Cross-polarization Discrimination Research Articles

Ridged Apertures for LEO Direct Radiating Arrays in Ka-Band

This paper presents an extensive performance analysis of open-ended waveguide elements for direct radiating arrays with a high scan angle (±50° /60°). The evaluated designs are based on square and hexagonal apertures loaded with ridges. Both square and triangular lattices are considered in the framework of Ka-band downlink design requirements for future LEO mega-constellations. The parameter space defined by the monomodal condition has been explored to find an optimum value for each structure. The analyses carried out with both infinite and finite full-wave models in terms of active reflection coefficient, scan loss and cross-polar discrimination are in good agreement.

Differentially Fed Shorted Triangular Patch Antenna with High Cross-Polar Discrimination and Pattern Symmetry

A differentially fed shorted triangular patch antenna with high cross-polar discrimination (XPD) and pattern symmetry about the boresight is presented. A new shorted triangular patch configuration is projected that uses a shorting wall at the middle apart from the widely explored back short. Two dedicated L-probes have been conceived for the excitation of the antenna in the TM11 and TM20 modes. The differentially fed antenna exhibits 49.43% impedance bandwidth and produces XPD ≈ 43 dB without any pattern tilt and 9 dBi gain. The achieved high XPD, patterns without tilt, and wider bandwidth are the superiority of the proposed antenna compared to earlier reports. An X-band prototype has been realized and experimentally validated. Relevant experimental results are also presented.

A Compact Dual-Polarized Vivaldi Antenna with High Gain for Tree Radar Applications.

A dual-polarized compact Vivaldi antenna with high gain performance is proposed for tree radar applications. The proposed design introduces an array configuration consisting of two pairs of two Vivaldi elements to optimize the operating bandwidth and gain while providing dual-polarization capability. To enhance the gain of the proposed antenna over a certain frequency range of interest, directors and edge slots are incorporated into each Vivaldi element. To further enhance the overall antenna gain, a metal back reflector is used. The measurement results of the fabricated antenna show that the proposed antenna achieves a high gain of 5.5 to 14.8 dBi over broadband from 0.5 GHz to 3 GHz. Moreover, it achieves cross-polarization discrimination larger than 20 dB, ensuring high polarization purity. The fabricated antenna is used to detect and image the defects inside tree trunks. The results show that the proposed antenna yields a better-migrated image with a clear defect region compared to that obtained by a commercial Horn antenna.

A droplet-shape inspired wideband bow-tie dielectric resonator antenna for sub-6 GHz and IoT applications

In this article, an approach to realizing a dielectric resonator based bow-tie shaped antenna for the sub-6 GHz, 5G and IoT applications is discussed that utilizes droplet-shaped radiators for its two arms. The droplet-shaped radiating element is systematically derived to obtain a wider bandwidth response by truncating the sides of an aperture-coupled cylindrical DRA operating at HE11δ mode. The proposed bow-tie dielectric resonator antenna (DRA) is a modified dipole structure that uses a balanced line to differentially feed the two radiating segments to attain an overall wideband characteristics. A wideband matching balun circuit facilitates the antenna feeding which produces equal amplitude signals with 180° phase difference at its two output ports throughout the band of interest. The measurement of the proposed antenna confirms that it can serve several 5G bands like n77 (3300–4200 MHz), n78 (3300–3800 MHz), n48 (3550–3700 MHz) and n79 (4400–5000 MHz) with an overall wide bandwidth of 42.7% in the sub-6 GHz range. This planar configuration has a realized gain value ≥7.5 dBi within 3.37–3.91 GHz and it remains higher than 6 dBi almost throughout the working bandwidth of 3.18–4.91 GHz with considerably wide beamwidth. This broadband DRA has a consistent broadsided radiation pattern with cross-polarization discrimination (XPD)> 20 dB and its radiation efficiency varies between 60%–70% within 3.2–4.8 GHz. The antenna occupies a volume 1.2λ×1.2λ×0.1λ corresponding to its lower frequency of operation and it can support many more significant applications including WiMAX (3.3–3.8 GHz), Citizens Broadband Radio Service (CBRS) (3.55–3.7 GHz) and LTE (3.41–3.5 GHz uplink/3.51–3.6 GHz downlink). All these characteristics make this antenna a suitable candidate for use in transceiver modules for indoor communication, base stations, and vehicular communication.

Dual Linearly Polarized 2-bit Programmable Metasurface With High Cross-Polarization Discrimination

Dual Linearly Polarized 2-bit Programmable Metasurface With High Cross-Polarization Discrimination

A Compact 1:3 Power Divider Incorporating 180° Shifted Path for Polarization Purity Enhanced Base Station Subarray

This paper presents a compact 1:3 power divider and a base station subarray antenna with enhanced polarization purity exhibiting high cross-polarization discrimination (XPD) and high input port isolation. The compact 1:3 power divider incorporating a 180° shifted path is proposed to achieve both polarization purity and the wideband characteristics of the subarray antenna, which is difficult to implement using the conventional dual-feed method in limited areas. Using the proposed power divider, a dual-polarized quadruple Π-probe feed stacked patch antenna array is designed, which achieves a wide bandwidth of over 30% (< -13 dB) from 1.68 GHz to 2.25 GHz. The XPD is increased by approximately 8 dB and 5 dB at 1.71 GHz and 2.11 GHz, respectively, to attain an increase in the isolation bandwidth (< -20 dB) from 14% to 43%. Furthermore, the measurement results of a 4 × 3 antenna array confirm the effectiveness of the proposed design in terms of XPD and isolation while maintaining the bandwidth and beam performance. This study demonstrates a relatively wide bandwidth between patch antennas, despite the use of multiple subarrays. The comparative results also show a relatively better frontto-back ratio and isolation of the proposed design.

Polarization adaptation to improve cell border area bitrates and system capacity in small cells

The target of this paper is to show the impact of polarization adaptation on the received signal quality in an outdoor small-cell deployment scenario. The signal-to-interference ratio (SIR) is the key factor in defining the achievable data rate, and the capacity of the cell. At the cell border area, the SIR value is typically low and causes a significant decrease in the system capacity and achievable data rates. These bad SIR areas at the cell border can be improved by using orthogonal polarizations in the neighboring cells rather than using all polarizations over the whole cell coverage area. For the research work of this paper, a series of measurements were carried out to measure a received signal power and a cross polarization discrimination (XPD) ratio while the signal is transmitted and received with a different set of polarizations. In the measurements, we have considered horizontal, vertical, +/− 45° slanted polarizations, and two different environments, urban street and open space, and three frequency bands, 970−1030 MHz, 2000−2030 MHz and 3364−3400 MHz. The measurement results revealed that at a different distance from the transmitter, for horizontal/vertical polarization, the average XPD is around 24.7 dB and 31.7 dB in the urban street and open area environments, respectively. For +/− 45° slanted polarization, the average XPD is around 11.5 dB and 12.1 dB in the urban street and open area environments, respectively. This paper goes on to propose polarization adaptation in each cell, where the primary polarization is valid for the whole service area of the cell, and secondary polarization is only used in close proximity of the base station antenna. Considering the results, it is emphasized that system capacity can be significantly improved by having only one channel with good SIR values compared to multiple channels with bad SIR values. However, MIMO channels with orthogonal polarizations or with spatial multiplexing can be utilized in the closed vicinity of the base station, i.e., in an area with good SIR values. It is shown that the overall cell capacity can be increased by almost 35% by utilizing polarization adaptation compared to MIMO 2 × 2.

Multi-mode wideband antenna based on multi-mode resonator

A multi-mode wideband antenna based on multi-mode resonator is proposed with stable radiation patterns, which is composed of metal radiators, parasitic resonators, shorted patches fed by the U-shaped feedline, and a box-shaped reflector. A prototype of the proposed antenna is designed, fabricated, and tested. Measured results show that the antenna achieves an impedance bandwidth of 37.5% (0.67–0.98 GHz) for |S11| < −15 dB, a half-power beam width (HPBW) of 67.5 ± 2.4 degree at H-plane (horizontal plane), and a gain of 8.0 ± 0.5 dBi. Furthermore, the cross-polarization discrimination (XPD) is more than 15 dB at 0 degrees and at least 11.2 dB within ±60 degrees at H-plane, respectively. The proposed antenna can be used in the modern communication systems for LTE700/GSM850/GSM900.

Direct printable X-band low profile broadband reflectarray antenna using copper foils

This work reports on a compact and broadband reflectarray antenna that can be directly applied to the exterior surface of a nanosatellite. The design is composed of an annular ring with a wheel-shaped concentric structure loaded with two circular stubs acting as delay lines for maximum phase angle coverage. The design offers a phase variation of 576° in the X-band along with a peak measured gain of 26.6 dBi and an aperture efficiency of 49.24%. The design also offers low side lobe levels of −13 dB and −18 dB in both E- and H-planes at 11 GHz, respectively. Cross-polarization discrimination is also sufficiently large and is better than −32 dB and −36 dB for E- and H-planes, respectively. Moreover, the proposed printable reflectarray exhibited a 1-dB gain Bandwidth (BW) of 31.5 %. The design is produced by applying copper foils on float glass with a thickness of 2 mm as a proof of concept.

A 3-D Pattern-Reconfigurable Antenna Array With Multipolarization

In this letter, a 3-D pattern reconfigurable antenna array with multi-polarization is presented. It comprises four vertically placed reconfigurable end-fire dipole-pair elements and a compact four-path switchable feed network. By utilizing switchable operating dipoles of each element and appropriate pathways on the feed network, the antenna can achieve adaptive control of broadside patterns and backfire patterns with independent left-handed/right-handed circular polarization (LHCP/RHCP) and ±45° linear polarization (LP) in the elevation plane. Moreover, four end-fire patterns with vertical polarization (VP) can be adaptively controlled in the azimuth plane. The proposed antenna is fabricated and measured. With a compact 3-D structure of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math>$0.49\lambda_0 \times 0.49\lambda_0 \times 0.39\lambda_0$</tex-math></inline-formula> , the measured -10 dB overlapped impedance band for the twelve operating states is 2.3 GHz-2.75 GHz (17.8%). Besides, the corresponding crosspolarization discrimination (XPD) is more than 17.4 dB.

Millimeter-Wave Wideband ±45° Dual-Polarized Phased Array Antenna Based on Compact Wideband Widebeam Dipole Element Antenna

To meet the requirements of a millimeter-wave (mmWave) communication system prototype complying with 5G (24.25-29.5GHz) and B5G/6G (30-33GHz) standards, this letter presents a compact wideband widebeam ±45° dual-polarized dipole element antenna to form a wideband phased array antenna (PAA) covering the entire 24-33GHz (∼31.6%) band. First, by placing two orthogonal coupling feeding baluns over a dual-polarized dipole to excite the dipole's two pairs of orthogonal arms and employing four parasitic patches, a ±45° dual-polarized dipole element antenna is developed, showing a compact size (0.34λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.34λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> @24GHz), wide -14-dB impedance bandwidth (24-33GHz, 31.6%), wide 3-dB beamwidth (>100°), high polarization isolation (>25dB), and high cross-polarization discrimination (XPD) (>25dB) within the -14-dB impedance bandwidth. Then, based on the element antenna, a 4×4-element ±45° dual-polarized PAA is designed, fabricated using the LTCC process, and measured. The measurements show that, within the entire 24-33GHz band, the broadside scanning gain of the PAA is up to 14dBi, and the 3-dB gain variation scanning range is >±41° with a peak up to ±60º.

A Novel Bow-Tie Balun-Fed Dual-Polarized Crossed Dipole Antenna

A broadband dual-polarized crossed dipole antenna is proposed in this paper. To achieve a wide impedance bandwidth and low-profile configuration, a novel bow-tie balun is applied to this antenna. Firstly, the working mechanisms of both bow-tie baluns and the antenna are introduced. Then, the parametric study and design guidelines are presented. Finally, the optimized antenna is fabricated, measured, and analyzed. The simulated and measured results show that the antenna has a wide impedance bandwidth from 2.42 GHz to 6.48 GHz. The fractional bandwidth is 91.2%. Moreover, within the whole band, the E-plane and H-plane radiation patterns are stable. The port isolation is greater than 20 dB, and the cross-polarization discrimination ratio is better than 25 dB. The proposed antenna achieves a realized gain of 7.5 dBi ± 0.5 dBi. It can be a good candidate for sub-6 GHz wireless communications or short-range radar applications.

A Survey of Five Generations of MIMO Multiband Base Station Antennas

AbstractAs telecommunication systems evolve, there is an increasing demand for multi‐band MIMO base‐station antennas. Antenna arrays are generally used to support multiple frequencies with multiple ports in a compact size. However, this can result in significant degradation in scattering patterns and return loss/port isolation due to the close proximity of the radiation from the array. Various techniques have been proposed in the literature to address these issues. This paper presents an overview of the challenges faced by base station antennas (BSAs) over time and their general solutions. With the technological advancements of communication systems, accompanied by high data rates, high‐frequency antenna designs and MIMO operations have been introduced at the base station level. Base station antennas encountered design challenges, including broad bandwidth, high isolation levels, stable half‐power beam width, beam squint reduction, high cross polarization discrimination (XPD), gain improvement, beam steering, compact size, and cost reduction. This survey provides information on the solutions adopted by researchers over time for each design challenge, with citations. Additionally, the authors discuss techniques developed to overcome these challenges, demonstrating the evolution of BSAs from the first to the fifth generation of telecommunication systems.

A stacked dielectric magnetoelectric dipole antenna with embedded ceramics

Abstract A stacked dielectric magnetoelectric antenna with embedded ceramics (SDMEA-EC) is proposed. The antenna consists of a stacked dielectric resonator antenna with embedded ceramics and a leaf-shaped electric dipole (LSE-Dipole). To improve the performance of the magnetoelectric dipole antenna, a novel verification method is proposed by analyzing equivalent magnetic currents to meet the Huygens element principle. The stacked structure with embedded ceramics is helpful for expanding the impedance bandwidth. The electric dipole not only participates in the radiation but also is a part of the feed network, which simplifies the overall structure. The prototype of the proposed stacked dielectric resonator magnetoelectric antenna achieves an impedance bandwidth of 20.2 % in the high frequency band (5.35 GHz–6.55 GHz) and 13.4 % in the low frequency band (4.54 GHz–5.19 GHz), an over 6.7 dBi gain, and a cross-polarization discrimination (XPD) of greater than 30 dB.

A Low-Profile Dual-Polarized Substrate Integrated Magneto-Electric Dipole MIMO Antenna

A magneto-electric dipole (MED) MIMO antenna with low-profile, dual-polarized, and substrate integrated properties is proposed. The antenna element is composed of four fan-shaped patches lying on the radiation plane and four vertical metal vias linking the patches and the ground. Compared with the common MED antennas, the proposed MED antenna element has a lower profile of 0.1λ. Besides, it is fed by microstrip lines via two orthogonal H-shaped slots, resulting in a broad impedance bandwidth of 40% (3-4.5 GHz) and a steady gain in the entire operational band. The ports isolation is higher than 27 dB, the cross-polarization discrimination (XPD) is higher than 37 dB, and the measured radiation efficiency is greater than 70%. Furthermore, four antenna elements are utilized to form a MIMO antenna, which can obtain better ports isolation characteristics under the condition that the element spacing is half wavelength. Finally, the MIMO antenna is simulated, fabricated and measured. The results verify the rationality of the design.

XPD Enhancement of Dipole Antenna Arrays by Inducing Coherent Current From Feeding Line

Cross-polarization discrimination (XPD) is a critical parameter in designing dual-polarized antennas, particularly for MIMO (Multiple-Input Multiple-Output) base station antenna arrays. A high XPD level leads to a high isolation between two polarized waves and a high input signal-to-noise ratio of the system. In this paper, a new scheme for enhancing XPD of a ±45° dual- polarized dipole antenna pair, the most prevalent antenna element form for MIMO base station antenna arrays, is proposed and is applied to a dipole antenna array. The new scheme induces the required coherent currents on a pair of vertical monopoles from the feeding line. Specifically, a 3-U structure that is printed on the circuit board of the feeding line is proposed. The structure couples the signal from the feeding line and excites two opposite currents on the vertical monopoles, whose radiated fields effectively compensate the θ-component of electric field in a wide scanning angle. The working principle of the scheme is elaborated in detail with a simplified analytic model. The scheme is applied to a dipole array, in which each 3-U structure is personally designed to accommodate the complex array environment. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed scheme.

Structural and Radio Frequency Co-Design and Optimization of Large Deployable Reflectarrays for Space Missions

The structural and Radio-Frequency (RF) design and optimization of a large deployable faceted reflectarray (RA) generating double polarization contour beam are presented in this work. The issue addressed is the thermoelastic stability of large RAs and the impact of the thermoelastic deformation (TED) under transverse thermal gradient on the RA performances. Finite elements TED analysis are conducted on a deployable RA with self-standing structures, demonstrating the detrimental effects of the in-orbit TED impact on the RA performances, estimated to be above 3 dB losses. To this extent, a novel structural solution is proposed, based on the employ of reliable mechanical support capable to mitigate the TED. The mechanical design reorientation is contingent on the RF design reformulation. The proposed novel mechanical and RF co-design concept and methodology allows the conception of a low profile, thermo-structurally stable RA with compliant radiation patterns and high cross-polarization discrimination in the worst-case thermal load. This methodology is based on a direct optimization of nine panels faceted RA composed of advanced high-order Phoenix cells directly optimized to fulfill the contoured beam requirements and by respecting the local periodicity requirements of the layout.

Additively Manufactured Half-Gutman Lens Antenna for Mobile Satellite Communications

In this letter, we present an additively manufactured half-Gutman lens antenna operating at 30 GHz. The hemispherical lens allows for a compact beamformer while maintaining the wide scanning capabilities of Gutman lenses. This solution further enables to better integrate the feed system when compared to a more conventional half-Luneburg lens antenna design as the focal arc is moved inside the lens. The graded-index of the lens is implemented with a periodic structure arranged in a body-centred cubic (BCC) lattice. We demonstrate that the BCC structure provides attractive properties for the design of inhomogeneous dielectric lenses. Importantly, the BCC structure can be used to alleviate the manufacturing constrains compared to conventional periodic structures. The lens is fed by a dielectric-loaded square waveguide. The proposed antenna produces a directive beam with a simulated and measured peak gain of 26.2 and 25.3 dBi. The antenna can steer its beam in a 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> range in elevation with measured scan loss and sidelobe levels below 1 dB and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 10 dB, which agree with the simulated values. The measured cross polarization discrimination is better than 20 dB. The proposed antenna is intended for the ground segment of the emerging low-Earth-orbit satellite communication applications.

140-GHz Wideband Array Antenna-in-Package Using Multimode Resonance

A 140-GHz wideband array antenna-in-package (AiP) that uses multimode resonance is proposed based on a low-profile multilayer printed circuit board (PCB), which can be incorporated with flip-chip technology and an integrated transceiver. Using the multiple resonances of a patch and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4 monopole-type feeder, a simulated impedance bandwidth of 53% and stable radiation performance over the operating band were achieved. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> 4 antenna array achieves a gain of up to 18.1 dBi, a radiation efficiency of 80%, and a cross-polarization discrimination (XPD) of over 20 dB. By combining the elements with a feed network composed of striplines, single and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> 4 antenna arrays were designed and fabricated. The capacitance caused by the limitations of the fabrication process was analyzed and overcome using a novel capped-cavity structure. From the experiment, a −10 dB impedance bandwidth of 31% was measured.

Uniformly Improved Cross-Polar Discrimination in a Dielectric Resonator Antenna by Conduction-Current Control

This work, for the first time, investigates the comprehensive sources of cross-polarized (XP) radiation from a dielectric resonator antenna (DRA). The study uses a recently developed theory on DRA radiation and models the XP sources with the help of well-known definition by Ludwig. This eventually focuses on the conduction-current distribution on the metallic ground. The interpretation leads to a concept of synthesizing effective conduction current in order to satisfy the required condition of low XP fields. A representative prototype of a cylindrical DRA on engineered ground plane has been realized to operate in C-band. It exhibits nearly 12% matching bandwidth with more than 25 dB co-to-cross polar discrimination over both orthogonal (H-) and diagonal (D-) planes. Relative improvement in XP level promised by the measured data is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 15 dB in D- and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 10 dB in H-planes. This proof of concept may now be extended to other DRA geometries and for practical applications in the near future.