New Publications are available for Other dielectric applications and devices
http://dl-live.theiet.org
New Publications are available now online for this publication.
Please follow the links to view the publication.A sensing optimal proposal based on intelligent street lighting system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0816
This paper introduces an intelligent street lighting system (ISLS) based on wireless sensor networks (WSNs) which uses pyroelectric infrared sensors (PIR) detect pedestrians and vehicles. One goal of our research is to design an optimal proposal of deploying PIR in ISLS. We present a mathematical model for sensing area of PIR, and analyze the factors that affect the sensing area of PIR. An optimal sensor deployment scheme is proposed, taking into account the sensing requirement of community street. The simulation results confirm that the deploying algorithm is feasible in community street.Analysis of dielectric resonator antenna arrays with supporting perforated rods
http://dl-live.theiet.org/content/conferences/10.1049/ic.2007.1421
Arrays of dielectric resonator antenna (DRA) elements are formed from one piece of materials. Perforated bonding dielectric rods are are applied to connect the individual DRA elements and completely eliminate all the rest of the dielectric materials between the DRA elements. This technique of fabricating DRAs using perforations eliminates the need to position and bond individual DRA elements in an array. The dielectric rods have low dielectric constant and thin enough to avoid guiding waves around the design frequency of the array itself. A 4-element array is fabricated. The array is excited by narrow slots and designed to operate at 10 GHz. The performance of the 4-element prototype array with bonding rods is compared with a corresponding array without the bonding rods. Measured and simulated return loss and radiation patterns are presented for the array. Also, a larger 4×4 array is fabricated and tested. The results are presented to show the effect of the presence of the bonding rods. Parametric study on DRA height and feeding slot width is performed to achieve better matching. (5 pages)Pyramidal dielectric resonator antenna for wideband applications
http://dl-live.theiet.org/content/conferences/10.1049/ic.2007.0892
A coaxial-fed pyramidal dielectric resonator antenna (DRA) is studied theoretically and experimentally. Pyramidal dielectric resonator antennas are attractive candidates for many wireless applications, since they exhibit wide impedance bandwidth and stable radiation characteristics. Their operation relies on the excitation of multiple modes at nearby frequencies in order to obtain a wide operational bandwidth through the overlap of their resonances. The design concept is an evolution of the rectangular DRA; the pyramidal DRA offers however certain advantages such as more symmetrical radiation patterns and additional degrees of freedom for mode impedance-matching. (4 pages)Wideband saline-water antenna
http://dl-live.theiet.org/content/conferences/10.1049/ic_20050312
Basic monopole antennas are becoming less suitable for wireless communications because most applications demand multi-band operation. Dielectric resonator antennas (DRAs) can be made with a wide range of materials and allow many excitation methods. We are investigating liquid dielectrics as DRAs at frequencies between 1-4 GHz. In this paper we report a variable height liquid antenna. We used pure water which has good dielectric properties for frequencies up to 2 GHZ salt (NaCl salinity S<4ppt) was added to reduce the dielectric response of water at high frequencies (<2 GHz). As a development to where the match was tuned by varying the length of the antenna; the resonant frequency of the proposed antenna is now changed by varying the liquid column height.Investigation of rectangular dielectric resonator antennas for direction finding application
http://dl-live.theiet.org/content/conferences/10.1049/cp_20030186
A DOA receiver using RDRAs as receiving elements has been described. The receiver operates at 2.37 GHz. It has been demonstrated in the laboratory scale that the direction of arrival can be determined using the DOA receiver with two RDRAs. The receiver has benefited from the low level mutual coupling and low cross polarisation level of the RDRAs, which reduces the interference between channels and simplifies the design of circuits for phase measurements.Microstrip-slot coupled rectangular dielectric resonator antenna: theoretical modelling and experiments
http://dl-live.theiet.org/content/conferences/10.1049/cp_20030187
A microstrip-slot coupled rectangular dielectric resonator antenna (RDRA) operated at the fundamental mode of operation is investigated numerically and experimentally. The effect of slot size on the radiation performance of the RDRA is studied. The antenna structure is simulated using the High Frequency Structure Simulator (HFSS) software package. A few experimental set-ups were examined and the antenna parameters were measured. The simulated results are presented and compared with those obtained by experiments. It is shown that the size of the slot can significantly affect the radiation properties of the RDRA and there are good agreements between numerical and experimental results.An LTCC based differential microwave DRO module
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020214
Low temperature co-fired ceramic (LTCC) technology is a multi-layer ceramic process that is well suited to the realisation of low cost, high performance RF and microwave components. This paper describes the design, fabrication and evaluation of a 21.3 GHz differential dielectric resonator oscillator (DRO) module fabricated in LTCC. It has a measured output power of +3 dBm and an amplitude imbalance between the output ports of <0.2 dB. The measured phase noise is -102 dBc/Hz at 100 kHz offset from carrier. The module was the prototype of a commercial product that is now under development. The commercial product will also include a small voltage tuning range to allow phase locking of the DRO for applications such as clock generation in 40 Gb/s optical transceivers. (9 pages)Investigation of rectangular dielectric resonator antennas for switching polarisation diversity communication systems
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010247
In this paper a new application of a rectangular dielectric resonator antenna (RDRA) is presented. The experimental and simulation results of the RDRA show that the difference between the co- and cross-polar radiation is at least 15 dB. Using a single RDRA excited by two probes at two modes TE<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">x</sup><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">111</sub> and TE<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">y</sup><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">111</sub>, an antenna to receive two orthogonal polarisation waves is made. A communication system including a transmitter with two orthogonal dipoles and correspondence switching polarisation diversity receiver at 2.36 GHz was designed and implemented to demonstrate polarisation diversity using RDRA as the receiver antenna.Model for the analysis of microstrip cylindrical antennas: efficient calculation of the necessary Green's functions
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010362
Conformal antennas are of great interest, because there are lots of applications which require non-planar surfaces and therefore non-planar substrates, for example circular ones. To analyse such structures corresponding rigorous theoretical approaches should be developed. Because of the more complex geometry conformal antennas are less investigated than planar ones. However in general the lines of reasoning may be very similar. Here we follow an approach that was proposed and successfully realised for planar multilayer antennas. The main idea of this approach is to solve the problem in the spatial domain. This line of strategy is realised for circular microstrip patch antennas. In this paper the problem of a patch microstrip antenna printed on a circular metal-dielectric substrate (circular metal rod coated by a dielectric layer) is discussed. Mixed-potential integral equations for the electric field are constructed. These equations contain spatial Green's functions for sheet electric currents and they can be solved using the moment method. In order to realise the proposed scheme we should be able to calculate spatial Green's functions very efficiently. This is really a key point of the problem, which is successfully solved in this paper.Rectangular dielectric resonator antennas: theoretical modelling and experiments
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010419
A rectangular dielectric resonator antenna (RDRA) is investigated theoretically and experimentally. The conventional dielectric waveguide model (CDWM) and the finite element method (FEM) are employed to calculate the radiation characteristics of the antenna. The results are presented and compared with those obtained experimentally. It is concluded that the CDWM can be used for a first order estimation of antenna parameters, but more accurate results can be obtained using the FEM for radiation patterns.Study of frequency selective surface (FSS) resonator elements on a circular dielectric rod antenna for mobile communications
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010394
This paper reports on the development of antennas for mobile communications systems based on a dielectric rod antenna fed from a circular waveguide. The results presented are for a linearly polarised antenna with a partial frequency selective surface (FSS) cover and without an endcap. The complete system was modelled using the transmission line matrix (TLM) method. This allowed an accurate design to be achieved before committing to any hardware production. Good agreement between measured and modelled results has been observed. Clear beamforming by the addition of FSS elements has also been demonstrated.The determination of the resonance frequency of the TE<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">III</sub><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">Y</sup> mode in a rectangular dielectric resonator for antenna application
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010237
The conventional dielectric waveguide model (CDWM) is used to determine the resonance frequency of a rectangular dielectric resonator operating at the TE<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">111</sub><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">y</sup> mode for antenna application. A fitted closed form formula is obtained for the prediction of the resonance frequency. The results obtained are compared with the experimental results and that determined using the Marcatili (1969) and effective dielectric constant (EDC) methods. The formula provides a simple method for the estimation of the resonance frequency of the TE<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">111</sub><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">y</sup> mode with an error ranging from -9.3% to +2.05% for ɛr<100.Broadband suspended plate antenna with vertical grounded wall
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010239
A novel feeding scheme was proposed to feed a suspended plate antenna for broadband applications and investigated experimentally. The feeding consists of a thin vertical dielectric slab. One of two surfaces of the slab was completely covered by a grounded wall and a probe-fed strip was etched onto other surface. The two prototypes with square and circular plates fed by the proposed feeding were designed and fabricated. Both square and circular plates were put parallel to the ground plane and perpendicular to the grounded walls. The plates were fed by the probe-fed strips at the midpoints of their edges close to the grounded wall. The input impedance and radiation patterns of the antennas were examined experimentally. The results showed that 50% bandwidth were achieved and radiation patterns were similar to those of the planar inverted-L or -F antennas.A method for calculating profiles of a dielectric thick lenses
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010309
Hasanov and Polat (see International Journal of Electronics and Communications (AEO), vol.54, no.2, p.109-113, 2000) investigated the transformation of a plane wavefront to another plane wavefront after passing through a thick lens and described the class of optical mappings realizable by means of such lenses. However, it is desirable to describe the class of optical mappings and calculate the lens profiles for a more general case when incoming and outgoing wavefronts have arbitrary shapes. For two reflecting surfaces a similar problem has been solved by Gasanov (1991). The aim of this paper is to provide a method for calculating the profiles of symmetric thick lenses which realize an a priori given optical mapping between spherical and plane wavefronts. It is shown that this mapping may be chosen freely and be used for various purposes such as satisfying Abbe's sine law or Herscel's condition exactly. We have shown, that calculating the profiles of lenses can be reduced to solving two first-order differential equations which can be solved separately. It is also shown that the geometry of the problem provides a natural condition to control the accuracy for the numerical solution of the obtained differential equations.Dielectric resonator antennas and applications
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000611
Dielectric resonator antennas (DRAs) are usually made of dielectric resonators with ɛ<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">r</sub> ranging from 10 to 100. The resonance mode used for radiation depends on the geometry of the resonator and the required radiation patterns. The fields of the mode need not to be strongly confined within the resonator, so that it can be easily fed to produce high efficiency radiation. Cylindrical and rectangular dielectric resonators are the two most common geometries for antenna application. Cylindrical dielectric resonators operating at the HE<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">11δ</sub> mode have been shown to be able to radiate as an antenna. Rectangular DRAs operating at TE<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">111</sub><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">y</sup> mode have also been demonstrated to provide similar radiation characteristics. In this paper, results of theoretical and experimental studies of both cylindrical and rectangular DRAs are presented. The dependence of the antenna parameters including the radiation pattern, directivity and bandwidth on the dielectric constant and physical dimensions of the resonator are addressed. Some applications of the DRAs are also discussed. (6 pages)Multiple-probe dielectric resonator antennas for asset tracking applications
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000610
Dielectric resonator antennas (DRAs) are volumetric devices that can be more efficient than conventional antennas at high frequencies and smaller by approximately the square root of the relative permittivity of the material. Research at Sheffield and Griffith universities has shown that by using several feeds they can be designed to be directional with electronic beam steering. DRAs can also have radio direction finding capabilities by comparing the same signal in two beams or by using monopulse processing. The ability to locate a radio source and form an optimal beam in that direction, combined with nulls that can sometimes be used to cancel out unwanted signals, may give these antennas a limited adaptive or `smart' capability. Optimal beam configuration can also help to extend battery life, which may be important when the asset is not easily recovered, as is the case in some biotelemetry applications. The presentation will describe a number of multi-probe, multi-beam DRAs designed for use on both tags and short-range communications, such as Bluetooth, and for radio direction finding applications such as tag tracking and microbase-stations. A typical 870 MHz multi-beam 360° direction finding DRA system is 32 mm across and 13 mm high using an ɛ<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">r</sub> of 80 and smaller for higher ɛ<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">r</sub> materials. The construction of these antennas lend themselves to integration into the manufacture of the communications circuits, thus reducing cost when appropriately designed these antennas are considered to provide better performance than conventional antennas when operating in close proximity to conductive structures. (4 pages)Temperature compensated high Q and high thermal conductivity dielectrics for Ku and Ka band communications
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000650
Aluminium oxide is a favourable candidate for use as a dielectric resonator in Ku and Ka band microwave devices especially at high powers due to its very low tanδ~2×10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-5</sup> at 10 GHz, modest relative permittivity of 9.8 and high thermal conductivity of 30 W/mK. However, its temperature coefficient of the resonant frequency TCf of -60 ppm/K is rather high for practical purpose. The application of a film of titanium oxide which has an opposite sign TCf of +450 ppm/K onto an alumina puck, produces a composite in which the TCf can be tuned to be zero across a large temperature range. The tanδ of the composite at zero TCf is 3.3×10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-5</sup> (Q<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">d</sub>=30,000) at room temperature and 10 GHz. (4 pages)Low cost linear arrays using polystyrene foam substrate
http://dl-live.theiet.org/content/conferences/10.1049/ic_19980077
The antennas described in this paper employ further developments of a method of construction used in a flat-plate antenna for DBS applications described by Henderson and James (1987). This was a high-gain array antenna intended for operation between 11.7 and 12.1 GHz, and at these frequencies, dielectric losses in conventional substrates are unacceptably high, but the low-loss substrates available then were too expensive to use in a product intended for the consumer market. The solution adopted therefore was to use an inexpensive substrate material with a low relative permittivity, and thereby achieve low dielectric losses. Henderson et al. used a flexible plastic foam with a relative permittivity of 1.06 as the substrate material. In this paper, the study is extended to explore the use of an expanded polystyrene foam with a relative permittivity of around 1.05 which although exhibiting greater probable variation in its mechanical and electrical properties, is even less expensive and more widely available. (5 pages)Microwave dielectrics
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971054
In the last 20 years the field of microwave communications has seen exceptional growth. It has been estimated that there are over 55,000 new users of cellular communications every day. This is largely due to the wish of most people for mobility as a key feature of communications. This growth places an enormous burden on the filters to the extent that filters using current technology simply cannot cope with the increased traffic demand. There is a requirement for systems with lower insertion loss, steeper filter skirts, better selectivity and ideally all of these with miniaturisation. In this paper, dielectric resonators are discussed. The interest in dielectric resonators is a direct consequence of the hurdles facing current technology. Dielectric resonators are now being developed with extremely attractive properties as well as the inherent potential for miniaturisation. The key properties are seen to be the dielectric loss (tan δ) the dielectric constant (ε') and the temperature coefficient of the resonant frequency (TCf). (5 pages)Application of Superfish for the modelling of dielectric resonator structures
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971272
Superfish is a finite difference package written to solve the TM and TE resonant frequencies and field distributions in an RF cavity with two dimensional Cartesian or three dimensional cylindrical symmetry. Only the azimuthally symmetric modes are found for cylindrically symmetric cavities and the modes are found one at a time. In this paper Superfish is applied to the modelling of a dielectric resonator structure. (5 pages)Application of low loss dielectric and high temperature superconducting materials in microwave filters
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970695
Recently cryogenically cooled low loss dielectric materials and high temperature superconducting films have received much attention. The authors report on the latest dielectric materials and on the possible electrical designs of electrically small filters using these novel materials. (4 pages)Application of Superfish for modelling cavity and dielectric structures
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971265
Superfish is a finite difference package written to solve the TM and TE resonant frequencies and field distributions in an RF cavity with two dimensional cartesian or three dimensional cylindrical symmetry. In this paper it is applied to the modelling of cavity resonators, and dielectric resonators enclosed in conductive housings. (6 pages)Dielectric resonator antennas supported by ‘infinite’ and finite ground planes
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970301
Dielectric resonator antennas have received an increased attention in recent years. For the convenience of feed, they are normally used with the support of a ground plane of a finite size. We report our experimental study of the size effect of the ground plane on a cylindrical dielectric resonator antenna coupled using a probe. The parameters studied include resonance frequency, radiation pattern, gain and bandwidth and they are compared with those obtained theoretically assuming the ground plane is of infinite size. It shows that the largest effect occurs when the diameter of the ground plane is small or less than one half of a wavelength. (4 pages)A comparative study of circular microstrip and cylindrical dielectric resonator antennas
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970203
The performance of circular microstrip antennas is compared with that of cylindrical dielectric resonator antennas for two operating frequencies (4.1 GHz and 7.0 GHz). The results for the resonant frequency, radiation pattern, antenna directivity, unloaded Q-factor, impedance bandwidth and radiation efficiency are presented, indicating that the performance of the cylindrical dielectric resonator antennas compares well with that of circular microstrip antennas. (5 pages)The potential use of HTS filters in satellite payloads
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960593
The surface resistance values for various thin films (YBaCaCuO, GdBaCuO and TlBaCaCuO) already show significant improvements over conventional conductors on various substrates. Low loss YBCO and TlBaCaCuO thick films on yttria-stabilised zirconia (YSZ) have been reported by Birmingham and Oxford Universities respectively. Thick films have the added advantage that they can coat large area curved surfaces. A method to characterise HTS materials and substrates using a ring resonators has been developed by Portsmouth University, and measurements on TlBaCaCuO rings are being undertaken. A 4-pole extracted pole filter fabricated from GdBaCuO was commissioned from Marconi Research Centre (MRC). It has been characterised for MMS by Portsmouth University over two temperature cycles between 50 K and 90 K. Excellent reproducibility was seen over each temperature cycle with the supplied data from MRC. The design of a 4-pole elliptic filter using TlBaCaCuO on an MgO substrate is discussed. Work on single crystal dielectric resonator filters is ongoing. The significant advantages and disadvantages of DR/HTS technology have been assessed and are discussed. (4 pages)HTS shielded dielectric resonators
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960598
Single crystal dielectrics and HTS thin films have been shown to possess very high quality factors (Q). This makes them highly desirable in the area of cellular and satellite communications. A disadvantage is that single Crystal dielectrics are expensive. Dielectrics resonators produced by sintering are well known but generally do not possess high enough Q factors to offer significant performance advantage. We show that by careful attention to the quality of the ceramic processing and to the sintering conditions, very high Q dielectric resonators can be produced. Room temperature Q of 5×10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">4</sup> is routinely measured at 10 GHz. We present preliminary results on sintered dielectrics and HTS thick film shields which demonstrate that Q's well in excess of 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">5</sup> are achievable at 10 GHz and 77 K. This opens up the possibility of constructing inexpensive filters with exceptionally low insertion loss. (5 pages)Performance of YBCO thick films in high-Q structures
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960597
Over the past 10 years a wide variety of different resonant structures have been fabricated from High Temperature Superconductor (HTS) materials for an extensive range of possible RF and microwave applications. The near term applications are those that make use of passive components such as high Q resonators for low phase noise oscillators and high performance filters for satellite or communications purposes. Although there are several different HTS materials, such as YBCO, BSCCO and TBBCO, each particular material can be subdivided according to their means of production and, for microwave applications, there are essentially two types. The first is thin film material which is an epitaxial film, usually <1 micron thick and grown by techniques such as Molecular Beam Epitaxy (MBE) or laser ablation on a single crystal substrate such as MgO or LaAlO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>. The second is thick film material 50-100 microns in thickness which is polycrystalline and is deposited in the form of a viscous ink upon a polycrystalline substrate. This paper is concerned with thick film YBCO films on zirconia substrates fabricated either by doctor blading or screen printing techniques. One advantage of the thick film approach is that films can be deposited onto large areas and curved to form three dimensional structures which are impossible to construct using thin film deposition techniques. A range of very high Q resonant structures have been realized and these are compared and contrasted in the paper. (6 pages)Enhanced transposed gain microwave oscillators
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960062
This paper describes the design of two low noise microwave oscillators operating at 7.6 GHz. These oscillators use room temperature sapphire resonators operating in the TE<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">01</sub>δ mode which demonstrate unloaded Q's of 44,000. Silicon transposed gain amplifiers are used to produce near-flicker-free gain. Oscillators with flicker noise corners around 1 kHz and a phase noise of -143 dBc/Hz at 10 kHz offset and -121 dBc/Hz at 1 kHz are demonstrated. This is within 3 dB of the theoretically predicted minimum noise. This performance is 12 dB better that in oscillators presented at the 1995 IEEE MTT conference and 1995 FCS conference. This improvement is achieved by using high level mixers.Electromagnetic and mechanical behaviours of whispering gallery mode resonators
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960031
Frequency and time metrology, modern telecommunication systems and space applications require X-band signal sources with increasing phase noise performances. In this field, the sapphire whispering gallery mode resonator (WGMR) seems to be very attractive. Exceptional phase noise performances have been recently reported for X-band sources based on such type of resonator. Although the WGMR structure seems relatively simple, the design of an operational resonator brings out a number of technological problems, especially for space applications where in-board systems are submitted to severe environmental stresses. This paper resumes our investigations on the design of an X-band WGMR for space applications. We present the measurement results of sapphire permittivity, electromagnetic resonance frequency determination and studies of vibrational behaviour of WGMR.Dielectric loaded HTS resonators
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960601
There exists considerable experience worldwide in research and development of high Q dielectric resonators based on sapphire and conventional superconductors at liquid helium temperatures. Stable microwave loop oscillators have been built, based on high Q resonators and cryogenic microwave functional elements such as low noise semiconductor amplifiers, phase shifters and filters operating at liquid helium temperatures and more recently at 70 K. As a result of the recent availability of reliable low power cryocoolers it has become possible to design dielectric loaded resonators making use of ultralow microwave loss properties of thin films of high temperature superconductors (HTS) such as YBa<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>Cu<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">7-x</sub>. (3 pages)Derivation of an equivalent multiport description of dielectric periodic gratings based on the coupled-wave theory
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960216
This paper deals with the derivation of an equivalent multiport description for modelling and simulation of dielectric periodic gratings. The method presented can be applied to scalar as well as to vectorial diffraction analysis. The approach is based on the coupled-wave theory where the field strengths are represented by infinite sums of their space harmonics. Finally, a vectorial differential equation is obtained which has the same structure as the telegraph's equations in the frequency domain describing the wave propagation on coupled transmission lines. Hence, already existing solution methodologies can be applied and the grating can be interpreted as a multiport where each port represents one diffraction order. Besides the derivation of the approach an intensive study of the important properties of the eigenvalues and eigenvectors of the reduced system is made.Dielectric resonator probe arrays with sectoral hard horn for wideband spatial power combiners/dividers
http://dl-live.theiet.org/content/journals/10.1049/iet-map_20060048
Analysis of dielectric resonator probe (DRP) arrays operating in an oversized hard waveguide with sectoral hard horn excitation is presented. A single DRP excited by a coaxial probe is first investigated inside a hollow rectangular waveguide and a waveguide loaded with hard walls, respectively. Simulation results are compared with measurement results and show a good agreement. Then, a one-dimensional DRP array is analysed inside a dielectric-loaded, oversized waveguide with sectoral hard horn excitation. A full-wave analysis based on the region-by-region finite-difference time-domain technique is applied for the optimisation of array parameters such as inter-element coupling, active reflection coefficients and uniform excitation. Numerical results are compared with those generated by using commercial software and exhibit a very good agreement.Fundamental characteristics of microstrip resonators loaded with dielectric rods for suppression of spurious responses
http://dl-live.theiet.org/content/journals/10.1049/ip-map_20050215
Characteristics of a class of microstrip resonators which are loaded with dielectric rods, are investigated by a finite-difference time-domain (FDTD) method. Dielectric rods to be inserted between a strip conductor and the ground plane have higher relative permittivity than that of the substrate. When a basic half-wavelength (λ/2) microstrip resonator is loaded with two dielectric rods, the electric length of a loaded half-wavelength (λ/2) resonator becomes longer than λ/2, which makes its fundamental resonant frequency (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i>′<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub>) to be generated on the region lower than that of an unloaded λ/2 resonator (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub>) and its first spurious response <i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>sp</i>1</sub> is generated on the region higher than 2<i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i>′<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub>. Therefore, to shift <i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i>′<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub> back to <i xmlns="http://pub2web.metastore.ingenta.com/ns/">f</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub>, the resonator's length is to be reduced, and this, in turns, suppresses the spurious responses. A tapped resonator employing the proposed method is capable of realising the improved spurious responses together with an attenuation pole in the stopband, and of reducing the resonator's length as well. A resonator employing the presented method is fabricated using low-temperature cofired ceramic (LTCC) materials, and the analysis is verified by comparing the computed results with the measurement.Analysis of a dielectric resonator antenna in a cylindrical conducting cavity: HEM modes
http://dl-live.theiet.org/content/journals/10.1049/ip-map_19949773
Numerical modelling has been performed for the hybrid HEM modes of a flush-mounted dielectric resonator antenna in a cylindrical conducting cavity. The antenna is formed by a conducting cavity with a dielectric post and radiates through an annular slot in the upper ground plane. Coupled aperture magnetic current integral equations are used to model the slot and the effect of the post resonator and the cavity are included via Green's function techniques. The moment method is applied to the coupled integral equations and the complex resonant frequencies for the antenna structure are found by searching for the zeros of the determinant of the impedance matrix in the complex frequency plane. The radiation Q factor, slot field distribution and radiation field are subsequently computed at the resonant frequency. The HEM modes with the lowest resonant frequencies have been investigated for different geometrical configurations.Design of monofilar and bifilar Archimedean spiral resonators for metamaterial applications
http://dl-live.theiet.org/content/journals/10.1049/iet-map.2008.0298
Archimedean spiral resonators as the unit inclusion for a metamaterial structure is studied. These inclusions are very compact, which make them a good candidate for practical metamaterial applications. Equivalent circuit models and analytical design formulas are derived for monofilar and bifilar spiral resonators. The circuit parameters and resonance frequencies are directly predicted by the geometry of the spiral and dielectric substrate/resonator configuration. Numerical simulations on both bulk and planar designs show that the predicted resonance frequencies are accurate enough for a preliminary design. Finally, complementary spiral structures, that is, spiral-shaped apertures in the ground plane, are considered. Loading two transmission lines with a complementary monofilar and a complementary bifilar spiral resonator, two planar band rejection structures are built. Measured results for two prototypes present a good accuracy.Calculation of dielectric resonators with complicated constitutive parameters
http://dl-live.theiet.org/content/journals/10.1049/ip-map_19952357
A novel approach for calculation of resonant frequencies of dielectric resonators in waveguides or cavities is presented. The resonant sample may be made from different materials: high-permittivity dielectrics, magnetic materials, chirals or general bi-anisotropic materials. The resonant frequencies of high-permittivity dielectric resonators in a cylindrical cavity are calculated and compared with the literature to validate the proposed method. Numerical results of chiral and Faraday chiral resonators are also given.Study of a microwave ferrite resonator antenna, based on a ferrimagnetic composite (Gd<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>Fe<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">5</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">12</sub>)GdIG<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>X</i></sub>–(Y<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>Fe<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">5</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">12</sub>)YIG<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1−<i>X</i></sub>
http://dl-live.theiet.org/content/journals/10.1049/iet-map.2008.0301
The authors report a study on microwave properties of a ferrimagnetic ceramic composite (Gd<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>Fe<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">5</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">12</sub>)GdIG<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>X</i></sub>–(Y<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>Fe<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">5</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">12</sub>)YIG<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1−<i>X</i></sub>. The magnetic and dielectric measurements at microwave frequency were made through the Hakki–Coleman's procedure and through the excitation of a cylindrical ferrite resonator antenna (FRA). The hysteresis loops of the GdIG<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>X</i></sub>YIG<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1−<i>X</i></sub> ferrimagnetic composite were obtained. The numerical simulation study was performed using Ansoft's High Frequency Structure Simulator (HFSS™) software. The agreement between the experimental data and the simulated results is very good. These results demonstrated that, by varying the material composition of the resonator, ferrimagnetic composite GdIG<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>X</i></sub>YIG<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1−<i>X</i></sub> could operate as a magneto-dielectric antenna with bandwidth in the range of 7.5–11% and in the frequency range of 4.4–5.3 GHz. Additionally, all FRAs presented a low negative value of <i xmlns="http://pub2web.metastore.ingenta.com/ns/">τ</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">f</sub>, which indicates suitability for microwave applications such as mobile communication systems or satellite broadcast systems.Microstrip-fed array of multisegment dielectric resonator antennas
http://dl-live.theiet.org/content/journals/10.1049/ip-map_19971375
A novel antenna is presented consisting of an array of multisegment dielectric resonator antennas fed by a multilayer microstrip branch-line network. A prototype array has been designed and fabricated at X-band and its measured performance includes a gain peak of 15.4 dBi with a 3 dB gain bandwidth of 17% and an efficiency of 66%. This array can be used as a medium gain, wideband antenna, or can form a subarray in a large low-profile structure for high gain applications.Numerical analysis of an aperture coupled rectangular dielectric resonator antenna using a surface formulation and the method of moments
http://dl-live.theiet.org/content/journals/10.1049/ip-map_19990209
A rigorous analysis of an aperture coupled rectangular dielectric resonator antenna (DRA) is presented. The method is based on a surface integral equation approach by which the dielectric resonator (DR) is treated via a set of combined field integral equations (CFIE). The CFIE and associated coupling is then formulated with sets of mixed potential integral equations (MPIE). The coupled integral equations are solved by the method of moments (MoM) in the spatial domain using Galerkin's procedure. Complex images are employed in the calculation to enhance numerical efficiency. Numerical tests have shown that only a relatively small impedance matrix is needed to compute the parameters of the antenna with good accuracy. The numerical model is demonstrated to be a very versatile and practical design tool which can analyse the DRA with minimal computation effort.Moment method solution of aperture-coupled hemispherical dielectric resonator antenna using exact modal Green's function
http://dl-live.theiet.org/content/journals/10.1049/ip-map_19941323
An aperture-coupled hemispherical dielectric resonator (DR) antenna excited at the end-fire TE<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">221</sub> mode has been studied. The exact magnetic-field Green's function of the DR antenna is presented, and the moment method is used to solve the equivalent current in the slot. From the magnetic current, the return loss of the antenna configuration is evaluated. The results are compared with the single-mode results and measurements available in the literature. Compared with the single-mode theory, the solution of the present theory is very general in terms of the slot position and the frequency range.Analysis of U-slot-excited dielectric resonator antennas with a backing cavity
http://dl-live.theiet.org/content/journals/10.1049/ip-map_20050179
The U-slot-excited dielectric resonator antenna (DRA) with a backing cavity is analysed theoretically and experimentally. It is found that the U-slot can be used to enhance the impedance bandwidth or to produce circularly polarised (CP) fields. By solving the equivalent magnetic current in the slot using the method of moments, the return loss, axial ratio and radiation pattern are obtained. The effects of changing the U-slot parameters on the antenna characteristics are investigated.Synthesis and microwave characterisation of (Zr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.8</sub>Sn<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.2</sub>)TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">4</sub>–epoxy composite and its application in wideband stacked rectangular dielectric resonator antenna
http://dl-live.theiet.org/content/journals/10.1049/iet-map.2011.0467
In this study, (Zr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.8</sub>Sn<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.2</sub>)TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">4</sub>–epoxy composites are synthesised, characterised and used in dielectric resonator antenna applications. (Zr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.8</sub>Sn<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.2</sub>)TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">4</sub> and epoxy are mixed in five different ratios, that is, 50:50, 60:40, 70:30, 80:20 and 90:10 with small amount of hardner (HY 951). The crystal structure and cell parameters of (Zr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.8</sub>Sn<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.2</sub>)TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">4</sub> are confined by Rietveld analysis. The complex permittivity of the composite is measured at different microwave frequencies in X-band (8.2–12.4 GHz). It has been found that the permittivity is reduced by increasing the percentage of epoxy in composite system. The optimised weight percentage ratio of (Zr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.8</sub>Sn<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.2</sub>)TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">4</sub> and epoxy composite material are used in a two-layer rectangular dielectric resonator antenna using coaxial excitation for obtaining wideband performance. The effects of the antenna parameters like length, width and probe length are investigated using Ansoft's high-frequency structure simulator (HFSS) software. The agreement between simulated and experimental data is very good. The proposed design provides the measured impedance bandwidth of 58.7% (at resonance frequency 8.40 GHz) from 6.45 to 11.38 GHz for reflection coefficient (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">S</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">11</sub>) of less than −10 dB with a measured average gain of 6.99 dB in the frequency range of 6.0–11.5 GHz. The radiation patterns are consistent throughout the operational bandwidth.Computation of coupling between whispering gallery mode dielectric resonators and a microstrip transmission line
http://dl-live.theiet.org/content/journals/10.1049/ip-map_19951899
Whispering gallery mode dielectric resonators have high quality factors, compatibility with microwave integrated circuits and reasonable mechanical dimensions even at millimeter wavelength frequencies. For practical use dielectric resonators must be coupled to an external transmission line. A simple mathematical model of the coupling between a dielectric resonator acting in WGE mode and a transmission line is proposed. Finally, measured quality factors are compared with the proposed model.Low profile wideband embedded dielectric resonator
http://dl-live.theiet.org/content/journals/10.1049/iet-map_20060028
A dielectric resonator antenna (DRA) made of high dielectric constant substrate is studied. Embedding a higher dielectric disk inside the substrate disk enhances the bandwidth. A narrow slot excites the DRA. Embedded DRAs of different shapes are considered for wideband applications. An eye-shaped DRA made with a circular dielectric resonator disk embedded in an elliptical-shaped ‘host’ DRA is found to have an impedance bandwidth of 28% with stable broadside patterns.Gaussian beam tracking through a curved interface: comparison with a method of moments
http://dl-live.theiet.org/content/journals/10.1049/ip-map_20030434
Propagation and refraction of Gaussian beams originating in the Gabor frame decomposition of source fields is studied with application to the analysis of dielectric lenses. Accuracy of asymptotic closed-form expressions used for Gaussian beam tracking (GBT) through dielectric interfaces is evaluated numerically. The numerical results obtained by GBT for a variety of configurations are compared with those computed by the multifilament current version of the method of moments. It is demonstrated that the GBT method is an attractive fast technique for design and optimisation of lens antennas and quasi-optical systems.Improved approximation for effective permeability in microwave ferrites
http://dl-live.theiet.org/content/journals/10.1049/ip-map_19960596
The nonlinear eigenvalue problem of microwave ferrite phase shift and control components is in general a function of three frequency-dependent variables. Below ferrimagnetic resonance a reasonably accurate approximation has been used to reduce the number of frequency-dependent variables to two, thereby simplifying the eigenvalue problem. Above resonance, accurate solutions are only achievable via a computationally expensive iterative solution of the nonlinear eigenvalue problem. To avoid this, a new approximation is proposed, and supporting modal frequency calculations presented for two axisymmetric configurations suggest that the effective permeability can be computed to within 6% accuracy.Gap capacitance of a coaxial resonator using simplified mode matching
http://dl-live.theiet.org/content/journals/10.1049/ip-map_20040727
The gap capacitance of a single coaxial resonator is found using a simplified rigorous mode matching method to calculate its resonant frequency. A method of finding the coefficients of the modal field expansions is also shown. The capacitance results for this type of structure are presented graphically and also as a normalised cubic polynomial. The results agree very closely with those obtained from measurements.Temperature-compensated frequency discriminator based on dielectric resonator
http://dl-live.theiet.org/content/journals/10.1049/ip-map_20040271
A planar circuit realisation of the Pound-type frequency discriminator has been implemented with a dielectric resonator in a microstrip environment. By taking advantage of the nature of the planar geometry, the circuit is further simplified and the original performance is maintained. Various frequency discriminators with centre frequencies around 4.2 GHz have been constructed and tested. It is demonstrated with analytical models and substantiated by measurement results that the dielectric resonator, with its own temperature coefficient of the resonant frequency, offers a degree of freedom that proves to be effective for temperature compensation in the design of the frequency discriminator. A temperature coefficient of 3.6 ppm/°C for the centre frequency is achieved with readily available dielectric resonator and substrate material from commercial sources. Further improvement of the system thermal stability can be obtained by tailoring the thermal property of the dielectric resonator to the chosen microstrip substrate.Shadow blockage effects on the aperture efficiency of dielectric Fresnel lenses
http://dl-live.theiet.org/content/journals/10.1049/ip-map_20000800
The effects of shadow blockage on the efficiency of a dielectric Fresnel lens is investigated. Since shadow blockage is a strong function of the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">F</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">D</i> value, it should be factored into the design, especially for compact lenses designed with a small <i xmlns="http://pub2web.metastore.ingenta.com/ns/">F</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">D</i>. Equations are derived, based on ray tracing, to determine the decrease in aperture efficiency due to shadow blockage. Design curves have been generated to plot shadow efficiency against lens diameter for various values of <i xmlns="http://pub2web.metastore.ingenta.com/ns/">F</i>/<i xmlns="http://pub2web.metastore.ingenta.com/ns/">D</i>. Good agreement with measured radiation patterns is also demonstrated.Active antenna top-cover frequency pulling effects
http://dl-live.theiet.org/content/journals/10.1049/ip-map_19941433
Active antenna load pulling effects are analysed in the presence of a partially reflecting superstrate (dielectric cover). The analytical and experimental results obtained exhibit distortion in the frequency pulling pattern of the active antenna. The results obtained can be used to design optimum cover placement or to postmanufacture tune the frequency of the active antenna module.