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Reconfigurable intelligent surface (RIS) is anticipated to augment the performance of beyond fifth-generation (B5G) and sixth-generation (6G) networks by intelligently manipulating the state of its components. Rather than employing reflective RIS for aided communications, this paper proposes an innovative transmissive RIS-enabled transceiver (TRTC) architecture that can accomplish the functions of traditional multi-antenna systems in a cost-effective and energy-efficient manner. First, the proposed network architecture and its corresponding transmission scheme are elaborated from the perspectives of downlink (DL) and uplink (UL) transmissions. Then, we illustrate several significant advantages and differences of TRTC compared to other multiantenna systems. Furthermore, the downlink modulation and extraction principle based on time-modulation array (TMA) is introduced in detail to tackle the multi-stream communications. Moreover, a near-far field channel model appropriate for this architecture is proposed. Based on the channel model, we summarize some state-of-the-art channel estimation schemes, and the channel estimation scheme of TRTC is also provided. Considering the optimization for DL and UL communications, we present numerical simulations that confirm the superiority of the proposed optimization algorithm. Lastly, numerous prospective research avenues for TRTC systems are delineated to inspire further exploration. [ABSTRACT FROM AUTHOR]

Holographic multiple-input multiple-output (HMIMO) systems constitute a promising technology in support of next-generation wireless communications, thus paving the way for a smart programmable radio environment. However, despite their significant potentials, further fundamental issues remain to be addressed, such as the acquisition of accurate channel information. Indeed, the conventional angular-domain channel representation is no longer adequate for characterizing the sparsity inherent in HMIMO channels. [ABSTRACT FROM AUTHOR]

This paper introduces a multi-resonance feed structure to control the input impedance for achieving a dual wide-impedance bandwidth technology. According to the simulation, the bandwidth of the proposed antenna structure was approximately 330 MHz with the lower band (ranging from 670 MHz to 1000 MHz) and 1210 MHz with the higher band (ranging from 1670 MHz to 2880 MHz) under a 3:1 voltage standing wave ratio. Moreover, the average efficiency was significantly increased from 26.6% (reference) to 46.5% (proposed) at the lower band (ranging from 550 MHz to 1020 MHz) and even higher at the higher band, increasing from 15.5% (reference) to 61.2% (proposed) (ranging from 1400 MHz to 3000 MHz). The radiation pattern also showed satisfactory antenna radiation performance. This proposed technology has the advantage of achieving input impedance matching more easily and covers most fifth-generation (5G) NR operating bands in FR1 (n1, n3, n5, n8, n25, n30, n41, n66), indicating its promising application to 5G communication.

This paper presents the methodology followed for the design of a quad-ridged flared horn (QRFH) feed for the VLBI Global Observing System (VGOS) antennas. The study demonstrates the potential undesired effects caused by the presence of non-fundamental modes at the throat of the horn antenna, and how they can be avoided following some design considerations. The approach consists of a separate design of the feeding transition and the flared section of the horn, and it can be extrapolated to other implementations. Firstly, the geometry of the coaxial to quad-ridged waveguide (QRWG) transition is defined. The proposed design technique ensures negligible propagation of higher order modes at the waveguide interface. Secondly, the ridges and sidewall profiles of the flared part are optimized to achieve the desired performance in terms of input reflection and aperture efficiency on the VGOS 13.2-meter displaced-axis two-reflector radio telescope. Following the optimized design, five QRFH antenna units have been manufactured and tested, all showing reflection coefficients better than -10 dB and predicted aperture efficiencies better than 55 % in the band from 2.2 to 14 GHz. The excellent agreement between simulations and experimental results demonstrates the validity of the proposed methodology.

In this letter, a method named double phase-compensation is first proposed to drastically reduce the profile of traditional transmitarray antenna (TA) based on ray tracing principle. Previously, the folded transmitarray antenna (FTA) has realized the profile reduction to 1/3. It is known that there is an urgent need for more compact antenna nowadays. If the FTA's profile is further reduced, the focus-to-diameter (F/D) ratio should be decreased which will result in obvious aperture efficiency reduction. To further reduce the FTA's profile with unchanged F/D for keeping high efficiency, the extra phase compensation is innovatively added on the FTA's reflector. Hence the TA's profile can be reduced to lower than 1/3 and be flexibly adjusted as needed. Three FTA models are designed for comparison and demonstration. The simulation and experimental results indicate that the extra phase compensation successfully alleviates the efficiency drop caused by directly reducing the profile of FTA. Significantly, the method provides an efficient approach to further improve the compactness of antenna system and is very meaningful for TA miniaturization. [ABSTRACT FROM AUTHOR]

In this letter, a differential antenna with high common-mode (CM) rejection is proposed, which consists of dual improved half-mode substrate-integrated waveguide (HMSIW) cavities and a square substrate-integrated waveguide (SIW) coupling-feeding cavity (CFC). First, a novel approach to enhance the differential-mode (DM) radiation performance by flipping the symmetrical TE201 cavity is presented. The two E-field components excited from reversed magnetic walls are superposed in phase. Then, a pair of improved HMSIW cavities with oppositely magnetic walls is adopted to suppress the CM and enhance the uniformity of the radiation pattern on E- and H-planes. The square TE202 CFC with four coupling holes is discussed for the DM excitation. Meanwhile, it is equivalent to a band-stop filter further to improve CM rejection under CM excitation. The four perturbation holes in the CFC for the adjacent E-field isolation are analyzed. Finally, the proposed antenna is fabricated. The measured and simulated results show good agreement. The high CM rejection (27.3 dB) is achieved through the two-step rejection of the radiator and CFC. [ABSTRACT FROM AUTHOR]

In practice, the broadband feeding network on the back side of an antenna can have a nonnegligible effect on the antenna's back radiation due to the feeding network's radiation contribution. Thus, a back-radiation cancellation scheme is proposed by co-designing the antenna and its feeding network to solve this problem. The antenna and its feeding network can be viewed as a two-element array. Their radiation toward the antenna's backward direction can cancel each other when both have equal amplitude and opposite phases along the back direction. A differential fed dielectric resonator antenna (DRA) through a rat-race coupler (${180}^\circ $ hybrid coupler) and a T-shaped broadband differential feeding network are compared and analyzed to verify the proposed scheme. In addition, a $1\!\times\!4$ DRA array with a T-shaped broadband differential feeding network in a previous work (where the feeding network's radiation effect on the back side was overlooked) is used for experimental validation of the proposed scheme. Simulations and measurements demonstrate significant back-radiation suppression than the ideal differential feeding network. [ABSTRACT FROM AUTHOR]

A broadband circularly polarized metasurface antenna with low radar cross section (RCS) is proposed. Four metasurface elements are arranged orthogonally in a 2×2 array and fed with a 90° phase difference to achieve circular polarization radiation. Each metasurface element is a nonuniform subarray of 4×4 metallic patches. Attributed to the nonuniform property of the metasurface element, two characteristic modes with different resonant frequencies but with similar surface current distributions are formed. By optimizing the geometric parameters of the nonuniform element, the two modes are merged with each other, resulting in bandwidth (BW) broadening of the proposed antenna. Simulated and measured results show that the designed antenna has a −10 dB impedance BW of 49.60%, 3 dB axial ratio BW of 33.13%, and peak gain of 13.17 dBic. Moreover, the RCS reduction is higher than 6 dB in the entire operation frequency band. Additionally, the antenna has a low profile of 0.08λ (λ is the free-space wavelength at an operation frequency of 8.25 GHz). [ABSTRACT FROM AUTHOR]

This letter proposes a wideband high-gain left-/right-handed circularly polarized (L/RHCP) patch antenna using a mirror flip approach. The antenna consists of a ring-shaped metal square patch with truncated corners and a two-port feed network in a simple construction. The dual-port feed and truncated corners realize a wide axial ratio bandwidth (ARBW). Moreover, the L/RHCP is easily changed by mirroring the flipped feed network without redesigning the overall topology. The impedance bandwidth (IBW) (S11 < −10 dB) of 58.6% (2.97–5.43 GHz)/47.6% (2.8–4.55 GHz) and 3 dB ARBW of 44.3% (3.09–4.85 GHz)/34.6% (2.96–4.2 GHz) are achieved for L/RHCP antenna. Finally, two prototypes were fabricated and measured for validation. The proposed L/RHCP patch antenna was found to be insensitive to feed position. The IBWs of the proposed LHCP and RHCP antennas showed a wide degree of overlap. The low profile, high gain, small size, and higher robustness of our antenna than traditional patch antennas demonstrate the advantageous of our design for communication, power transmission, and medical fields. [ABSTRACT FROM AUTHOR]

This brief presents a high-efficiency shared-aperture multiple antenna system. Unlike general shared-aperture antennas, the proposed antenna system with the size of $0.384 {\times } 0.384 {\times } 0.171 {\mathrm {\lambda }} ^{3}$ makes high reuse the aperture in the two respective frequency bands, and the antenna structures of the two bands can each generate positive mutual enhancement for their radiating characteristics in the two bands. The flat Luneburg lens can realize beam steering capability for mm-wave antenna from 25.5 to 29.5 GHz with the gain of 19.3 dBi and improve the wide-angle scanning matching impedance for the Sub-6 GHz antenna from 3.2 to 3.45 GHz with the gain of 6.2 dBi. Meanwhile, as the radiating patch of the Sub-6 GHz antenna, the meta-surface can reduce the focal distance of the lens and maintain the high gain of the mm-wave antenna. Hence, a compact antenna system can achieve beam steering capabilities (up to 112°) in the Sub-6 GHz band and (up to 56°) mm-wave band with high gain, respectively. And the port isolation of the proposed antenna system between two frequency bands is generally better than 25 dB and even up to 40 dB at the Sub-6 GHz band. As reported in the simulated and measured results in a linear array, the antenna system shows good radiating performance with a dual-polarization state. Hence, the proposed multiple antenna system is a good candidate for 5G applications because of the high-efficiency, beam steering with high gain and full 5G band. [ABSTRACT FROM AUTHOR]

A wide variety of desirable antenna beam patterns can be synthesized by optimal excitation and phasing of the HE11 and HE12 modes in scalar corrugated feedhorns. However, the bandwidth of such two-mode horns is often limited by modal dispersion. In this paper we introduce a class of low dispersion, two-mode feedhorns that can operate, in some cases, over operating bandwidths of 40-50%. We provide example designs that include horns with high coupling efficiency to: 1) a pure HE11 mode for single-mode excitation of corrugated pipe transmission lines; 2) a LG00 and LG02 combination for radiometry, with narrow beams; 3) a pure Laguerre Gaussian LG00 mode for quasi-optical instrumentation with constant phase centers; 4) a constant gain antenna for uniform illumination with frequency; 5) Airy patterns or “top hat” patterns for radar or communications applications, designed to maximize aperture efficiencies when used with larger reflect or lens antennas. More generally, we show methods to generate and phase multiple ${\text{HE}}_{1n}$ modes, to synthesize symmetric output beams at any desired frequency or gain.

Because the width of antenna elements exceeds half of the air wavelength, resulting in too large element spacing, the scanning angle of traditional endfire circularly polarized (CP) antenna array is usually less than 60°. In order to solve the above problem, a CP quasi-Yagi antenna element is proposed in this letter, whose width is less than half of the air wavelength. Further, an 1 × 8 endfire CP antenna array is designed. Because the element spacing is about half a wavelength, the scanning angle of the proposed endfire CP antenna array can reach 60°. Moreover, the axial ratios of all beams are less than 3 dB in the scanning angle range of (0°, 60°). The final measured results are basically consistent with the simulated results [ABSTRACT FROM AUTHOR]

Beam-steerable Risley prism antennas (RPAs) typically require at least three separated components, including a stationary feed source and two independently rotatable gradient-phase-shift surfaces. In this letter, we propose a simplified two-component RPA configuration that employs a gradient-phase feed source and a gradient-phase transmitarray. The proposed configuration is validated by a novel circularly polarized (CP) RPA in the $K$ -band through simulations. It consists of an $\text{8}\times \text{8}$ gradient-phase CP patch array feed and a 10 cm diameter CP transmitarray. The total height of this system is 14.6 mm, which is less than one wavelength at 19 GHz. A left-hand CP beam scan from broadside to $\text{55}^\circ$ is demonstrated. The simulated RPA achieved a broadside directivity of 22.3 dBi at 19 GHz (42.7% aperture efficiency) and a 3 dB directivity bandwidth of 9.2%. [ABSTRACT FROM AUTHOR]

We analyze the secrecy performance of a wireless system with limited feedback, where the channel state information (CSI) is imperfectly known at a multi-antenna source. In order to mitigate the adverse effects of limited feedback and eavesdropper attack on secrecy transmission, we propose the quantized secrecy precoding (QSP) oriented adaptive transmit antenna selection (ATAS) scheme denoted as QSP-ATAS, where the transmit antennas with poor channel quality are inactivated by adjusting the channel gain threshold. Besides, the conventional single transmit antenna selection (STAS) scheme without secrecy precoding (NSP-STAS), where only the optimal transmit antenna has the chance to be selected for transmission, is considered as a baseline. Since that both the number of active transmit antennas and the number of quantization bits affect the quantization error, we define the effective secrecy throughput as the difference between the secrecy data rate and feedback rate to evaluate the system performance. We conduct an effective secrecy throughput analysis for both QSP-ATAS and NSP-STAS schemes and show the existence of the maximal effective secrecy throughput of proposed QSP-ATAS scheme. Furthermore, an optimization analysis of the QSP-ATAS scheme is carried out for the sake of further improving the effective secrecy throughput with regard to the channel gain threshold. Numerical simulation results demonstrate that our proposed QSP-ATAS scheme performs better than the conventional NSP-STAS scheme in terms of the effective secrecy throughput. [ABSTRACT FROM AUTHOR]

Here, we propose a low-profile polarizing technique integrated in a parallel plate waveguide (PPW) configuration, compatible with fully metallic geodesic lens antennas. The geodesic shape of the antenna is chosen to resemble the operation of a Luneburg lens. The lens is fed with 11 waveguide ports with 10° separation producing 11 switchable beams in an angular range of $\pm \mathrm{50}^{\circ }$. Two metallic polarizing screens are loaded into the aperture of the antenna to rotate the electric field from a vertical linear polarization, which is the polarization of the transverse electromagnetic (TEM) mode supported in the lens, to a $+ \mathrm{45}^{\circ }$ linear polarization. Since the polarizing unit cells are integrated into the aperture of the antenna, the final design is compact. In addition, the size of the polarizing unit cells is about $0.55\lambda $ at the central frequency of operation making the antenna suitable to produce an array formed of stacked lenses. A prototype of the antenna in the $\text{K}_{\text {a}}$ -band was manufactured and tested, verifying the performance obtained in simulations. [ABSTRACT FROM AUTHOR]

This communication presents a novel systematic design of a high-aperture-efficiency and 2-D beam-scanning nematic liquid-crystal (LC)-based reflectarray (LCRA) that operates in the sixth-generation (6G) midband (7–24 GHz). Despite a 260° phase range, the maximum aperture efficiency is 35.8% at an aperture dimension (F/D) ratio of 0.58, the highest aperture efficiency at the lowest F/D ratio among LCRAs designed to operate on the mmWave band. The proposed LC-based reflectarray unit cell (LC-RUC) has significantly low reflection loss compared to other LC-RUCs. Also, the bias topology of the proposed LC-RUC makes the LCRA capable of 2-D beam scanning. The beam-scanning range of the proposed LCRA is ±50° on the xoz plane and 0°–65° in the yoz plane at 9.55 GHz. A $2 \times 2 $ patch array antenna is designed as the feed antenna to achieve a small F/D ratio system and ease of optimization. When designing the feed antenna, the number of elements or the element spacing is considered to achieve high feed efficiency. In addition, the fabricated planar feed antenna can be easily integrated with a 3-D printed jig in which the focal length can be adjusted for optimization. The lowest side lobe level (SLL) of the proposed LCRA is −15.5 dB. [ABSTRACT FROM AUTHOR]

High-performance miniaturized antennas are one of the goals that have been pursued in the design of wireless communication systems for implantable medical devices. In this article, a 915 MHz novel-shape loop antenna conforming to the inner wall of the capsule is developed by comprehensively adopting meander and symmetrical structure patch, folding technique, and vector current reversal technique. Through electromagnetic simulation, testing, and experimentation, the antenna shows good characteristics such as small size, ultra-wideband, circular polarization, strong robustness, and safety. Specific performances include the following: 1) the size of the developed miniaturized loop conformal antenna is only 30.5 mm $\times $ 4.6 mm $\times $ 0.05 mm and the maximum gain is −21.5 dBi at 915 MHz, which solves the problem of low gain due to the small antenna radiation area; 2) the antenna has a 4.5 GHz ultra-wideband impedance matching bandwidth ($\vert S_{11}\vert < -10$ dB) from 0.5 to 5 GHz. Even if the parameters such as the implantation depth and the thickness of the capsule shell change, or there exists a wireless power transfer system, the antenna can still cover the required frequency band with strong robustness; and 3) the specific absorption rate (SAR) of human tissues radiated by the antenna is far lower than the safety limit in IEEE standards and ICNIRP guidelines. The experimental platform using pork to simulate human tissues was built for antenna performance testing and communication testing. The measurement results verified the good resonance performance, radiation characteristics, and omnidirectionality of the developed antenna. The antenna link loss model is also given, which has been used in wireless communication and localization. [ABSTRACT FROM AUTHOR]

In this article, a wideband shared-aperture phased array antenna is proposed for synthetic aperture radar (SAR) applications. A metal cavity-backed slot antenna and a slot antenna are used as the L- and X-band antenna elements, respectively. Notably, the X-band antenna elements are mounted on top of the L-band ones, and their interactions are successfully isolated by loading a layer of frequency selective surface (FSS). The FSS layer reflects the electromagnetic waves in X-band and allows transmission of the L-band electromagnetic waves, making the shared-aperture antenna work properly in L- and X-bands. Furthermore, a circular patch is designed to improve the bandwidth of the X-band antenna. Simulations indicate that the proposed antenna has impedance bandwidths of 46% in X-band (7.5–12 GHz) and 21% in L-band (1.7–2.1 GHz). Moreover, the X-band antenna can scan up to ±60° in the E-plane and ±30° in the H-plane with voltage standing wave ratio (VSWR) below 3. To verify the design method, a shared-aperture antenna prototype, which consists of $6\times6$ X-band elements and one L-band element, has been fabricated and measured. Finally, the measured results agree well with the simulated ones. [ABSTRACT FROM AUTHOR]

In this article, a novel design of broadband circularly polarized (CP) folded reflectarray (FRA) antenna is proposed. The CP FRA consists of two kinds of metasurfaces (MSs) and a linearly polarized (LP) open waveguide antenna as the feeding source. The bottom MS functions as the main reflector, which is capable of realizing cross-polarization conversion and beam focusing simultaneously. The upper MS is utilized as a subreflector, which could reflect LP wave coming from the feeding source and transmit its orthogonal counterpart into CP wave. For demonstration, the MS-assisted CP FRA antenna is fabricated and measured. Numerical results are consistent with experimental ones, illustrating a peak gain of 24.1 dBi and a peak aperture efficiency of 51% at 9.9 GHz. The 3 dB gain bandwidth and 3 dB axial ratio (AR) bandwidth are achieved as 27.5% (8.8–11.6 GHz) and 43.9% (8–12.5 GHz), respectively. The proposed CP FRA provides a new avenue to realize broadband high-efficiency CP antenna, which may find great potentials in modern wireless communication systems. [ABSTRACT FROM AUTHOR]

This communication presents a vertically stacked substrate-integrated waveguide (SIW) antenna array that enables different array configurations with the minimum number of SIW layers. This achievement lies in the modular feature offered by the proposed design. Specifically, four distinct array configurations can be produced with only three different designs of SIW layers. Depending on the number of SIW layers employed in the stacked antenna, the directivity in the E-plane is modified. To obtain an equal and in-phase power distribution among the array elements, H- and E-plane corporate feeding networks are efficiently implemented in each array configuration. Array configurations of one, two, four, and eight radiating layers are offered by the proposed modular array, where each radiating layer is formed by eight H-plane horn antennas. The simulated directivity for the array configurations ranges from 15.8 to 23.8 dBi and the main beam direction remains fixed along the operating frequency range. The array design has been manufactured, and an agreement between simulated and measured results is observed. The measured impedance bandwidth in all the array configurations is from 35 to 41 GHz (15.79% bandwidth) with a reduction in the E-plane beamwidth as the number of radiating layers increases. [ABSTRACT FROM AUTHOR]

A dual-polarized Ku-band and single-polarized Ka-band shared-aperture phased array antenna is proposed in this article. The endfire dipole antenna is designed as the radiating element of both bands. To eliminate the shading effect of the horizontal-polarized Ku-band antenna caused by the common ground, the director is loaded on the Ka-band antenna to increase the height of the equivalent phase center of the Ka-band antenna. The high-order mode of the horizontal-polarized Ku-band antenna is excited when the Ka-band antenna scans to a wide angle in H-plane within the frequency range of 33–34 GHz. An etched square ring is loaded on the Ku-band radiating arm to induce the reverse current to prevent such a high-order mode. The scanning blind spots occur at 33 and 35.8 GHz when the Ka-band antenna scans to 50° in E-plane owing to the mutual coupling between the Ka-band antenna and the vertical-polarized Ku-band antenna. A metallic strip is loaded on the vertical-polarized Ku-band antenna to eliminate the blind spot at 33 GHz. The feeding position of the vertical-polarized Ku-band antenna is elevated to eliminate the blind spot at 35.8 GHz. The periodic cell and finite array are simulated to verify the design proposed in this article. The results demonstrate that the design is effective and the beam-scanning coverage reaches $\pm \mathrm{50}^{\circ }$ at both bands. The active voltage standing wave ratio (VSWR) is not greater than 3.5 at 15–17 and 33–36 GHz in the whole beam-scanning coverage. A prototype of the 4 $\times $ 4 Ku-band and 8 $\times $ 8 Ka-band shared-aperture array is fabricated and measured. The measured results agree well with the simulated ones. [ABSTRACT FROM AUTHOR]

Conventional transmitarray antennas are designed to produce a directional pattern with the beam peak in a single direction when the feed is placed at a distinct location. A real-life application requiring conical beam scanning necessitates the development of antennas with patterns that sweep out a cone in space through successive excitation of feeds placed at multiple locations along the body of the revolution ring focus. In this communication, we propose transmitarrays as an antenna solution that can achieve the conical beam sweep. Compared to the previously reported transmitarrays, the development of an off-axis-fed transmitarray for conical beam scanning requires significant advancements regarding the synthesis and optimization of the off-axis-fed transmitarray. A novel synthesis algorithm is presented based on the optimization of the feed location and a modified transmitarray phase compensation. To validate the approach, an 18 cm transmitarray with a thickness of 0.8 cm operating at 13.4 GHz is designed, simulated, prototyped, and measured. Predictions obtained by full-wave simulations agree well with the measured results. The conical beam scanning capability of the transmitarray is demonstrated through measurements taken with the feed placed at five locations within the ring focus. [ABSTRACT FROM AUTHOR]

In this article, a cascaded metasurface (MS) with circular-polarization-selective properties is proposed, which can achieve high reflection for left-handed circular polarization (LCP) and high transmission for right-handed circular polarization (RCP). Such MS, constructed by cascading two kinds of MS sheets, can conduct decoupled geometric phase modulations for the LCP reflection channel and RCP transmission channel by respectively rotating the two elements in the two MS sheets. In order to show its practical applications, first, the proposed MS is applied to design a reconfigurable circularly polarized (CP) transmit-reflect-array antenna (TRA) that can be switched between a high-gain LCP transmitarray antenna and a high-gain LCP reflectarray antenna (RA) dependent on the polarization state of the feed antenna. The simulated results validate its function-switchable and high-gain characteristics. Second, a CP bidirectional antenna is designed utilizing the proposed MS and validated by a fabricated prototype with good agreement between the measured and simulated performances. The results indicate that the joint bandwidth (BW) for both forward and backward aperture efficiencies larger than 20% and axial ratios smaller than 3 dB is about 16% (9.4–11 GHz), across which the antenna realizes bidirectional high-gain and high-purity LCP radiations. [ABSTRACT FROM AUTHOR]

A design methodology of the dual-band Fabry–Perot-cavity (FPC) antenna is proposed, realizing dual-broadband high gain and keeping the simplicity of one low-profile resonant cavity. A ray optics model is applied to obtain the phase resonance condition for dual-band FPC antennas. The proposed antenna employs a tightly stratified partial-reflective-surface (PRS), an artificial-magnetic-conductor (AMC) ground, and a dual-band microstrip feed. The PRS modulates independently the dual-band reflection coefficient to maintain a large amplitude and a positive phase gradient. Meanwhile, an AMC ground is distinctively employed to compensate for the transmission phase difference of the lower band when the cavity height meets half the wavelength of the upper one, enabling eventually a low-profile uni-cavity. Furthermore, a dual-band microstrip feed with two asymmetric slots is customized as the primary radiator. Detailed electromagnetic studies are carried out to illustrate the operating mechanisms of these components. Finally, a proof-of-concept prototype is fabricated covering the entire global 2.4 and 5 GHz WiFi bands. The measurement results agree well with the simulation, and the 3 dB gain bandwidths of 7.2% and 16.2% with peak gains of 13.6 and 15.0 dBi over two wide bands of 2.42–2.60 and 5.1–6 GHz are achieved, respectively, with a single cavity height of 26.8 mm. [ABSTRACT FROM AUTHOR]

In this communication, a circularly polarized (CP) double-folded transmitarray antenna (DFTA) is proposed and experimentally verified for the first time in the open literature. It is designed based on a receiver–transmitter metasurface (RTMS) and a polarization rotating (PR) metasurface (MS). A linearly polarized (LP) patch antenna is integrated on the RTMS instead of a horn antenna to feed the DFTA. Through double-folded reflecting, twice PR, LP wave receiving, CP wave transmitting, and transmission phase manipulating, the LP spherical wave from the feed is transformed into the high-gain pencil-shaped CP beam. The strategies innovatively break the restriction that the previous folded reflectarray (FRA) and folded transmitarray (FTA) antennas are only LP. Moreover, the double-folded design further reduces the antenna profile to about 1/4 of the focal length. The simulation and experiment results are in good agreement, which exhibits a peak gain of 21.8 dBic at 9.8 GHz and a maximum aperture efficiency of 40%. Meanwhile, the DFTA obtains a −1 dB gain bandwidth of 6% (9.6–10.2 GHz), in which the axial ratio is lower than 1.5 dB. [ABSTRACT FROM AUTHOR]

A broadband circularly polarized (CP) magnetoelectric (ME) dipole antenna loaded with parasitic loop is presented in this communication. The proposed ME dipole antenna is fed through the slot-coupled feeding method, in which a microstrip line is used to couple the energy to the antenna by the slot etched on the ground plane. By introducing a parasitic loop coplanar with the horizontal patch, extra CP modes are generated due to the coupling with the radiation patch. Combining with the original CP mode, the simulated 3 dB axial-ratio (AR) bandwidth is enhanced from 12.2% to 45.8% with an increment of 33.6%. The measured results show that the 10 dB impedance bandwidth is 55.3% (3.4–6.0 GHz) and the 3 dB AR bandwidth is 42.1% (3.62–5.55 GHz). Moreover, the proposed antenna owns flat gain and stable unidirectional radiation patterns within the designated frequency band. [ABSTRACT FROM AUTHOR]

In this communication, a Fabry–Perot (FP) conical beam antenna with multipolarization reconfigurable capability is proposed. A single-layer partially reflective surface (PRS) with circular slots is designed for the prescribed flare angle determined by the height of the FP antenna and resonant frequency. A group of Vivaldi patches with a set of shorting vias around a common central axis on a printed circuit board (PCB) are used as the primary source, which is fed by nested coaxial waveguide. Vivaldi patches coupled with parallel baluns, which are connected to the internal coaxial waveguide, are used to produce a horizontally polarized conical beam. A vertically polarized conical beam can be obtained when the external coaxial waveguide is used to feed the Vivaldi patches. When circularly polarized conical beams are required, the internal and external coaxial waveguides need to be excited at the same time with the same amplitude and the proper phase difference. A prototype of the proposed FP conical beam antenna with multipolarization reconfigurable capability at 12 GHz is designed, fabricated, and measured to verify the concept. The measured results are in good agreement with the simulated ones. A maximum gain of $\ge 12.8$ dBic is achieved with the proposed FP conical beam antenna for the two circular polarization states, with an axial ratio (AR) and impedance bandwidth (IBW) of $\ge 16.7$ % and 8%, respectively. The maximum gain and IBW for the horizontal polarization (HP) and vertical polarization (VP) are $>13.2$ dBi and 9.2%, respectively. [ABSTRACT FROM AUTHOR]

An on-body matched differentially fed magnetoelectric (ME) dipole antenna is proposed for the head imaging system to detect intracranial hemorrhage (ICH). The ME dipole with its differential feed achieves a wide impedance bandwidth of 137% from 0.45 to 2.4 GHz. The antenna exhibits unidirectional and symmetrical radiation patterns in the near-field region, leading to a stable main beam toward the 2-D imaging domain inside the human head. The high front-to-back ratio (FBR) above 18 dB is realized in the whole frequency band by this antenna. The values of specific absorption rate (SAR) always remain safe level under 0.82 W/kg in the entire band with an input power of 10 dBm. To validate the detection capability of the proposed antenna, a head imaging system composed of eight antenna elements in a co-polarization state is designed and fabricated. The reconstructed 2-D images of the head interior using a confocal imaging algorithm demonstrate the successful detection and localization of the circular bleeding area as small as 3 mm in radius numerically and 5 mm in radius experimentally, and it has the capability to detect multiple bleeding areas of the human brain, which indicates the head imaging system has the potential to be used in clinical trials. [ABSTRACT FROM AUTHOR]

A high gain, wide bandwidth (BW), and low-profile $D$ -band magnetoelectric dipole antenna-in-package (AiP) is proposed in this article. The unit antenna with a cavity backed slot is first evaluated by a substrate integrated waveguide (SIW) feed structure. The simulated impedance BW of the unit antenna covers 27 GHz from 132 to 159 GHz with stable broadside radiation patterns. Then, a $4\times $ 2 array based on the proposed unit antenna is designed and verified on a four layer BT-based organic substrate. The array design is composed of an isolation, a $2\times $ 2 subarray, a two-way SIW power divider, and a probe pad to SIW transition. The $2\times $ 2 subarray is realized by a four-way broad wall coupler with a V-junction design in particular. Tested by probing on substrate in the direct far-field chamber, the measured impedance BW covers 23.4 GHz from 135.4 to 158.8 GHz with a peak gain of 14.1 dBi at 150 GHz. The average of measured gains within the 130–160-GHz band is 12 dBi. Modeled with the dimensions of structural analysis results from optical microscope (OM) and cross-sectional scanning electron microscope (SEM) inspection, the post-simulation result shows a good agreement with the measurement result, including impedance BW, radiation patterns, and gains. This article demonstrates that the proposed AiP using the low-cost BT-based substrate manufacturing technology can be a good candidate for the future $D$ -band applications. [ABSTRACT FROM AUTHOR]

An eight-port planar leaky-wave antenna (LWA) is proposed. This antenna has the capability of beam steering at an elevation angle by changing the frequency at eight azimuth angles. The antenna is planar and has an array of ring slots embedded in a microstrip parallel plate waveguide. We investigate the simulation and experimental results. The measured results have good agreement with the simulation and confirmed the leaky-wave (LW) concept. The proposed antenna yields an attractive, simple, and cost-effective beam scanning over the 3-D space. [ABSTRACT FROM AUTHOR]

A 28 GHz substrate-integrated filtering dielectric resonator antenna (DRA) and its 2 $\times $ 2 arrays are investigated. The cylindrical DRA, enclosed by two rings of air vias and metallic vias, is fabricated out of a high-permittivity substrate. It is excited by a microstrip feedline on a second substrate through four slots on the common ground plane of the antenna and feed substrates. The metallic vias and ground plane form a substrate-integrated cavity, which enhances the antenna gain in the passband by $\sim 1$ dB. A cavity mode, the DRA HEM $^{\text {y}}_{11\delta } $ mode, and a perturbed HEM $^{\text {y}}_{11\delta } $ mode are simultaneously excited, giving a wideband substrate-integrated DRA. A dual-loop structure is introduced to the DRA to provide two radiation nulls that give a filtering response. To demonstrate the idea, a 28 GHz filtering DRA and its 2 $\times $ 2 arrays were designed, fabricated, and measured. Reasonable agreement between the measured and simulated results is observed. [ABSTRACT FROM AUTHOR]

An optimization approach for multiport pixel antenna design using ${N}$ -port characteristic mode analysis (CMA) and sequential feeding port selection is proposed. CMA is utilized to characterize the maximum number of independent or orthogonal resonant modes that can be formed in the limited space constrained by the size of the pixel antenna. Once the maximum number of orthogonal resonance modes is found sequential feeding port selection is proposed to find the optimum feed positions to independently excite each of the orthogonal resonance modes. The resulting design does not need additional complex feeding networks or impedance matching circuits, making the physical implementation of the design straightforward, compact and practical. Two examples are provided to verify the performance of the proposed approach, including a 3-port pixel antenna and a 4-port pixel antenna operating at 2.4 GHz. The performance of the optimized antennas is very good, and verifies the usefulness of the proposed approach. [ABSTRACT FROM AUTHOR]

In this article, a technique to obtain a high-gain multibeam antenna for millimeter-wave (mmW) fifth-generation (5G) base stations (BSs) is proposed using the Fabry–Pérot Cavity (FPC) structures. A thin single metallodielectric layer is used as the partially reflective surface (PRS) layer to enhance the radiation performance of the FPC antenna (FPCA) and provide an off-axis pencil beam. As the feeding structure illuminating the PRS layer, a cylindrical cavity is designed using a right-angle-type semi-waveguide (RATSW) structure. An array of coaxial probes is used to obtain beam switching at the azimuth plane by exciting different probes. To confirm the functionality of the proposed FPCA, a prototype is fabricated with five coaxial probes to generate five radiation beams; however, the structure can be extended to provide more antenna beams using higher number of probes. The cavity structure of the proposed antenna is fabricated by the 3-D printing technology as an easy manufacturing process. The measurement results show that multiple switchable beams with high antenna gain are obtained over the desired frequency bandwidth of 27–30 GHz. The maximum measured gain is 19 dBi at 27.5 GHz when a single probe is excited. A conceptional scenario for the potential applications of the proposed antenna in the 5G BSs is presented. [ABSTRACT FROM AUTHOR]

This article presents a design methodology and a realization of an antenna radiating circular polarization (CP) for Frequency Modulated Continuous Wave (FMCW) radar at mm-wave frequencies on-chip, which combines antennas of different resonance frequencies to increase the operation bandwidth and allow for high-resolution radar. The antenna consists of four dipoles with an on-chip ground plane operating at two resonance frequencies combined with a matching and feeding network, which enables both frequency selectivity in advantage for the resonant antenna and radiation of circular polarization. The dipole arms are based on shorted ${\lambda }{/4}$ resonators, which are enhanced with series capacitances for increased radiation efficiency. A method for the broadband characterization of CP antennas and the measurement results of the designed CP antenna are presented. It is shown that the antenna covers a bandwidth between 220 and 260 GHz, indicating the feasibility of both the measurement method and the antenna concept. [ABSTRACT FROM AUTHOR]

This article presents 3-D printed metal-only dual-band millimeter-wave circularly polarized (CP) reflectarrays (RAs). The RAs’ unit cell (UC) is made of an anisotropic metal brick mounted on a full metal ground. In-plane rotating the metal brick introduces geometric Pancharatnam–Berry (PB) phase shifting, and vertically adjusting the position of the UC provides propagation phase shifting. The geometric PB and propagation phase shifting offer two different degrees of freedom, enabling independent wavefront shaping of CP wave over dual-band. Specifically, the low-band CP beam shaping solely depends on the propagation phase. In contrast, the high-band CP beam shaping depends on the geometric PB and the propagation phases. The coupling issue between dual-band is minimal because of the unique dual-band phase-shifting methods. In addition, 3-D printed dual-band left-hand CP (LHCP) horn antennas are designed, printed, and used as the feed. To demonstrate, two RA antennas with different dual-band CP beam directions are fabricated and measured. [ABSTRACT FROM AUTHOR]

In this article, a fast and efficient hybrid method that combines the volume-surface integral equation (VSIE) and the modified surface integration (MSI) method is proposed to evaluate the electromagnetic (EM) performance of the large-/medium-sized radome-enclosed antennas (REAs). An approximate equivalence principle is presented to formulate the physical model for the EM radiation of the REA, and then, the full-wave VSIE for the antennas and the high-frequency MSI method for the dielectric radome are coupled with each other in an iterative manner. Since mutual interactions up to the second order among the antennas and the radome are considered, the method shows good accuracy in both the near- and far-field regions of the REA system. In addition, all the computation processes involved in the method, including the method of moments (MoM) solution of the VSIE, surface integrations (SIs) in the MSI, and ray tracing for determining the local transmission matrix for the dielectric radome, are accelerated by the multilevel fast multipole algorithm (MLFMA), which makes the method highly efficient in terms of both computational time and memory requirement. Numerical results show that the proposed hybrid method can predict the EM performance, e.g., the input impedance and radiation pattern, of the REA system with good accuracy compared with the full-wave simulations. [ABSTRACT FROM AUTHOR]

A compact dual-wideband millimeter-wave magnetoelectric (ME) dipole antenna based on dual-mode operation is proposed in this article. The ME dipole consists of two mirrored U-shaped patches, a substrate integrated waveguide (SIW) cavity with slotted top and two metallized vias connecting the patches to the slot. The two mirrored U-shaped patches work as an electric dipole (E-dipole), while the slot on the top of the SIW cavity and two metallized vias works as a magnetic dipole (M-dipole). In the lower frequency band, $0.5\lambda $ modes of the E-dipole and the M-dipole are excited to form the $0.5\lambda $ mode of the ME dipole. In the higher frequency band, $1\lambda $ modes of the E-dipole and the M-dipole are excited to form the $1\lambda $ mode of the ME dipole. In order to achieve compact structure and wide bandwidths, an SIW cavity is designed to feed the antenna. The proposed design shows that the measured impedance bandwidths (return loss larger than 10 dB) are 24–29.3 and 35.5–43.5 GHz at least with the achieved gain of 4.8–6.1 and 6.8–8.7 dBi, respectively. The designed antenna is suitable for 5G dual-band millimeter-wave applications. [ABSTRACT FROM AUTHOR]

In this article, an accurate analytical model for the calculation of the resonant length of a surface-wave-excited plasma antenna based on the distribution of the plasma density along the column is presented. In the proposed method, the propagation and attenuation constants for a surface-wave-excited plasma column are derived by solving the surface wave propagation problem on a three-layer tube, and as a result, the distribution of the plasma density along the column is investigated. Specifically, it is shown that a plasma column acts as a slow wave medium. Therefore, the resonant length of a plasma antenna is less than the resonant length of its metallic counterpart. For the experimental validation of the presented model, an efficient coupling structure for feeding the excitation wave to the plasma antenna is proposed that allows frequency tunability and reconfigurability of the antenna. A prototype of the proposed structure has been designed and fabricated. Good agreement between the analytical, numerical, and measurement results validates the proposed model. [ABSTRACT FROM AUTHOR]

We propose a polarization-twisting metasurface antenna (PTMA) to generate the dual-band dual-circularly polarized (CP) radiation by integrating a dual-linear-to-circular polarization converter (DLCPC) with a linear polarization conversion metasurface (LPCM) in the Ku-band. The DLCPC possesses the functionality of polarization selection and is capable of transforming the linearly polarized (LP) waves into right hand CP (RHCP) waves in low-frequency (LF) and left hand CP (LHCP) waves in high frequency (HF). Based on the DLCPC, the dual-band dual-CP PTMA is designed and fabricated, and then, the measured results indicate that the PTMA is capable of realizing the RHCP radiation in LF and the LHCP radiation in HF. In the meanwhile, the common bandwidths of −1.5 dB gains and 3 dB axial ratios are 12.25–12.95 and 14.00–14.55 GHz, respectively. Our design, by integrating the DLCPC and LPCM to construct the dual-band dual-CP PTMA, should, thus, pave the way for building up more efficient wireless communication systems with the requirement of different CPs as the receiver and the transmitter at downlink and uplink in the Ku-band. [ABSTRACT FROM AUTHOR]

This article introduces a transmitarray antenna presenting excellent filtering and dual-polarization properties. Conventional transmitarrays resort to multilayered frequency-selective surfaces (FSSs) for filtering responses. In contrast, we propose a planar dual-polarized filtering antenna as an illumination source to enable a filtering transmitarray. The V-band dual-polarized filtering antenna is excited by a substrate integrated waveguide (SIW) feeding structure. By a novel trisection feed and a well-design radiating element, up to four radiation nulls are produced, leading to an excellent filtering response validated with experimental results. Subsequently, the antenna is employed to illuminate a phase-shifting surface (PSS), achieving outstanding filtering response, stable dual-polarization characteristics, low profile, and ease of integration. The proposed antenna and transmitarray demonstrate significant potential in V-band millimeter-wave (mmW) applications. [ABSTRACT FROM AUTHOR]

This communication presents a millimeter-wave wideband dual-polarized low-temperature cofired ceramics (LTCC) antenna array based on metasurfaces (MSs) for beam-scanning applications. Benefiting from the wideband and large-freedom property of MS-based structures, a novel ±45° dual-polarized wideband MS-based antenna (MSA) element with high isolation is designed. The antenna element is fed by two orthogonal striplines on different layers, through a crosslike dog-bone slot and a narrow slot, respectively, to realize the two polarizations. The feeding structure consists of slot–stripline–slot–stripline from top to bottom and is specially designed to improve the polarization isolation of the antenna element. The proposed MSA element is compactly arranged with a small distance ($ < 0.5\lambda$) to construct a 4 $\times $ 4 array integrated in an LTCC package, where via walls with metal ring strips are loaded between adjacent elements to reduce the gain fluctuation. Consequently, the array can achieve a good beam-scanning capability over a wide band of 19.5% with a maximum scanning angle up to ±55° and a small gain variation of less than 3 dB. Meanwhile, the active $S$ parameters almost always remain below −10 dB, enabling good impedance matching when scanning at all angles. With these features, the proposed design has potential for application in 5G base-station systems. [ABSTRACT FROM AUTHOR]

Mechanical antennas have garnered interest as a potential method of transmitting extremely low-frequency (ELF) to very-low-frequency (VLF) radiation in a manner that possesses a high efficiency of radiation and a low form factor. In this article, we investigate these claims by solving for the exact field solutions for one particular example, a rotational-oscillating charged thin spherical shell. The field solutions allow the analysis of the radiation pattern, radiation efficiency, and spectral output as a function of several geometric and kinematic quantities of the sphere. The results indicate that high efficiency with a low form-factor appears to be plausible, assuming that the required mechanical conditions for the motion can be achieved. [ABSTRACT FROM AUTHOR]

In this article, a radio-frequency (RF) power-amplifier (PA) system configuration for the on-board energy conversion is proposed for unmanned aerial vehicle base station's (UAV-BS's) battery charging. First, the PA system utilizes the internal RF source for energy conversion so that perpetual battery charging is possible without external power sources. Therefore, a continuous battery charging of the UAV-BS is possible while providing wireless network coverage by hovering over the target location. In addition, the proposed PA system offers a higher RF power control resolution than the existing PA works, which is desirable for precise power control of the UAV-BS. The objective of simultaneous RF power control and battery charging by the PA system is achieved by activating one Wilkinson power divider (WPD) with a specific power splitting ratio in the power divider bank. The simulations show that the dynamic activation of ten distinct unequal split WPDs of the proposed PA system improves the RF power control resolution by $157$ and $396{\,}\%$ compared to the existing PAs. Additionally, the simulations show that the PA's power added efficiency fluctuation is reduced by $54$ and $82{\,}\%$ compared to the existing PAs. In addition, it will be shown that the proposed on-board battery charging increases the hovering time by $7.4{\,}\%$. Furthermore, an energy-efficiency optimization framework for UAV-BS's is proposed considering real-world communication system's hardware imperfections, and the proposed result suggests that UAV-BS's flight time may decrease by $50{\,}\%$ depending upon the type of UAV-BS RF components. [ABSTRACT FROM AUTHOR]

A new method for the design of multilayer printed partially reflective surface (PRS) is proposed to achieve broadband, high efficiency, and miniaturization of Fabry–Pérot resonant antenna (FPRA). In this letter, every two-layer structure is regarded as a resonator to obtain a narrowband positive reflection phase gradient and then cascaded to obtain a broadband. Finally, a three-layer PRS is designed and integrated to form a C-band compact FPRA with overall dimensions of 0.65 λ0×0.65 λ0×0.52 λ0 (λ0 is the free-space wavelength at the center frequency). The antenna was simulated, fabricated, and validated. The results show it has a high aperture efficiency due to the small aperture and a wide impedance bandwidth well covering 4.0–9.57 GHz. [ABSTRACT FROM AUTHOR]

In this letter, we present a simple-feed dual-polarized Fabry–Perot antenna with broadband and high-isolation for in-band full-duplex applications. Its feeding element consists of a two-port patch antenna with one aperture coupled port and one microstrip-line-fed port for a high isolation without adding any out-of-phase power divider. For broadband and high-gain radiation, the two-port patch is incorporated with a stacked-patch and partially reflecting surface while maintaining the structure symmetry. The final design with an overall size of $\sim\! 1.9\lambda _{\text{min}}$  × 1.9 $\lambda _{\text{min}}$  × 0.48 $\lambda _{\text{min}}$ ($\lambda _{\text{min}}$ is the free-space wavelength at the lowest operational frequency) has been fabricated and tested. The measurements result in a 10 dB return loss bandwidth of 19.1% (4.84–5.86 GHz), an isolation of $\ge$ 43 dB, a realized broadside gain of 12.4–14.2 dBi, cross-polarization level of $\le$ −30 dB, and side-lobe level of $\le$ −18 dB across 5.00–5.95 GHz. [ABSTRACT FROM AUTHOR]

Holographic Multiple Input Multiple Output (HMIMO), which integrates massive antenna elements into a compact space to achieve a spatially continuous aperture, plays an important role in future wireless networks. With numerous antenna elements, it is hard to implement the HMIMO via phased arrays due to unacceptable power consumption. To address this issue, reconfigurable refractive surface (RRS) is an energy-efficient enabler of HMIMO since the surface is free of expensive phase shifters. Unlike traditional metasurfaces working as passive relays, the RRS is used as transmit antennas, where the far-field approximation does not hold anymore, urging a new performance analysis framework. In this letter, we first derive the data rate of an RRS-based single-user downlink system, and then compare its power consumption with the phased array. Simulation results verify our analysis and show that the RRS is an energy-efficient way to HMIMO. [ABSTRACT FROM AUTHOR]

In order to fully exploit the advantages of massive multiple-input multiple-output (mMIMO), it is critical for the transmitter to accurately acquire the channel state information (CSI). Deep learning (DL)-based methods have been proposed for CSI compression and feedback to the transmitter. Although most existing DL-based methods consider the CSI matrix as an image, structural features of the CSI image are rarely exploited in neural network design. As such, we propose a model of self-information that dynamically measures the amount of information contained in each patch of a CSI image from the perspective of structural features. Then, by applying the self-information model, we propose a model-and-data-driven network for CSI compression and feedback, namely IdasNet. The IdasNet includes the design of a module of self-information deletion and selection (IDAS), an encoder of informative feature compression (IFC), and a decoder of informative feature recovery (IFR). In particular, the model-driven module of IDAS pre-compresses the CSI image by removing informative redundancy in terms of the self-information. The encoder of IFC then conducts feature compression to the pre-compressed CSI image and generates a feature codeword which contains two components, i.e., codeword values and position indices of the codeword values. Subsequently, the IFR decoder decouples the codeword values as well as position indices to recover the CSI image. Experimental results verify that the proposed IdasNet noticeably outperforms existing DL-based networks under various compression ratios while it has the number of network parameters reduced by orders-of-magnitude compared with various existing methods. [ABSTRACT FROM AUTHOR]

The irregularly located element array within the antenna aperture can be applied to obtain narrow main lobe width and low sidelobe levels with fewer elements as compared with the traditional (periodic) array configurations. In this article, a reconfigurable reflectarray antenna (RRA) combined with hyperuniform disordered distribution is presented. Based on the theoretical radiation pattern of reflectarray, it has been found that the proposed array with reduced elements holds a similar radiation pattern as that of a corresponding periodic array. Meanwhile, the reflectarray avoids the design of complicated feeding network for the disordered phased array antenna. In addition, for a reconfigurable reflectarray to achieve beam scanning, active devices are necessary. In such case, the design of RRA with fewer elements is of particular importance. A 1 bit RRA of 64 elements prototype has been designed, fabricated, and measured. The side length of each element is $0.625\lambda $. Experimental results agree well with the full-wave simulations, and scan beams within ± 50° range have been obtained with a peak gain of 17.4 dBi at 12.5 GHz. [ABSTRACT FROM AUTHOR]

This article presents a state-of-the-art 3-D-printed dielectric reflectarray antenna featuring one-shot deployability and wide-angle beam-scanning ability. The design is enabled by a series of a “kirigami”-inspired two-stage snapping-like element structure that can be retracted by 66% to save space. The prototype is fabricated with a stereolithography (SLA) 3-D printing method with the Formlabs Flexible 80A photopolymer. A bifocal phase distribution method is utilized to optimize the RF performance of the array, realized −30° to −10° and 10° to 30° beam-scanning ability. The outcome of this work demonstrated a high-performance dielectric reflectarray design with ease of fabrication for 5G and satellite communication applications. [ABSTRACT FROM AUTHOR]

Compressive arrays have recently been proposed as a new technique for reducing the number of controls in a beamforming system for a given array aperture, promising improved performance over existing thinned-array and subarray techniques. Checkered networks, feed networks consisting of interconnected couplers and fixed phase shifters, have been suggested for realizing the required overlapped subarrays. Although a checkered network has previously been implemented in microstrip, an integrated compressive array, comprising both the antenna elements and the feed network, is required to demonstrate the practical feasibility of such systems. Results for the first successfully manufactured checkered-network compressive array with integrated antenna elements are presented, thereby showing that compressive arrays are promising for use in a variety of real-world beamforming applications. Analysis of the results shows that steered-beam squint is a greater issue than previously assumed, and design guidelines are presented for minimizing the risk of excessive steered-beam squint in manufactured compressive arrays. [ABSTRACT FROM AUTHOR]