Resonant Cavity Antenna Research Articles

Enhanced bandwidth, low sidelobe resonant cavity antenna using tapered complementary FSS layers

A novel resonant cavity antenna (RCA) with low sidelobe levels over an enhanced bandwidth is presented. Radiation bandwidth of the antenna is increased by using a pair of complementary FSS layers, giving a positive reflection phase over a wide frequency range, as the proposed PRS. Low sidelobes are achieved by lowering the reflection amplitude of the PRS along its length while keeping reflection phase almost the same throughout the operating band. The performance of the proposed PRS is validated by creating a circular aperture RCA and measuring its radiation characteristics. The cavity is excited by an aperture coupled patch antenna having a broad impedance bandwidth. Prototype RCA gives a peak realized gain of 16.1 dBi and a 3-dB gain bandwidth of 8.6% ranging from 14.5 to 15.8 GHz. Measured sidelobe levels are reduced, respectively, to less than −17 dB and −23 dB in the E- and H-plane of the prototype antenna.

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.

Low-Cost Ultrawideband High-Gain Compact Resonant Cavity Antenna

A 3-D printed planar permittivity-gradient superstrate (PGS) is used to improve the directive radiation characteristics of a waveguide-fed compact resonant cavity antenna (CRCA). Far-field directivity of classical uniform superstrate-based RCAs is limited due to nonuniform aperture phase distribution caused by even transmission through the superstrate. Transverse PGS has been used here to remarkably improve aperture phase distribution and hence directive radiation performance of RCAs. Furthermore, the PGS was rapidly prototyped in one hour and 43 min using a low-cost acrylo-butadiene styrene (ABS) filament without using traditional multistep milling and machining. Single step fabrication was performed and effective dielectric constant of the ABS was varied through controlled infill percentage in different regions of the PGS. Measurements of a prototype indicate unrivaled results, from a smaller footprint, which includes peak directivity of 16.048 dB, 3 dB directivity bandwidth of 49.65% and sidelobe levels lower than -10.4 dB throughout the operating frequency band. The 3-D printed PGS thus outperforms all previously reported superstrates, for RCAs, by demonstrating similar radiation performance with an equivalent material cost of only 0.41 USD.

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.

A D-Band 3D-Printed Antenna

This article reports the design and fabrication of a novel all-metal antenna operating in the millimeter-wave band. Based on the resonant cavity antenna (RCA) concept, the principle of antenna operation is explained, and parametric studies of several key design parameters are provided. A novel impedance matching technique is introduced to broaden the antenna return loss bandwidth. Two gain enhancement methods have been employed to achieve a more directive beam with reduced side lobes and back lobes. The D-band antenna prototypes are produced using i) all-metal printing without any postprocessing; ii) dielectric printing with copper metallization applied later. Comparisons of the simulated and measured results amongst the antennas fabricated using the two additive manufacturing techniques are made. Measurement results of the two antenna prototypes show that the proposed design can achieve a 14.2% bandwidth with a maximum gain of 15.5 dBi at 135 GHz. The present work is the first D-band resonant cavity antenna fabricated using two different 3D printing methods.

Millimeter-Wave Low-Loss Multifeed Superstrate-Based Antenna

A low-loss multifeed antenna with controlled polarization and beam steering is presented. A low-profile resonant cavity antenna is fed by multiple spherical dielectric resonators (DRs), demonstrating its multifeed capabilities. Each of the DRs are themselves fed from four different sides by microstrip resonators on a planar circuit board. The beam pointing direction and polarization of the antenna are controlled by the signal phases at the respective input ports. Several antennas with varying feed topology are investigated, showing the versatility of this method. A 16-way 34 GHz prototype is built and measured, demonstrating high overall efficiency (considering power combining loss and antenna loss) of 80%.

Design of Wideband Resonant Cavity Antenna using Particle Swarm Optimization

A wideband optimization technique of a Resonant Cavity Antenna (RCA) is demonstrated using a very simple and efficient Particle Swarm Optimization (PSO) approach. The proposed optimization method appears to be attractive as it is driven conveniently by a commercial EM-simulator. This may be treated as a 70-dimensional as well as a wideband optimization problem to optimize ten antenna parameters. The proposed technique offers maximum about 17.6 dBi broadside gain using the optimally designed antenna. The peak-gain is maintained above 11 dBi over the 50% antenna bandwidth.

Beam-Scanning Antenna Based on Near-Electric Field Phase Transformation and Refraction of Electromagnetic Wave Through Dielectric Structures

An elegant combination of electric near-field phase transformation technique and electromagnetic-wave refraction, implemented through a pair of 3D printed dielectric structures, has been used to demonstrate a Ka-band beam-scanning antenna system. The system comprises a resonant-cavity antenna (RCA), which is used as a base antenna, a stepped dielectric (SD), and a dielectric wedge (DW). The SD is suspended above RCA in the near-field region to focus its broadside beam at an offset angle of 20°. The DW is placed above the SD and its two opening angles are selected such that the offset-angle focused beam tilts further and moves back to the broadside when the DW is co- and counter-aligned with the SD, respectively. The total height of the antenna system is 8.1λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at the operating frequency of 30 GHz. The total cost of the material used for printing the two dielectric structures in prototyping is only 6 USD. It has been demonstrated through measurements of the prototype that by rotating the DW around its own axis, the antenna beam can be scanned in both azimuth and elevation planes. The measured results indicate that antenna beam can effectively be scanned to any arbitrary angular position within a conical region having an apex angle of 68°, while maintaining peak-gain value within the 3 dB limit of the maximum gain of 16 dBi.

Comparative Study of Optimization Algorithms on the Design of Broadband Antennas

Broadband antennas find many applications in modern communication systems, such as Wi-Fi, 5G, and SatCom. Multiple competing optimization methods are available for the application to antenna design, while it would be preferable to know in advance if any method is superior. Here, an application of the cross-entropy method, along with particle swarm optimization and covariance matrix adaptation evolutionary strategy, to the design of broadband antennas is presented. The first example is an aperture-coupled microstrip patch antenna that has 9.5 dBi peak directivity and 53% bandwidth after optimization. It is then used as a feed in a high-gain broadband resonant cavity antenna. Using an all-dielectric superstrate with a transverse permittivity gradient, a compact thin resonant cavity antenna with a peak directivity of 19 dBi and 40% 3-dB bandwidth was designed. A comparative analysis of the cross-entropy method, particle swarm optimization, and covariance matrix adaptation evolutionary strategy applied to these two problems was carried out to provide the basis for further optimization of antennas in radio frequency and microwave frequency bands. We found that although all three methods reached a similar solution, the cross-entropy method has a speed advantage. It improves our ability to optimize existing designs and has wider applicability beyond antenna engineering.

An Optically Transparent Metasurface-Based Resonant Cavity Fed by Patch Antenna for Improved Gain.

An optically transparent metasurface (MS) is proposed to design a resonant cavity fed by a patch antenna operating at 5.6 GHz. In the proposed MS, a transparent micro metal mesh conductive (MMMC) film is used as the transparent conducting film (TCF), and it has a high optical transmittance of more than 75% and a low sheet resistance of 0.7 Ω/sq. The MS is composed of a layer of glass substrate and a layer of MMMC film. The unit cell of MS consists of a square patch using MMMC film patterned on a square glass substrate. The transparent MS, patch antenna, ground plane, and air-filled half-wavelength cavity form a resonant cavity antenna, to achieve an improved gain. The MS is designed, optimized and analyzed using the EM simulation software CST. Results show that the MS can improve the simulated boresight gain from 4.7 to 13.2 dBi by 8.5 dB, without affecting the impedance bandwidth (IMBW) much. The losses of MS with different values of sheet resistance are also studied, showing the MS using MMMC with sheet resistance of 0.7 Ω/sq has very small losses.

High-Gain Low-Profile Chip-Fed Resonant Cavity Antennas for Millimeter-Wave Bands

This letter demonstrates a novel integration approach to design high gain chip-fed antennas in V -band and W -band. An on-chip spherical dielectric resonator is integrated with a resonant cavity antenna, which resulted in high radiation efficiency and increased gain. The proposed approach minimizes the use of chip area and provides several advantages, such as, low profile and ease of assembly in comparison to similar antennas, reaching 17.8 dBi and 18.4 dBi gain for V -band and W -band, respectively.

Dual‐polarized high gain resonant cavity antenna for radio frequency energy harvesting

A Fabry pérot antenna with a multilayer superstrate having nonuniform unit cells has been investigated as a receiving antenna for radio frequency (RF) energy harvesting applications. Here, the primary radiator is selected as a dual-polarized aperture coupled microstrip antenna with a double-layer superstrate. This antenna excites orthogonal polarizations, vertical (V) and horizontal (H) in the frequency band of 6.2 and 5.8 GHz, respectively, due to the presence of two orthogonal H-shaped slots in its ground plane. The proposed antenna provides a gain enhancement of 9.8 and 10.1 dBi at the respective frequencies. The rectifying circuit is designed for a frequency of 5.8 GHz using a voltage doubler topology. The circuit provides a power conversion efficiency of 41% at 0 dBm input power.

A Wideband Resonant Cavity Antenna With Compact Partially Reflective Surface

A novel wideband resonant cavity antenna (RCA) with compact partially reflective surface (PRS) is presented, which is composed of a superstrate and a feed antenna. The superstrate is a dielectric slab with double-deck periodic array structure, where the superstratum is composed of square loop cells and substratum is composed of square loop aperture cells. This shows positive reflection coefficient phase, which in turn helps in obtaining wider RCA bandwidth. Contrary to the patch cell periodic array, a periodic array composed of square loop cells provides further compact structure. The feed system is a wideband aperture-coupled patch antenna, which is composed of square patch, ground plane with I-shaped slot, and fork-shaped feed network. This dual-arm feed network helps in obtaining the maximum gain at the center frequency. The superstrate with positive reflection coefficient phase provides the minimum gain at the resonant frequency. This in turn helps RCA in obtaining invariant gain in the operation band. Experimental verification was performed and the results show that this RCA offers fractional bandwidth of around 23.6% at $X$ -band (8.88–11.25 GHz, S11 ≤ −10 dB) and gain (13.36–13.92 dBi) is almost invariant over the bandwidth. The measured patterns are symmetric with low cross-polarization levels.

Design of high gain, wideband microstrip resonant cavity antenna using FSS superstrate with equivalent circuit model

A high directivity wideband resonant cavity antenna (RCA) is proposed in which a compact wideband microstrip patch antenna (MPA) is utilized as radiator. Through introducing an interdigital capacitor (IDC) in the patch, a planar metamaterial (MTM) unit cell in the ground plane and cutting two vertical slits from the slot, size reduction of the radiator is realized. To improve the directivity of the proposed MPA, a wideband FSS superstrate is designed and placed above the MPA making the whole antenna to operate as RCA. By using image theory, even and odd modes in RCA are analysed and the distance between FSS and the radiator is adjusted leading to optimum directivity and bandwidth in the proposed RCA. Maximum directivity enhancement in the designed RCA compared to the single element radiator is 4.2 dBi in the impedance matching bandwidth. The measured bandwidth and maximum gain of the proposed RCA are 24.9% and 11.2 dBi, respectively. Additionally, an equivalent circuit model for MPA and designed RCA is developed. The proposed antenna exhibits high gain and low cross polarization level making it a good candidate for radar applications. The final designed antenna is fabricated and the measurement results agree well with the simulation results.

3-D-Printed Phase-Rectifying Transparent Superstrate for Resonant-Cavity Antenna

A three-dimensional (3-D)-printed nonplanar highly transmitting superstrate is presented to improve the directive radiation characteristics of a resonant-cavity antenna (RCA). Classical RCAs are reported with nonuniform aperture-field distribution that compromises their far-field directivity. The concept of near-field phase correction has been used here to design a phase-rectifying transparent superstrate (PRTS), which was fabricated using the 3-D printing technology. The PRTS is printed using easily accessible polylactic acid filament. It has a significantly lower cost and weight compared to its recently published counterparts, while its performance is comparable. The 3-D printing technology yielded the prototype in less than 4 h, which is considerably less compared to the traditional machining methods. Measurements of the prototype indicated close correspondence between the predicted and the measured results. Significant increase in the antenna performance has been achieved, due to the rectification of the aperture phase distribution. Notable aspects encompass 7.3 dB increase in the antenna peak directivity (from 13–20.3 dBi), significant sidelobe level suppression, and an improvement of aperture efficiency by 36.1%, with a PRTS that costs less than 2.5 USD.

A Stripline-Based Planar Wideband Feed for High-Gain Antennas with Partially Reflecting Superstructure.

This paper presents a new planar feeding structure for wideband resonant-cavity antennas (RCAs). The feeding structure consists of two stacked dielectric slabs with an air-gap in between. A U-shaped slot, etched in the top metal-cladding over the upper dielectric slab, is fed by a planar stripline printed on the back side of the dielectric slab. The lower dielectric slab backed by a ground plane, is used to reduce back radiation. To validate the wideband performance of the new structure, in an RCA configuration, it was integrated with a wideband all-dielectric single-layer partially reflecting superstructure (PRS) with a transverse permittivity gradient (TPG). The single-layer RCA fed by the U-slot feeding structure demonstrated a peak directivity of 18.5 dBi with a 3 dB directivity bandwidth of 32%. An RCA prototype was fabricated and experimental results are presented.

Single-Dielectric Wideband Partially Reflecting Surface With Variable Reflection Components for Realization of a Compact High-Gain Resonant Cavity Antenna

This communication presents a design methodology for a compact low-cost partially reflecting surface (PRS) for a wideband high-gain resonant cavity antenna (RCA) which requires only a single commercial dielectric slab. The PRS has one nonuniform double-sided printed dielectric, which exhibits a negative transverse-reflection magnitude gradient and, at the same time, a progressive reflection phase gradient over frequency. In addition, a partially shielded cavity is proposed as a method to optimize the directivity bandwidth and the peak directivity of RCAs. A prototype of the PRS was fabricated and tested with a partially shielded cavity, showing good agreement between the predicted and measured results. The measured peak directivity of the antenna is 16.2 dBi at 11.4 GHz with a 3 dB bandwidth of 22%. The measured peak gain and 3 dB gain bandwidth are 15.75 dBi and 21.5%, respectively. The PRS has a radius of 29.25 mm ( $1.1\lambda _{0}$ ) with a thickness of 1.52 mm ( $0.12\lambda _{g}$ ), and the overall height of the antenna is $0.6\lambda _{0} $ , where $\lambda _{0}$ and $\lambda _{g}$ are the free-space and guided wavelengths at the center frequency of 11.4 GHz.

Compact High Gain Resonant Cavity Antenna With via Hole Feed Patch and Hybrid Parasitic Ring Superstrate

A compact and high gain resonant cavity antenna (RCA) is investigated in this work. At first, a ray-tracing model and the full-wave analysis are presented to clarify the characteristics of RCA in cases of finite lateral size and inhomogeneous superstrate. In consequence, a novel compact, high gain, and wideband RCA is proposed. The RCA consists of a via hole feed patch and an array of hybrid parasitic rings fabricated on a superstrate. The via holes feed patch with a high radiation directivity significantly enhances the RCA’s gain. On another hand, the dimension and bandwidth of the RCA are improved by the hybrid parasitic ring superstrate which is constituted by non-periodic parasitic patch and rings. Finally, a prototype of the RCA is fabricated and measured. With only the dimension of $1.35\lambda _{0}\times 1.35\lambda _{0}\times 0.63\lambda _{0}$ , the peak gain of 15.8 dBi and 3 dB gain bandwidth of 10.7% are obtained.

Selectivity of a resonant cavity antenna

The main selective characteristics of a Resonant Cavity Antenna, which is a radiating element of the antenna array of a glide path station, are presented. The results of rigorous electrodynamic modeling of a resonator antenna and experimental results of studies on antenna samples are presented

Design of high gain, broadband resonant cavity antenna with meta-material inspired superstrate

A broadband high gain planar meta-material based Resonant Cavity Antenna (RCA) operating at C-band is proposed. The RCA is modeled using simple ray tracing method. The unit cell metamaterial consists of Artificial Magnetic Conductor (AMC) and square patch laminated on either side of a lossy commercial dielectric material of dielectric constant 4.4 & thickness 1.6 mm, is used as the superstrate to design RCA. Square patch is the capacitive type and that AMC as inductive. Effects of the reflection phase of the substrate decide the high gain of the antenna. A cylindrical dielectric resonator antenna (CDRA) is embedded into the cavity as a feed. The proposed antenna achieves 22.4 dBi gain with 2 layers of 4 × 4 array superstrate with a bandwidth of around 5.1 GHz. The full-wave analysis is performed to extract the impedance matching, radiation pattern & gain of the composite RCA. A prototype antenna is fabricated and tested for verification of experimental results which was found to be well correlated. It also shows that the proposed RCA achieves −10 dB impedance bandwidth of 72.72% ranging from 4 to 9.1 GHz with a high gain around 22.4 dBi.