IET Microwaves, Antennas & Propagation
Volume 14, Issue 3, 26 February 2020
Volumes & issues:
Volume 14, Issue 3
26 February 2020
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- Author(s): Han Ren ; Hanxiang Zhang ; Bayaner Arigong
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 143 –148
- DOI: 10.1049/iet-map.2019.0336
- Type: Article
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p.
143
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(6)
A novel compact 3 × 3 Nolen matrix beamforming network is proposed in this study. Unlike the Butler matrix and Blass matrix, in this design, the proposed feeding network only requires couplers and phase shifters and removes crossovers and load terminations. To minimise the size, the authors’ proposed novel Nolen matrix is realised by lumped-element couplers. First, the design theory for 3 × 3 Nolen matrix is derived, and the associated pyramidal layout consisting of three couplers with two coupling ratios and three-phase shifters is proposed. Based on the determined topology, the S-parameters of the proposed feeding network and desired coupling ratios are derived, and it is found that the phase differences among the output ports are dependent on the characteristics of the couplers. Then, each coupler is realised by using lumped-elements (including inductors and capacitors) in the proposed topologies, where the values of the elements are obtained by analysing the ABCD -matrix of the branch lines in the couplers. To verify the proposed concept, an experimental prototype working at 1 GHz is fabricated and tested. The simulation and measurement results agree well with each other, and an ultra-compact size 0.17λ × 0.06λ is implemented to achieve more than 90% size reduction comparing with the previous designs.
- Author(s): Behnam Ghassemiparvin and Nima Ghalichechian
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 149 –153
- DOI: 10.1049/iet-map.2019.0473
- Type: Article
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p.
149
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The authors map the differences between various reconfigurable antennas and present a payoff metric for each type. They evaluate three distinct schemes of reconfiguration: pattern, frequency, and polarisation. They show that the often neglected losses play a pivotal role in the effectiveness of reconfigurable systems. For each of the pattern, polarisation and frequency reconfigurable antennas, they define a quantity that reflects the number of non-overlapping radiation patterns, orthogonality of the polarisation states, and the covered fractional bandwidth, respectively. Then, these quantities are divided by the amount of added losses. Thus, these metrics capture both the increased diversity due to the reconfiguration states and the associated losses. Moreover, the relationship between these metrics and the capacity of a communication system is discussed. Finally, application of the payoff metrics is demonstrated by comparing several reconfigurable antenna architectures from the literature. They show that established payoff metrics can be successfully used to evaluate and quantify the merits of reconfigurable antennas by using only antenna parameters rather than going through system-level analysis.
- Author(s): Md Abu Saleh Tajin ; Oday Bshara ; Yuqiao Liu ; Ariana Levitt ; Genevieve Dion ; Kapil R. Dandekar
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 154 –158
- DOI: 10.1049/iet-map.2019.0503
- Type: Article
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p.
154
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(5)
Flexible antennas have the potential to transform wearable and fabric-based wireless sensing technologies. The antenna discussed in this study is part of a sensing system that uses the back-scattered power level as the decision metric. For a good wireless sensor, it is necessary to offer a feasible read range and maintain good distinctions in the back-scattered power levels between the different states (i.e. level of stretch) of the antenna. Moreover, effects due to human body proximity should be minimised. For these reasons, the radiation efficiency is a crucial parameter to investigate. This study presents the radiation efficiency measurement of the proposed flexible knitted ‘Bellyband’ antenna at two different levels of stretch in a reverberation chamber. This work validates the reverberation chamber measurements through comparison with simulations and anechoic chamber measurements at 900 MHz. Moreover, this work demonstrates how the approach can be used to quantify bellyband antenna efficiency in the vicinity of a human body. Finally, the efficiency results were used to predict the read range of Bellyband radio frequency identification technology.
- Author(s): Aiai Wang ; Mingbao Yan ; Jieqiu Zhang ; Lin Zhen ; Jiafu Wang ; Shaobo Qu
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 159 –162
- DOI: 10.1049/iet-map.2019.0637
- Type: Article
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p.
159
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In this study, an absorptive/transmissive integrated frequency selective surface based on lumped resistance elements is presented. This technique is based on loading the lumped resistance element on the square ring, cascading a special filter. A flat band response can be obtained from the two transmission poles in each transmission window. Simulated results show that the −0.5 dB bandwidths are about 1.61 GHz (3.63–5.24 GHz) and 3.35 GHz (14.22–17.56 GHz), respectively. There is a wide absorptive band between the two transmission windows. The −10 dB absorptive bandwidth is about 5.16 GHz (8.04–13.20 GHz). In addition, the design procedure and operating principle were given, and the result was further discussed. Furthermore, the proposed structure was fabricated and measured. The measured results demonstrated the high selectivity, good angular and polarisation stability of the proposed design.
- Author(s): Amedeo Capozzoli ; Laura Celentano ; Claudio Curcio ; Angelo Liseno ; Salvatore Savarese
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 163 –173
- DOI: 10.1049/iet-map.2019.0178
- Type: Article
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p.
163
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The near-field (NF) acquisition time depends on the sampling strategy and on the measurement hardware. Optimised sampling based on singular value optimisation dramatically reduces the number of measurement points and the scanning path length compared to conventional samplings, without impairing the far-field reconstruction. Furthermore, an optimised control approach, tracking a sufficiently smooth trajectory allows better performance in terms of velocity and precision, significantly reducing the scanning time. We show that the combined use of an optimised sampling and an optimised controller drastically reduces the measurement time. The sampling strategy provides a raster grid of optimally selected rows hosting samples optimally arranged according to a row-wise non-uniform distribution. The optimised control drives the NF scanner and the vector network analyser to acquire the data along each row by a continuous probe movement with a variable velocity, accelerating and decelerating between two consecutive sampling points. The sparsity of the NF locations enables a significant increase in the average speed between two consecutive points. The controller is realised with a proportional-integral-derivative law with a compensation signal and a filter downstream. The controller does not demand complex hardware and can be realised in an extremely simple, cheap and off-the-shelf solution.
- Author(s): Melika Momenzadeh and Arash Ahmadi
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 174 –182
- DOI: 10.1049/iet-map.2019.0244
- Type: Article
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p.
174
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In this study, a broadband high-power combiner for digital video broadcasting-terrestrial (DVB-T) applications is presented. The proposed broadband combiner is a combination of a bisection Wilkinson power combiner, some coaxial baluns and 50-Ω terminating resistors. For increased power capability and wideband performance, the floating resistors are replaced by, two 50-Ω terminating resistors using coaxial baluns. The wideband combiner is analysed by even and odd mode method. As the inherent capacitance of the terminating resistors is lower compared to the capacitance of a floating resistor, the isolation and return loss are less affected in wideband applications. The proposed power combiner covers the frequency range of 470–860 MHz, which is intended for DVB-T applications. A second planar wideband high-power combiner is also introduced in this study as another extension to the proposed power combiner, in which the coaxial baluns have been replaced with overlay quadrature hybrids. This combiner features a planar structure and utilises some standard 50-Ω terminating resistors as the isolation resistor. The electrical performance of these power combiners is compared to each other. The first and the second power combiners are designed to handle up to 600 and 400 W output power, respectively.
- Author(s): Mohammad Alibakhshikenari ; Bal S. Virdee ; Panchamkumar Shukla ; Chan H. See ; Raed A. Abd-Alhameed ; Francisco Falcone ; Karim Quazzane ; Ernesto Limiti
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 183 –188
- DOI: 10.1049/iet-map.2019.0362
- Type: Article
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p.
183
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A metamaterial photonic bandgap (MTM-PBG) periodic structure is used as a decoupling frame to improve the isolation between transmit–receive (T/R) sections of the densely packed array antenna in synthetic aperture radar (SAR) and multiple-input–multiple-output (MIMO) systems. With this technique the MTM-PBG structure is shown to effectively suppress surface wave propagations between the T/R array antennas by an average of 12 dB. MTM-PBG layer comprises a periodic arrangement of dielectric circles etched in the cross-shaped microstrip frame that is inserted between the radiating elements. Unlike other recently reported methods, the advantages of the proposed technique are: (i) simplicity; (ii) cost effectiveness as there is no need for short-circuited via-holes or three-dimensional metal walls; and (iii) can be retrofitted in existing array antennas. The proposed T/R array antennas were designed to operate over an arbitrary frequency range (9.25–11 GHz) with a fractional bandwidth of 17.28%. With this technique (i) the side-lobes are reduced; (ii) there is minimal effect on the gain performance; and (iii) the minimum edge-to-edge gap between adjacent radiating elements can be reduced to 0.15λ at 9.25 GHz.
- Author(s): Guiping Jin ; Guangjie Zeng ; Ju Yang ; Yechun Xu ; Shaowei Liao
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 189 –193
- DOI: 10.1049/iet-map.2019.0566
- Type: Article
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p.
189
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A new dual-polarised high-gain triple-band differential-fed antenna is proposed in this study. The antenna adopts a differential feeding scheme, in which a high-frequency radiator for 3.5 GHz Sub-6 GHz 5G band and 5 GHz WLAN band, and two pairs of low-frequency radiators for 2.45 GHz WLAN band are effectively combined to obtain multiband operation. To filter out unwanted frequency band, four half-wavelength slots are introduced to generate a notch band between 3.8 and 4.8 GHz. Experimental results show that the proposed antenna achieves 10-dB impedance bandwidths of 2.37–2.61 GHz for the low-frequency band, 3.27–3.76 GHz for the intermediate frequency band, and 4.87–5.98 GHz for the high-frequency band. The gains of the antenna are all above 8.0 dBi for all the three bands. The antenna exhibits a good directivity and low cross-polarisation level (below −20 dB); thus it is a good candidate for WLAN and Sub-6 GHz 5G wireless access point systems.
- Author(s): Joysmita Chatterjee ; Akhilesh Mohan ; Vivek Dixit
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 194 –202
- DOI: 10.1049/iet-map.2019.0517
- Type: Article
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194
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A dual-port antenna system designed for cognitive radio applications is presented in this study. The structure comprises of an ultra-wideband (UWB) sensing antenna and a reconfigurable communicating antenna. The former is a stepped slot structure with an offset feed, which covers the whole UWB frequency band from 3 to 10.6 GHz, whereas the latter is a dual-band slot antenna (DBSA) fed with a fork-shaped microstrip-line feed and loaded with two identical layers of meandered metasurfaces (MSs). Frequency agility is realised by rotating the MS layers for the DBSA antenna. The dual-band communicating antenna has three switchable states with tuning ranges of 28 and 45% in the lower- and upper-frequency bands, respectively. The degree of isolation and gain in all three states are appreciable. The proposed structure is fabricated and measured, which has a good agreement with the simulated results.
- Author(s): Djaouida Belmessaoud ; Khaled Rouabah ; Idris Messaoudene ; Tayeb A. Denidni
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 203 –210
- DOI: 10.1049/iet-map.2019.0365
- Type: Article
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p.
203
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In this study, the authors propose a simple structure of a new broadband planar slot antenna using a wide single-layer frequency selective surface (FSS) stopband. The proposed design is realised in two stages. First, the performances of the FSS unit cells are investigated using the finite element method of high-frequency structure simulator. Besides, the FSS structure considered as a stop-band filter in the bandwidth , is also validated by computer simulation technology microwave studio. Second, this FSS reflector is combined with a miniaturised wideband planar slot antenna . The final proposed combination is also designed, optimised, fabricated and validated by measurements. The obtained results show an operating impedance bandwidth of including the Worldwide interoperability for Microwave Access band, the C band for satellite applications, and the Wireless Local Area Network band. Furthermore, the antenna provides an measured maximum gain. Compared to the same antenna without FSS, a maximum gain enhancement of is achieved by the proposed structure. In addition, the back lobes are reduced in the proposed structure by , compared to a simple antenna. The total size of the proposed antenna, integrating the FSS, is .
- Author(s): Jaehyun Choi ; Sangho Lim ; Wonbin Hong
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 211 –214
- DOI: 10.1049/iet-map.2019.0451
- Type: Article
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p.
211
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This study reports methods of alleviating the effect on inductive near-field communication (NFC) coils caused by fully enclosed metallic-frames for wearable devices such as smartwatches. Two techniques that, respectively, involve creating two short-circuit passages to modify the distribution of the out-of-phase current on the metallic-frame and reducing the out-of-phase current amplitude by devising an asymmetric coil topology is presented and studied in detail. Extensive simulation, prototyping and measurement are carried out for 13.56 MHz NFC applications. The presented techniques can, respectively, improve the induced magnetic coupling by 43 and 30% under identical conditions in the presence of the metallic frame. Furthermore, both methods comply with the NFC forum certification and do not require the need to increase the drive current and power consumption of the NFC circuitry.
- Author(s): Lee Yeng Seng ; Soh Ping Jack ; You Kok Yeow ; Wee Fwen Hoon ; Lee Chia Yew ; Gan Hong Seng ; Fareq Malek
- Source: IET Microwaves, Antennas & Propagation, Volume 14, Issue 3, p. 215 –222
- DOI: 10.1049/iet-map.2019.0571
- Type: Article
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p.
215
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The size of pyramidal microwave absorbers (PMA) is one of the main considerations for their selection for use in anechoic chambers. In this work, a new type of PMA is introduced, with rice husk (RH) as its filler. Meanwhile, a lossy base layer is also introduced in the PMA using a combined RH and carbon nanotube (CNT) composite. To do so, the dielectric properties of the RH-CNT composite are first investigated from 2–18 GHz by using a dielectric probe. Next, the microwave absorption properties of the PMA were investigated in terms of different height of the pyramidal structure and base layer. The free-space method was used to measure the microwave absorption of PMA at oblique incident angles of 0° to 60°, respectively. Results indicated good microwave absorption characteristics in the 2–6 GHz with a height of 11.5 cm the PMA structure, and 1 cm thickness of the base layer. The lossy base layer is found to increase the bandwidth of the absorber and improve the microwave absorption of PMA in the lower GHz frequencies. Further investigations concluded that the microwave absorption performance of the PMA is dependent on its dielectric properties, size and base layer.
Ultra-compact 3 × 3 Nolen matrix beamforming network
Reconfigurable antennas: quantifying payoffs for pattern, frequency, and polarisation reconfiguration
Efficiency measurement of the flexible on-body antenna at varying levels of stretch in a reverberation chamber
Absorptive/transmissive integrated frequency selective structure based on lumped resistance elements
Twice optimised near-field scanning system for antenna characterisation
High-power combiners with terminating resistors for DTV applications in the frequency range of 470–860 MHz
Isolation enhancement of densely packed array antennas with periodic MTM-photonic bandgap for SAR and MIMO systems
Dual-polarised high-gain triple-band differential antenna for WLAN and Sub-6 GHz 5G applications
Frequency reconfigurable slot antenna using metasurface for cognitive radio applications
Broadband planar slot antenna using a simple single-layer FSS stopband
Efficient NFC coil antennas for fully enclosed metallic-framed wearable devices
Enhanced microwave absorption of rice husk-based pyramidal microwave absorber with different lossy base layer
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