Dr Qi Luo received his B.Eng degree in Communication Engineering from Xi'an University of Technology and Architecture (China, 2004), M.Sc degree in Data Communication from University of Sheffield (The UK, 2006) and PhD degree in Electrical and Computer Engineering from the University of Porto (Portugal, 2012).

During 2006-2007, he works at INESC Porto, Portugal, as a research fellow. He was with Surrey Space Center, the University of Surrey during 2012-2013. Since February 2013, he joined the Broadband and Wireless Communications Research Group, School of Engineering and Digital Arts, University of Kent. He has many year’s experiences in the antenna and array antenna design. He is involved in several European FP7 and EPSRC funded projects, responsible for the design of beam-steering smart antennas for high-speed Ka-band Satcom terminals and high-efficiency/ high-power multi-beam active Tx/Rx onboard antenna arrays (Ku/Ka band) for satellite communications.

He has published many articles and papers in high impact peer-reviewed journals and conferences. He co-authored a book on Circularly Polarized Antennas  (Wiley-IEEE, Feb. 2014, co-authored with S.Gao and F. Zhu), and a book chapter on ‘Smart Antennas for Satellite Communications’ in Handbook of Antenna Technologies (Springer Singapore). Meanwhile, he serves as the reviewers for several international journals and conferences including IEEE Transactions on Antennas & Propagation, IEEE Magazine on Antennas & Propagation, IET Microwaves, Antennas & Propagation, and European Conference on Antenna & Propagation. He was awarded as the outstanding reviewer for IEEE Transactions in Antenna and Propagations in 2015.

His main areas of expertise include phased arrays, smart antennas, reflectarrays, transmitarrays, circularly polarized antennas, electrically small antennas, MIMO antennas, and multiband antennas.

Research interests

Dr Qi Luo’s research interests lie in the field of smart antenna array, compact antenna and microwave component design. 

He also has experiences in designing and developing different types of antennas including microstrip antennas, printed monopole antenna, planar inverted-F antenna (PIFA) and microwave components at millimetre-wave bands.



  • 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.
  • 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]. 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.
  • 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.
  • Zhou, Y. et al. (2018). Tightly Coupled Array Antennas for Ultra-Wideband Wireless Systems. IEEE Access [Online]. 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.
  • 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
  • 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.
  • 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.
  • 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.
  • Zhang, L. et al. (2017). Single-Layer Wideband Circularly Polarized High-Efficiency Reflectarray for Satellite Communications. IEEE Transactions on Antennas and Propagation [Online]. Available at: https://dx.doi.org/10.1109/TAP.2017.2722824.
    This paper presents a single-layer circularly polarized (CP) reflectarray which achieves large bandwidth in terms of axial ratio (AR), gain, aperture efficiency and radiation pattern. By using a novel wideband S-shaped phasing element, an offset-fed reflectarray with 20° offset beam is designed based on the element angular rotation method. Theoretical analysis is given to analyze the effect of angular rotated elements on the performance of the reflectarray, which indicates that the AR bandwidth of the reflectarray can exceed the AR bandwidth of the feed horn. Furthermore, the influence of the differential spatial phase delay is analyzed quantitatively, and the performance of S-element-based reflectarrays with different aperture sizes are investigated and discussed. To verify these concepts, a 180mm×180mm prototype with 15×15 elements is fabricated and measured. The measured results confirm that the proposed reflectarray achieves a 68.5% 3-dB AR bandwidth (7.0 GHz to 14.3 GHz) and a 47.8% 3-dB gain bandwidth (8.6 GHz to 14 GHz). Moreover, the aperture efficiency is larger than 50% in a 33% bandwidth and larger than 30% in a 64% bandwidth.
  • 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.
  • Zhang, L. et al. (2017). Wideband dual circularly polarized beam-scanning array for Ka-band satellite communications. Microwave and Optical Technology Letters [Online] 59:1962-1967. Available at: https://doi.org/10.1002/mop.30655.
    This article presents a wideband dual circularly polarized (CP) array which has two independent beams in orthogonal circular polarizations and the two beams can scan to ±23° individually. The proposed array consists of stacked patches fed by 90° hybrid couplers. To achieve two independent beams, the beam-forming networks (BFNs) for the left-hand circular polarization (LHCP) beam and right-hand circular polarization (RHCP) beam are printed on two separate layers with ground plane between them. This arrangement facilitates the integration of the BFNs and reduces the fabrication complexity. Two prototypes with different beam-scanning angles are fabricated and measured. The measured results confirm that the array achieves good impedance matching, larger than 20 dB isolation and smaller than 3 dB axial ratio (AR) from 27 to 30 GHz when the array scans to ±23°. Due to the independent beam-scanning ability, high isolation between the LHCP and RHCP beams and the wide bandwidth, the proposed array is promising for high data-rate Ka-band satellite communications which utilize polarization diversity.
  • 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.
  • Zheng, S. et al. (2017). A Broadband Dual Circularly Polarized Conical Four-Arm Sinuous Antenna. IEEE Transactions on Antennas and Propagation [Online] 66:71-80. Available at: https://doi.org/10.1109/TAP.2017.2772301?
    A novel wideband four-arm sinuous antenna with dual circular polarizations (CPs) and unidirectional radiation is proposed. Different from the conventional designs, this sinuous antenna is realized in a conical form and no ground plane or absorptive cavity is required to obtain unidirectional radiation. The beamforming network for dual circularly polarized operations consists of a wideband quadrature coupler and two wideband baluns, and an auxiliary feeding patch is introduced to facilitate the connection between baluns and sinuous arms. The design of baluns and coupler is inspired from the printed exponentially tapered microstrip balun and broadside-coupled microstrip coupler, respectively. The dynamic differential evolution algorithm is employed to optimize the geometry of coupler for optimal performance. For both polarizations, the presented antenna has wide impedance bandwidth, good axial ratio, moderate realized gain, and front-to-back ratio within 2–5 GHz. An antenna prototype is fabricated and tested. The agreement between simulation and measurement results validates the proposed antenna framework. The demonstrated antenna has advantages of wide bandwidth, dual CPs, unidirectional radiation, lightweight, and low cost, and is promising for applications in wireless systems.
  • Zhang, L. et al. (2016). Planar Ultra-Thin Small Beam-Switching Antenna. IEEE Transactions on Antennas and Propagation [Online]. Available at: http://doi.org/10.1109/TAP.2016.2620490.
    A novel planar ultrathin electronically steerable parasitic array radiator (ESPAR) is presented in this paper. Through theoretical analysis of the electric fields of orthogonally crossed dipoles in phase quadrature, it is found that the crossed dipoles radiate linearly polarized wave with a rotational electric field in the azimuth plane. This characteristic is then utilized to design a planar crossed dipole ESPAR, termed as “CD-ESPAR.” Furthermore, a simple but effective impedance matching method is also proposed and analyzed. To verify these concepts, a prototype with compact size and very low profile (0.42 ?0 × 0.42 ?0 ×0.006 ?0) resonating at 2.3 GHz is designed, fabricated, and measured. The measured results indicate that the proposed antenna achieves more than 17.8% impedance bandwidth and can produce four directional beams, covering the whole azimuth plane. Owing to its planar ultrathin structure, compact size, electronically beam-switching ability, low power, and low cost characteristics, it is promising for applications in wireless communications
  • Zhang, L. et al. (2016). Inverted-S Antenna with Wideband Circular Polarization and Wide Axial Ratio Beamwidth. IEEE Transactions on Antennas and Propagation [Online] 65:1740-1748. Available at: https://doi.org/10.1109/TAP.2016.2628714.
    A novel broadband circularly polarized (CP) antenna with wide axial ratio (AR) beamwidth is proposed. It is composed of two curved arms shaped like an inverted “S”. The mechanisms of wideband CP operation and wide AR beamwidth are explained. To validate the concept, a prototype at C-band is manufactured and measured. Experimental results confirm that the antenna achieves an impedance bandwidth of 63% and a CP bandwidth of 42%. Furthermore, maximum AR beamwidth of 140o is achieved and wide AR beamwidth can be maintained in a frequency bandwidth of 35% in nearly all elevation planes. In addition, the antenna has the advantage of being easily extended to arrays. A 4-element array using the proposed antenna is investigated through both simulations and experiments, and achieves 60% CP bandwidth and wide AR beamwidth. The proposed inverted-S antenna can realize wide CP bandwidth and wide AR beamwidth, and is easy to form wideband CP arrays.
  • Luo, Q. et al. (2016). Dual Circularly-Polarized Equilateral Triangular Patch Array. IEEE Transactions on Antennas and Propagation [Online] 64:2255-2262. Available at: http://dx.doi.org/10.1109/TAP.2016.2551260.
    Abstract—This paper presents a novel sequentially rotated patch array antenna with dual circular-polarizations (CP). The present design has the advantages of compact size, simple feed networks, low cross-polarization and high isolation. The radiating elements are dual linearly-polarized (LP) equilateral triangular patches with hybrid feeds. The vertical polarization of the patch antenna is obtained by using an aperture-coupled feed and the horizontal polarization is obtained by using a proximity feed. These two feeds are orthogonally positioned and are printed on different PCB layers, which leads to the high isolation between these two ports and facilitates the design of the feed networks. The array antenna consists of six such dual-LP triangular patches sequentially rotated by 60o and fed by separated feed networks. Since linearly polarized antenna elements are used, the design of the feed network is much simplified. Through sequentially varying the feeding phase by ?60o, dual circular-polarizations are obtained. The operation principle of the array antenna is also analytically explained in this paper. To verify the design
    concept, one dual LP equilateral triangular patch and one dual CP equilateral triangular patch array resonating at 10.5 GHz are designed, fabricated and tested. There is a good agreement between the simulation and measurement results, both of which show that the array antenna exhibits high port isolation and good circular polarizations with low cross polarization at different planes. The proposed design technique can be applied to the design of dual CP array antennas operating at other frequency
    Index Terms—dual circular polarization, sequential rotation,
    microstrip, hybrid feed, high isolation
  • Qi, L., Gao, S. and Zhang, L. (2015). Wideband multilayer dual circularly-polarised antenna for array application. IET Electronic Letter [Online] 51:2087-2089. Available at: http://dx.doi.org/10.1049/el.2015.3343.
    A wideband multilayer antenna with dual circular polarisations (CPs) is presented. The antenna consists of stacked square patches fed by striplines and a branch line coupler. Two orthogonally positioned H-shaped slots are used as the coupling aperture for the striplines. The dual-CP radiation is obtained by exciting the TM01 and TM10 modes of the radiating element with 90° phase differences. The presented dual-CP antenna has a multilayer configuration with a compact size and it is suitable to be applied to the design of array antennas. To verify this design concept, one prototype operating in the K-band is designed and fabricated. The measurement results show that the prototype has more than 13% impedance bandwidth with good CP radiations
  • Zhang, L. et al. (2015). Single-Feed Ultra-Wideband Circularly Polarized Antenna With Enhanced Front-to-Back Ratio. IEEE Transactions on Antennas and Propagation [Online] 64:355-360. Available at: http://doi.org/10.1109/TAP.2015.2501844.
    This communication presents a single-feed ultra-wideband circularly polarized (CP) antenna with high front-to-back ratio (FBR). The antenna is composed of two orthogonally placed elliptical dipoles printed on both sides of a substrate. To realize high FBR, a novel composite cavity is also proposed and integrated with the presented crossed dipoles, which effectively reduces the backlobe of the crossed dipoles. Simulation results are in good agreement with the measured results that demonstrate an impedance bandwidth from 0.9 to 2.95 GHz (106.5%) and a 3-dB axial ratio (AR) bandwidth from 1 to 2.87 GHz (96.6%). The measured FBR is about 30 dB across the whole global navigation satellite system (GNSS) band. Compared with other reported single-feed wideband CP antennas, the antenna has advantages such as a wider CP bandwidth and lower backlobe radiation
  • Zhang, L. et al. (2015). Single-feed ultra-wideband circularly polarized antenna with enhanced front-to-back ratio. IEEE Transactions on Antennas and Propagation [Online] PP:1-1. Available at: http://dx.doi.org/10.1109/TAP.2015.2501844.
    This communication presents a single-feed ultra-wideband circularly polarized (CP) antenna with high front-to-back ratio (FBR). The antenna is composed of two orthogonally placed elliptical dipoles printed on both sides of a substrate. To realize high front-to-back ratio, a novel composite cavity is also proposed and integrated with the presented crossed dipoles, which effectively reduces the back-lobe of the crossed dipoles. Simulation results are in good agreement with measured results which demonstrate an impedance bandwidth from 0.9 to 2.95GHz (106.5%) and a 3-dB axial ratio bandwidth from 1 to 2.87GHz (96.6%). The measured FBR is about 30dB across the whole GNSS band. Compared with other reported single-feed wideband CP antennas, the antenna has advantages such as a wider CP bandwidth and lower back-lobe radiation.
  • Gu, C. et al. (2015). Compact Smart Antenna with Electronic Beam-Switching and Reconfigurable Polarizations. IEEE Transactions on Antennas and Propagation [Online]:1-1. Available at: http://doi.org/10.1109/TAP.2015.2490239.
    This paper presents a compact-size, low-cost smart antenna with electronically switchable radiation patterns and reconfigurable polarizations. This antenna can be dynamically switched to realize three different polarizations including two orthogonal linear polarizations and one diagonally linear polarization. By closely placing several electronically reconfigurable parasitic elements around the driven antenna, the beam switching can be achieved in any of the three polarization states. In this design, a polarization reconfigurable square patch antenna with a simple feeding network is used as the driven element. The parasitic element is composed of a printed dipole with a PIN diode. By using different combinations of PIN diode ON/OFF states, the radiation pattern can be switched towards different directions to cover an angle range of 0° to 360° in the azimuth plane. The concept is confirmed by a series of measurements. This smart antenna has the advantages of compact size, low cost, low power consumption, reconfigurable polarizations and beams.
  • Luo, Q. et al. (2015). Design and Analysis of a Reflectarray Using Slot Antenna Elements for Ka band Satcom. IEEE Transactions on Antennas & Propagation [Online]. Available at: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=7035049.
  • Luo, Q., Gao, S. and Zhou, D. (2014). Intelligent antenna technology for mobile satellite communications. e & i Elektrotechnik und Informationstechnik [Online] 131:155-160. Available at: http://dx.doi.org/10.1007/s00502-014-0212-2.
    Intelligent antenna is important for mobile satellite communications because it can increase the channel capacity, spectrum efficiency and coverage range of the communication systems. This paper overviews the technology for intelligent arrays with design examples. A detailed list of references is given in the end of this paper.
  • Chaloun, T. et al. (2014). Wide-angle scanning active transmit/receive reflectarray. IET Microwaves, Antennas & Propagation [Online] 8:811-818. Available at: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6882309.
    A highly integrated phased array transmit/receive architecture is presented. Multilayer microstrip antennas with a scanning potential up to 60° are combined, on a common manifold, with SiGe MMICs including four RF channels each, together with the necessary digital control circuits. Power distribution and combining are realised by the concept of a folded planar reflectarray. This study also includes the necessary solutions for multilayer interconnects and efficient heat removal from the active circuits. To prove the concept, passive arrays with different fixed beam positions have been tested successfully; followed by a first active array demonstrating excellent scanning performance up to 60° both in E- and H-plane.


  • Gao, S., Luo, Q. and Zhu, F. (2014). Circularly Polarized Antennas. [Online]. Wiley (UK). Available at: http://eu.wiley.com/WileyCDA/WileyTitle/productCd-111837441X.html.
    This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arrays
    In this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Advanced designs such as small-size CP antennas, broadband, wideband and ultra-wideband CP antennas are also discussed, as well as multi-band CP antennas and dual CP antennas. The design and analysis of different types of CP array antennas such as broadband CP patch arrays, dual-band CP arrays, CP printed slot arrays, single-band and multi-band CP reflectarrays, high-gain CP waveguide slot antennas, CP dielectric resonator antenna arrays, CP active arrays, millimetre-waveband CP arrays in LTCC, and CP arrays with electronically beam-switching or beam-steering capabilities are described in detail. Case studies are provided to illustrate the design and implementation of CP antennas in practical scenarios such as dual-band Global Navigation Satellite Systems (GNSS) receivers, satellite communication mobile terminals at the S-band, Radio Frequency Identification (RFID) readers at 2.4 GHz, and Ka-band high-speed satellite communication applications. It also includes the detailed designs for a wideband Logarithmic spiral antenna that can operate from 3.4-7.7 GHz. In addition, the book offers a detailed review of the recent developments of different types of CP antennas and arrays.
    •Presents comprehensive discussions of design techniques for different types of CP antennas: small-size CP antennas, broadband CP antennas, multi-band CP antennas and CP arrays.
    •Covers a wide range of antenna technologies such as microstrip antennas, helix, quadrifilar helix antenna, printed quadrifilar helix antenna, dielectric resonator antennas, printed slots, spiral antennas, monopoles, waveguide slot arrays, reflectarrays, active arrays, millimetre-wave arrays in LTCC, electronically beam-switching arrays and electronically beam-steerable arrays.
    •Reviews recent developments in different types of CP antennas and arrays, reported by industries, researchers and academics worldwide.
    •Includes numerous case studies to demonstrate how to design and implement different CP antennas in practical scenarios.
    •Provides both an introduction for students in the field and an in-depth reference for antenna/RF engineers who work on the development of CP antennas.

    Circularly Polarized Antennas will be an invaluable guide for researchers in R&D organizations; system engineers (antenna, telecom, space and satellite); postgraduates studying the subjects of antenna and propagation, electromagnetics, RF/microwave/millimetre-wave systems, satellite communications and so on; technical managers and professionals in the areas of antennas and propagation.

Book section

  • Luo, Q. and Gao, S. (2015). Smart Antennas for Satellite Communications. in: Chen, Z. N. ed. Handbook of Antenna Technologies. Singapore: Springer Singapore, pp. 1-32. Available at: http://dx.doi.org/10.1007/978-981-4560-75-7_103-1.
    Smart antennas are important for satellite communications because they can increase the channel capacity,
    spectrum efficiency, and coverage range of the communication systems. This chapter reviews the
    technology for smart array antenna design with examples. Applications of smart antennas for satellite
    ground stations and direct broadcast satellite systems are also presented in this chapter. A detailed list of
    references is given in the end of this chapter.
  • Luo, Q., Pereira, J. and Salgado, H. (2014). Low Cost Compact Multiband Printed Monopole Antennas and Arrays for Wireless Communications. in: Progress in Compact Antennas. Intech.

Conference or workshop item

  • He, X. et al. (2018). (Ba, Sr)(Ti, Mn)O3 Perovskite Films for Co-Planar Waveguide Tunable Microwave Phase Shifters. in: 13th European Microwave Integrated Circuits Conference (EuMIC). IEEE, pp. 166-169. Available at: https://doi.org/10.23919/EuMIC.2018.8539889.
    BaxSr1-xTiyMn1-yO 3 BSTO thin films have been synthesized using a molecular beam epitaxy system. Novel coplanar waveguide tunable phase shifters have been developed using these Mn-doped perovskite films. The presented phase shifters operate with a phase shift angle of 12 degrees at 10GHz. at an applied bias of 10V on an area smaller than 1mm 2 , Insertion loss of ~3.2 dB is extracted from the S-parameter measurement. Small changes of composition lead to a significant variation of device phase shift, demonstrating the importance of synthesizing suitable structure BSTO film.
  • Luo, Q., Zhang, L. and Gao, S. (2015). Wideband Monofilar Square Spiral Antenna at Ka-band frequencies. in: IEEE International Symposium on Antennas and Propagation/URSI.
  • Zhang, L., Gao, S. and Luo, Q. (2015). Low-Profile Compact-Size Electronically Beam-Switching Antenna for Wireless Communications. in: 9th European Conference on Antennas and Propagation (EuCAP), 2015. pp. 1-4.
    This paper presents a novel compact-size low-profile low-cost smart antenna which could electronically switch the beam for radiating towards different directions covering the full range of 360 degree in the azimuth plane. Through DC control of the on/off status of four embedded PIN diodes sequentially, the antenna can switch its beam in sequence towards different directions. It is able to achieve a bandwidth over 22% and the antenna gain over 3 dBi under all kinds of states of four PIN diodes. Meanwhile, it can achieve a front to back ratio (FBR) of over 15 dB. Compared to other low-cost smart antennas reported, the height of this antenna has been significantly reduced and its main advantages include low profile, compact size, planar structure, low cost and the capability of covering the full range of 360 degree in the azimuth plane through electronically control of PIN diodes. It is promising for application in wireless communication systems.
  • Luo, Q. and Gao, S. (2015). Interleaved Dual-band Circularly Polarized Active Array Antenna for Satellite Communications. in: 9th European Conference on Antennas and Propagation (EuCAP), 2015.
    This paper describes the concept of a novel interleaved circularly polarized active array antenna for satellite communication applications at X-band. The array consists of two equilateral triangular patch arrays with hexagonal lattice, and each of them operates at different frequency bands. This presented interleaved array antenna can operate at dual frequency bands with independently beam steering capability when incorporated with phase shifters and MMICs, thus suitable for simultaneously transmitting or receiving in both user and feeder links for satellite on-board applications. The incorporation of MMIC GaN based high power amplifier to each radiating element is planned, to obtain high radiated power level by space combining from the multi-pixel active array antenna. Preliminary simulation results on the X-band GaN power amplifier are also presented in this paper.
  • Long, Z., Gao, S. and Luo, Q. (2014). Polarization Reconfigurable Loop Antenna for Satellite Communications. in: Loughborough Antennas & Propagation Conference.
    This paper presents a polarization reconfigurable printed antenna which could alter its polarization status electronically to right-hand circular polarization (RHCP), left-hand circular polarization (LHCP) or linear polarization (LP). By inserting four PIN diodes into the symmetric gaps of a dual-loop planar antenna, the proposed antenna can switch its polarization status by controlling the on-off state of PIN diodes electronically. Meanwhile, a parallel stripline (PSL) has been employed as an impedance transformer for this antenna. It is shown that the antenna can achieve a 5.4% 3-dB AR bandwidth with a wider impedance bandwidth of 12.5% for both RHCP and LHCP and a 7.1% impedance bandwidth for LP. The proposed antenna has a uni-directional radiation pattern with a high peak gain of 9.8 dBi under all polarization status. The antenna can achieve polarization reconfigurability and a high gain, while having a low profile and low cost. It is promising for applications in satellite communications and terrestrial wireless communication systems.
  • Luo, Q., Gao, S. and Sumantyo, J. (2014). Smart Antennas for Mobile Satellite Communications. in: The Asia-Pacific Conference on Antennas and Propagation (APCAP 2014).
  • Gao, S. and Luo, Q. (2014). Low-Cost Smart Antennas for Advanced Wireless Systems. in: The International Workshop on Antenna Technology (iWAT). Institute of Electrical and Electronics Engineers. Available at: http://dx.doi.org/10.1109/IWAT.2014.6958618.
    Smart antenna is a key technology for mobile communications, satellite communications, radar and sensors as it can enable the wireless systems to achieve the optimum performance by electronically steering its maximum radiation towards the desired directions while forming nulls against interfering sources. Traditional smart antennas are, however, complicated in structure, bulky, power hungry and costly. For commercial applications, it is important to reduce the size, mass, power consumption and cost of smart antennas. Firstly, this paper presents an introduction to smart antennas, followed by a brief review of various types of low-cost smart antennas. Then, several recent examples of low-cost smart antennas reported by the author's group are presented and discussed. These antennas are capable of achieving electronic beam steering within a wide angular range, while having compact sizes, low power consumption and low cost. A detailed list of references is given in the end of this paper.
  • Luo, Q. et al. (2013). Antenna array elements for Ka-band satellite communication on the move. in: Antennas and Propagation Conference (LAPC), 2013 Loughborough. pp. 135-139. Available at: http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6711868&tag=1.
    Two dual-polarised reflectarray unit cells for the folded reflectarray and one linearly polarized array element for direct radiating array for Ka-band SatCom on the move are presented in this paper. All of these antenna unit cells have multi-layered structure and are designed for the smart array antenna with beams that can be steered to large scanning angles. The unit cells for reflectarray are designed to operate at 29.5-30.8GHz band for both transmitting and receiving while the antenna element for the direct radiating array is designed to have a dual band operation: 29.5-30.8GHz for transmitting and 19.7-21.0GHz for receiving. These three antenna elements have a low profile and the simulation results show that they exhibit good radiation performance over the required frequency bands.


  • Luo, Q. et al. (2019). Multibeam Dual-Circularly Polarized Reflectarray for Connected and Autonomous Vehicles. IEEE Transactions on Vehicular Technology.
    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.
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