transmission line model can be steered by varying the inductance of lumped elements.
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      Design of Mechanically Reconfigurable Meander Antenna Using the Galinstan Liquid Metal
      • Author(s): J.M. Floc'h  and  I. Ben Trad
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      • p. (4 pp.)
        In this paper, a mechanically controlled frequency agile antenna was successfully designed, manufactured and characterized for wireless communication applications in the frequency range 0.5-3 GHz. The agility property is obtained by adjusting the floating ground plane dimensions placed under the meander patch using a liquid metal, the Galinstan with electrical conductivity 3.46x106 S / m (20 ° C). To do so, we inject progressively the Galinstan into the channels using a syringe depending on the desired size. Two prototypes were fabricated and obtained results are presented and discussed.
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      Development of a reconfigurable modular GPS beamformer for design and test
      • Author(s): E.M. Lloyd  and  R.J. Watson
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      • p. (5 pp.)
        When creating a new antenna design it is often necessary to test many different configurations, in real environments as well as in simulations. Different array antennas need different feed arrangements, which can make testing many designs extremely costly. The aim of this research is to create a test bed that would allow many different configurations to be tested with minimal expense of time and money. This was done by creating a modular design that was easily reconfigurable, allowing stages to be added, removed and rearranged as necessary. This paper presents the design of the individual modules and characterises their performance, demonstrating that the modular approach offers good performance and will allow multiple designs to be evaluated without compromise.
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