Partially Reflective Surface Research Articles

Novel low‐profile dual‐band and dual‐polarization Fabry‐Pérot resonator antenna

This article presents a novel dual-band and dual-polarization Fabry-Pérot resonator antenna (FPRA). The proposed FPRA consists of a partially reflective surface (PRS), an electromagnetic bandgap (EBG) structure, and a dual-band and dual-polarization planar patch antenna. The novel PRS with a large positive reflection phase gradient (PRPG) is etched on a single-layer superstrate. The EBG structure is adopted as the reflection plane to reduce the profile of FPRA. A rectangular microstrip patch antenna integrated into the center of the EBG structure is used as a dual-band and dual-polarization feed for FPRA. A dual-band and dual-polarization FPRA is proposed, fabricated and measured. The measurement results demonstrate that the proposed FPRA has peak gains of 14.3 dBi with the horizontal polarization (H-pol) at 12.4 GHz and 16.8 dBi with vertical polarization (V-pol) at 14.1 GHz. Moreover, the measured 3-dB gain bandwidths in the lower and higher bands are 7.3% and 3.6%, respectively, which cover receiving (Rx) and transmitting (Tx) bands of satellite communication in the Ku band.

Quarter Wavelength Fabry–Perot Cavity Antenna with Wideband Low Monostatic Radar Cross Section and Off-Broadside Peak Radiation

Since antennas are strong radar targets, their radar cross section (RCS) reduction and radiation enhancement is of utmost necessity, particularly for stealth platforms. This work proposes the design of a Fabry–Perot Cavity (FPC) antenna which has wideband low monostatic RCS. While in the transmission mode, not only is gain enhancement achieved, but radiation beam is also deflected in the elevation plane. Moreover, the design is low-profile, i.e., the cavity height is ~λ/4. A patch antenna designed at 6 GHz serves as the excitation source of the cavity constructed between the metallic ground plane and superstrate. The superstrate structure is formed with absorptive frequency selective surface (AFSS) in conjunction with dual-sided partially reflective surface (PRS). Resistor loaded metallic rings serve as the AFSS, while PRS is constructed from inductive gradated mesh structure on one side to realize phase gradient for beam deflection; the other side has fixed capacitive elements. Results show that wideband RCS reduction was achieved from 4–16 GHz, with average RCS reduction of about 8.5 dB over the reference patch antenna. Off-broadside peak radiation at −38° was achieved, with gain approaching ~9.4 dB. Simulation and measurement results are presented.

Tilted Beam Fabry–Perot Antenna with Enhanced Gain and Broadband Low Backscattering

Communication with low radar signature platforms requires antennas with low backscatter, to uphold the low observability attribute of the platforms. In this work, we present the design for a Fabry–Perot (F-P) cavity antenna with low monostatic radar cross section (RCS) and enhanced gain. In addition, peak radiation is tilted inthe elevation plane. This is achieved by incorporating phase gradient metasurface (PGM) with absorptive frequency selective surface (FSS). The periodic surface of metallic square loops with lumped resistors forms the absorptive surface, placed on top of a partially reflecting surface (PRS) with an intervening air gap. The double-sided PRS consists of uniform metallic patches etched in a periodic fashion on its upper side. The bottom surface consists of variable-sized metallic patches, to realize phase gradient. The superstrate assembly is placed at about half free space wavelength above the patch antenna resonating at 6.6 GHz. The antenna’s ground plane and PRS together construct the F-P cavity. A peak gain of 11.5 dBi is achieved at 13° tilt of the elevation plane. Wideband RCS reduction is achieved, spanning 5.6–16 GHz, for x- and y-polarizations of normally incident plane wave. The average RCS reduction is 13 dB. Simulation results with experimental verifications are presented.

Resonator Rectenna Design Based on Metamaterials for Low-RF Energy Harvesting

In this paper, the design of a resonator rectenna, based on metamaterials and capable of harvesting radio-frequency energy at 2.45 GHz to power any low-power devices, is presented. The proposed design uses a simple and inexpensive circuit consisting of a microstrip patch antenna with a mushroom-like electromagnetic band gap (EBG), partially reflective surface (PRS) structure, rectifier circuit, voltage multiplier circuit, and 2.45 GHz Wi-Fi module. The mushroom-like EBG sheet was fabricated on an FR4 substrate surrounding the conventional patch antenna to suppress surface waves so as to enhance the antenna performance. Furthermore, the antenna performance was improved more by utilizing the slotted I-shaped structure as a superstrate called a PRS surface. The enhancement occurred via the reflection of the transmitted power. The proposed rectenna achieved a maximum directive gain of 11.62 dBi covering the industrial, scientific, and medical radio band of 2.40–2.48 GHz. A Wi-Fi 4231 access point transmitted signals in the 2.45 GHz band. The rectenna, located 45 anticlockwise relative to the access point, could achieve a maximum power of 0.53 μW. In this study, the rectenna was fully characterized and charged to low-power devices.

A High-Gain Leaky-Wave Antenna Using Resonant Cavity Structure With Unidirectional Frequency Scanning Capability for 5G Applications

This paper presents a high-gain leaky-wave antenna based on a resonant cavity (RC) structure with the capability of unidirectional beam scanning over predefined frequencies and desired beam angles. Frequency scanning is achieved by implementing a properly-designed single-layer partially reflective surface (PRS) based on a simple ray tracing-based design procedure. In the proposed structure, two techniques are combined to make the beam scanning unidirectional. First, a metallic wall is placed at a proper distance from the radiator to suppress the antenna propagation at undesired directions. Second, a feed antenna with a tilted beam is designed as the main radiating element inside the cavity to radiate over desired beam angles. A prototype of the proposed antenna is fabricated and measured demonstrating a beam scanning from $12^{o}$ to $46^{o}$ over the frequency band from 25 to 31 GHz. Moreover, a maximum gain of 15.4 dBi is achieved at 26 GHz on the elevation plane with tilted angle of $22^{o}$ . The proposed leaky-wave antenna is suitable for various wireless applications, in particular the $5^{th}$ generation of cellular networks and small cell base station antenna (BSA) applications.

2.5-D Partially Reflective Surface for Resonant Cavity Antennas: Design and Synthesis

A new concept of 2.5-D partially reflective surface (PRS), with its potential applications in the design of resonant cavity antennas (RCAs), is presented. The proposed structure is in the form of a closed circular loop in which a pair of orthogonally split circular rings, printed on both sides of a substrate, is connected in series by four vertical vias to constitute the 2.5-D PRS unit cell. The 2.5-D PRS has a miniaturized unit cell size, in terms of wavelength, enabling the placement of a large number of unit cells in a given small area, and offers the flexibility of arranging those unit cells in different configurations. The unit cells are arranged in this work in a tapered configuration to construct the PRS. Based on the tapered 2.5-D PRS, a circular aperture RCA with an aperture area of 2.04λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ( λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> being wavelength at the center frequency of 4.2 GHz) is designed, fabricated, and measured for its input reflection coefficient and radiation patterns. The prototype antenna yields a peak realized gain, 3 dB gain bandwidth overlapping with the impedance bandwidth, and an aperture efficiency, respectively, of 13.7 dBi, 26.2%, and 91.6%.

Design of a wideband single-layer partially reflective surface for a circularly-polarized resonant cavity antenna

This paper presents the design of a wideband single-layer partially reflective surface (PRS) for a circularly-polarized (CP) resonant cavity antenna (RCA). The proposed single layer double-sided PRS structure has complementary design which results in an increase in the 3-dB gain bandwidth of the antenna over a wide bandwidth due to creating both inductive and capacitive features. Indeed, this complementary structure gives opposite phase behavior which leads to a reverse phase gradient over a wide range of frequencies. Instead of using conventional multi-layer PRS structures or PRSs with thick unit cell for broaden the bandwidth, we have used a thin single-layer PRS structure with the capability to enhance the antenna gain over a wide bandwidth. A CP stacked patch antenna (SPA) is used as a main radiating element inside the RCA structure. To verify the significant effect of the proposed PRS on the antenna performance, the entire RCA structure is fabricated and the results show a reasonable agreement between simulations and measurements. The measurement results show an 3-dB axial ration (AR) and impedance bandwidths of 21% and 32%, respectively. The antenna gain is more than 10.5 dBic over the 3-dB gain bandwidth from 5.8 to 7.3 GHz, i.e 22.9%, with a peak gain of 13.2 dBic.

A Radiation Pattern Reconfigurable Fabry–Pérot Antenna Based on Liquid Metal

A new beam controllable Fabry–Perot (FP) antenna utilizing a liquid-metal partially reflective surface (PRS) is investigated. The proposed PRS can be divided into three different liquid-metal-filled areas. By injecting the liquid metal into specific zones, the antenna beam direction and 3 dB beamwidth can be controlled separately, providing an easy control method for the radiation pattern reconfigurable FP antenna. The experimental results demonstrate that the proposed antenna works at 5.1 GHz. Five beam directions in the elevation plane ( $\varphi = 90^{\circ }$ ) and four antenna horizontal beam widths can be obtained. The FP antenna is simple in design and is easily fabricated as well. It will be a good candidate antenna for future wireless communication systems.

Low‐profile and wideband gain enhanced Fabry–Perot cavity antenna using gradient PRS and AMC

Low-profile and wideband gain enhancement Fabry–Perot cavity antennas (FPCA) is proposed using gradient Partially Reflective Surface (PRS) and gradient Artificial Magnetic Conductor (AMC). A wideband source antenna is designed with a −10 dB impedance bandwidth of 58.1% (6.1–11.1 GHz). The PRS is constructed by a complementary frequency-Selective Surfaces (FSS) with a square hole and four small patches in a unit, which realizes phase increasing with frequency. The PRS and the AMC are gradient alone x-direction to achieve wideband phase compensation. While they are uniform in y-direction to realize better gain enhancement. Compared with the source antenna, the gain enhancement of the proposed FPCA is about 4–7 dBi. Moreover, the simulated and measured 3-dB gain bandwidths are 7.26–10.33 GHz (34.8%) and 6.8–10.8 GHz (46%), respectively. The gain enhanced bandwidth is about 52.3% (6.5–11.1 GHz). The impedance bandwidth is 6–11.1 GHz (59.65%). By using the gradient size AMC, the profile of the FPCA is reduced from 0.5λ0 to 0.2λ0, where λ0 is the wavelength of 8.5 GHz. The proposed FPCA has the characteristics of wide impedance bandwidth, wide 3-dB gain bandwidth, wide gain enhanced bandwidth and low-profile.

Wideband Fabry–Perot Resonator Antenna Employing Multilayer Partially Reflective Surface

A method for designing wideband Fabry–Perot resonator antennas (FPRAs) using multilayer partially reflective surface (PRS) is presented. The proposed partially reflecting structure employs a pair of closely spaced PRSs to obtain a positive reflection phase gradient over a wide range of frequencies. Each PRS layer is composed of complementary square apertures and patches printed on either side of a thin dielectric sheet. The distance between the two PRS layers is only $\lambda _{\mathrm {o}}/12$ ( $\lambda _{\mathrm {o}}$ being wavelength at the center frequency of 13 GHz). Due to the presence of strong couplings between the two PRS layers, the designed PRS unit cell gives a positive reflection phase gradient from 11 to 15 GHz, thereby forming the basis of a wideband FPRA. Based on the proposed PRS, a compact FPRA with overall dimensions of $2.4\lambda _{\mathrm {o}} \times 2.4\lambda _{\mathrm {o}} \times 0.66\lambda _{\mathrm {o}}$ is designed and experimentally validated, which gives a 3 dB gain bandwidth and a maximum realized gain of 32.3% and 14 dBi, respectively.

155 GHz Dual-Polarized Fabry–Perot Cavity Antenna Using LTCC-Based Feeding Source and Phase-Shifting Surface

This communication introduces a design of a dual-polarized Fabry-Perot cavity (FPC) antenna operated at the D-band. A novel phase-shifting surface (PSS) made of a single dielectric material based on the low-temperature cofired ceramic (LTCC) technology is applied to this antenna. The proposed PSS functions as a partially reflective surface (PRS) with a transverse permittivity gradient (TPG), contributing to a directive beam radiation. A dual-polarized LTCC-based feeding source with bandwidth enhancement is designed to feed the cavity. For verification, a dual-polarized LTCC FPC antenna prototype operating at 155 GHz was designed, fabricated, and measured. It consists of the feeding source, the PSS, and a 3-D printed supporter. The measured peak gains of the horizontal and vertical polarizations are 17.5 and 17.1 dBi, respectively. The overlapped impedance bandwidth for both the polarizations is 10.4%. These performances ensure that the proposed dual-polarized LTCC antenna is a promising candidate for D-band applications.

A High Gain Millimeter-Wave Circularly Polarized Fabry–Pérot Antenna Using PRS-Integrated Polarizer

This communication introduces a new structure of polarizer for generating millimeter-wave (MMW) circular polarization (CP) in a Fabry-Pérot cavity (FPC) antenna. It is the first of its kind, which integrates a 3D-printed polarizer with an inserted partially reflective surface (PRS), which contributes to a wideband CP operation with high antenna gain. The realization of CP and gain enhancement can be controlled independently by optimizing the structures of the dielectric part and the PRS of the polarizer, respectively. The proposed antenna consists of a feeding source, a substrate-integrated quasi-curve reflector, and the proposed polarizer. The feeding source and the reflector are able to be fabricated by the conventional PCB technology which is low-cost and convenient in circuitry integration. For validation, a prototype of the FPC antenna with the proposed polarizer operating at 60 GHz has been designed, fabricated, and measured. The peak gain of the antenna reaches to 20 dBic. The antenna achieves an impedance bandwidth of 20% from 54.5 to 66.7 GHz for the reflection coefficient of less than -10 dB. The axial ratio (AR) bandwidth is 12.7% from 56.5 to 64 GHz for AR ≤3 dB. The experimental results confirm a good agreement between simulation and measurement.

Frequency scanning Fabry–Pérot cavity antenna with single 2D‐varying partial reflecting surface

This study presents a frequency scanning Fabry–Pérot cavity antenna with a single 2D varying partially reflecting surface (PRS) operating from 9.4 to 10.6 GHz. A probe-fed stacked rectangular patch antenna is applied as the primary source. A PRS consisting of 9 × 9 cells, whose sizes vary with azimuth, is mounted upon the source to modulate the phase efficiently. Due to the opposite correlations between scan angle and frequency in the forward and backward regions, phase distributions in the forward region are dominant in frequency scanning. The scan angle increases with frequency, as the negative correlation between the reflection phase of PRS and frequency. It is demonstrated that the beam angle is scanned from 11° to 35° with over 10 dBi gain and over 88% radiation efficiency within the band. The results in simulations and measurements validate the frequency scanning performance. It also provides the possibility that phase distributions in the forward region and the backward region could have the same weights in frequency scanning for better performances. Besides, without electronic/mechanical tuning, or PRS size varying, the proposed antenna is simple for design and operation.

Resonant Cavity Antennas for 5G Communication Systems: A Review

Resonant cavity antennas (RCAs) are suitable candidates to achieve high-directivity with a low-cost and easy fabrication process. The stable functionality of the RCAs over different frequency bands, as well as, their pattern reconfigurability make them an attractive antenna structure for the next generation wireless communication systems, i.e., fifth generation (5G). The variety of designs and analytical techniques regarding the main radiator and partially reflective surface (PRS) configurations allow dramatic progress and advances in the area of RCAs. Adding different functionalities in a single structure by using additional layers is another appealing feature of the RCA structures, which has opened the various fields of studies toward 5G applications. This paper reviews the recent advances on the RCAs along with the analytical methods, and various capabilities that make them suitable to be used in 5G communication systems. To discuss different capabilities of RCA structures, some applicable fields of studies are followed in different sections of this paper. To indicate different techniques in achieving various capabilities, some recent state-of-the-art designs are demonstrated and investigated. Since wideband high-gain antennas with different functionalities are highly required for the next generation of wireless communication, the main focus of this paper is to discuss primarily the antenna gain and bandwidth. Finally, a brief conclusion is drawn to have a quick overview of the content of this paper.

Wideband High-Gain Circularly Polarized Resonant Cavity Antenna With a Thin Complementary Partially Reflective Surface

In this communication, a new wideband resonant cavity antenna (RCA) with circular polarization is proposed. A wideband circularly polarized (CP) crossed-dipole antenna acts as the main radiating element inside the cavity. The dipole is designed based on self-complementary structures and utilizes several parasitic patches and posts to obtain wideband circular polarization and impedance characteristics. The incorporation of the proposed antenna with a new broadband thin single-layer dual-sided partially reflective surface (PRS) designed based on the complementary structure contributes to the improvement of the antenna gain in a broad bandwidth. The fabrication of the PRS on both sides of a thin single laminate substrate reduces thickness of the PRS compared with conventional multilayer PRS structures, in which the layers are separated by a gap distance. The measured results, which are in agreement with the simulations, show that the proposed antenna has a maximum measured gain of 12.5 dBic, while the 3 dB gain bandwidth and 3 dB axial ratio bandwidths are 39% and 43.37%, respectively. The measured results demonstrate the wideband functionality of the proposed antenna.

Beam Tilting Approaches Based on Phase Gradient Surface for mmWave Antennas

This article presents four different approaches utilized in beam tilting that are based on the phase gradient (phase shifting) surfaces. Each approach is individually analyzed and then compared to other techniques. Beam tilting is obtained through various techniques by transforming the phase distribution of Fabry–Perot cavity antenna (FPCA) in the near-field region by means of inexpensive and passive surfaces including wedge-shaped dielectric lens (WSDL), discrete multilevel grating dielectric (DMGD), printed gradient surface (PGS), and perforated dielectric gradient surface (PDGS). To enhance efficiency in the millimeter-wave (MMW) band, the FPCA is fed through printed ridge gap waveguide. In addition, considerable enhancement in radiation performance of the antenna at 60 GHz is acquired by a partially reflective surface (PRS), including a gain enhancement from 6.5 to 22 dB. To validate the suggested methodology and performance of the designs, several prototypes are chosen for fabricating. A satisfactory agreement between the numerical results and experimental ones is achieved. The proposed designs are also applicable for MMW frequencies especially the narrower band communication system.

A new inhomogeneous partially reflecting surface for Fabry‐Perot antenna to reduce side lobe level

In this article, an extension of the spatial filter method to study Fabry-Perot antennas with homogeneous or inhomogeneous partially reflecting surface (PRS) of finite size is proposed. This tool was subsequently validated through the study of different Fabry-Perot antennas, with homogeneous PRS and inhomogeneous GRadient-INdex (GRIN) PRS that present very high side lobe level (SLL). Since they are due to structure truncation, a new inhomogeneous PRS to reduce the SLL is designed with the new analytical tool. The new inhomogeneous PRS for Fabry-Perot antenna is characterized by simulations and measurements. Compared to the homogeneous PRS antenna, the proposed PRS allows a SLL reduction of 5 dB without decreasing the 14 dBi directivity.

Mutual coupling reduction in Fabry‐Pérot cavity antenna array

AbstractThis letter presents the mutual coupling reduction in Fabry‐Pérot (FP) cavity antenna array. Partially reflecting surface (PRS) and analogous artificial magnetic conductor reflectarray in the cavity participate in phase and magnitude modulation with spatial decoupling solution. With the proper design for the cells of PRS and reflectarray, along with the distance between them, scattered and surface waves are analyzed independently to achieve the trade‐off between mutual coupling reduction and high directivity. With decoupling optimization, S21 decreases from −20 to −30 dB, and the gain of the decoupling FP cavity antenna array fed by single source drops acceptably from 14.3 to 13.6 dBi simultaneously. The low E‐plane coupling coefficient and envelope correlation coefficient are achieved. Besides, the height of the decoupling FP cavity antenna array is lower than 6.3 mm owing to the participation of reflectarray. That the measured results are in good agreements with simulated results verifies the decoupling FP cavity antenna array performances.

Development of Multilayer Partially Reflective Surfaces for Highly Directive Cavity Antennas: A Study

This paper proposes a novel triple-layer partially reflecting surface (PRS) for designing a highly directive antenna. The proposed PRS design has 54% improvement in impedance bandwidth with existing design. The design has multiple cavities, optimized for improved gain and bandwidth performance. The PRS arrays are printed on the dielectric substrate, placed above the ground plane at a height of approximately half wavelength. The reference square microstrip patch antenna operating at a frequency of 5.8 GHz with a gain of 3.77 dBi is enhanced to 13.54 dBi. The measured S11 of the fabricated prototype is −22.12 dB with a VSWR of 1.17 : 1. Measured 3 dB gain bandwidth of the antenna is 390 MHz which is an improvement of 50% compared with the reference antenna. This highly directive antenna is suitable for WiMAX wireless application.

Dual-polarized antenna design integrated with metasurface and partially reflective surface for 5G communication

A design of electrical down-tilt dual-polarized base station antenna array (BSAA) for 5G communication applications is presented in this paper, which is realized by integrating with reconfigurable reflective metasurface and partially reflective surface (PRS). By controlling the varactor diodes which are inserted into the reflective elements, we can adjust the mainlobe direction of BSAA. Moreover, the PRS over the array is utilized to construct Fabry-Perot (FP) cavity with reflective metasurface and ground plane. Based on this design approach, a 1 × 6 dual-polarized BSAA operating from 3.4 GHz to 3.6 GHz is designed and fabricated. Simulated and measured results show that the gain is enhanced about 2.56 dB by PRS while side lobe level (SLL) is less than −20 dB. The mainlobe of the antenna array can be adjusted accurately within ±5° for beam down-tilt. The cross polarization discrimination (XPD) is less than −40 dB.