Portrait of Professor Steven Gao

Professor Steven Gao

Professor
Director of Postgraduate Studies (Research)

About

Professor Steven (Shichang) Gao is Chair of RF and Microwave Engineering, and the Director of Post-gradudate Studies (Research) at School of Engineering and Digital Arts, University of Kent, UK.

He is an expert in the fields of antennas, RF/microwave/millimetre-wave engineering, radio propagation, electromagnetic field theory and applications. He authored, co-authored and co-edited 3 books including Space Antenna Handbook (Wiley, 2012), Circularly Polarized Antennas (Wiley-IEEE, 2014), and Low-cost Smart Antennas (Wiley, 2019), over 300 papers in international journals and conferences, and 8 patents. He is a Fellow of IEEE, the Royal Aeronautical Society and IET, and was a Distinguished Lecturer of IEEE Antennas and Propagation Society (2014-2016). 

He started his career since 1994 while at China Research Institute of Radiowave Propagation (China). Then he worked as a Post-doctoral Research Fellow at National University of Singapore (Singapore), a Research Fellow at Birmingham University (UK), a Visiting Scholar at Swiss Federal Institute of Technology (ETH Zurich, Switzerland), a Visiting Fellow at Chiba University (Japan), and a Visiting Scholar at University of California at Santa Barbara (US). He was a Senior Lecturer, Reader and Head of Antenna and Microwave Group at Northumbria University (UK) during 2002-2007, and the Head of Satellite Antennas and RF System Group at Surrey Space Centre, University of Surrey (UK) during 2007-2012. He joined the University of Kent as a Professor in 2013. He has held Visiting Professorships at many universities such as Northwestern Polytechnic University (China), University of Calabria (Italy), Xidian University (China), Shanghai University (China), etc.

He is an Associate Editor of several international Journals (IEEE Transactions on Antennas and PropagationRadio Science; IEEE Access; IET Circuit, Devices and Systems; Electronics Letters), and the Editor-in-Chief for Wiley Book Series on "Microwave and Wireless Technologies". He was General Chair of 2013 Loughborough Antenna and Propagation Conference, Lead Guest Editor of Proceedings of the IEEE for Special Issue on "Small Satellites"(2018), Lead Guest Editor of IEEE Trans on Antennas and Propagation for Special Issue on "Antennas for Satellite Communication"(2015), Guest Editor of IET Circuits, Devices & Systems for Special Issue in “Photonic and RF Communications Systems” (2014), Chair of Special Session on “Satellite Communication Antennas” in CSNDSP'2012, Co-Chair of Workshop on "New Technology Development for Space" in 2015 IEEE Microwave Symposium, etc. He is a member of the editorial boards of many Journals such as  International Journal of Space Science and Engineering (US),Chinese Journal of Electronics (China), Chinese Journal of Radio Science (China), etc. He was a Plenary/Invited Speaker of many international conferences and workshops (IEEE APWC'2017, UCMMT'2017, iWAT’2017, AES'2014, IWAT'2014, SOMIRES'2013, APCAP'2014, etc).

He received over 20 research grants funded by EU, EPSRC and industries. Recently he was Principal Investigator for "Millimeter-wave intelligent array antennas for Ka-band satellite communications on the move" (FLEXWIN, funded by EU FP7), "Advanced reflectarray antennas for space-borne synthetic aperture radars" (funded by the Royal Academy of Engineering, UK), "Gallium Nitride integrated millimeter-wave active phased array multi-beam transceivers for SATellites" (GaNSat, funded by EU FP7 Space Programme), etc. Currently he is a Principal Investigator for several Research Projects including "Adaptive multi-band small MIMO antennas for next-generation smart phones" (funded by Huawei), "Low-cost THz wideband smart antennas design and fabrication using 3D Printing" (WISDOM, funded by EPSRC), "Lead Niobate-based Tunable Dielectrics for Smart Microwave and Millimeter-wave Systems" (EPSRC), “Low-Profile Ultra-Wideband Wide-Scanning Multi-Function Beam-Steerable Array Antennas” (EPSRC), "Digital Beamforming Synthetic Aperture Radars onboard small satellites constellations "(DIFFERENT, funded by EU FP7 Space Programme), etc.


Research interests

Antennas, smart antennas, phased arrays, MIMO, antenna and radio propagation for 4G/5G/6G mobile communications, mobile terminal antennas, base station antennas, antennas for satellite communications, antennas for small satellites, RF/microwave/millimetre-wave circuits and RF front ends, mobile communication systems, satellite communications, inter-satellite links, wireless power transfer, UWB radars, GNSS reflectometry, synthetic-aperture radars, electromagnetic modelling and small satellites

Teaching

  • Antennas and Propagation
  • RF/Microwave Engineering
  • Satellite and Optical Communication
  • Communication Systems
  • Electronic and RF Circuits

Supervision

Prof. Steven Gao is an expert in the fields of antennas, smart antennas, phased arrays, MIMO, mobile communication antennas, radio propagation, satellite antenna, deployable antennas, RF/microwave/millimetre-wave/THz circuits and RF front ends (high-efficiency RF/microwave power amplifiers, filters), 5G mobile communications, satellite communications, wireless power transfer, UWB radars, GNSS reflectometry, synthetic-aperture radars, electromagnetic modelling and small satellites.

He is looking for potential PhD students. Ideally he/she has completed MSc study and may be funded by his/her government scholarship (e.g., China Scholarship Council or similar government scholarships in other countries) or other sources. 

Professional

He received URSI Young Scientist Award from International Union of Radio Science (URSI), 2002, Japan Society of Promotion Science (JSPS) Fellowship Award, Japan, 2005, Best Paper Award, LAPC, 2012, JSPS Award, Japan, 2013, Royal Academy of Engineering Visiting Fellow Award, UK, 2013, IET Premium Award for the Best Paper in IET Microwave, Antennas and Propagation, 2016, CST University Publication Award, 2017, etc.    

Publications

Showing 50 of 151 total publications in the Kent Academic Repository. View all publications.

Article

  • Sitompul, P. et al. (2019). A Circularly Polarized Circularly-Slotted-Patch Antenna with Two Asymmetrical Rectangular Truncations for Nanosatellite Antenna. Progress In Electromagnetics Research C [Online] 90:225-236. Available at: https://doi.org/10.2528/PIERC18120503.
    In this paper, a circularly polarized slot-patch antenna for nanosatellite is presented. The
    novel design of the circularly polarized wave conducted by two asymmetrical rectangular-truncation
    techniques implemented on a circularly-slotted-patch on the front side and a deformed-shifted-feedline
    on the back side of the substrate. The antenna is printed on substrates with the dielectric constant of
    2.17 and thickness of 1.6 mm. The resonant frequency of the proposed antenna is set at 2.2 GHz with
    the minimum requirement of the axial ratio bandwidth (ARBW) of 300 MHz. The proposed antenna
    produces under 10 dB impedance bandwidth (IBW) 1.2765 GHz or equal to 58% (1.7235–3 GHz) with
    Left-Handed Circular Polarization (LHCP). The average antenna gain reaches 4.5 dBic at 2.2 GHz and
    the ARBW 327.5 MHz or about 14.88% (2.0275–2.355 GHz). This paper includes the description and
    presentation of the completed discussion.
  • Lou, T. et al. (2019). Low-Cost Electrical Beam-Scanning Leaky-Wave Antenna Based on Bent Corrugated Substrate Integrated Waveguide. IEEE Antennas and Wireless Propagation Letters [Online] 18:353-357. Available at: https://doi.org/10.1109/LAWP.2019.2890995.
    This letter presents a novel low-cost leaky-wave antenna (LWA) with the fixed-frequency beam-scanning capability. An improved half-mode corrugated substrate integrated waveguide structure is proposed as the guiding wave structure to reduce the transverse size of the antenna. A novel electronic phase-shifting structure, composed of fan-shaped open stubs with different sizes and PIN diodes, is proposed for beam scanning. This LWA uses interdigital slots as radiating elements, and the phase-shifting structure is placed between the adjacent radiating elements. By changing the switching states of these PIN diodes, the phase difference between the adjacent radiating elements can be controlled. To verify the concept, one prototype of the 2 × 6 array antenna at C -band is designed, simulated, fabricated, and measured. The antenna demonstrates a beam-scanning range of 25° (34°–59°) at fixed frequency, a peak gain of 12.4 dBi with the gain variation less than 2.3 dB. The antenna has low cost and can be easily fabricated using standard printed circuit board process.
  • Luo, Q. et al. (2019). Multibeam Dual-Circularly Polarized Reflectarray for Connected and Autonomous Vehicles. IEEE Transactions on Vehicular Technology [Online] 68:3574-3585. Available at: http://dx.doi.org/10.1109/TVT.2019.2897218.
    This paper presents a multibeam dual-circularly polarized (CP) reflectarray for connected and autonomous vehicles.
    The developed reflectarray uses one aperture to realize dualband and multibeam operation. At each frequency band, there
    are two simultaneously shaped beams with different circular
    polarizations. Totally four beams are obtained with a single feed
    and each of the beams can be independently controlled. A simple
    but effective polarization suppression technique is introduced to
    suppress cross polarizations at large scan angles so the CP beam
    of the reflectarray can be configured to point at large angles.
    Thus, the present reflectarray is suitable to be applied to vehicles
    for reliable high data-rate satellite communications. To validate
    the design concept, an X-band prototype was designed, fabricated
    and measured. The design concept is flexible and can be applied
    to the design of dual-band, dual-CP reflectarray with different
    frequencies ratios. Moreover, the present design can also be
    extended to a continuous beam-steering design by incorporating
    phase shifters.
  • Arnieri, E. et al. (2019). An Integrated Radar Tile for Digital Beamforming X-/Ka-Band Synthetic Aperture Radar Instruments. IEEE Transactions on Microwave Theory and Techniques [Online] 67:1197-1206. Available at: https://doi.org/10.1109/TMTT.2018.2889038.
    This paper presents the first experimental assessment of a highly integrated dual-band dual-polarized antenna tile designed for synthetic aperture radar (SAR) digital beamforming (DBF) satellite applications. The demonstrator described in this paper is the first comprehensive experimental validation of an RF module providing the X-band and Ka-band (9.6- and 35.75-GHz) operation with custom downconversion stages. All the antennas, transitions, and downconversion chips are integrated in the same antenna tile fabricated using a customized 15-layer high density interconnect process. The designed tile goes to the limits of the proposed technology and for the high trace density and for the size of the vertical transitions. The proposed results represent the state of the art in terms of compactness for a DBF SAR RF module even though the demonstrator was manufactured with a standard low-cost technology. The experimental assessment proves the validity of the proposed manufacturing and integration approaches showing a substantial agreement between the performance of the individual blocks and of the integrated system.
  • Wen, L. et al. (2019). A Low-Cost Differentially Driven Dual-Polarized Patch Antenna by Using Open Loop Resonators. IEEE Transactions on Antennas and Propagation [Online] 67:2745-2750. Available at: http://dx.doi.org/10.1109/TAP.2019.2896491.
    A novel differentially driven dual-polarized patch antenna is presented in this communication. The proposed antenna is a low-cost design with a simple configuration, which avoids using the conventional high cost multi-layer PCB technology. The antenna is composed of two intersected open loop resonators, which are connected to each other at the center. By using the electric coupling from the intersected resonators, two orthogonal radiating modes are excited from the top radiating patch. With the even and odd mode current distributions on the intersected resonators, high port isolation and low cross-polarization level are obtained. The external quality factor of the resonator is illustrated by using the analytical model of a double loaded resonator. To demonstrate the design method, the proposed antenna and array are designed, fabricated, and measured. Compared to the traditionally designed capacitively coupled antenna, two times wider impedance bandwidth is obtained for the proposed antenna with high isolation (>38.5 dB) and low cross-polarization level (<-33 dB). The antenna array is designed for 5G base stations, which features the compact size and low reflection coefficient (<-15 dB). In addition, beam scanning performance of the antenna array is also investigated for base station applications.
  • Mao, C. et al. (2019). Planar Sub-Millimeter-Wave Array Antenna with Enhanced Gain and Reduced Sidelobes for 5G Broadcast Applications. IEEE Transactions on Antennas and Propagation [Online] 67:160-168. Available at: http://dx.doi.org/10.1109/TAP.2018.2874796.
    In this paper, a compact, broadband, planar array
    antenna with omnidirectional radiation in horizontal plane is
    proposed for the 26 GHz fifth-generation (5G) broadcast
    applications. The antenna element is composed of two dipoles and
    a substrate integrated cavity (SIC) as the power splitter. The two
    dipoles are placed side-by-side at both sides of the SIC and they
    are compensated with each other to form an omni-directional
    pattern in horizontal plane. By properly combing the resonant
    frequencies of the dipoles and the SIC, a wide impedance
    bandwidth from 24 to 29.5 GHz is achieved. To realize a large
    array while reducing the complexity, loss and size of the feeding
    network, a novel dual-port structure combined with radiation and
    power splitting functions is proposed for the 1st time. The
    amplitude and phase on each element of the array can be tuned,
    and therefore, the grating lobes level can be significantly reduced.
    Based on the dual-port structure, an 8-element array with an
    enhanced gain of over 12 dBi is designed and prototyped. The
    proposed antenna also features low profile, low weight and low
    cost, which is desirable for 5G commercial applications. Measured
    results agree well with the simulations, showing that the proposed
    high-gain array antenna has a broad bandwidth, omni-directional
    pattern in horizontal plane, and low side-lobes.
  • Duan, Z. et al. (2018). Integrated Design of Wideband Omnidirectional Antenna and Electronic Components for Wireless Capsule Endoscopy Systems. IEEE Access [Online] 6:29626-29636. Available at: https://doi.org/10.1109/ACCESS.2018.2840689.
    This paper presents a wideband antenna with
    omnidirectional radiation pattern for wireless capsule endoscopy
    (WCE) systems. The proposed antenna radiates as a slot structure
    formed between a central copper cylinder and a copper strip
    attached to the interior surface of biocompatible polyimide shell.
    Main features of the antenna include: 1). An integrated design of
    the antenna and electronic components in the capsule is employed.
    And, by utilizing the entire inner space of the capsule, the
    radiating aperture of antenna is increased to the maximum; 2).
    The copper cylinder can be used to house electronic components,
    therefore the potential electromagnetic interferences (EMI)
    brought by battery and electronic circuits are reduced to the
    minimum; 3) The antenna in tissue has a wide bandwidth from
    0.721 to 1.705 GHz, covering both 0.902-0.928 GHz Industrial,
    Scientific, and Medical (ISM) band and 1.395-1.4 GHz Wireless
    Medical Telemetry Service (WMTS) band. This is achieved by
    optimizing the stepped width of copper strip; 4). The antenna
    inside human tissues has stable omnidirectional radiation patterns
    across all operating frequencies. This is an indispensable
    characteristic due to the unpredictable orientation of capsule in
    the gastrointestinal (GI) tract. Stable patterns are achieved by
    having strong electric fields concentrated within the top substrate
    pointing at the same direction. The integrated design concept,
    wideband impedance matching and stable omnidirectional
    radiation patterns make the proposed antenna a promising
    candidate for future WCE system.
  • Zhou, Y. et al. (2018). Tightly Coupled Array Antennas for Ultra-Wideband Wireless Systems. IEEE Access [Online] 6:61851-61866. Available at: http://dx.doi.org/10.1109/ACCESS.2018.2873741.
    Tightly coupled array (TCA) antenna has become a hot topic of research recently, due to its
    potential of enabling one single antenna array to operate over an extremely wide frequency range. Such an
    array antenna is promising for applications in numerous wideband/multi-band and multi-function wireless
    systems such as wideband high-resolution radars, 5G mobile communications, satellite communications,
    global navigation satellite systems, sensors, wireless power transmission, internet of things and so on. Many
    papers on this topic have been published by researchers internationally. This paper provides a detailed
    review of the recent development on TCA that utilizes the capacitive coupling. The basic principles and the
    historical evolution of the TCAs are introduced firstly. Then, recent development in the analysis and design
    of TCAs, such as equivalent circuit analysis, bandwidth limitation analysis, array elements, feed structures,
    substrates/superstrates loading, etc., are explained and discussed. The performances of the state-of-the-art
    TCAs are presented and a comparison amongst some TCAs reported recently is summarized and discussed.
    To illustrate the practical designs of TCA, one case study is provided, and the detailed design procedures of
    the TCA are explained so as to demonstrate the TCA design methodology. Simulated results including the
    VSWR at different angles of scanning, patterns and antenna gain are shown and discussed. A conclusion
    and future work are given in the end.
  • Gao, S. et al. (2018). Advanced Antennas for Small Satellites. Proceedings of the IEEE [Online] 106:391-403. Available at: https://doi.org/10.1109/JPROC.2018.2804664.
    Antenna is one of the key components onboard small satellites as its design determines the performance of all the wireless systems including telemetry, tracking and control, high-speed data downlink, navigation, intersatellite communications, intrasatellite communications, wireless power transfer, radars and sensors, etc. This paper presents a review of recent development in advanced antennas for small satellites (MiniSat, MicroSat, NanoSat, CubeSat, etc.). A number of recent examples of antennas for small satellite applications are shown and discussed. A conclusion and future development in antennas for small satellites are given in the end.
  • Wen, Y. et al. (2018). Dual-Polarized and Wide-Angle Scanning Microstrip Phased Array. IEEE Transactions on Antennas and Propagation [Online]. Available at: https://doi.org/10.1109/TAP.2018.2835521.
    In this paper, a novel microstrip phased array with dual-polarized and wide-angle scanning in the 2-dimensional (2D) space is proposed. The element antenna consists of a mushroom-shaped patch and two circular patches. Each circular patch is connected with one feeding port. The mushroom-shaped patch is excited via capacitive coupling through the gaps between the mushroom-shaped patch and the circular patch. The zeroth-order resonance (ZOR) and TM010 mode resonance are simultaneously generated in the mushroom-shaped patch. The 3dB beamwidth of the element antenna in the 2D space is in the range between 110° and 125°. One 6×6 phased array based on the antenna element is designed, fabricated and measured. The phased array shows dual-polarized wide-angle beam scanning in a range of ±66° in both x-z and y-z planes with the scan loss of 3.5dB.
  • Mao, C., Gao, S. and Wang, Y. (2018). Dual-Band Full-Duplex Tx/Rx Antennas for Vehicular Communications. IEEE Transactions on Vehicular Technology [Online] PP:1-1. Available at: https://doi.org/10.1109/TVT.2017.2789250.
    This paper proposes a novel dual-band full-duplex antenna/array for intelligent transport systems (ITS) applications. Different from traditional single-port single-band antennas, the two ports of the antenna are highly isolated and designed to operate at different frequency bands simultaneously. Such a property could support the full-duplex operation-mode, which significantly simplifies the complexity of the RF frontend subsystem. The other contribution of this work is that multiple functions such as filtering, duplexing and radiation are combined into one single device, resulting in a simplified RF frontend. This co-design multifunctional device could also remove the separate filters, duplexers and interfaces between them, resulting in the reduction of the size, weight and cost. In addition, cross-coupling is investigated and employed to generate additional transmission zeros so as to improve the channel isolation and out-of-band interference. To verify the concept, an antenna element and two 2 × 2 arrays at C-band are designed, prototyped and tested. All the measurements agree well with the simulations, showing two full-duplex channels of 4.58 - 4.83 GHz and 5.86 - 6.2 GHz for transmitting and receiving, respectively. The proposed antennas also exhibit excellent performance in terms of channel isolations, frequency selectivity, out-of-band rejections and gains.
  • Qin, F. et al. (2018). A High-Gain Transmitarray for Generating Dual-Mode OAM Beams. IEEE Access [Online] 6:61006-61013. Available at: http://dx.doi.org/10.1109/ACCESS.2018.2875680.
    This paper proposes a novel transmitarray antenna which can achieve high gain and
    produce dual-mode orbital angular momentum (OAM) beams in Ku band. Two back-to-back wideband
    dual-polarized microstrip antennas are employed as the unit cells, which are connected using metalized
    via holes. Full 360 o phase ranges can be obtained by varying the length of feeding lines in two
    orthogonal polarizations. Due to high isolation between the two orthogonal polarizations, dual-mode
    OAM beams can be formed simultaneously by tuning phase distributions in x- and y-polarizations,
    respectively. The approach for generating OAM beams is explained. To verify this concept, one
    prototype carrying 0 and +1 mode OAM beams is designed, fabricated and measured. Experimental
    results demonstrate that the both 0 and +1 mode OAM beams can be generated successfully, and the
    measured results agree well with the simulated results. Because of high directivity and focusing effects
    of transmitarray, the proposed +1 mode OAM beam has stable performance at a long propagation
    distance. The maximum gain reaches 26 dBi and 20 dBi in 0 and +1 mode OAM beams, respectively.
    Meanwhile, a narrow divergence angle of +/-5 o is obtained in +1 mode OAM beam. Compared to other
    OAM antennas reported, main advantages of the proposed antenna include high gain, narrow divergence
    angle?low cost, planar structure and the capability of producing dual-mode OAM beams.
  • Cai, Y. et al. (2018). A Low-Profile Frequency Reconfigurable Grid-Slotted Patch Antenna. IEEE Access [Online] 6:36305-36312. Available at: https://doi.org/10.1109/ACCESS.2018.2850926.
    This paper presents a novel low-profile high gain frequency reconfigurable patch antenna with unidirectional radiation pattern by using a grid-slotted patch with tunable varactors loading. The antenna consists of two stacked substrates and three metal layers. A grid-slotted patch with two tunable varactors is placed on the top layer, a microstrip line is placed in the middle of two substrates, and the ground plane is on the bottom layer. A single dc voltage applied on two varactors is used to control the working frequencies of the proposed antenna. By altering the bias voltage, the working frequency of the proposed antenna can be continuously changed within a wide range from 2.45 to 3.55 GHz. The antenna maintains broadside radiation and stable radiation pattern in all the operating modes. The measured antenna gain of the proposed antenna rises from 4.25 to 8.49 dBi with the working frequency increases from 2.45 to 3.55 GHz. Compared to other frequency-reconfigurable antennas available in the literature, the proposed antenna has advantages of a wide frequency tuning range over a bandwidth of 1.45:1, high frequency selectivity, low profile (0.016 free-space wavelength at 2.45 GHz), high gain, stable unidirectional pattern, simple structure, and low cost. These advantages make it a promising candidate for cognitive radio and future wireless communication systems
  • Zhang, L. et al. (2018). Wideband Circularly Polarized Tightly Coupled Array. IEEE Transactions on Antennas and Propagation [Online] 66:6382-6387. Available at: http://dx.doi.org/10.1109/TAP.2018.2867031.
    Tightly coupled arrays (TCA) have received considerable
    interests recently. Although various TCAs have been reported, they are
    limited to single or dual linear polarizations. Considering the importance of
    circular polarization (CP) in various wireless systems, it is meaningful to
    design a CP TCA with a simple configuration. This paper presents a
    circularly polarized tightly coupled crossed dipole array (CP-TCCDA) with
    wide overlapped impedance bandwidth and axial ratio (AR) bandwidth. A
    tightly coupled crossed dipole unit cell is investigated and the comparison
    with an isolated crossed dipole of the same size indicates that the VSWR<3
    bandwidth is increased from 3:1 to 7.1:1 while the 3-dB AR bandwidth is
    increased from 1.3:1 to 2.1:1. Analysisis given to explain the principles of AR
    bandwidth improvement and is verified by the comparison of radiated Efields
    between a CP-TCCDA and a conventional crossed dipole array. To
    verify the design concept, a 4×4 CP-TCCDA with feeding network is
    fabricated and measured. The measured results confirm that the proposed
    array achieves VSWR<3 bandwidth from 2.06GHz to 6.46 GHz (3.14:1) and
    3-dB AR bandwidth from 2.35GHz to 5.6GHz (2.38:1), which are much
    wider than the bandwidth of an isolated element and a conventional array
    using the same element.
  • Dong, Y. et al. (2018). Broadband Circularly Polarized Filtering Antennas. IEEE Access [Online] 6:76302-76312. Available at: https://doi.org/10.1109/ACCESS.2018.2883494.
    This paper consists of two parts. The first part presents a review of the recent development in broadband circularly polarized filtering antennas. The second part presents a novel design of broadband integrated filtering antenna based on eighth-mode SIW (EMSIW) resonators for rectenna applications. This work has three main novel contributions. First, by adjusting the external quality factors and coupling coefficients of the resonators in this filtering antenna, optimum input impedance with a complex value can be realized within the filtering antenna. Thus there is no need for an external impedance matching network, which is usually required between the antenna and the rectifying circuits; Second, compared with traditional microstrip resonators, high-Q EMSIW cavities are used to increase antenna gain; third, the coupling gap between the EMSIW resonators also acts as the feeding structure of the radiator. So the feeding structures are all on the middle layer. The ground plane on the back side is a complete structure without any defects. This novel structure design improves front-to-back ratio to enhance the antenna receiving efficiency. To validate this method, two C-band circularly polarized integrated filtering antennas with an input impedance of 50 $\Omega $ and complex impedance are designed, simulated, and fabricated. The measured results show that the operating frequency bandwidth of the proposed antennas is more than 14.5% at C-band with the gain above 8 dBi. The 3-dB axial ratio bandwidth is larger than 8.5% and the front-to-back ratio is higher than 18 dB. Moreover, the proposed antenna with complex impedance is conjugate matched with the input impedance of a specific rectifying circuit at 5.8 GHz and harmonics suppression at the second-harmonic frequency is achieved.
  • Mao, C. et al. (2018). Integrated Dual-Band Filtering/Duplexing Antennas. IEEE Access [Online] 6. Available at: https://doi.org/10.1109/ACCESS.2018.2805224.
    In this paper, the state-of-the-art integrated filtering antennas with dual-band operation are first reviewed. Then, two designs of dual-band microstrip filtering antennas with a low frequency-ratio are presented. The 1st design is a dual-band dual-polarization (DBDP) antenna with a frequency ratio of 1.2 on a single patch, by employing the coupled resonator technique. Two bands at each polarization are achieved by vertically coupling a hairpin resonator with a patch through a slot in the ground plane and then coupled to a dual-mode stub loaded resonator (SLR). Each band exhibits a 2nd-order filtering performance with improved bandwidth and out-of-band rejection. Such an integration technique could significantly reduce the dimension and complexity of traditional DBDP antennas/arrays. In the 2nd design, a novel dual-port dual-band antenna (with a frequency ratio of 1.38) with the integrated filtering and duplexing functions is proposed. The frequency duplexing function is implemented by coupling a single patch with two sets of resonator-based filtering channels via a U-slot resonator inserted in the ground. This device seamlessly integrates the functions of duplexers, filters and antennas in a very compact structure.
  • Wen, L. et al. (2018). A Wideband Dual-Polarized Antenna Using Shorted Dipoles. IEEE Access [Online] 6:39725-39733. Available at: http://dx.doi.org/10.1109/ACCESS.2018.2855425.
    A novel design method of a wideband dual-polarized antenna is presented by using shorted dipoles, integrated baluns, and crossed feed lines. Simulation and equivalent circuit analysis of the antenna are given. To validate the design method, an antenna prototype is designed, optimized, fabricated, and measured. Measured results verify that the proposed antenna has an impedance bandwidth of 74.5% (from 1.69 to 3.7 GHz) for VSWR <; 1.5 at both ports, and the isolation between the two ports is over 30 dB. Stable gain of 8-8.7 dBi and half-power beamwidth (HPBW) of 65°-70° are obtained for 2G/3G/4G base station frequency bands (1.7-2.7 GHz). Compared to the other reported dual-polarized dipole antennas, the presented antenna achieves wide impedance bandwidth, high port isolation, stable antenna gain, and HPBW with a simple structure and compact size.
  • Santosa, C. et al. (2018). Development of a Low Profile Wide-Bandwidth Circularly Polarized Microstrip Antenna for C-Band Airborne CP-SAR Sensor. Progress In Electromagnetics Research C [Online] 81:77-88. Available at: http://www.jpier.org/PIERC/pierc81/08.17110901.pdf.
    In this paper, a low-profile wide bandwidth circularly polarized microstrip antenna is
    proposed as element for a C-band airborne circularly polarized synthetic aperture radar sensor. Several
    bandwidth improvement techniques were proposed and implemented. In order to increase impedance
    bandwidth, the antenna is constructed using double-stacked substrate with low dielectric constant,
    modified radiating shape for multi-resonant frequency, and a circle-slotted parasitic patch. Generation
    of the circularly polarized wave employs a simple square patch with curve corner-truncation as radiating
    element. The asymmetric position of the feeding is attempted to improve the axial-ratio bandwidth.
    To avoid a complicated feed network, the antenna is fed by single-feed proximity-coupled microstrip
    line. The effect of copper-covering on the upper layer for decrease undesired radiation wave emitted by
    the feeding is also studied and presented. Measurement results show that the impedance bandwidth
    and axial ratio bandwidth are 20.9% (1,100 MHz) and 4.7% (250 MHz), respectively. Meanwhile the
    measured gain is 7 dBic at the frequency of 5.3 GHz.
  • Luo, Q. et al. (2018). Wideband Transmitarray With Reduced Profile. IEEE Antennas and Wireless Propagation Letters [Online] 17:450-453. Available at: https://doi.org/10.1109/LAWP.2018.2794605.
    This letter presents a wideband transmitarray (TA) with reduced profile. A novel unit cell based on a wideband bandpass filter is developed and applied to the design of the TA. The TA consists of two identical tri-layer frequency selective surfaces (FSS), thus it has a lower profile compared to traditional designs which use at least four FSS layers separated by quarterwavelength air gaps to obtain the 360o phase shift range. The FSS has a pair of square patches printed on the top and bottom
    layers, and a square slot loaded by four microstrip lines printed on the middle layer. The phase shift is achieved by simultaneously adjusting the size of the square patches. Within the frequency band of interest, the developed unit cell shows low insertion loss and sufficient phase shift range. An equivalent circuit model is
    developed to better understand the operating principles of the FSS. To validate the design concept, one prototype operating at 13.5 GHz is designed, fabricated and measured. The measurement results show that the designed TA achieves 16% 1-dB gain bandwidth and 60% aperture efficiency. The developed unit cell has symmetric configurations so it can also be applied to the design of dual-polarized or circularly polarized TAs.
  • Wen, L. et al. (2018). Compact Dual-Polarized Shared-Dipole Antennas for Base Station Applications. IEEE Transactions on Antennas and Propagation [Online]. Available at: https://doi.org/10.1109/TAP.2018.2871717.
    Crossed dipole antennas have been widely employed for dual-polarization in wireless communication systems in recent years. In this paper, a novel design concept of dual-polarized shared-dipole (DPSD) antenna is presented. Different from the traditional crossed dipole (CD) antennas, the arms of the DPSD antenna are shared for two orthogonal polarizations. This design technique leads to significant size reduction and high isolation compared to the traditional CD antennas. The operation principle of the proposed antenna is theoretically analyzed. To validate the presented design concept, two novel DPSD antennas are designed, fabricated and measured. The first design is a four-port DPSD antenna, which is a straightforward demonstration of the operation principle of the DPSD antenna. The second design is a highly integrated DPSD antenna, which avoids the use of feed network and provides a simple configuration to design the dual-polarized antenna. Both of the DPSD antennas are designed to operate at 1.7-2.7 GHz for base station applications. The simulated and measured results confirm that the two DPSD antennas have wide bandwidth with VSWR<1.5 and isolation>35 dB. In addition, stable gain and HPBW are obtained with the variance less than ±0.55 dB and ±3.5° respectively.
  • Wen, L. et al. (2018). A Balanced Feed Filtering Antenna With Novel Coupling Structure for Low-Sidelobe Radar Applications. IEEE Access [Online] 6:77169-77178. Available at: https://doi.org/10.1109/ACCESS.2018.2878793.
    A fourth-order filtering patch antenna with a novel coupling structure is presented in this paper. Using the proposed coupling structure, both the balanced coupling feed and cross-coupling are realized. Two identical slots etched on the ground plane are utilized to excite the radiating patch with the reduced cross-polarization level. A short slot etched on the ground plane is employed for cross-coupling, which introduces two controllable radiation nulls with a steep roll-off rate. In addition, owing to the split-ring resonators and hairpin resonators, the improved impedance bandwidth is achieved with the fourth-order filtering response. To demonstrate the proposed design techniques, both the filtering antenna element and the low-sidelobe array are designed, fabricated, and measured. The measured results show that the proposed antenna has the impedance bandwidth of 12% (4.78–5.39 GHz) with the total height of 0.06?0 , the cross-polarization level lower than ?31 dB, and two radiation nulls with the suppression higher than 31 dB. For the low-sidelobe antenna array, wide impedance bandwidth is also obtained with the sidelobe level below ?28.7 dB, the cross-polarization level below ?34 dB, and the out-of-band suppression better than 25 dB.
  • Wen, L. et al. (2018). A Wideband Dual-Polarized Antenna Using Shorted Dipoles. IEEE Access [Online]. Available at: http://dx.doi.org/10.1109/ACCESS.2018.2855425.
    A novel design method of wideband dual-polarized antenna is presented by using shorted dipoles, integrated baluns, and crossed feed lines. Simulation and equivalent circuit analysis of the antenna are given. To validate the design method, an antenna prototype is designed, optimized, fabricated and measured. Measured results verify that the proposed antenna has an impedance bandwidth of 74.5% (from 1.69 GHz to 3.7 GHz) for VSWR<1.5 at both ports and the isolation between the two ports is over 30 dB. Stable gain of 8.0-8.7 dBi and HPBW of 65-70° are obtained for 2G/3G/4G base station frequency bands (1.7-2.7 GHz). Compared to the other reported dual-polarized dipole antennas, the presented antenna achieves wide impedance bandwidth, high port isolation, stable antenna gain, and half-power beamwidth (HPBW) with a simple structure and compact size
  • Wan, W., Geyi, W. and Gao, S. (2018). Optimum Design of Low-Cost Dual-Mode Beam- Steerable Arrays for Customer-Premises Equipment Applications. IEEE Access [Online] 6:16092-16098. Available at: https://doi.org/10.1109/ACCESS.2018.2813299.
    Two novel designs of dual-mode beam-steerable array antennas are proposed for customer-
    premises equipment applications. To obtain the optimal distribution of excitations for the arrays, the gain
    and front-back ratio of the array systems are optimized by using the method of maximum power transmission
    efficiency. The first design operates at 2.45 GHz and uses four folded monopoles of height<1/10 wavelength
    and a sleeve of height of 1/4 wavelength underneath the monopoles. The peak gain and the front-to-back ratio
    are 6.7 dBi and 7.8 dB respectively. The second design operates at 830MHz and uses four Yagi monopoles as
    elements with a common reflector and four directors. The peak gain and the front-to-back ratio for the second
    design are 6.0 dBi and 16.8 dB respectively. The proposed antennas have advantages including: low cost
    and compact size; dual-mode operation including the modes of omnidirectional radiation and directional
    radiation; and in the mode of directional radiation, the beam can be electronically steered to achieve the full
    coverage of the azimuthal plane. It achieves higher gain than the traditional electronically steerable passive
    array radiator antenna.
  • Yu, F. et al. (2018). Polarization-insensitive wide-angle-reception metasurface with simplified structure for harvesting electromagnetic energy. Applied Physics Letters [Online] 113. Available at: http://dx.doi.org/10.1063/1.5046927.
    This paper reports the design, fabrication, and measurement of a metasurface with wide-angle-reception and polarization-insensitive characteristics for harvesting electromagnetic energy. Unlike the metasurface unit cell with multiple vias reported in the literature, it realizes polarization-insensitive characteristics using a single via, which reduces the complexity of the structure significantly. The harvesting and absorption efficiencies at the normal and oblique incidences, energy distribution, and the surface current for different polarization angles are investigated. The simulation results show that the maximum harvesting efficiency is 88% at the center frequency of 5.8 GHz for the arbitrary polarization at the normal incidence of 0°. Within the oblique incidence range of 75°, the maximum efficiency remains higher than 77% for the random polarization. A 5 × 5 array has been fabricated and measured, and the good agreement with the simulated results is obtained.
  • Liu, G. et al. (2018). Bandwidth enhancement of three-device Doherty power amplifier based on symmetric devices. IEICE Electronics Express [Online] 15. Available at: https://doi.org/10.1587/elex.15.20171222.
    This paper proposes a method for extending the bandwidth of
    a three-device Doherty power amplifier (DPA) based on symmetric devices.
    ?/4 transmission lines are inserted between each peaking amplifier output
    and carrier amplifier output to compensate load impedance of carrier amplifier.
    In order to achieve perfect load modulation, carrier amplifier output
    circuit total electrical length is designed to 90 degrees, and the peak amplifier
    output total electrical length is designed to 180 degrees. The proposed
    method is demonstrated by designing a three-device broadband DPA using
    three 10-W packaged GaN HEMT devices. Measurement results show that
    over 40% drain efficiency is achieved at 9-dB back-off power, over the
    frequency band of 1.45–2.35 GHz, accounting for 46% fractional bandwidth.
  • Wang, Q. et al. (2018). A Framework of Non-Orthogonal Slotted Aloha (NOSA) Protocol for TDMA-Based Random Multiple Access in IoT-Oriented Satellite Networks. IEEE Access [Online] 6:77542-77553. Available at: https://doi.org/10.1109/ACCESS.2018.2883399.
    There is an urgent demand for massive machine-type terminals to have access into time-division multiple access (TDMA)-based satellite networks by means of random multiple access (RMA). Several RMA protocols have been proposed by exploiting packet repetitions and interference cancellation to achieve high throughput. In this paper, a framework of non-orthogonal slotted aloha (NOSA) protocol is reported to achieve even higher throughput. With a specifically designed tile-based frame structure, it introduces the intra-tile sparse mapping as a special kind of pre-coded packet repetitions and exploits the joint multi-packet detection to blindly detect superimposed packets. By further employing inter-tile packet repetitions and interference cancellation, the NOSA protocol is able to achieve high throughput with affordable complexity while keeping the same transmission efficiency as and comparable power consumptions to available protocols. Simulation results show that the NOSA prototype has the potential in providing RMA for massive machine-type terminals in practical TDMA-based satellite networks.
  • Gao, S. et al. (2018). Issue Small Satellites. Proceedings of the IEEE [Online] 106:339-342. Available at: https://doi.org/10.1109/JPROC.2018.2805267.
    Small satellite is a disruptive technology in space industries. Traditionally, space industries were dominated by satellites which have thousands of kilograms and are bulky and expensive. Small satellites denote a new generation of miniaturized satellites which, by taking advantages of modern technologies (e.g., integrated circuits, digital signal processing, MEMS, and additive manufacturing), can achieve a significant reduction in volume, mass, development time, and cost of satellites. During recent decades, small satellites, including CubeSats, NanoSats, MiniSats, and MicroSats, have undergone rapid developments, and are playing an increasingly larger role in exploration, technology demonstration, scientific research, and education. These miniature satellites provide a low-cost platform for missions, including planetary space exploration, Earth observations, fundamental Earth and space science, and developing precursor science instruments like laser communications and millimeter-wave communications for intersatellite and intrasatellite links, and autonomous movement capabilities. They also allow educators an inexpensive means to engage students in all phases of satellite development, operation, and exploitation through real-world, hands-on research and development experience on rideshare launch opportunities. A number of miniaturized satellites can form spaceborne wireless sensor networks in the space, which are also going to play an important role in Internet of Space (IoS) of the future
  • Mao, C. et al. (2017). X/Ka-Band Dual-Polarized Digital Beamforming Synthetic Aperture Radar. IEEE Transactions on Microwave Theory and Techniques [Online] 65:4400-4407. Available at: http://dx.doi.org/10.1109/TMTT.2017.2690435.
    This paper presents a digital beamforming (DBF) synthetic aperture radar (SAR) for future spaceborne earth observation systems. The objective of the DBF-SAR system is to achieve a low cost, lightweight, low-power consumption, and dual-band (X/Ka) dual-polarized module for the next-generation spaceborne SAR system in Europe. The architectures and modules of the proposed DBF-SAR system are designed according to a realistic mission scenario, which is compatible with the future small/microsatellites platforms. This system fills an important gap in the conception of the future DBF-SAR, facilitating a high level of integration and complexity reduction. The proposed system is considered not only the first demonstrator of a receive-only spaceborne DBF system, but also the first X/Ka-band dual-polarized SAR system with shared aperture. This paper presents a description of the proposed instrument hardware and first experimental validations. The concept and design of the DBF multistatic SAR system are discussed and presented first, followed by the design of subsystems such as DBF networks, microwave integrated circuit, and antennas. Simulated and measured results of the subsystems are presented, demonstrating that the proposed SAR instrument architecture is well-suited for the future SAR applications.
  • Li, W. et al. (2017). Polarization-Reconfigurable Circularly Polarized Planar Antenna Using Switchable Polarizer. IEEE Transactions on Antennas and Propagation [Online] 65:4470-4477. Available at: https://dx.doi.org/10.1109/TAP.2017.2730240.
    A novel polarization-reconfigurable planar antenna is presented. The antenna consists of an electronically reconfigurable polarizer integrated with a printed slot. By changing the states of the PIN diodes on the polarizer, the linearly polarized (LP) waves radiated by the slot can be converted to either right-hand circularly polarized (RHCP) or left-hand circularly polarized (LHCP) waves. The polarizer contains 16 unit cells arranged as a 4 × 4 array. The antenna radiates RHCP waves if the PIN diodes on the top side of the polarizer are switched ON, while LHCP waves are radiated if the PIN diodes of the bottom side of the polarizer are switched ON instead. The physical mechanisms of the antenna are discussed and the parametric study is carried out by full-wave simulations. To verify the concept, one prototype at 2.5 GHz is designed, fabricated and measured. Good agreement between the measured and simulated results is obtained. The antenna achieves a gain ? 8.5 dBic in both RHCP and LHCP with aperture efficiency of 70%. Advantages of the proposed design include electronicallyreconfigurable polarizations for RHCP or LHCP, low profile, low cost, high isolation between the DC bias circuit and RF signals, high power handling capability and easy extension to large-scale arrays without increasing the complexity of the DC bias circuit. To the best knowledge of the authors, this is the first report of an electronically polarization-reconfigurable circularly polarized antenna with a single-substrate polarizer.
  • Xu, H. et al. (2017). Multimode Decoupling Technique with Independent Tuning Characteristic for Mobile Terminals. IEEE Transactions on Antennas and Propagation [Online] 65:6739-6751. Available at: https://doi.org/10.1109/TAP.2017.2754445.
    The isolation between antenna elements is a key metric in some promising 5G technologies such as beamforming and in-band full-duplex (IBFD). However, multimode decoupling technology remains a great challenge especially for mobile terminals. One difficulty in achieving multi decoupling modes is that the operating modes of closely-packed decoupling elements have very strong mutual effect, which makes the tuning complicated and even unfeasible. Thus, in physical principle, a novel idea of achieving the stability of the boundary conditions of decoupling elements is proposed to solve the mutual effect problem; in physical structure, a metal boundary is adopted to realize the stability. One distinguished feature of the proposed technique is that the independent tuning characteristic can be maintained even if the number of decoupling elements increases. Therefore, wideband/multiband high isolation can be achieved by using multi decoupling elements. To validate the concept, two case studies are given. In a quad-mode decoupling design, the isolation is enhanced from 12.7 dB to > 21 dB within 22.0% bandwidth by using a 0.295?0 × 0.059?0 × 0.007?0 decoupling structure. The mechanism of decoupling technique and the mutual effect between decoupling elements are investigated.
  • Mao, C. et al. (2017). A Shared-Aperture Dual-Band Dual-Polarized Filtering-Antenna-Array with Improved Frequency Response. IEEE Transactions on Antennas and Propagation [Online] 65:1836-1844. Available at: http://dx.doi.org/10.1109/TAP.2017.2670325.
    In this paper, a novel dual-band dual-polarized (DBDP) array antenna with low frequency ratio and integrated filtering characteristics is proposed. By employing a dual-mode stub-loaded resonator (SLR) to feed and tune with two patches, the two feed networks for each polarization can be combined, resulting in the reduction of the feed networks and the input ports. In addition, owing to the native dual resonant features of the SLR, the proposed antenna exhibits 2nd-order filtering characteristics with improved bandwidth and out-of-band rejections. The antenna is synthesized and the design methodology is explained. The coupling coefficients between the SLR and the patches are investigated. To verify the design concept, a C/X-band element and a 2 × 2 array are optimized and prototyped. Measured results agree well with the simulations, showing good performance in terms of bandwidth, filtering, harmonic suppression and radiation at both bands. Such an integrated array design can be used to simplify the feed of a reflector antenna. To prove the concept, a paraboloid reflector fed by the proposed array is conceived and measured directivities of 24.6 dBi (24.7 dBi) and 28.6 dBi (29.2 dBi) for the X-polarization (Y-polarization) are obtained for the low- and high-band operations, respectively.
  • Qin, F. et al. (2017). A Tri-Band Low-Profile High-Gain Planar Antenna Using Fabry-Perot Cavity. IEEE Transactions on Antennas and Propagation [Online] 65:2683-2688. Available at: http://dx.doi.org/10.1109/TAP.2017.2670564.
    A tri-band high-gain antenna with a planar structure and low profile is proposed. The principle of operation is explained. It is based on Fary-Perot cavity antenna (FPCA) with two frequency selective surface (FSS) layers. Two different resonant frequencies are generated by the two resonant cavities formed by the ground plane and each of the two FSS layers, respectively. A third resonant frequency is produced by combining the two FSS layers together. Advantages of this tri-band antenna includes low profile, high gain, easy fabrication and low cost. Low
    profile is achieved by designing the combined FSS layers as an artificial magnetic conductor (AMC) with a reflection coefficient having 0o phase shift and high magnitude. In addition, a large frequency ratio, which is often a problem for multiband array antennas, can be achieved here. To verify this concept, a C/X/Ku band FPCA is designed and one prototype is fabricated and tested. Experimental results agree well with the simulated results. High gain performance with good impedance matching in three bands is obtained, which reaches a peak gain of 14.2 dBi at 5.2 GHz, 18.9 dBi at 9.6 GHz and 19.8 dBi at 14.7 GHz, respectively. The overall height of antenna is only 20.2 mm, which is about 1/3 wavelength at its lowest operating frequency, which means a reduction of 30% compared to the height of traditional FPCA antenna.
  • Mao, C., Gao, S. and Wang, Y. (2017). Broadband High-Gain Beam-Scanning Antenna Array for Millimeter-Wave Applications. IEEE Transactions on Antennas and Propagation [Online] 65. Available at: https://doi.org/10.1109/TAP.2017.2724640.
    A novel method of achieving low-profile, broadband microstrip array antennas with high antenna gain is proposed for millimeter-wave (mm-wave) applications. The element employs a novel 3rd-order vertically coupled resonant structure that a U-slot resonator in the ground is used to couple with the feeding resonator and the radiating patch, simultaneously. This proposed structure can significantly improve the bandwidth and frequency selectivity without increasing the thickness of the antenna. Then, to achieve the subarray, a new wideband power divider with loaded resonators is employed, which can be used to further improve the bandwidth. To demonstrate the working schemes of broadside radiation and scanned beam, two 4 × 4 array antennas are implemented on the same board. Measured results agree well with the simulations, showing a wide bandwidth from 22 to 32 GHz (FBW = 37%) with the gain of around 19 dBi. The beam scanning array can realize a scanning angle of over 25 degrees over a broadband. In addition, due to the filtering features are integrated in the design, the proposed antenna could also reduce the complexity and potential cost of the frontends.
  • Mao, C. et al. (2017). Compact Broadband Dual-Sense Circularly Polarized Microstrip Antenna/Array With Enhanced Isolation. IEEE Transactions on Antennas and Propagation [Online] 65:7073-7082. Available at: https://doi.org/10.1109/TAP.2017.2766440.
    This paper presents a novel method of designing the compact dual-sense circularly polarized (CP) microstrip antenna/array with improved impedance bandwidth, axial ratio (AR) bandwidth, and interpolarization isolation. The left-hand and right-hand CP characteristics are achieved simultaneously by conceiving a vertically coupled resonant structure for the first time. Different from traditional methods, the antenna shows a compact size but exhibits the wide impedance and 3 dB AR bandwidths. For each input, two coupling paths are purposely designed to excite the TM10 and TM01-mode of the patch, respectively. By composing different coupling units in the two paths, an intrinsic ±90° phase difference over a broadband can be obtained, resulting in the broadband CP characteristics. In addition, a novel method of using the neutralization line between the two feeds is investigated to improve the isolation between the polarizations. Based on the dual-sense CP element, a 1×4 dual-sense CP array is composed to exemplify its potential applications in large arrays. Compared with traditional CP antennas, the proposed antennas have the advantages of compact size, simplified feed, broad impedance and 3 dB AR bandwidths, and improved isolation. Experimental results verify the predictions.
  • Gu, C. et al. (2017). Dual-Band Electronically Beam-Switched Antenna Using Slot Active Frequency Selective Surface. IEEE Transactions on Antennas and Propagation [Online] 65:1393-1398. Available at: http://dx.doi.org/10.1109/TAP.2016.2647578.
    Abstract—A dual-band electronically beam-switching antenna using a cylindrical active frequency selective surface (AFSS) is presented. The antenna structure consists of a slot AFSS and an omnidirectional dual-band feed antenna. The PIN diodes of half the AFSS are switched ON and OFF respectively to reconfigure the surface as transparent and opaque to the incident EM waves. Thus by controlling the bias voltages to different columns, the directive beams can be swept in 4 steps covering the whole azimuth plane. A design validation based on a metallic reflector antenna is performed to predict the performances of the proposed AFSS antenna. To validate the design concept, the transmission coefficients of the active FSS sheet are experimentally examined. Then an antenna prototype operating at 2.5 GHz and 5.3 GHz frequency bands is fabricated and measured. Simulation and measurement results of the fabricated antenna are presented to verify the design principle. A comparison between this work and previous (single-band) designs is given to better interpret the characteristics of the dual-band AFSS antenna.
  • Cheng, Z. et al. (2017). Design of 0.8–2.7 GHz High Power Class-F Harmonic-Tuned Power Amplifier with Parasitic Compensation Circuit. Active and Passive Electronic Components [Online] 2017:1-8. Available at: https://doi.org/10.1155/2017/2543917.
    The design, implementation, and measurements of a high efficiency and high power wideband GaN HEMT power amplifier are presented. Package parasitic effect is reduced significantly by a novel compensation circuit design to improve the accuracy of impedance matching. An improved structure is proposed based on the traditional Class-F structure with all even harmonics and the third harmonic effectively controlled, respectively. Also the stepped-impedance matching method is applied to the third harmonic control network, which has a positive effect on the expansion bandwidth. CGH40025F power transistor is utilized to build the power amplifier working at 0.8 to 2.7?GHz, with the measured saturated output power 20–50?W, drain efficiency 52%–76%, and gain level above 10?dB. The second and the third harmonic suppression levels are maintained at ?16 to ?36?dBc and ?16 to ?33?dBc, respectively. The simulation and the measurement results of the proposed power amplifier show good consistency.

Conference or workshop item

  • Lehu, W. et al. (2019). A Compact and Wideband Dual-Polarized Antenna Using Folded Loops. in: The Loughborough Antennas & Propagation Conference (LAPC 2018). New York, USA: IEEE / IET, pp. 21 -21. Available at: https://doi.org/10.1049/cp.2018.1442.
    A novel dual-polarized antenna using folded loops is presented in this paper. The proposed dual-polarized antenna is composed of four triangle loops, which is developed from a single polarized antenna with two triangle loops. By using folded method, a linear polarized loop antenna is elaborately transformed into a dual-polarized antenna with the only increase of feed port for another polarization. Design method of the proposed dual-polarized antenna is discussed and illustrated in this paper. By virtue of the folded design method, the proposed antenna shows a compact size compared to the referenced designs. In addition, wide impedance bandwidth is also achieved with simple configuration. To demonstrate the design method, the proposed antenna is implemented and measured. The measured results prove that the antenna has a wideband impedance bandwidth for base stations with VSWR<1.5 and isolation >35 dB from 1.7 GHz to 2.7 GHz. Furthermore, stable gain and HPBW are also obtained for base station applications.
  • Wang, Y., Zhu, F. and Gao, S. (2019). Design of a low-profile wideband patch antenna with L-shaped feeding mechanism. in: International Applied Computational Electromagnetics Society Symposium. IEEE. Available at: https://doi.org/10.23919/ACESS.2018.8669243.
    This paper has presented the design of a novel low-profile wideband patch antenna. The antenna structure is formed of three layers of substrates with the radiating patches on the top, the grounded patches in the middle and the feeding portion at the bottom. The large operating frequency bandwidth has been obtained due to the L-shaped feeding technique. Moreover, the low cross-polarization level can also be achieved as the feeding structure can be regarded as the preferred differential feeding. The obtained results can confirm that the proposed antenna has achieved a wide impedance bandwidth (VSWR ≤ 2) of about 60% (3-5.5 GHz) and the whole height of the antenna is 6 mm (around 0.06λ l at the lowest operating frequency). The obtained cross-polarization level is less than-30dB compared with co-polarization.
  • Wang, Y., Zhu, F. and Gao, S. (2019). 24-GHz Circularly Polarized Substrate Integrated Waveguide-Fed Patch Antenna. in: International Applied Computational Electromagnetics Society Symposium. IEEE, pp. 1-2. Available at: https://doi.org/10.23919/ACESS.2018.8669193.
    This paper has presented the design of a 24-GHz patch antenna with characteristics of good circular polarization, simple structure and easy fabrication. The printed antenna consists of two layers of substrates with the lower one for achieving a short-ended substrate integrated waveguide (SIW) and the upper one for supporting the rectangular radiating patch. The left-handed circularly polarized wave has been obtained by etching a 450 rotated cross-shaped slot on the broad wall of the SIW. The obtained results can confirm that the proposed antenna has achieved an impedance bandwidth (|S 11 | ≤-10 dB) of 23.1-25.3GHz and the 3-dB axial ratio bandwidth of 23.2-24.7GHz.
  • Qingling, Y. et al. (2019). Antenna Array Antenna Array Driven by Broadband Integrated Multibeam Network With Flat Amplitudes and Phases. in: The Loughborough Antennas & Propagation Conference (LAPC 2018). IEEE, p. . Available at: https://doi.org/10.1049/cp.2018.1457.
    This paper presents a broadband integrated Butler Matrix beamforming network (BFN). This proposed Butler Matrix BFN operates between the bandwidth of 28 GHz to 32 GHz and is implemented with subtrate integrated waveguides (SIWs). To facilitate the design and enhance the output amplitude and phase response, the phase shifters are incorporated into the design of directional couplers. Thus, the design of phase shifters doe not take the phase of crossover as a reference. The compensating SIW phase shifter is introduced into the design of −45° phase shifter, which helps to enhance the phase response over the operating bandwidth. The simulated phase dispersions of the designed Butler Matrix BFN are with peak to peak errors of only 13°, and the amplitude response over the bandwidth is −6 3 ± 1.2 dB. The designed Butler Matrix BFN would be a potential candidate in future 5G communications and other wireless communication systems.
  • Sumantvo, J. et al. (2019). Hinotori-C: A Full Polarimetric C Band Airborne Circularly Polarized Synthetic Aperture Radar for Disaster Monitoring. in: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama). New York, USA: IEEE, pp. 1466-1473. Available at: https://doi.org/10.23919/PIERS.2018.8597722.
    This paper aims to present the design and development work of a full polarimetric Circularly Polarized Synthetic Aperture Radar (CP-SAR) system. The CP-SAR sensor is operating in C band with center frequency of 5.3 GHz, operational bandwidth ranged from 100 MHz to 400 MHz, and transmitting peak power of 280 watt. Four circularly polarized antennas (2 units with left handed circularly polarized and 2 units with right handed circularly polarized) were designed and developed with approximately 22 dBic of gain, and beamwidth of 13° and 6° in range and azimuth direction, respectively. This paper also presents the results from the laboratory test and ground test of the CP-SAR sensor, as well as, the flight test results obtained from the maiden flight of the CP-SAR system using CASA/IPTN CN235-MPA aircraft.
  • Zhu, F. et al. (2018). Design of a Low-Profile 3:1 Bandwidth Wide-Scan Tightly Coupled Phased Array Antenna. in: 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT). IEEE. Available at: https://doi.org/10.1109/ICMMT.2018.8563283.
    A low-profile tightly coupled phased array antenna with the characteristics of 3:1 bandwidth and ±45 ° scan has been proposed in this paper. The array element consists of three layers of Duroid 5880 substrates and a couple of dipole arms. The novelty of the design is the loaded cross-shaped patch which is employed to avoid the common-mode resonance when unbalanced feeding the balanced dipoles. The obtained results confirm that, the array with 7mm spacing can operate from 7 to 21 GHz with VSWR ? 2.5 for 45°scan in both E-and H-planes. The absolute gain of embedded central element pattern is less than 0.6dB compared with the ideal gain, indicating low loss and good efficiency. It is also worth mentioning that, the whole thickness of the antenna is around 4.5mm, which means it is suitable for conformal platforms.
  • Sumantyo, J. et al. (2018). Hinotori-X1 Mission: X Band Walr-Sar Onboard Boeing 737–200 Aircraft. in: IEEE International Geoscience & Remote Sensing Symposium. IEEE, pp. 6488-6491. Available at: https://doi.org/10.1109/IGARSS.2018.8518811.
    We developed a novel concept for X-band (center frequency 9.4 GHz, HH polarization) airborne SAR, the Wide Area Long Range Synthetic Aperture Radar (WALR-SAR) onboard a Boeing 737-200 aircraft for simultaneous air and terrestrial disaster monitoring. This paper explains the configuration of our WALR-SAR system and slotted array antenna installed on the Boeing 737-200. Ground measurements of the slotted array antenna were realized to measure the characteristics of antenna and its results are discussed in this paper. Flight test of WALR-SAR onboard Boeing 737-200 in Hinotori-X1 (Firebird-X1) mission was performed during the period of 2 to 10 August 2017 at Pare-Pare and Makassar, Indonesia. Results show good performance of the WALR-SAR system and its image acquisition that covers the depression angle 0.5 to 42.0 degrees.
  • Sri Sumantyo, J. et al. (2018). Multiband Circularly Polarized Synthetic Aperture Radar (CP-SAR) Onboard Microsatellite Constellation. in: IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium. pp. 1974-1977. Available at: https://doi.org/10.1109/IGARSS.2018.8518397.
    Center for Environmental Remote Sensing, Chiba University develops multiband (L, C, and X bands) circularly polarized synthetic aperture radar (CP-SAR) for microsatellite SAR constellation (150 kg class). This paper explains the project, specification, antenna deployment, RF system, and ground-flight test of SAR system at Indonesia. In the future, this microsatellite SAR constellation will be employed to monitor global land deformation and environment.
  • Wang, Y., Zhu, F. and Gao, S. (2018). Planar Microstrip-Fed Broadband Circularly Polarized Antenna. in: 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT). IEEE, pp. 1-3. Available at: https://doi.org/10.1109/ICMMT.2018.8563456.
    The design of a printed microstrip-fed patch antenna featuring characteristics of wideband and circular polarization has been proposed. The planar antenna is evolved from a typical monopole consisting of a rectangular radiating patch and a rectangular ground plane. The circular polarization has been obtained by shifting offset the radiating patch in correspondence with the ground. Moreover, a tapered-shaped feeding line has been employed to improve the impedance matching across a wide frequency band and two stubs have been integrated with the antenna to enhance the axial ratio bandwidth. The obtained results have confirmed that, the bandwidths of the proposed antenna with VSWR ? 2 and axial ratio ? 3 are 140% and 75%, respectively. In addition, the peak realized gain ranges from 1.25 to 3.2 dBi across the operating frequency range.
  • Gu, C., Gao, S. and Sanz-Izquierdo, B. (2017). Low-cost wideband low-THz antennas for wireless communications and sensing. in: 10th UK-Europe-China Workshop on Millimetre Waves and Terahertz Technologies (UCMMT), 2017. IEEE. Available at: https://doi.org/10.1109/UCMMT.2017.8068470.
    Terahertz technology is expected to provide a significant improvement in wireless system performance. A common assumption is that traditional microwave devices can be scaled down to operate at higher frequency bands. However, it can be a challenge to directly transfer the design methodology from microwave to THz band as the size of the devices becomes a few millimeter large. The reduced antenna size at the THz band limits the suitable fabrication processes. This paper reviews a wide range of THz antennas and their fabrication methodology. Then based on the resonant cavity antenna concept, an all-metal 300 GHz wideband high-gain antenna is designed and simulated. The presented metallic antenna is suitable to be fabricated using 3D printing techniques, which can lead to a low-cost, reliable solution for the emerging THz applications.
  • Gu, C., Gao, S. and Sanz-Izquierdo, B. (2017). Wideband low-THz antennas for high-speed wireless communications. in: Electromagnetics in Advanced Applications (ICEAA), 2017 International Conference on. IEEE, pp. 141-145. Available at: https://doi.org/10.1109/APWC.2017.8062263.
    This paper presents a brief review of low THz antennas and discusses their corresponding manufacturing techniques. In addition, a new antenna is introduced for the 300 GHz frequency band. The design is an all-metal structure with interesting features such as compactness, high gain, and wide operational bandwidth. These characteristics make it a promising solution for future high-speed THz communication systems.

Forthcoming

  • Hu, C. et al. (2019). A Robust Technique without Additional Computational Cost in Evolutionary Antenna Optimization. IEEE Transactions on Antennas and Propagation [Online]. Available at: https://doi.org/10.1109/TAP.2019.2891661.
    A robustness-enhancing technique without additional computational cost in antenna optimization design is presented. The robustness is implemented by minimizing the variances of the gains, axial ratios and VSWRs over the required frequency band. It is demonstrated that the new technique has two obvious advantages. One is that it can ensure the antenna robustness without the extra computational overhead. The other one is that it is possible to broaden the bandwidth of the antenna. We apply this technique to design a microstrip antenna at 2.4GHz. Experimental results show that, by adopting this new technique, the evolved antenna is more robust than by using two other techniques.
  • Wen, L. et al. (2019). A Compact Windband Duel-Poloarized Antenna With Enhanced Upper Out-of-Band Suppression. IEEE Transactions on Antennas and Propagation.
  • Gu, C. et al. (2018). Wideband high-gain millimetre/submillimetre wave antenna using additive manufacturing. IET Microwaves, Antennas & Propagation [Online] 12:1758-1764. Available at: https://doi.org/10.1049/iet-map.2018.5412.
    This paper presents a novel design of a wideband high-gain resonant cavity antenna (RCA) for millimetre and
    submillimetre wave bands, and its fabrication using additive manufacturing. The proposed RCA antenna consists of a partially
    reflecting surface and three impedance matching layers fed by a waveguide. Additive manufacturing (AM) techniques are
    utilized to fabricate the design operating at 30 GHz. Two fabrication techniques are assessed for printing the antenna. The
    first technique is based on printing a dielectric material and fully coating the parts with a metallic layer, while the second
    technique involves printing the parts in a single process using metal 3D printing. The first technique offers a lightweight
    solution while the second technique can print the whole model in one run. The antenna design is investigated by both
    simulations and experiments. The measured results show an 3dB gain bandwidth of about 10%, and high gain over 15 dBi
    for all the three resulting antennas. Good agreement between simulation and measurement is obtained. The antenna has a
    low cost and achieved good performance in terms of wide bandwidth and high gain, thus it is potentially useful for highspeed
    wireless communications at millimetre-wave and sub-millimetre-wave frequencies.
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