3D FSS polarizer for millimeter‐wave antenna applications

In this article, a novel wideband polarizer is presented, to convert the linear polarization of a directive antenna into circular polarization. This innovative polarizer is based on a 3D frequency selective surface (FSS) and consists of an array of 4×4 metal axial‐mode helices. The proposed broadband polarizer operates in the 28 to 31 GHz frequency band. To demonstrate the principle, the 3D FSS is applied to a linearly polarized Yagi‐Uda antenna operating in the same millimeter‐wave frequency band. The measured and simulated results, by integrating the proposed 3D polarizer in front of the antenna, show that an axial ratio smaller than 3 dB is obtained over a wide bandwidth with gain enhancement.     

A novel millimeter‐wave dual‐band circularly polarized dielectric resonator antenna

In this article, a novel dual‐band circularly polarized (CP) dielectric resonator antenna (DRA) for millimeter‐wave (MMW) band is presented. The rectangular dielectric resonator with layered truncated corners is excited by a microstrip‐coupled cross‐slot. CP radiations in the lower band are realized by utilizing two quasi‐TE₁₁₁ modes operating at 21.7 GHz and 23.8 GHz, while CP radiations in the upper band are obtained by exciting a quasi‐TE₁₁₃ mode at 28.2 GHz. The dual‐band DRA is fabricated and measured. Due to the higher order mode, the average gain of the DRA in the upper band is about 3 dB higher than that in the lower band. The measured impedance bandwidths (|S₁₁| < ?10 dB) are 17.0% (20.5‐24.3 GHz) and 15.2% (26.1‐30.4 GHz), while the measured axial ratio (AR) bandwidths (AR < 3 dB) are 12.8% (21.2‐24.1 GHz) and 5% (27.4‐28.8 GHz). In addition, the peak gain values are 5 and 8 dBic.     

Metasurface cavity antenna for broadband high‐gain circularly polarized radiation

The article presents a microstrip patch (MSA) fed high gain circularly polarized metasurface cavity (CP‐MSC) antenna using a planar progressively‐phased‐reflector and a transmissive linear to circular polarization conversion metascreen. The bottom metasurface reflector consists of a remodeled Jerusalem cross to obtain 2π reflection phase variation. Linear to circular polarization conversion is achieved by a hexagonal ring based meta‐element with high transmission and bellow 3 dB axial ratio from 9.5 to 10.5 GHz. Simulated and measured results of assembled CP‐MSC antenna with MSA are in good agreement. The gain of the proposed cavity antenna with 10 and 10.5 GHz MSA are 14.9 and 16.3 dBi, respectively. Below 3 dB AR throughout the operating band denotes significant circular polarization performance of the proposed antenna.     

A high‐gain compact circularly polarized microstrip array antenna with simplified feed network

A broadband high‐gain circularly polarized (CP) microstrip antenna operating in X band is proposed. The circular polarization property is achieved by rotating four narrow band linearly polarized (LP) microstrip patch elements in sequence. Since the conventional series‐parallel feed network is not conducive to the miniaturization of the array, a corresponding simplified feed network is designed to realize the four‐way equal power division and sequential 90° phase shift. With this feed network, the impedance bandwidth (IBW) of the CP array is greatly improved compared with that of the LP element, while maintaining a miniaturized size. Then, parasitic patches are introduced to enhance the axial ratio bandwidth (ARBW). A prototype of this antenna is fabricated and tested. The size of proposed antenna is 0.93λ₀ × 0.93λ₀ × 0.017λ₀ (λ₀ denotes the space wavelength corresponding to the center frequency 10.4 GHz). The measured 10‐dB IBW and 3‐dB ARBW are 13.6% (9.8‐11.23 GHz), 11.2% (9.9‐11.07 GHz) respectively, and peak gain in the overlapping band is 9.8 dBi.     

Wideband circularly polarized leaky‐wave antenna with flat gain using printed ridge gap waveguide

A wideband beam scanning circularly polarized (CP) leaky‐wave antenna (LWA) at Ku band is proposed based on the printed ridge gap waveguide (PRGW). In this design, the printed technology is used to realize the ridge gap waveguide (RGW) structure, and a substrate layer is introduced to replace the air gap layer in conventional RGWs. The proposed beam scanning CP LWA has been fabricated. Measured results of the fabricated antenna prototype are carried out to verify the simulation analysis. It provides a wide impedance bandwidth of 22% ranging from 12 to 15 GHz while performing continuous frequency beam scanning from ?2° to +47°. Furthermore, it maintains the excellent CP characteristic with axial ratio (AR) below 1.5 dB and a flat gain response with variation less than 2 dB in the entire operation frequency band.     

Broadband circularly polarized printed falcate‐shaped monopole antenna

In this study, a simple broadband circularly polarized (CP) printed monopole antenna for S/C‐band applications is proposed. The CP antenna is composed of a falcate‐shaped monopole with a right‐angle trapezoid stub, then wide impedance and axial ratio (AR) bandwidths are achieved. By placing one rectangular split‐ring resonator above the stub for generating upper CP mode, both of impedance and CP performances are further improved. The proposed antenna is fabricated on a FR4 substrate and measured. The measured ?10‐dB impedance bandwidth is 107%, ranging from 2.4‐7.9 GHz, and the measured 3‐dB AR bandwidth is 94% (2.4‐6.6 GHz), covering the entire wireless local area network (WLAN) and WiMAX bands.     

Compact broadband circularly polarized slot‐patch antenna array

A simple design of circularly polarized slot‐patch antenna array with broadband operation and compact size is presented in this article. The antenna element consists of a circular slot and a semicircular patch, which are etched on both sides of a substrate. For the gain and axial ratio (AR) bandwidth enhancement, its array antennas are implemented in a 2 × 2 arrangement and fed by a sequential‐phase feeding network. The final 2 × 2 antenna array prototype with compact lateral dimension of 0.8λ_L × 0.8λ_L (λ_L is the lowest frequency within AR bandwidth) yielded a measured impedance bandwidth of 103.83% (2.76‐8.72 GHz) and a measured AR bandwidth of 94.62% (2.45‐6.85 GHz). The peak gain values within the AR bandwidth are from 2.85 to 8.71 dBi. A good agreement between the simulated and measured results is achieved. This antenna array is suitable for multiservice wireless systems covering WiMAX, WLAN and C‐band applications such as satellite communications.     

Broadband high‐gain slot grid array antenna for millimeter wave applications

A broadband high‐gain slot grid array antenna (SGAA) is proposed in this paper. Based on the electromagnetic complementarity principle, the metal elements in the traditional microstrip grid array antenna (GAA) are replaced by a wide slot element. Compared with the GAA, the proposed SGAA achieves broadband and high‐gain performance. In order to demonstrate this concept, a prototype with 9‐element SGAA is designed using wide slot radiation elements and fabricated on Rogers 5880 printed circuit board (PCB) substrates, which is fed by a 50 Ω coaxial probe. The measured and simulated results show a good agreement. The proposed SGAA achieves a measured peak gain of 14.8 dBi at 26.0 GHz, a 10‐dB impedance bandwidth from 22.2 to 28.5 GHz with a fractional bandwidth of 24.9%. These results indicate that the SGAA is with high performance and it is suitable for the fifth‐generation (5G) millimeter wave (mmW) wireless communication system.     

Design of a printed log‐periodic dipole array antenna with high gain for millimeter‐wave applications

In this article, a V‐band printed log‐periodic dipole array (PLPDA) antenna with high gain is proposed. The antenna prototype is designed, simulated, fabricated, and tested. Simulation results show that this antenna can operate from 42 to 82 GHz with a fractional impedance bandwidth of 64.5% covering the whole V‐band (50–75 GHz). The antenna has a measured impedance matching bandwidth that starts from 42 to beyond 65 GHz with good agreement between the experimental and simulated results. At 50 and 65 GHz, the antenna has a measured gain of 10.45 and 10.28 dBi, respectively, with a gain variation of 2.6 dBi across the measured frequency range. The antenna prototype exhibits also stable radiation patterns over the operating band. It achieves side‐lobe suppression better than 17.26 dB in the H‐plane and better than 8.95 dB in the E‐plane, respectively. In addition, the cross‐polarization component is 18.5 dB lower than the copolarization with front‐to‐back ratio lower than 24.1 dB in both E‐ and H‐planes across the desired frequency range. Based on a comparison of performance among the reported work in the literature, we can say that the proposed PLPDA antenna is a proper candidate to be used in many applications at V‐band frequency. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:185–193, 2015.     

3D printed dielectric lens for the gain enhancement of a broadband antenna

A novel 3D printed dielectric lens to enhance antenna gain parameters is presented. The lens is fabricated using a fused deposition method (FDM) which is a cost‐effective and an efficient 3D printing technique. Poly‐methyl methacrylate (PMMA) is used as a dielectric material due to its good RF properties. The thickness of the dielectric lens is 14 mm and provides a gain enhancement of up to 6.9 dBi over a wide frequency range. The dielectric lens is designed and computationally analyzed to demonstrate refractive index value close to zero. It has been shown that impedance‐matched near‐zero refractive index lens geometry eliminates strong reflections, and consequently enhances the antenna gain. A correlation is established between the individually, stacked unit cell layers and near‐zero refractive index cut‐off frequencies. The claim is substantiated through measured results using a broadband Vivaldi antenna. A gain enhancement of up to 6.9 dBi is recorded for the bandwidth from 13.5 to 24 GHz. An excellent correlation is reported between the measured and simulated results.     

3D‐printed cylindrical Luneburg lens antenna for millimeter‐wave applications

A 3D‐printed cylindrical Luneburg lens antenna working at 26 GHz is proposed in this article. The antenna consists of a feeding waveguide, a 3D‐printed cylinder, and a pair of printed metal grids which are stuck on the side faces of the cylinder. 3D‐printed structure ensures the convenience for processing and structural integrity of the Luneburg lens. Hole drilling technology is utilized for the design of the cylindrical lens. In the E‐plane, conversion of spherical waves into planar waves is achieved based on the gradient refractive index which is realized by the gradient equivalent relative dielectric constant. The main part of the lens contains a hole drilling region to realize the desired equivalent permittivity from 1.23 to 2, while another gradual‐thickness region realize the permittivity ranges from 1.23 to 1. H‐probe method is utilized for the optimization of the gradual‐thickness region in this article. And for the H‐plane, with the grids, H‐field distribution is optimized compared with the Luneburg lens antenna without the loading grids. Thus, the side lobe level (SLL) in H‐plane could be reduced. Meanwhile, a narrower half power beamwidth (HPBW) in H‐plane will be obtained due to the metal grids. Experiment results illustrate the feasibility and validity of the proposed 3D‐printed cylindrical Luneburg lens antenna.     

A dual‐broadband circularly polarized halved falcate‐shape printed monopole antenna

A halved falcate‐shape dual‐broadband circularly polarized printed monopole antenna is proposed. To generate the equal amplitude orthogonal modes, two halved falcate‐shaped antenna are used. Also, to provide the 90° phase difference between the two modes, three stubs are used in the ground plane of the antenna. The proposed antenna provides 22.6 (1.36–1.72 GHz) and 44.4% (5.25–8.25 GHz) 3 dB axial ratio bandwidth over the lower and upper bands, respectively. By adjusting the parameters of the antenna, the lower and upper band center frequencies can be tuned individually. The proposed antenna is fabricated, and results are compared with those of the simulation. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

A compact broadband coplanar waveguide fed circularly polarized printed monopole antenna with asymmetric modified ground plane

In this communication, a broadband circularly polarized (CP) monopole antenna with coplanar waveguide (CPW) feeding is proposed. It consists of a modified rectangular monopole, an asymmetric ground plane, a two‐linked inverted L‐shaped strips on the left CPW ground, and two rectangular horizontal slots in asymmetric CPW ground plane. The overall dimension is only 0.47λ _o × 0.47λ _o. The antenna prototype has been fabricated. The measured results indicate that a broad ?10 dB impedance bandwidth (IBW) of 107.5% (4.3 GHz, 1.85‐6.15 GHz) and a broad 3 dB axial ratio ARBW of 104.3% (4 GHz, 1.855‐5.9 GHz) can be achieved; the average realized gain is 2.3 dBi for the entire CP band. The proposed antenna is an attractive candidate for several wireless communication systems.     

一种紧凑型宽频带圆极化射频识别天线设计

针对现有圆极化天线难以同时满足宽频带和小型化应用需求的问题,面向全球超高频射频识别(RFID)读写应用,采用新型功分移相馈电网络、旋转短路辐射贴片和耦合贴片、馈电探针和短路探针,设计了一种紧凑型宽频带圆极化射频识别天线。测试结果表明,该天线回波损耗大于15dB的相对带宽为59%,轴比小于3dB的相对带宽为34%,在全球超高频RFID频段范围内,天线辐射增益大于2.7dBi,辐射方向十分对称和稳定,其半功率波束宽度大于101°,适用于宽角度范围读写;与现有圆极化天线的性能指标和结构相比,该天线的工作频段不仅能够覆盖全球超高频RFID频段,而且结构紧凑,有利于RFID系统的低成本设计和实施。     

Single‐fed broadband circularly polarized unidirectional antenna using folded plate with parasitic patch for universal UHF RFID readers

This research proposes a simple economical broadband circularly polarized antenna for universal ultra‐high frequency (UHF) RF identification (RFID) readers. The antenna utilizes a folded plate, a two‐corner truncated parasitic patch, and a ground plane. The folded plate, which is fabricated from one single plate, consists of a two‐corner truncated main patch, a wall patch, and a feed line, where the main patch is perpendicular to the wall patch, which is in turn perpendicular to the feed line. The folded plate enables currents to flow with a phase difference. The simulation results achieved an |S₁₁| < ?15 dB of 805–966 MHz (18% bandwidth), a 3‐dB axial ratio (AR) bandwidth of 834–962 MHz (14% AR bandwidth), and a gain higher than 8.6 dBic. The measured results obtained an |S₁₁| < ?15 dB of 806–970 MHz (18%), a 3‐dB AR bandwidth of 816–963 MHz (16%), and a gain greater than 7.8 dBic. The proposed antenna is applicable for universal UHF RFID readers as it covers the entire operating UHF RFID frequency range of 840–960 MHz. The parametric study and evolution of the proposed antenna are detailed in this research paper as well. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:575–587, 2016.     

A millimeter‐wave CMOS power amplifier design using high‐Q slow‐wave transmission lines

A three‐stage 60‐GHz power amplifier (PA) has been implemented in a 65 nm Complementary Metal Oxide Semiconductor (CMOS) technology. High‐quality‐factor slow‐wave coplanar waveguides (S‐CPW) were used for input, output and inter‐stage matching networks to improve the performance. Being biased for Class‐A operation, the PA exhibits a measured power gain G of 18.3 dB at the working frequency, with a 3‐dB bandwidth of 8.5 GHz. The measured 1‐dB output compression point (OCP_1dB) and the maximum saturated output power P_sat are 12 dBm and 14.2 dBm, respectively, with a DC power consumption of 156 mW under 1.2 V voltage supply. The measured peak power added efficiency PAE is 16%. The die area is 0.52 mm² (875 × 600 μm²) including all the pads, whereas the effective area is only 0.24 mm². In addition, the performance improvement of the PA in terms of G, OCP_1dB, P_sat, PAE and the figure of merit using S‐CPW instead of thin film microstrip have been demonstrated. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:99–109, 2016.     

Compact broadband circularly polarized Hook‐shaped microstrip antenna with DGS plane

A new antenna structure comprises of defected ground structure with hook‐shaped radiating patch designed for broad impedance bandwidth and axial ratio bandwidth is presented. In the proposed design, hook shaped radiating patch is orthogonally connected with printed strip patch and excited with 50Ω feed line at the upper side of the substrate. At the bottom side, a small rectangular slit is removed from the ground plane just underneath of radiating patch for better impedance matching along with broader bandwidth. The ground plane is defected by etching 3 symmetrical narrow slots for antenna compactness. The optimized antenna prototype is simulated, fabricated, and experimentally tested for far field and axial ratio performances in anechoic chamber. The measured results clearly show that it can yield an impedance bandwidth of approximately 27.60% centered at 2.17 GHz frequency and a 3‐dB AR bandwidth of approximately 25.20%. The measured gain range from 3 to 4.3 dBic in entire 3‐dB AR bandwidth with maximum gain of 4.30 dBic. The cross polar suppression was witnessed better than 15 dB along with wide beamwidth of 85°     

A high‐isolation dual‐polarized quad‐patch antenna fed by stacked substrate integrated waveguides for millimeter‐wave application

A high‐isolation dual‐polarized quad‐patch antenna fed by stacked substrate integrated waveguide (SIW) that is suitable for millimeter‐wave band is proposed in this paper. The antenna consists of a quad‐patch radiator, a two‐layer SIW feeding structure and two feeding ports for horizontal and vertical polarization. The two‐layer stacked SIW feeding structure achieves the high isolation between the two feeding ports (|S₂₁| ≤ ?45 dB). Based on the proposed element, a 1 × 4 antenna array with a simple series‐fed network is also designed and investigated. A prototype working at the frequency band from 38 to 40 GHz is fabricated and tested. The results indicate that the proposed antenna has good radiation performance at 38 GHz that covers future 5G applications.     

Polarizer superstrate and SRR‐loaded high‐gain dual band dual polarized waveguide slot array antenna

This article presents a high‐gain dual band dual polarized waveguide slot array antenna. Three split ring resonators (SRRs) are placed on the transverse plane of a slotted waveguide at uniform distance to achieve dual band response whereas a polarizer superstrate has been used to change the linear polarization of the lower band to circular polarization. Ansys HFSS 14.0 has been used for simulation and optimization purpose. Proposed antenna shows two 10 dB return loss bandwidth covering the frequency range 8.41‐8.88 and 9.31‐10.43 GHz, respectively. The lower band offers a circular polarization and upper band offers a linear polarization.     

Generation of Bessel beams with 3D‐printed lens

In this article, the 3D‐printed dielectric lens is proposed to generate Bessel beam in millimeter‐wave band. The dielectric lens is made of many square unit cells with the side length of a half wavelength. The unit cells with different thicknesses generate different insertion phase shift to the transmitted millimeter wave. The insertion phase distribution of the lens is calculated by comparing the phase distributions of the incident Gaussian beam and the desired output Bessel beam. Three types of lenses are simulated and fabricated using 3D printing technology with Nylon. The measured magnitude and phase distributions of zero‐order Bessel beam agree with the simulated results very well and the measured phase distributions of the first‐order Bessel beam carry orbital angular momentum.