Showing papers in "IEEE Transactions on Antennas and Propagation in 2016"

Eight-Port Orthogonally Dual-Polarized Antenna Array for 5G Smartphone Applications

Abstract: A dual-polarized hybrid eight-antenna array operating in the 2.6-GHz band (2550–2650 MHz) for 5G communication multi-input multi-output (MIMO) operation in the smartphone is presented. The proposed hybrid antenna array elements are symmetrically placed along the long edges of the smartphone, and they are composed of two different four-antenna array types (C-shaped coupled-fed and L-shaped monopole slot) that exhibit orthogonal polarization. Therefore, coupling between the two antenna array types can be reduced, and the MIMO system performances are enhanced. A prototype of the proposed eight-antenna array is manufactured and measured. A good impedance matching (10 dB return loss or better), desirable cross-polarization discrimination (better than 15 dB), and an acceptable isolation (better than 12.5 dB) are obtained. Envelope correlation coefficient and channel capacity are also calculated to evaluate the MIMO performances of the proposed antenna array.

A Novel Six-Band Dual CP Rectenna Using Improved Impedance Matching Technique for Ambient RF Energy Harvesting

Abstract: A novel six-band dual circular polarization (CP) rectenna for ambient radio frequency (RF) energy harvesting is presented. Due to the nonlinearity and complex input impedance of the rectifying circuit, the design of a multiband and/or broadband rectenna is always challenging and its performance can be easily affected by variation in the input power level and load. Therefore, an improved impedance matching technique is introduced, which is aimed to improve the performance of the rectifier with a varying condition. A broadband dual CP receiving antenna is proposed, which has a very wide bandwidth (from 550 to 2.5 GHz) and a compact size. An annular ring structure and a novel feeding technique are employed in order to reduce the size and improve the antenna performance. As a result, the proposed rectenna is the first design that covers six frequency bands, including part of the digital TV and most cellular mobile and WLAN bands in the U.K., while the optimal load range for a constant conversion efficiency is from 10 to 75 $\text{k}\Omega $ . The measured results show that the maximum harvested dc power of the rectenna in typical outdoor and indoor environments are 26 and 8 $\mu \text{W}$ , respectively; it can therefore be applied to a range of low-power wireless applications.

A 1-Bit $10 \times 10$ Reconfigurable Reflectarray Antenna: Design, Optimization, and Experiment

Abstract: An electronically reconfigurable reflectarray antenna (RRA) with $10\times10$ elements is presented with a detailed design procedure for an improved beam-scanning performance. The element, designed at Ku band using a simple patch structure with one PIN diode and two substrate layers, can be electronically controlled to generate two states with 180° phase difference and low reflection loss. A reflectarray prototype is fabricated and experimentally studied for proof of principle. The limitations of the small aperture size are analyzed in detail, and synthetic optimizations of both feed location and aperture phase distribution are used to improve the beam-scanning performance of the prototype. Experimental results agree well with the full-wave simulations, and scan beams within ${\pm}{50}^\circ$ range are obtained with a maximum aperture efficiency of 17.9% at 12.5 GHz. Consistent scan beams are obtained from 11.75 to 13.25 GHz. Furthermore, the versatile beam-forming capability of the RRA is also demonstrated by a wide-beam pattern synthesis. A fast beam-switching time ( $12\;\upmu \text{s}$ ) is theoretically analyzed and verified by the measurement.

Wideband RCS Reduction of a Slot Array Antenna Using Polarization Conversion Metasurfaces

Abstract: A new approach to reducing the monostatic radar cross section (RCS) and preserving the radiation characteristics of a slot array antenna by employing polarization conversion metasurfaces (PCMs) is presented in this communication. The PCM is arranged in a chessboard configuration consisting of fishbone-shaped element. It is placed on the surface of the slot array antenna. The characteristics and mechanism of the RCS reduction are analyzed. Simulated and experimental results show that the monostatic RCS reduction band of the antenna with PCM ranges between 6.0 and 18.0 GHz for normally impinging both $x$ - and $y$ -polarized waves. The radiation characteristics of the antenna are well preserved simultaneously in terms of the impedance bandwidth, radiation patterns, and realized boresight gains.

Arbitrary Power-Conserving Field Transformations With Passive Lossless Omega-Type Bianisotropic Metasurfaces

Abstract: We present a general theory for designing realistic omega-type bianisotropic metasurfaces (O-BMSs), unlocking their full potential for molding electromagnetic fields. These metasurfaces, characterized by electric surface impedance, magnetic surface admittance, and magnetoelectric coupling coefficient, were previously considered for wavefront manipulation. However, previous reports mainly considered plane-wave excitations, and implementations included cumbersome metallic features. In this paper, we prove that any field transformation that locally conserves real power can be implemented via passive and lossless meta-atoms characterized by closed-form expressions; this allows rigorous incorporation of arbitrary source and scattering configurations. Subsequently, we show that O-BMS meta-atoms can be implemented using an asymmetric stack of three impedance sheets, an appealing structure for printed circuit board fabrication. Our formulation reveals that, as opposed to Huygens’ metasurfaces, which exhibit negligible magnetoelectric coupling, O-BMSs are not limited to controlling the phase of transmitted fields, but can rather achieve a high level of control over the amplitude and phase of reflected fields. This is demonstrated by designing O-BMSs for reflectionless wide-angle refraction, independent surface-wave guiding, and a highly directive low-profile antenna, verified with full-wave simulations. This straightforward methodology facilitates the development of O-BMS-based devices for controlling the near and far fields of arbitrary sources in complex scattering configurations.

A Low-Profile High-Gain and Wideband Filtering Antenna With Metasurface

Abstract: A low-profile, high-gain, and wideband metasurface (MS)-based filtering antenna with high selectivity is investigated in this communication. The planar MS consists of nonuniform metallic patch cells, and it is fed by two separated microstrip-coupled slots from the bottom. The separation between the two slots together with a shorting via is used to provide good filtering performance in the lower stopband, whereas the MS is elaborately designed to provide a sharp roll-off rate at upper band edge for the filtering function. The MS also simultaneously works as a high-efficient radiator, enhancing the impedance bandwidth and antenna gain of the feeding slots. To verify the design, a prototype operating at 5 GHz has been fabricated and measured. The reflection coefficient, radiation pattern, antenna gain, and efficiency are studied, and reasonable agreement between the measured and simulated results is observed. The prototype with dimensions of 1.3 $\lambda_{0}\times1.3\ \lambda_{0}\times0.06\ \lambda_{0}$ has a 10-dB impedance bandwidth of 28.4%, an average gain of 8.2 dBi within passband, and an out-of-band suppression level of more than 20 dB within a very wide stop-band.

A 60-GHz Wideband Circularly Polarized Aperture-Coupled Magneto-Electric Dipole Antenna Array

Abstract: A novel circularly polarized (CP) aperture-coupled magneto-electric (ME) dipole antenna is proposed. The CP ME-dipole antenna fed by a transverse slot etched on the broad wall of a section of shorted-end substrate integrated waveguide (SIW) is convenient to integrate into substrates. An impedance bandwidth of wider than 28.8%, a wide 3-dB axial ratio (AR) bandwidth of 25.9%, and gain of $7.7 \pm 1.4\,{\text{dBic}}$ over the operating band are achieved. Additionally, since the CP radiation is generated by the combination of two orthogonal ME-dipole modes, the antenna element has stable unidirectional radiation patterns that are almost identical in two principle planes throughout the operating band, which is desirable to array applications. By employing the proposed CP ME-dipole as radiating elements, an $8 \times 8$ high-gain wideband planar antenna array is proposed for 60-GHz millimeter-wave applications. A fabrication procedure of using conductive adhesive films to bond all print circuit board (PCB) layers together is successfully implemented to realize the array design with a three-layered geometry, which has advantages of low costs and possibility of large-scale manufacture. The measured impedance bandwidth of the fabricated prototype is 18.2% for $\vert{\rm S}_{11}\vert . Because of the wide AR bandwidth of the new antenna element, a wide AR bandwidth of 16.5% can be achieved by this array without the use of sequential feed. Gain up to 26.1 dBic and good radiation efficiency of around 70% are also obtained due to the use of a full-corporate SIW feed network with low insertion loss at millimeter-wave frequencies.

Synthesis of Modulated-Metasurface Antennas With Amplitude, Phase, and Polarization Control

Abstract: An effective synthesis procedure for planar antennas realized with nonuniform metasurfaces (MTSs) excited by a point source is presented. This synthesis potentiates previous formulations by introducing a control of the amplitude of the aperture field while improving the polarization and phase performances. The class of MTS antennas we are dealing with is realized by using subwavelength patches of different dimensions printed on a grounded slab, illuminated by a transverse magnetic point source. These antennas are based on the interaction between a cylindrical surface-wave and the periodic modulation of the MTS, which leads to radiation through a leaky-wave (LW) effect. This new design method permits a systematic and simple synthesis of amplitude, phase, and polarization of the aperture field by designing the boundary conditions imposed by the MTS. The polarization control is based on the local value of the MTS anisotropy, the phase is controlled by the shape and periodicity of the modulation, and the amplitude is controlled by the local leakage attenuation parameter of the LW. The synthesis is based on analytical formulas derived by an adiabatic Floquet-wave expansion of currents and fields over the surface, which are simultaneously published in this journal issue. The effectiveness of the procedure is tested through several numerical examples involving realistic structures.

A Multibeam End-Fire Magnetoelectric Dipole Antenna Array for Millimeter-Wave Applications

Abstract: A novel substrate integrated waveguide (SIW)-fed end-fire magnetoelectric (ME) dipole antenna is proposed. The antenna consisting of an open-ended SIW and a pair of electric dipoles has a simple structure that can be integrated into substrates conveniently. Both the open-ended SIW and the electric dipoles are effectively radiated together. Excellent performance, including a bandwidth of 44%, symmetrical radiation patterns that are almost identical in two orthogonal planes, low backward radiation, low cross polarizations, stable gain of around 5 dBi, and wide beamwidth of around 110°, are also obtained. An $8 \times 8$ SIW Butler matrix is then designed. Modifications to the geometry of the matrix provide more spacing to locate SIW phase shifters and phase compensation structures with wide bandwidth. By employing the proposed end-fire ME-dipole antenna array and the $8 \times 8$ Butler matrix, an eight-beam antenna array is realized. The fabricated prototype demonstrates that wide bandwidth, stable radiation patterns with cross polarizations of less than −28 dB and gain varying from 9 to 12 dBi can be obtained. The proposed multibeam end-fire ME-dipole antenna array would be an attractive candidate for millimeter-wave wireless applications due to its good performance, ease of integration, and low fabrication cost.

Generation of OAM Beams Using Phased Array in the Microwave Band

Abstract: A system is proposed to generate vortex electromagnetic (EM) beams in the microwave band, which generates high-order vortex beams at the X-frequency band for the first time. First, the orbital angular momentum (OAM)-generating system is designed and the signal model based on the uniform circular array is presented. Subsequently, the mathematical model with array error contributions is established and, comprehensively, numerical simulations are conducted to analyze how amplitude and phase errors affect the radiation field and the EM vortex imaging. The experimental results validate that the proposed system can readily generate vortex beams of high quality, which are in agreement with the simulated results. The work paves the way to applications of OAM-carrying beams as well as a novel information-rich radar paradigm.

Frequency-Controlled Broad-Angle Beam Scanning of Patch Array Fed by Spoof Surface Plasmon Polaritons

Abstract: Frequency-controlled broadband and broad-angle beam scanning is proposed using a circular-patch array fed by planar spoof surface plasmon polaritons (SPPs). Here, a row of circularly metallic patches is placed near an ultrathin planar spoof SPP waveguide. When the SPP wave is transmitted through the waveguide, the circular patches are fed at the same time. Because of the phase difference fed to the patches, the proposed structure can realize wide-angle beam scanning from backward direction to forward direction as the frequency changes, breaking the limit of traditional leaky-wave antennas. Both numerical simulations and measured results demonstrate good performance of the proposed structure. It is shown that the scanning angle can reach 55° with an average gain level of 9.8 dBi. The proposed frequency scanning patch array is of great value in planar integrated communication systems.

Broadband Polarization Rotation Reflective Surfaces and Their Applications to RCS Reduction

Abstract: A novel broadband polarization rotation (PR) reflective surface (PRRS) with a high polarization conversion ratio (PCR) is proposed, which can reflect the linearly polarized incident wave with 90° PR. The proposed PRRS consists of a periodic array of square patches printed on a substrate, which is backed by a metallic ground. By connecting the square patch with the ground using two nonsymmetric vias, a 49% PR bandwidth is achieved with a high PCR of 96%, which is a significant improvement from the state-of-the-art 29% PR bandwidth. Moreover, the frequency responses within the operation frequency band are consistent under oblique incident waves. Furthermore, another ultra-wideband PRRS with a periodic array of quasi-L-shaped patches is proposed, which increases the PR bandwidth further to 103%. In addition, the designed PRRS is applied to wideband radar cross section (RCS) reduction. Different arrangements of the unit cells of the PRRS are proposed and their effects on RCS reduction are investigated. To validate the simulation results, prototypes of the PRRSs are fabricated and measured. The measured results are in good agreement with the simulated ones.

60-GHz Dual-Polarized Two-Dimensional Switch-Beam Wideband Antenna Array of Aperture-Coupled Magneto-Electric Dipoles

Abstract: A dual-polarized aperture-coupled magneto-electric (ME) dipole antenna is proposed. Two separate substrate-integrated waveguides (SIWs) implemented in two printed circuit board (PCB) laminates are used to feed the antenna. The simulated $- {10}$ -dB impedance bandwidth of the antenna is 21% together with an isolation of over 45 dB between the two input ports. Good radiation characteristics, including almost identical unidirectional radiation patterns in two orthogonal planes, front-to-back ratio larger than 20 dB, cross-polarization levels less than $- {23}\;{\text{dB}}$ , and a stable gain around 8 dBi over the operating band, are achieved. By employing the proposed radiating element, a ${2} \times {2}$ wideband antenna array working at the 60-GHz band is designed, fabricated, and tested, which can generate two-dimensional (2-D) multiple beams with dual polarization. A measured $- {10}\;\text{dB}$ impedance bandwidth wider than 22% and a gain up to 12.5 dBi are obtained. Owing to the superiority of the ME dipole, the radiation pattern of the array is also stable over the operating frequencies and nearly identical in two orthogonal planes for both of the polarizations. With advantages of desirable performance, convenience of fabrication and integration, and low cost, the proposed antenna and array are attractive for millimeter-wave wireless communication systems.

Dual-Band Base Station Array Using Filtering Antenna Elements for Mutual Coupling Suppression

Abstract: This paper presents a novel dual-band base station antenna array using filtering antenna elements for size miniaturization. It consists of two $1 \times 6$ subarrays arranged side by side, which are designed for Digital Cellular System (DCS: 1710–1880 MHz) and Wideband Code Division Multiple Access (WCDMA: 1920–2170 MHz) applications. The two subarrays are composed of filtering antenna elements with high in-band radiation efficiency and out-of-band radiation rejection levels. The radiation of the DCS subarray is suppressed in the WCDMA band and vice versa. Mutual coupling between the two subarrays, therefore, can be suppressed and high isolation can be obtained with reduced subarray spacing. For demonstration, a dual-band filtering antenna array is designed and fabricated. The overall width of the array is only 206 mm, which is much narrower than that of typical industrial products ( $\sim 290$ mm). An isolation of 35 dB is obtained between the two subarrays without any decoupling network. The measured antenna gains are about 14.2 and 14.5 dBi for DCS and WCDMA bands, respectively, and the 3-dB beamwidths of the horizontal radiation patterns are 65° ± 5°. In addition, null filling below the main beam in the vertical radiation patterns is realized by elaborately designing a feed network to manipulate the output magnitude and phase of each array element. The proposed array is suitable for potential base station applications.

Mutual Coupling Reduction by Novel Fractal Defected Ground Structure Bandgap Filter

Abstract: This paper presents a novel fractal defected ground structure (FDGS) to reduce mutual coupling between coplanar spaced microstrip antenna elements. The structure of the proposed FDGS is studied. Bandgap characteristic of second and third iterative FDGS is achieved. The second and third iterative FDGSs are used to reduce mutual coupling between microstrip antenna elements. Mutual coupling reduction performance of third iterative FDGS is better than that of second iterative FDGS. And dimension of FDGS can be decreased by using higher level iterative FDGS. The third iterative FDGS is fabricated and measured. Simulated and measured results both show that more than 35-dB mutual coupling reduction is obtained by using the third iterative FDGS. Moreover, the envelope correlation of antenna elements with FDGS is quite smaller than that of antenna elements without FDGS.

Ultrawideband Array With 70° Scanning Using FSS Superstrate

Abstract: We present a wideband tightly coupled dipole array (TCDA) with integrated balun and a novel superstrate consisting of printed frequency selective surface (FSS) for wide angle scanning. Although previous TCDAs have had decent scanning performance up to ±60°, use of dielectric superstrates are usually required, resulting in additional cost and fabrication complexity. In this paper, we replace the bulky dielectric layer(s) with periodic printed elements and yet achieve wide-angle and wideband impedance matching. The proposed approach provides superior performance of 6.1:1 bandwidth (0.5–3.1 GHz) with VSWR $E$ plane, ±70° in $D$ plane and ±60° in $H$ plane. The FSS, radiating dipoles and feed lines are designed and fabricated on the same vertically oriented printed circuit board, resulting in a low-cost and lightweight structure as compared to other low profile arrays. Measured scanning patterns of a $12 \times 12$ prototype are presented, showing good agreement with simulations.

Leaky-Wave Antennas Based on Noncutoff Substrate Integrated Waveguide Supporting Beam Scanning From Backward to Forward

Abstract: In this paper, we propose an approach to realize substrate integrated waveguide (SIW)-based leaky-wave antennas (LWAs) supporting continuous beam scanning from backward to forward above the cutoff frequency. First, through phase delay analysis, it was found that SIWs with straight transverse slots support backward and forward radiation of the $-1$ -order mode with an open-stopband (OSB) in between. Subsequently, by introducing additional longitudinal slots as parallel components, the OSB can be suppressed, leading to continuous beam scanning at least from $-40^\circ$ through broadside to 35°. The proposed method only requires a planar structure and obtains less dispersive beam scanning compared with a composite right/left-handed (CRLH) LWA. Both simulations and measurements verify the intended beam scanning operation while verifying the underlying theory.

Low Side-Lobe Substrate-Integrated-Waveguide Antenna Array Using Broadband Unequal Feeding Network for Millimeter-Wave Handset Device

Abstract: A low side-lobe substrate-integrated-waveguide (SIW) antenna array is presented at the 28-GHz band using broadband unequal feeding network for millimeter-wave (mm-wave) handset devices. The ground-plane size of the proposed antenna is fixed to half of the size of the Samsung Galaxy Note 4. The antenna array has been implemented with a multilayer structure created by stacking three substrates and a copper plate. An 8-way SIW feeding network with broadband 4-stage T-junction dividers and a cavity-backed antenna are investigated to obtain broadband performance. The proposed unequal T-junction dividers with phase compensation are introduced and designed for various output ratios. Applying Taylor beam-pattern synthesis in the 8-way SIW feeding network, low side-lobe performance is achieved. The measured result of the fabricated antenna has 2.3 GHz bandwidth within $\text{S}_11\,{ . The fabricated antenna can be performed with a gain up to 13.97 dBi with a low cross-polarization and symmetrical fan beam radiation patterns with low side-lobe levels. Most of the measured results are validated with the simulated results. The proposed antenna array provides low cost, broadband performance, and good radiation performances with low side-lobe levels for mm-wave handset devices.

Dual-Polarized Filtering Antenna With High Selectivity and Low Cross Polarization

Abstract: This paper presents a dual-polarized patch antenna with quasi-elliptic bandpass responses. The proposed antenna is mainly composed of a feeding network, a driven patch, and a stacked patch, with its entire height being $0.09\lambda $ . The feeding network consists of two orthogonal H-shaped lines that coupled to the driven patch, each for one polarization. The elaborately-designed feeding lines not only ensure a sharp roll-off rate at the lower band edge, but also help to achieve low cross polarization and high isolation between two feeding ports. On the other hand, the upper stacked patch provides improved suppression levels at the upper stopband and also an enhanced gain within passband. Consequently, a compact dual-polarized antenna with satisfying filtering performance is obtained, without using extra filtering circuits. For demonstration, an antenna is designed to fit the specification of LTE band (2.49–2.69 GHz). The implemented antenna achieves an average a gain of 9 dBi, a cross-polarization ratio of 29 dB, an isolation of 35 dB within LTE band. The out-of-band suppression level is more than 40 dB within the 2G and 3G frequency bands from 1.71–2.17 GHz. It can be used as the antenna elements in multiband base station antenna arrays to reduce the mutual coupling.

Design and Fabrication of a High-Gain 60-GHz Corrugated Slot Antenna Array With Ridge Gap Waveguide Distribution Layer

Abstract: A wideband high-gain high-efficiency $16 \times 16$ -element slot antenna array is presented for 60-GHz band applications. The antenna is designed based on gap waveguide technology. The most important advantage of using this technology is its ability to decrease complexity and cost of fabrication because there is no requirement of electrical contact between the three layers of the antenna structure. The three layers are a corrugated metal plate with radiating slots, a subarray cavity layer, and a ridge gap waveguide (RGW) feed network layer. The corporate feed network is realized by a texture of pins and guiding ridges in a metal plate. Also, in order to excite the antenna with a standard V-band rectangular waveguide, a transition from RGW to WR-15 is designed. The radiating elements, corrugations, cavity layer, power dividers, and transition are designed and optimized to suppress the reflection coefficient at the input WR-15 port over the desired frequency range from 57 to 66 GHz. Finally, the $16 \times 16$ -element slot antenna array is fabricated by the standard milling technology. The measured results demonstrate about 16% of reflection coefficient bandwidth ( $\vert S_{11}\vert dB) covering the 56–65.7-GHz frequency range, and the measured gain is larger than 32.5 dBi over the band with more than 70% antenna efficiency.

Wideband Linear-to-Circular Polarization Converters Based on Miniaturized-Element Frequency Selective Surfaces

Abstract: We introduce a new technique for designing wideband polarization converters based on miniaturized-element frequency selective surfaces (MEFSSs). The proposed structure is a two-dimensionally anisotropic periodic structure composed of arrays of subwavelength capacitive patches and inductive wire grids separated by thin dielectric substrates. The structure is designed to behave differently for field components of the two orthogonal polarizations and transmits a circularly polarized wave once illuminated by a linearly polarized plane wave. Using equivalent circuit models for MEFSSs, a synthesis procedure is developed that can be used to design the polarization converter from its required bandwidth and center frequency of operation. Using this procedure, a prototype of the proposed polarization converter operating within the X-band is designed, fabricated, and experimentally characterized using a free-space measurement system. The measurement results confirm the theoretical predictions and the design procedure of the structure and demonstrate that the proposed MEFSS-based polarization converter operates in a wide field of view of $\pm45^{\circ}$ with a fractional bandwidth of 40%.

Stacked Patch Antenna With Dual-Polarization and Low Mutual Coupling for Massive MIMO

Abstract: Massive multiple input and multiple output (MIMO) has attracted significant interests in both academia and industry. It has been considered as one of most promising technologies for 5G wireless systems. The large-scale antenna array for base stations naturally becomes the key to deploy the Massive MIMO technologies. In this communication, we present a dual-polarized antenna array with 144 ports for Massive MIMO operating at 3.7 GHz. The proposed array consists of 18 low profile subarrays. Each subarray consists of four single units. Each single antenna unit consists of one vertically polarized port and one horizontally polarized port connected to power splitters, which serve as a feeding network. A stacked patch design is used to construct the single unit with the feeding network, which gives higher gain and lower mutual coupling within the size of a conversional dual-port patch antenna. Simulation results of the proposed single antenna unit, sub-array, and Massive MIMO array are verified by measurement.

Compact Multimode Multielement Antenna for Indoor UWB Massive MIMO

Abstract: In this paper, we present a concept for a compact ultra-wideband multielement antenna (MEA) for massive MIMO indoor base stations. The antenna concept is based on the simultaneous excitation of different characteristic modes on each element of the MEA. This enables an effective 484 port antenna using only 121 physical antenna elements. Thereby, a size reduction of 54% compared to a generic MEA based on crossed dipoles is achieved. The antenna operates in the ultra-wide frequency band of 6–8.5 GHz with a reflection coefficient of $\text{s}_{\text{ii}} and the interelement and intraelement mutual coupling of the antenna ports is $\text{s}_{\text{ji}} \le -\text{20 dB}$ .

CubeSat Deployable Ka-Band Mesh Reflector Antenna Development for Earth Science Missions

Abstract: CubeSats are positioned to play a key role in Earth Science, wherein multiple copies of the same RADAR instrument are launched in desirable formations, allowing for the measurement of atmospheric processes over a short evolutionary timescale. To achieve this goal, such CubeSats require a high-gain antenna (HGA) that fits in a highly constrained volume. This paper presents a novel mesh deployable Ka-band antenna design that folds in a 1.5 U $(10\times 10 \times 15 \,\text{cm}^{3})$ stowage volume suitable for 6 U $(10\times 20 \times 30 \,\text{cm}^{3})$ class CubeSats. Considering all aspects of the deployable mesh reflector antenna including the feed, detailed simulations and measurements show that 42.6-dBi gain and 52% aperture efficiency is achievable at 35.75 GHz. The mechanical deployment mechanism and associated challenges are also described, as they are critical components of a deployable CubeSat antenna. Both solid and mesh prototype antennas have been developed and measurement results show excellent agreement with simulations.

Varactor-Tunable Second-Order Bandpass Frequency-Selective Surface With Embedded Bias Network

Abstract: A varactor-tunable second-order bandpass frequency-selective surface (FSS) for microwave frequencies is presented in this article. The FSS is composed of three stacked metallic layers. The wire grid in each layer in combination with metallic vias provides the bias for the varactors. This configuration eliminates the need for a dedicated bias network for the varactors, and thus avoids undesirable responses associated with the added bias grid. An equivalent circuit model together with an analytical design method is provided to simplify the design procedure of the FSS. The performance of the proposed structure is experimentally validated in a parallel-plate waveguide setup. Measurements show that by changing the varactor capacitance from 0.12 to 0.38 pF, the center frequency of the filter is tuned from 5.2 to 3.7 GHz with a consistent fractional bandwidth of 9% and with an insertion loss between 3 and 6 dB.

Gain-Enhanced Patch Antennas With Loading of Shorting Pins

Abstract: A new gain-enhanced patch antenna with loading of shorting pins is proposed in this paper. Four metallic pins are symmetrically placed in the two diagonals of a square patch resonator to electrically short the patch and ground plane. These shorting pins tremendously perturb the field distribution beneath the patch due to their shunt inductive effect. As these four pins are moved outward along the two orthogonal diagonals away from the center, their influence on the field distribution over the patch is strengthened to gradually raise its dominant mode, i.e., TM010 mode, resonant frequency as the pin-to-pin spacing is enlarged. At a fixed resonant frequency, the overall area of this proposed patch antenna with four pins results to be increased. As such, its radiation directivity or gain gets to be enhanced due to the enlarged antenna area. After extensive analysis is executed, two square patch antennas with and without loaded pins are designed and fabricated. The simulated and measured results agree with each other, and they have evidently demonstrated that the radiation directivity can be enhanced up to 11.0 dBi, or about 2.9 dB increment, by virtue of the proposed approach.

Dual-Band Patch Antenna With Filtering Performance and Harmonic Suppression

Abstract: A novel design of a dual-band antenna with integrated filtering performance is proposed. A low-profile aperture-coupled U-slot patch antenna is employed for the dual-band operation with a uniform polarization, which is fed by a dual-mode stub-loaded resonator (SLR). The U-slot patch works as a dual-mode resonator of the dual-band filter as well as the radiation element. The odd- and even-modes of the SLR are coupled and tuned with the U-slot patch, generating two second-order operation bands at 3.6 and 5.2 GHz. Compared with the traditional patch antenna, the proposed antenna exhibits improved bandwidth and frequency selectivity. In addition, the bandwidths can be controlled by adjusting the coupling strength between the SLR and the patch. Furthermore, the higher order harmonics can be suppressed over a broadband without increasing the footprint of the design. The measured and simulated results agree well with each other, showing excellent performance in terms of impedance matching, bandwidths, second-order filtering, out-of-band rejection, cross-polarization discrimination, and gains at both the bands.

Dual-Band and Dual-Circularly Polarized Shared-Aperture Array Antennas With Single-Layer Substrate

Abstract: This paper presents a new approach to implement planar shared-aperture dual-band dual-circular polarization (CP) array antennas. The antennas can be fabricated on a single-layer substrate and extended to a larger array easily. In this approach, each array element is obtained by connecting two patches working at different frequencies directly. To form arrays with higher gain, two kinds of feed networks are described, which can be applied in systems where narrowband and wideband are needed, respectively. One is using the conventional feed network and the other is using the sequential rotation technique to further improve the CP axial ratio (AR) performance. Two prototype arrays with $4 \times 4$ elements are fabricated and tested in $X/Ku$ bands. Experimental results show that good CP characteristics are obtained, which agree well with the simulation results. For the first narrow-band prototype array, the 3-dB AR bandwidth is around 1.5% for both bands. For the second array using the sequential rotation technique, the bandwidth of return loss and AR are wider. In the lower band centered at 12.1 GHz, the ${-}10\hbox{-}\text{dB}$ return loss bandwidth is 8.3% and the 3-dB AR bandwidth is 14.2% [right-hand CP (RHCP)]; in the higher band centered at 17.4 GHz, the corresponding data are 18.9% and 14.9% [left-hand CP (LHCP)], respectively.

A Double-Layer Transmitarray Antenna Using Malta Crosses With Vias

Abstract: A novel transmitarray element consisting of only two layers of modified Malta crosses printed on a dielectric substrate is proposed, and vias are employed to augment the transmission magnitude and enhance its phase shift range. A prototype transmitarray with a circular aperture of 338 mm in diameter is then designed, fabricated, and tested to validate the proposed design. The simulation and measurement results show good radiation characteristics with measured gain of 33.0 dBi at 20 GHz and aperture efficiency of 40%. The proposed element considerably simplifies the complexity of a transmitarray, reducing its thickness, mass, and cost.

A Novel Simple and Compact Microstrip-Fed Circularly Polarized Wide Slot Antenna With Wide Axial Ratio Bandwidth for C-Band Applications

Abstract: This communication presents a design of a new compact circularly polarized (CP) slot antenna fed by a microstrip feedline. The 3-dB axial ratio band can be achieved by simply protruding a horizontal stub from the ground plane toward the center of the wide slot (WS) and then feeding the WS with a microstrip feedline positioned to the side of the WS, underneath the protruded stub. The feedline and metallic stub are perpendicular to each other, and they resemble a T shape when viewed from the top. The proposed antenna is fabricated with an area of $25 \times 25\;{\rm mm}^{2}$ . Measurement results show that the antenna attains an ${\rm S}_{11}\le-10\;{\rm dB}$ impedance matching bandwidth of 90.2%, from 3.5 to 9.25 GHz, and a broadband 3 dB-AR bandwidth of 40%, ranging from 4.6 to 6.9 GHz. A peak gain of 0.8–4.5 dBi is achieved within the AR band. The proposed antenna is suitable for circular polarization applications in C band.