Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

An up-to-date literature overview on relevant approaches for controlling circuital characteristics and radiation properties of dielectric resonator antennas (DRAs) is presented The main advantages of DRAs are discussed in detail, while reviewing the most effective techniques for antenna feeding as well as for size reduction Furthermore, advanced design solutions for enhancing the realized gain of individual DRAs are investigated In this way, guidance is provided to radio frequency (RF) front-end designers in the selection of different antenna topologies useful to achieve the required antenna performance in terms of frequency response, gain, and polarization Particular attention is put in the analysis of the progress which is being made in the application of DRA technology at millimeter-wave frequencies

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Dielectric Resonator Antennas: Basic Concepts, Design Guidelines, and Recent Developments at Millimeter-Wave Frequencies

Based on a transformation optics method, a flat compact dual-polarized Luneburg lens antenna is proposed and implemented using the printed-circuit-board-stacked gradient-index metamaterials for beamscanning and multibeam applications at X-bands. The transformed material properties of the planar Luneburg lens are designed with 17-layered permittivity distribution of polynomials. Each layer is discretized into $41 \times 41$ pixels made of broadband and less polarization-dependent unit cells responsible for desired index distributions. The effects of transformation, approximation, and discretization on the lens performance are analyzed comprehensively. Also, to validate the implementation method, a flat Luneburg lens with a thickness of 14.1 mm, a focal length of 28 mm, and an aperture size of $98.9 \times 98.9$ mm2 is designed and tested. A stacked aperture-coupled patch antenna operating at 10 GHz is applied as a feeder. The measured results show that the proposed antenna can operate over a bandwidth of ~20% with an antenna efficiency of 32%, a cross-polarization level of <−17.1 dB, as well as the maximum gain of 15.9/16.35 dBi and a scanning angle of ±32°/±35° for two orthogonal polarizations, respectively. The presented flat Luneburg lens antenna featuring broad bandwidth, high gain, wide scanning angle, and easy fabrication has a high potential in 5G wireless communication, imaging, and remote sensing applications.

A Flat Dual-Polarized Transformation-Optics Beamscanning Luneburg Lens Antenna Using PCB-Stacked Gradient Index Metamaterials

This paper presents the complete design of a wideband transmit-array (TA) antenna with high gain and high efficiency for D-band applications based on the low-temperature co-fired ceramic technology. The proposed unit cell is composed of a pair of wideband magnetoelectric dipoles as the receive/transmit elements, together with a substrate-integrated waveguide (SIW) aperture-coupling transmission structure for independent phase adjustability. A 360° phase coverage is obtained by the proposed phasing element, and its phase response curves are nearly parallel within a broad frequency band, which indicates a wideband performance. To verify the design, the fabricated prototype is measured by using a vector network analyzer in a terahertz compact-range anechoic chamber. The measured peak gain is 33.45 dBi at 150 GHz with the aperture efficiency of 44.03%, and the measured 3 dB gain bandwidth is 124–158 GHz (24.29%). The good radiation performance ensures that the proposed SIW aperture-coupling TA antenna is a promising candidate for D-band applications.

140 GHz High-Gain LTCC-Integrated Transmit-Array Antenna Using a Wideband SIW Aperture-Coupling Phase Delay Structure

A Reconfigurable Multifunctional Metasurface for Full-Space Control of Electromagnetic Waves

The design, simulation, and measurement results of a high-gain broadband gradient refractive index (GRIN) planar lens fed by an antipodal exponential taper slot antenna (ATSA) are presented. As a constituent part of this lens, a novel nonresonant metamaterial unit cell, composed of bilayer triple rectangular rings, is proposed and its equivalent circuit model is developed and described. It is shown that, by utilizing this element, stronger capacitive couplings between adjacent metallic layers are realized resulting in a large refractive index variation of about 2.5, and hence, a thin lens with a thickness of $0.38\lambda_{0}$ , where $\lambda_{0}$ is the wavelength at 9.5 GHz. In addition, since the unit cell is designed to resonate at higher frequencies, its refractive index response is smoothly increased over a broad frequency range and this considerably enhances the operating bandwidth of the lens. The achieved measured results demonstrate a broad matching and $-3\;{\rm dB}$ gain bandwidths of 52% (7–12 GHz) and 65% (7–13.2 GHz), respectively. Furthermore, this lens offers a high aperture efficiency of 50% (21.2 dB gain) at the center frequency, and its sidelobe and cross-polarization levels are less than $-20\;{\rm dB}$ and $-26\;{\rm dB}$ across the entire matched band, respectively.

A High-Gain Broadband Gradient Refractive Index Metasurface Lens Antenna

A broadband and high gain transmit array (TA) antenna, operating at 60 GHz, is proposed. To meet the design requirements of a TA antenna with polarisation-insensitive radiation performance, an optimal multi-layer unit cell (UC) is introduced. The dimensions of the UC are parametrically expressed to realise a linear transmission phase response with a variation range of 270° and insertion loss <;-3 dB over the desired frequency band ranging from 58 to 64 GHz. A new planar array composed of 2 × 4 aperture-coupled-patches interleaved with a soft-surface is also designed as a feed for the proposed TA. Furthermore, a hybrid method based on full-wave simulations and analytical formulations is developed to calculate the radiation characteristics of the TA antenna and the results are compared to the ones achieved with full-wave simulations. The designed TA antenna is fabricated and the measurement results are presented. The obtained results show peak aperture efficiencies of 38.48% (30.85 dB peak gain) and 32.37% (30.1 dB peak gain), and -1 dB gain bandwidths of 7.7 and 8.2% from the full-wave simulations and measurements, respectively. Such a broadband and high gain antenna is deemed to be suitable for mm-wave backhaul links in 5G cellular systems.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-map.2018.5768

Design and analysis of a millimetre-wave high gain antenna

A primary advantage of antenna arrays is their spatial selectivity, which has been widely utilized to support various applications, such as beam-steering, blocker rejection, massive multi-in--multi-out (MIMO), targeting communication, radar, and imaging. In this article, we exploit and engineer this spatial selectivity in an MIMO array for directionally secured wireless communication. We propose constellation decomposition array (CDA) and spatial carrier aggregation (SCA) schemes to achieve high throughput keyless physical layer security using antenna arrays. In CDA, lower order quadratic-amplitude modulation (QAM) signals are fed into an MIMO array and are spatially combined in the target direction to realize desired higher order QAM signals but distort the modulation in unintended directions. In SCA, we feed different carriers to different elements in an MIMO array to perform spectral carrier aggregation spatially. In addition, we adopt temporal swapping to further enhance security by creating one-to-many symbol mapping in unintended directions. The concept is demonstrated on an eight-channel MIMO transmitter (TX) fabricated in 45-nm CMOS silicon on insulator (SOI) and on-board antenna array for over-the-air (OTA) measurements. Using four channels of the TX array in the CDA mode, an information beamwidth of 5°/10° is realized by spatially constructing a single carrier 64QAM signal using three QPSK signals or one QPSK signal plus one 16QAM signal with a total 64QAM data rate up to 3 Gb/s. Using SCA with two carriers of 64QAM signals and temporal swapping, an rms error vector magnitude (EVM) of 6.3% at broadside with an aggregated data rate of 1.2 Gb/s is achieved, in contrast to greatly distorted rms EVM of 10% at only 4° angle.

A 25–34-GHz Eight-Element MIMO Transmitter for Keyless High Throughput Directionally Secure Communication

A new high gain hybrid dielectric resonator antenna (HDRA) is proposed for millimeter-wave (mm-wave) communication systems operating in the frequency range of 57–64 GHz. A ring-shape dielectric resonator (DR) is excited by an aperture-coupled patch antenna to achieve multiple resonances and widen the antenna bandwidth. To enhance the antenna gain, the HDRA is surrounded with a metallic dented-cavity. In addition, the performance of its radiation pattern is improved by using grounded-metallic rings. The simulation results demonstrate a good performance in terms of bandwidths, gain, and radiation patterns.

A broadband and high gain millimeter-wave hybrid dielectric resonator antenna

A single layer conventional mushroom-like electromagnetic bandgap structure is proposed to enhance the gain of a coaxial fed patch antenna. This EBG configuration is used in both E- and H-plane directions to investigate their effect on the antenna radiation pattern. The primary simulation results demonstrate that, without noticeably losing the matching bandwidth, more than two times gain enhancement is achieved by effectively converting the suppressed surface waves into the radiated ones.

Elham Erfani

Papers

A High-Gain Broadband Gradient Refractive Index Metasurface Lens Antenna

Design and analysis of a millimetre-wave high gain antenna

A 25–34-GHz Eight-Element MIMO Transmitter for Keyless High Throughput Directionally Secure Communication

A broadband and high gain millimeter-wave hybrid dielectric resonator antenna

On the antenna gain enhancement using artificial materials