dB Gain Bandwidth Research Articles

A Multibeam Folded Reflectarray Antenna With Wide Coverage and Integrated Primary Sources for Millimeter-Wave Massive MIMO Applications

A millimeter-wave multibeam folded reflectarray antenna (FRA) with wide coverage in the azimuth plane and integrated planar primary sources for massive multiple-input multiple-output wireless communications is proposed. The substrate-integrated waveguide series-fed aperture-coupled rectangular patch antenna arrays are used as the primary sources, which makes it possible to be integrated with transceiver circuits seamlessly. A bifocal design methodology is used for improving the beam coverage and performance. A 19-beam prototype which consists of three seven-beam FRAs is designed, fabricated, and measured, enabling 30° coverage with a beam crossing level of −3 dB. The measured maximum beam gain is 25.9 dBi at 42 GHz, while the measured overall bandwidth, i.e., $\vert S_{11}\vert and 3 dB gain bandwidth, is 39–43 GHz. The proposed antenna has the advantages of easy fabrication, high gain, low cost, low profile, wide angular coverage, and co-planar integration with transceiver circuits, etc.

Wideband Low Axial Ratio and High-Gain Sequentially Rotated Antenna Array

A 2 × 2 sequentially rotated antenna array with high gain and wide axial ratio (AR) bandwidth is designed. The antenna element consists of a microstrip patch fed with a series power divider through four L-shaped probes. Low AR ≤ 1 dB is guaranteed by reiterating the employment of the series power divider at the array level, and optimizing the antenna element impedance matching bandwidth performance. A prototype of the antenna array is manufactured for the ultrahigh frequency radio frequency identification bandwidth, with overall size 1.32 × 1.32 × 0.065 λ3. Measurement shows a S 11 ≤ −10 dB bandwidth of 36.5% (0.76–1.1 GHz), an AR ≤ 3 dB bandwidth of 28.8% (0.823–1.1 GHz) with AR ≤ 1 dB within 0.846–1.015 GHz (18.2%). Moreover, a peak gain of 13.2 dBic, and a 3 dB gain bandwidth of 26.1% are observed. The presented antenna exhibits outstanding AR performance and high gain despite its low design and implementation complexity.

Broadband Folded Transmitarray Antenna Based on an Ultrathin Transmission Polarizer

In this paper, low-profile broadband planar folded transmitarray antennas (FTAs) are proposed and studied based on a novel Fabry–Perot polarizer. A novel element is proposed to carry out high-efficiency transmission, the phase compensation and the 90° polarization rotation at the same time. The element consists of two identical dielectric slabs, sandwiched by three metal layers, and has a thickness of only about $0.1\lambda $ . To verify this element, a transmitarray antenna is first designed and its highly efficient radiation performance is demonstrated by both simulations and the experiments. Low-profile FTAs are then designed and studied. The results show that the advantages of broad bandwidth, high gain, lower profile, planar geometry, and ease of integration can be achieved. The experiments of the FTA antenna demonstrate a 3 dB gain bandwidths of 18% and a peak gain of 25.2 dBi.

Multilayer Compact Grid Antenna Array for 79 GHz Automotive Radar Applications

A novel wideband compact grid antenna array is developed for 79 GHz multiple–input multiple-output radar applications. The key issue is the stable radiation pattern with flat-gain characteristic along the whole frequency bandwidth, which is very advantageous for the targeted radar applications. The antenna is taped out with the new high-resolution multilayer printed circuit board (PCB) technology called “Any-Layer PCB.” This technology provides the possibility to stack microvias in PCBs and reduce the fabrication cost compared with other multilayer technologies in millimeter-wave bands. With this feature, the width of the array has been compacted with 17.2%, which leads to a higher sidelobe suppression and an enhancement of the field of view in radar applications. A combined impedance and 3 dB gain bandwidth of 9.6% is achieved. The gain and sidelobe level are 13.52 and –14 dB at 79 GHz, respectively.

Design and fabrication of a wideband reflectarray antenna in Ku and K bands

The purpose of this paper is design of a wide band single layer reflectarray antenna using a new broadband cell. The proposed cell consists of two parts. The first part is a circular patch and the second one is a ring with some additional stubs, which are attached to the patch and ring in a symmetrical form. The circular patch and ring elements are designed at frequencies of 20 GHz and 15 GHz respectively. In order to increase the reflectarray antenna bandwidth, at first the dimensions of the patch, ring and stubs are optimized to attain uniform phase response in the frequency range from 11 GHz to 20 GHz. Then an air layer is considered under the dielectric substrate. The reflectarray antenna is designed based on this optimized wideband unit cell. A wideband horn antenna is also designed as a feed antenna for the proposed reflectarray structure. The reflectarray antenna with horn are simulated. The 1 dB gain-bandwidth of 4.66 GHz is obtained (27.4% fractional bandwidth) in the frequency band of 14.72 GHz to19.38 GHz. Finally, the reflectarray antenna is fabricated and tested. It can be seen that there is a good agreement between simulation and measurement results.

Design of Single-Layered Ultrawideband High-Efficiency Circularly Polarized Reflectarray

In this letter, we present a single-layered circularly polarized reflectarray antenna with a broad operating bandwidth in terms of realized gain, axial ratio (AR), radiation pattern, and aperture efficiency (AE). By employing multiple plasmon resonances, the proposed quasi-I-shaped element achieves a broadband linearly polarized conversion effect, which will contribute to a broadband reflectarray design. Thus, based on the element angular rotation method, a broadband offset-fed reflectarray with size of 215 × 215 mm2 and cells of 43 × 43 is designed, simulated, and then fabricated and measured. Good performances can be observed from both simulated and measured results, which confirm that the reflectarray antenna achieves a 75% 3 dB AR bandwidth (10–22 GHz) and a 49.7% 3 dB gain bandwidth (12.4–20.6 GHz). Furthermore, the measured AE exceeds 50% within a 28.2% bandwidth.

Transmitarray Design With Enhanced Aperture Efficiency Using Small Frequency Selective Surface Cells and Discrete Jones Matrix Analysis

We present a four-layer transmitarray antenna using small and dense frequency selective surface (FSS) cells and a horn antenna operated in a Ku band satellite downlink (10.7 to 12.75 GHz in Europe). The FSS offers a full transmission phase range of 360° and low loss between the incident and the transmitted waves: the magnitudes of the transmitted waves were equal to or better than −3.5 dB for incident transverse electric and transverse magnetic waves up to 30° in oblique angle. The transmitarray was fabricated using FR-4 boards with a loss tangent of about 0.02. FR-4 boards with lower loss tangents at the operating Ku band were not used because of the requirement for low cost. We also present the design of the horn antenna used to illuminate the transmitarray. The design applies discrete Jones matrix analysis; the final full transmitarray (333 unit cells) with the horn antenna were co-simulated using a full-wave simulation tool. The measured and simulation results are in excellent agreement. With a cell pitch of 0.39 $\lambda _{0}$ , the transmitarray achieves a dynamic range of 20 dB. The measured gain of the transmitarray prototype is 26.2 dB at a center frequency of 11.7 GHz, resulting in an aperture efficiency of about 62%. The measured results were achieved with a very small transmitarray (backpack-fit versus truck-carried). The −1 dB gain bandwidth of the transmitarray antenna is 12.6% at the center frequency (11.7 GHz).

Wideband high‐gain millimetre/submillimetre wave antenna using additive manufacturing

This study presents a novel design of a wideband high-gain resonant cavity antenna (RCA) for millimetre and submillimetre wave bands, and its fabrication using additive manufacturing (AM). The proposed RCA antenna consists of a partially reflecting surface and three impedance matching layers fed by a waveguide. AM techniques are utilised to fabricate the design operating at 30 GHz. Two fabrication techniques are assessed for printing the antenna. The first technique is based on printing a dielectric material and fully coating the parts with a metallic layer, while the second technique involves printing the parts in a single process using metal three-dimensional printing. The first technique offers a lightweight solution while the second technique can print the whole model in one run. The antenna design is investigated by both simulations and experiments. The measured results show a 3 dB gain bandwidth of about 10%, and high gain over 15 dBi for all the three resulting antennas. Good agreement between simulation and measurement is obtained. The antenna is of low cost and achieved good performance in terms of wide bandwidth and high gain, thus it is potentially useful for high-speed wireless communications at millimetre-wave and sub-millimetre-wave frequencies.

Single-Layer Circularly Polarized Wide Band Reflectarray Antenna with High Aperture Efficiency

A circularly polarized broadband low-cost reflectarray in Ku-band is presented using a novel single-layer subwavelength phase-shifting element. The proposed subwavelength element consists of the concentric split ring and the crossed bowtie. The linear reflected phase response curve with 360° phase coverage is obtained. For experimental verification, an array of 25 × 25 reflectarray prototype has been designed and manufactured by employing the angular rotation technique. The measurements are in good agreement with the simulations. The measured gain at the center frequency of 12.5 GHz is 26.6 dBi, corresponding to the aperture efficiency of 52.5%, and the 1 dB gain bandwidth is 26.4%.

Enhanced Reflectarray Antenna Using Elements With Reduced Reflection Phase Sensitivity

An enhanced reflectarray (RA) antenna built of elements with reduced reflection phase sensitivity is presented. The proposed unit element is composed of a concentric, multiresonance circular-ring structure with variable sizes. By changing the outer and inner radius of the interior ring in the opposite directions, a reduction in the phase sensitivity to manufacturing inaccuracy is achieved without extra contribution to the 360° phase range and aggravating the losses in the unit element is achieved. In addition, the margin between normal and oblique incidence of a phase response for angles up to 40° is smaller than 10°, which results in a high-efficiency, wideband performance. Measurement results show the maximum gain of 26.4 dBi at 10 GHz, aperture efficiency of 44.27%, and 16.3% 1 dB gain bandwidth. In order to improve the bandwidth of antenna, the phase constant ( $\psi _{{{\circ}}}$ ) value at the RA aperture is gradually tuned and optimized. The designed antenna with $\psi _{{{\circ}}}= \,{{- {\text{125}}^\circ }}$ has a peak gain 26.6 dBi at 10.2 GHz and aperture efficiency of 44.56%, and the 1 dB gain bandwidth is about 23.3% (9.67–12 GHz). In comparison with the conventional antenna ( $\psi_{\circ}= {{0^\circ }}$ ), the 1 dB bandwidth shows a 43% improvement.

Circularly Polarized Transmitarray Antennas at Ka-Band

This letter presents the simulation, optimization, and demonstration of a collimated-beam transmitarray and a quad-beam transmitarray operating at Ka-band. Both transmitarrays are based on a 3 bit unit cell implementing both phase-shift and linear-to-circular polarization conversion functions. The collimated-beam transmitarray presents a measured gain of 33.8 dBi (corresponding to an aperture efficiency of 51.2%) and a 3 dB gain bandwidth larger than 15.9%. The quad-beam transmitarray phase distribution has been optimized by a genetic algorithm code coupled with an analytical tool. The array is designed to radiate four beams at θ0 = ± 25° in the horizontal and vertical planes at the frequency of optimization.

Wideband Fabry–Perot Antennas Employing Multilayer of Closely Spaced Thin Dielectric Slabs

In this letter, a method to design wideband Fabry–Perot resonator (FPR) antennas is presented. The structure employs closely spaced truncated thin dielectric slabs as a partial reflecting surface (PRS). An analytical design process based on transmission line theory is proposed. The criterion for wideband FPR antennas is generalized for a highly truncated PRS, i.e., the PRS only needs to exhibit a resonance at the center frequency of the band. Based on the finding, a compact FPR antenna is optimized and experimentally validated with a wide 3 dB gain bandwidth of about 86% and maximum realized gain of 14.2 dBi.

Design and Experiment of a Near-Zero-Thickness High-Gain Transmit-Reflect-Array Antenna Using Anisotropic Metasurface

Combining a reflectarray and a transmitarray together, a novel array antenna with bidirectional high-gain beams is proposed in this paper. A novel single-layer metal-only defected square-ring slot element, which has a near-zero thickness, is introduced as the phasing element. Full 360° phase shift range is achieved by utilizing the cross-polarized field of the phasing element. As a bidirectional high-gain antenna (bi-HGA), a transmit-reflect-array using the proposed elements is then designed, fabricated, and measured. It is only composed of a thin metallic sheet with 420 mm side length, spatially fed by a corrugated horn. Well-defined pencil beams are formed in broadside directions on both sides. The measured gains of the transmitted and reflected beams at 10 GHz are 25.5 dBi with 15% 1 dB gain bandwidth and 25 dBi with 14% 1 dB gain bandwidth, respectively. The proposed bi-HGA exhibits distinctive advantages of being ultrathin $(0.0067\lambda _{0})$ , lightweight, and low cost without using dielectric substrates, and is a promising candidate for bidirectional wireless communication applications.

Passive Opto-Antenna as Downlink Remote Antenna Unit for Radio Frequency Over Fiber

A novel remote antenna unit, intended for application in the downlink of an analog radio frequency over fiber system, is proposed, whose radiated power originates entirely from the optical signal supplied by a single multimode fiber. By operating the photodetector of the optical receiver at zero bias voltage, while omitting typical active components, such as transimpedance amplifiers, a fully passive unit, requiring no external power supply, is obtained. Instead, a careful co-design is performed to maximize the power transfer from photodetector to antenna within the frequency range of interest using an impedance matching network. A wideband cavity-backed slot antenna is implemented in an air-filled substrate-integrated-waveguide technology. The antenna feed plane serves as an integration platform for the optical receiver. The resulting downlink remote antenna unit is compact, cost-effective, energy-efficient, and extremely reliable. Therefore, it is an ideal building block for novel, highly specialized, ultrahigh density wireless communication systems, which require massive amounts of remote antenna units, deployed in attocells as small as ${\text{15 cm}} \times {\text{15 cm}}$ . A prototype operating in a wide frequency bandwidth ranging from 3.30 to 3.70 GHz is constructed and validated. In free-space conditions, a broadside gain of $-$ 0.2 dBi, a front-to-back ratio of 8.8 dB and linear polarization with a cross-polarization level of $-$ 28.8 dB are measured at 3.50 GHz. Furthermore, a $-$ 3 dB gain bandwidth of 500 MHz is observed. Finally, the prototype is deployed in a unidirectional data link, achieving a symbol rate of 80 MBd over a distance of 20 cm.

High-Efficient Wideband Transmitarray Antenna

A new structure for transmitarray antennas is presented. The proposed semiplanar transmitarray keeps certain geometrical curvature, that the required transmission phase range is reduced significantly from 360°, causing an increase in bandwidth and efficiency. The proposed antenna structure has varied element thickness—the central element being the thinnest and elements growing in thickness as we move toward the edges. To evaluate the new model, an X-band prototype antenna is fabricated with the number of layers for the elements growing from 2 to 5 from center to the edges of the aperture. The required phase range for the elements was reduced from 360° to 51.5°. Measurement results show that proposed antenna with aperture size of ${\text{21.8}}\lambda _{0}^{2}$ has 22.3 dBi maximum gain at 10.3 GHz. In addition, the proposed design achieves a 24.27% 1 dB gain bandwidth and 62% efficiency.

Broadband single‐layer reflectarray antenna for X‐band applications

A new type of X-band (8-12 GHz) unit cell structure on a single-layer for broadband reflectarray antennas is presented in this study. To obtain a broadband performance, a unit cell composed of a circular ring and a complementary diagonal patch ring is proposed. This new type unit cell is designed on a 0.183 × λ 0 (air-dielectric) thin dielectric substrate and has a 430 ° phasing range with slow phase variation. Based on the wide phase variation of the proposed unit cell, a centre-fed broadband reflectarray antenna is designed with 9 × 9 unit cells, 81 elements on a square plane geometry. The designed reflectarray has 40% aperture efficiency and 96% antenna efficiency at 10.5 GHz. The validity of the reflectarray antenna is verified through measurement and simulation results. The experimental and simulation results are in good harmony. The measured and simulated results show that the maximum gain of the reflectarray antenna is 21.6 dBi at 10.5 GHz and has 23% 1 dB gain bandwidth and 29% 3- dB gain bandwidth. Also, the minimum cross-polarisation discrimination is 31.2 dB at 11 GHz frequency.

A compact wideband and high gain GRIN metamaterial lens antenna system suitable for C, X, Ku band application

In this paper, a rectangular split ring resonator (RSRR) based gradient refractive index (GRIN) metamaterial structure arranged in 30 × 10 array of size 4 cm × 4 cm for lens antenna is addressed. The novelty in the design lies in the introduction of the splits in the rectangular rings in order to enhance the coupling of the currents between the rings. This ultimately results in the collimation of the field in the desired direction and improves the gain and bandwidth of the antenna system. The multilayer metamaterial structure is proposed to design a low loss, broadband, highly focusing thin lens. The metamaterial lens array is combined with a horn antenna system to achieve a gain improvement of 3–11 dB and cross polarization level below −23 dB in the frequency range of 3.5–19.5 GHz with a −3 dB gain bandwidth efficiency of 113%. The metamaterial medium parameters such as permittivity(ε), permeability(μ) and refractive index(η) variation of the proposed design is found to reveal its near zero values in the operating range, depicting it as a near zero metamaterial (NZMTM). The variation in the refractive index of the metamaterial lens is due to parasitic coupling between the metamaterial layers and that facilitates to design thin broadband lens antenna system. This broadband high gain lens antenna is found suitable for C, X, Ku band application.

Radar Cross Section Reduction of Low Profile Fabry-Perot Resonator Antenna Using Checker Board Artificial Magnetic Conductor

This paper presents a novel low profile, high gain Fabry-Perot resonator antenna with reduced radar cross section (RCS). An artificial magnetic conductor which provides zero degree reflection phase at resonant frequency is used as the ground plane of the antenna to obtain the low profile behavior. A checker board structure consisting of two artificial magnetic conductor (AMC) surfaces with antiphase reflection property is used as the superstrate to reduce the RCS. The bottom surface of superstrate is perforated to act as partially reflective surface to enhance the directivity of antenna. The antenna has a 3 dB gain bandwidth from 9.32 GHz to 9.77 GHz with a peak gain of 12.95 dBi at 9.6 GHz. The cavity antenna also has reduced reflectivity with a maximum reduction of 14.5 dB at 9.63 GHz.

Phase-Delay Versus Phase-Rotation Cells for Circular Polarization Transmit Arrays—Application to Satellite Ka-Band Beam Steering

Planar transmit arrays (TAs) have been an attractive solution as gain enhancers for various applications, e.g., satellite communications. The TA performance directly depends on its composing unit-cell characteristics. Planar unit cells can be categorized into two main types: phase-rotation (PR) and phase-delay (PD) cells. There is no hint in the literature about the relative merits of these two types of cells for circular polarization when assessing the final TA performance. This paper offers a systematic comparison between the cells' working principles and analyzes their impacts on TA performance. Examples of a PR-based TA and a PD-based TA are designed for single-band wide-angle beam steering operating at the satellite Ka-band. They are evaluated by simulation and measurement to quantify performance differences. No previous work employed a PR TA for wide-angle beam steering. This paper shows that PR TA offers a filtering effect toward the cross-polarization component of the source. This leads to better axial ratio and combined 3 dB axial ratio and 3 dB gain bandwidth. However, PD cells are easier to design and insensitive to feed polarization. The analysis in this paper allows a more informed decision when selecting the unit-cell category for any given TA application.

Wideband Transmitarray With Reduced Profile

This letter presents a wideband transmitarray (TA) with reduced profile. A novel unit cell based on a wideband bandpass filter is developed and applied to the design of the TA. The TA consists of two identical trilayer frequency selective surfaces (FSSs), thus it has a lower profile compared to traditional designs that use at least four FSS layers separated by quarter-wavelength air gaps to obtain the 360° phase shift range. The FSS has a pair of square patches printed on the top and bottom layers, and a square slot loaded by four microstrip lines printed on the middle layer. The phase shift is achieved by simultaneously adjusting the size of the square patches. Within the frequency band of interest, the developed unit cell shows low insertion loss and sufficient phase shift range. An equivalent circuit model is developed to better understand the operating principles of the FSS. To validate the design concept, one prototype operating at 13.5 GHz is designed, fabricated, and measured. The measurement results show that the designed TA achieves 16% 1 dB gain bandwidth and 60% aperture efficiency. The developed unit cell has symmetric configurations so it can also be applied to the design of dual-polarized or circularly polarized TAs.