Cross-polarization Discrimination Research Articles

Novel 1-Bit Beam-Scanning Reflectarray With Switchable Linear, Left-Handed, or Right-Handed Circular Polarization

This article proposes a novel reconfigurable reflectarray (RRA) with 1 bit beam scanning and switchable linear, left-handed (LH) circular, or right-handed (RH) circular polarization. To realize a multipolarization switchable RRA fed by a horn of arbitrarily fixed polarization, the unit cell’s reflection phases in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> -directions are independently controlled to meet the required differential phase in each state. Explicit reflection-phase relation will be given for switching from one polarization to another while fulfilling the 1 bit beam scanning. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10\times 10$ </tex-math></inline-formula> RRA was prototyped with each unit cell using only two p-i-n diodes to implement dual functions. The fabricated RRA was tested and it can experimentally demonstrate 2-D beam scanning and polarization switching among 45°/135° linear polarization and LH/RH circular polarization. In circular polarization, the measured peak gain, aperture efficiency, and 1 dB gain bandwidth are 17.2 dBic, 26%, and 8.2%, respectively. In linear polarization, the measured cross-polarization discrimination (XPD) of greater than 15 dB, peak gain of 16.8 dBi, aperture efficiency of 23.9%, and 1 dB bandwidth of 5.3% are obtained.

Massive MIMO With Dual-Polarized Antennas

This paper considers a single-cell massive MIMO (multiple-input multiple-output) system with dual-polarized antennas at both the base station and users. We study a channel model that includes the key practical aspects that arise when utilizing dual-polarization: channel cross-polar discrimination (XPD) and cross-polar correlations (XPC) at the transmitter and receiver. We derive the achievable uplink and downlink spectral efficiencies (SE) with and without successive interference cancellation (SIC) when using the linear minimum mean squared error (MMSE), zero-forcing (ZF), and maximum ratio (MR) combining/precoding schemes. The expressions depend on the statistical properties of the MMSE channel estimator obtained for the dual-polarized channel model. Closed-form uplink and downlink SE expressions for MR combining/precoding are derived. Using these expressions, we propose power-control algorithms that maximize the uplink and downlink sum SEs under uncorrelated fading but can be used to enhance performance also with correlated fading. We compare the SEs achieved in dual-polarized and uni-polarized setups numerically and evaluate the impact of XPD and XPC conditions. The simulations reveal that dual-polarized setups achieve 40-60\% higher SEs and the gains remain also under severe XPD and XPC. Dual-polarized also systems benefit more from advanced signal processing that compensates for imperfections.

Wide-Band Wide-Beam Circularly-Polarized Slot-Coupled Antenna for Wide-Angle Beam Scanning Arrays.

The design of a wide-band wide-beam circularly-polarized slot-coupled (WWCS) radiating element for wide-angle scanning arrays (WASAs) is addressed. The WWCS radiator exploits a simple geometry composed of a primary (driven) and a secondary (passive) element to generate wide-beam patterns with rotational symmetry and high polarization purity. The synthesis was carried out by means of a customized version of the System-by-Design (SbD) method to derive a WWCS radiator with circular polarization (CP) and wide-band impedance matching. The results of the numerical assessment, along with a tolerance analysis, confirm that the synthesized WWCS radiating element is a competitive solution for the implementation of large WASAs. More specifically, a representative design working at f0=2.45 [GHz] is shown having fractional bandwidth FBW≃15%, half-power beam-width HPBWf0≃180 [deg] in all elevation planes, and high polarization purity with broadside axial ratio ARf0=3.2 [dB] and cross-polar discrimination XPDf0=15 [dB]. Finally, the experimental assessment, carried out on a PCB-manufactured prototype, verifies the wide-band and wide-beam features of the designed WWCS radiator.

Very Compact Waveguide Orthomode Transducer in the K-Band for Broadband Communication Satellite Array Antennas

A very compact waveguide orthomode transducer (OMT) is described in this paper. The design is characterized with a twofold rotationally symmetric cross-section in the probing area, adapted from a side-coupling OMT design, simultaneously enabling low port-to-port coupling and high cross-polarization discrimination (XPD) over a fractional bandwidth of about 15-20%. Compared to previously reported compact waveguide OMTs, the proposed design is simpler, thus facilitating its manufacture at millimeter-wave frequencies. The concept is demonstrated with a design in the K-band for a broadband communication satellite downlink over the frequency band of 17.3-20.2 GHz. For test purposes, transitions to standard waveguide WR42 are included, and the OMT is assembled with a conical horn antenna. The measured reflection and coupling coefficients are below -19.5 dB and -22.9 dB, respectively, over the nominal bandwidth, and they are in good agreement with the simulation's results. The on-axis XPD, measured in an anechoic chamber, is better than 30 dB over the nominal bandwidth, which is also in line with simulations. The proposed waveguide OMT may be designed to fit in a lattice below one wavelength at the highest operating frequency, which is desirable for dual-polarized closely spaced array antennas in low and medium Earth orbit communication satellite systems. The simple mechanical design of the proposed OMT makes it particularly appealing for additive manufacturing techniques, as demonstrated with a variant of the design having folded single-mode waveguides, which preserves the RF properties of the original design.

Multipolarization Superposition Beamforming: Novel Scheme of Transmit Power Allocation and Subcarrier Assignment

The 5th generation (5G) new radio (NR) access technology and the beyond-5G future wireless communication require extremely high data rate and spectrum efficiency. Energy-efficient transmission/reception schemes are also regarded as an important component. The polarization domain has attracted substantial attention in this aspect. This paper is the first to propose multi-polarization superposition beamforming (MPS-Beamforming) with cross-polarization discrimination (XPD) and cross-polarization ratio (XPR)-aware transmit power allocation utilizing the 5G NR antenna panel structure. The appropriate orthogonal frequency division multiplexing (OFDM) subcarrier assignment algorithm is also proposed to verify the theoretical schemes via simulations. The detailed theoretical derivation along with comprehensive simulation results illustrate that the proposed novel scheme of MPS-Beamforming is significantly beneficial to the improvement of the performance in terms of the symbol error rate (SER) and signal-to-noise ratio (SNR) gain at the user equipment (UE). For instance, a provided practical wireless channel environment in the simulations exhibits 8 dB SNR gain for 10−4 SER in a deterministic channel, and 4 dB SNR gain for 10−5 SER in abundant statistical channel realizations.

Design of Dielectric Resonator Antenna Array With Wide-Angle Scanning Based on Dual Magnetic Currents

A wide-beam dielectric resonator antenna (DRA) and its related phased array with wide-angle scanning are presented in this article. To improve the scanning coverage and cross polarization discrimination (XPD) simultaneously, the wide-beam method utilizes dual magnetic currents (MCs) in the same direction. The operating principle is theoretically analyzed using suspended MC theory. Two wide-beam DRAs working in TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{y}_{1\delta 1}$ </tex-math></inline-formula> and TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{y}_{1\delta 3}$ </tex-math></inline-formula> modes with parasitic loops are studied to verify the presented beam-broadening method. The simulated 3 dB beamwidths of the two DRAs are higher than 205° and 140° in the E- and H-planes, respectively. Two wide-beam DRAs operating at 5.5 GHz were fabricated and measured. Based on the wide-beam DRA element, the passive eight-element array antenna and three feeding networks corresponding to scanning angles of 0°, 40°, and 80° were machined. The total array system is verified to have an enhanced beam scanning angle of ±85° with a gain fluctuation of 2.5 dB. The co-polarization is stable and the XPD is greater than 20 dB for any scanning angle.

Simulation Verification and Testing of Dual Circular Polarization Diversity

This paper presents a test method of satellite communication based on dual circular polarization diversity. A polarized channel model is established based on two validated models to obtain the bit error rate curve of MIMO system. Moreover, the specific antennas are chosen through the simulation result of the cross-polar discrimination (XPD). Finally, a hardware platform with USRPE310 and polarized-antenna is established to verify the simulation result.

REDUCING THE CROSS-POLARIZATION PATTERN IN A DUAL-POLARIZED ANTENNA USING SPIRAL AND SPLIT RING RESONATORS

This paper introduces the design of a new dual polarization rectangular microstrip patch antenna based on metamaterial structures at X-band. The work focuses on two distinct configurations of a microstrip patch antenna utilizing metamaterials. Pairs of spiral ring resonators are loaded into a rectangular patch antenna system in the first design. The second strategy involves inserting a split ring resonator at the end of microstrip feed lines. The utilization of metamaterial structures in the microstrip antenna system compensates for the patch antenna's asymmetric current distribution of the flow, resulting in symmetrical current distribution. The simulation results display an import cross-polarization cross-polarization discrimination (XPD) and good port decoupling. The antenna system has various characteristics, including a basic structure and metamaterial inclusions that take up a small amount of space, making the suggested metamaterial inclusions more beneficial for dual-linear polarized patch antenna construction. These prototypes are suitable to work for polarimetric radars.

Wideband and High Cross-Polarization Discrimination 45° Linearly Polarized Slot Array Antenna Without Cavity-Backed Layer

This letter presents a wideband and high cross-polarization discrimination (XPD) 8×8-slot full corporate- feed 45° linearly polarized slot array antenna. A new vertical 1-to-4 power divider consisting of one H-plane T-junction and two E-plane T-junctions is employed to replace the 1-to-4 cavity-backed power divider in the conventional designs, which balances the amplitude and phase distributions among the output ports. By further bending the output ports of the 1-to-4 power dividers upward 90° along the diagonal plane, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode in the signal path is smoothly shifted along the intended E- and H- planes and directly excites the 45° tilted radiation slots. Combined these features, the grating lobe suppression and XPD improvement over a wide frequency band can be achieved without introducing additional metal structures. For demonstration, a prototype covering 24–33 GHz is implemented. The experimental results are in good agreement with the simulation ones, which verifies the design concept.

Wideband Dual-Polarized Hollow-Waveguide Slot Array Antenna

A wideband dual-polarized slot array antenna based on hollow waveguide (HW) is presented in this article. Its wide bandwidth and high performance are enabled by two separate feeding networks, from the side and the bottom, using square coaxial line and ridge waveguide structures, respectively. The full-corporate-feed networks excite the radiation slots in a one-to-one fashion without using backed cavities. Tight element spacing is made possible, suppressing the grating lobe and maintaining high cross-polarization discrimination (XPD) across the wideband. This resolves a usual tradeoff between bandwidth and grating lobe. A double-ridge rectangular waveguide cavity is devised as an orthogonal mode splitter for isolation enhancement. Several design features are used to minimize the signal path length and facilitate routing. An <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> element prototype in K-band is designed, fabricated, and measured. Experimental results show that the antenna has a wide bandwidth of 23.4% (from 17 to 21.5 GHz) free from grating lobes. More than 25.5 dBi peak gain higher than 51.2 dB isolation and over 43.6 dB XPD are also obtained for the dual polarizations.

Electromagnetic Performance of Waveguide Polarizers with Sizes Obtained by Single-Mode Technique and by Trust Region Optimization

Modern wireless networks, stationary terrestrial and satellite systems use many modern technologies to increase communication channels information capacity. They save limited frequency resources. In satellite communications the polarization signal processing is applied to reuse the allocated frequency bands. Usage of circularly polarized electromagnetic waves, which transmit useful signals, reduces fading effects and eliminates disadvantages introduced by multipath propagation interferences. In this case the distortion levels for signals with an odd number of electromagnetic waves reflections in the receiving antenna systems will be reduced down to the thresholds of their cross-polarization isolation. Besides, in the case of orthogonal polarizations usage, the achieved information capacity of the applied wireless communication channel multiples almost by the factor of two. The type of polarization of the used electromagnetic wave strongly determinates the peculiarities of the process of its propagation in the space or transmission line. Polarization signal processing is frequently carried out in horn feed systems of the reflector antennas. Such feed networks and systems allow to transmit and receive signals with several kinds of polarization at the same time. The fundamental element of dual circular polarization antenna feed networks is a waveguide polarization duplexer. The phase, isolation and matching characteristics of a polarization converter strongly influence on the functionality and polarization discrimination possibilities of the entire reflector antenna system. Therefore, the development and optimization of the characteristics of waveguide polarizers for satellite communication antennas is a crucial technical problem, which must be solved by fast and accurate methods. The comparison of electromagnetic performance of waveguide polarizers with sizes obtained using a fast single-mode technique and by more accurate trust region optimization method is carried out in this research. The results for differential phase shift, level of voltage standing wave ratio, ellipticity coefficient and cross-polarization discrimination are shown and discussed.

Differentially Fed Dual-Polarized 2-D Multibeam Dielectric Resonator Antenna Array Based on Printed Ridge Gap Waveguide

In this article, a differentially fed dual-polarized dielectric resonator antenna (DRA) subarray excited by a substrate integrated waveguide (SIW) cavity is proposed. A #-shaped slot etched on the top wall of the SIW cavity is used to achieve the differential excitation due to the intrinsic field distribution of TE120 mode in the SIW. Based on the proposed antenna subarray, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times $ </tex-math></inline-formula> 2 dual-polarized 2-D multibeam DRA antenna array with simple structure is designed, fabricated, and measured, which can achieve high cross-polarization discrimination (XPD) in the direction of maximum radiation. To reduce substrate loss, the printed ridge gap waveguide (PRGW) technology is used to feed the SIW cavity. Two orthogonal PRGW Butler matrices are placed at different layers so as to realize 2-D beamforming scanning with dual-polarization. The SIW cavity is placed in the air gap of PRWG, which can increase the stability of the antenna structure. By cleverly combining the SIW cavity and PRGW structure, the proposed multibeam antenna array has the advantages of high XPD and high radiation efficiency. Measured results show that an impedance bandwidth of 10% (28.5–31.5 GHz) and a peak gain of 11.8 dBi are obtained. Also, the measured XPDs are 28.3 dB at the center frequency and larger than 19.2 dB over the band of operation. Besides, the measured radiation efficiency of 67% is achieved for both the polarizations at 30 GHz.

Investigation of Millimeter Wave’s Cross Polarization Discrimination in Sand and Dust Storms

The performance of electromagnetic wave links in sand and dust storms has received considerable interest of researchers in recent time, especially with emphasis on the signal attenuation. However, phase rotation and cross-polarization have not been sufficiently treated. This work investigates the cross-polarization discrimination as a result of sand and dust storms at high frequency such as the millimeter wave band. The paper introduces simple mathematical models of wave propagation in sand and dust storms, and developed based on the forward scattering amplitude of sand and dust particles using the Rayleigh technique. The suitability of the Rayleigh approximation for the models are validated by setting three different conditions. The results show that that the technique is valid for determining the scattering of ellipsoidal sand and dust particles for the sizes considered and frequency range. The scattering coefficients are thus derived and models for attenuation and phase rotation are proposed in terms of visibility. The results obtained from the proposed models show close agreement with some earlier published results when compared. Differential attenuation and differential phase rotation are computed and the cross-polarization discriminations are then predicted using the parameters from the models as inputs. The attenuation during dry sand and dust storms becomes significant only when the visibility is low and severe. At such visibility, the cross-polarization discriminations also become low (i.e. significant) and the same trend and pattern is found as the frequency is increased.

Wideband Antenna for High-Frequency 5G Wireless Communication

In this study, a wideband patch array antenna for high-frequency 5G wireless communication is proposed. The wideband high-frequency 5G antenna is needed to handle the increase in 5G data traffic. The proposed antenna, a 2 × 16 element array with gap-coupled parasitic elements and a multi-section or stepped transformer feeding network with feed cover to prevent unwanted feed radiation, can cover 5G new radio (NR) n257 (26.5–29.5 GHz), n258 (24.25–27.5 GHz), and n261 (27.5–28.35 GHz) bands. Using parasitic elements with a single substrate instead of cavity and stacked structures, a wide impedance bandwidth (dB magnitude of S&lt;sub&gt;11&lt;/sub&gt; &lt; –10) of 24.2% (23.75–32 GHz) is achieved. A high cross-polarization discrimination (XPD &gt; 25.2 dB) is achieved using orthogonal dual polarization. The peak gain obtained is 18.69 dB.

Compact 2-step Septulum Polarization Converters for Radars and Satellite Systems

This article presents the results of analysis, numerical simulations and optimization of new narrowband guide septulum polarization converters. Orthomode duplexers and polarization converter designs based on septulums are widely used in modern microwave systems with orthogonal circularly polarized signals. Septulum guide polarizer is an effective compact device, which transforms right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) electromagnetic modes into linearly polarized ones. At the same time it divides RHCP and LHCP modes and directs them to two different rectangular guides with high signal discrimination to each other. Thus, a septulum-based guide device integrates performance of a polarization transformer and of an orthomode duplexer. The main electromagnetic characteristics of the polarization converter were simulated in software based on the finite elements method in the frequency domain. The proposed design of a compact narrowband guide polarization converter has a septulum with two steps. Several designs of septulum polarization converters were developed and compared for different relative bandwidths of 5%, 10%, and 15%. The comparative investigation of the obtained designs was carried out. Main electromagnetic characteristics of optimal septulum polarization converters were compared. These include return losses, cross-polarization discrimination, ellipticity parameter, and ports discrimination. It was demonstrated that in 5% fractional bandwidth a compact 2-stepped septulum polarization converter has return losses greater than 22 dB. Its cross-polarization discrimination and ports discrimination are greater than 25 and 27 dB. Developed compact septulum polarization converters can be applied in modern antenna systems for radars and satellite communication systems.

Effect of dust storms on (GSM) signal north region of Libya

Propagation mechanisms are very complex and diverse, because of the separation between the receiver and the transmitter, attenuation (reduction or loss) of the signal strength occurs. Field study will be conducted in amid north region of Libya (Bani Walid), which has high wind speed, and high attenuation loss, desert climate, and frequent dust and sand storms. This phenomenon actually influenced on wireless communication systems (GSM signal), neither the effect of the humidity on the complex permittivity nor the antenna height on the visibility, where by its effect on both attenuation and cross-polarization constants in this region. Besides the expectation of different chemical analysis of the dust and sand. These samples were collected from five location, every location had one level and sand was collected from a height of 2m, collect the meteorological data for the region of this study, e.g. visibility, wind speed and relative humidity, and height of towers from Libyana technical station. The analysis of these samples were done in two laboratories, one in university of Tripoli (AL-Fateh University), and the second in the Industrial Research Center in Tripoli. In the analysis, we were looking for the chemical and physically composition, the chemical composition of dust and sand had been got to compute complex permittivity, density, and chemical and physical properties analysis for the samples. Determine equivalent diameter, particles-size distribution, and axes ratio for collected samples; determine equivalent diameter, particles-size distribution, and axes ratio for collected samples. Compute the attenuation loss and cross-polarization discrimination (XPD) change due to the effect of sand and dust storms on wireless communication systems (GSM signal) which coverage in the studied region.

ESTIMATION OF FEM AND FDTD METHODS FOR SIMULATION OF ELECTROMAGNETIC CHARACTERISTICS OF POLARIZATION TRANSFORMING DEVICES WITH DIAPHRAGMS

Context. Today, there is a rapid expansion of the range of modern branches of science and technology, which actively use satellite telecommunication systems to receive, process and transmit various information. These radioelectronic systems quite often require an increase of the volumes of information, which they are processing and transmitting. Increase of the volumes of transmitted information in two times can be achieved by using dual-polarization antenna systems and devices. Nowadays, most part of the specialists, who are engaged in the development of various modern polarization-processing microwave devices, carry out their numerical modeling and optimization using variational techniques, methods of integral equations, method of fields matching in partial regions. The methods with division of the internal region of the device into elementary cells are applied most actively. Among them in the time domain the most often used approach is finite difference method with the decomposition at hexagonal mesh, while and in the frequency domain the finite elements method with the adaptive tetrahedral mesh is applied. Therefore, the estimation of the speed and accuracy of these methods with the purpose of determination of more effective among them is a relevant problem. Objective. The goal of the research is comparison of speed and accuracy of the calculations of electromagnetic characteristics of waveguide polarizers using FEM and FDTD methods, as well as the comparison of the convergence of these methods for the analysis of polarization-processing microwave devices with diaphragms. Method. For the calculations and analysis of electromagnetic characteristics in the article we used the method of finite differences in the time domain (FDTD) and the method of finite elements in the frequency domain (FEM). In FEM the volume is split into the tetrahedral mesh cells. In FDTD the computational domain is divided into hexagonal mesh cells. Results. It was found that the convergence of voltage standing wave ratio for the waveguide polarizer is fast for both methods. It was obtained that the convergence of the characteristics of differential phase shift, axial ratio, and crosspolar discrimination of the developed microwave device turned out to be much more sensitive to the number of mesh cells used. Moreover, in the research it was obtained by calculations that the computation time by the finite elements method in the frequency domain is more than 2 times less than the corresponding time required for calculations by the finite difference time domain method. When using the finite elements method in the frequency domain the corresponding number of tetrahedral mesh cells is 10 times less than the number of hexagonal mesh cells, which are used in the finite difference time domain method. Conclusions. Performed investigations have shown that FEM in the frequency domain, which applies an adaptive tetrahedral mesh, is more efficient than the FDTD method for the calculations of phase and polarization characteristics of modern waveguide polarizers and other microwave devices for various applications.

Planar dual‐polarized differentially fed multibeam patch antenna array

A design of planar dual-polarized differentially fed multibeam patch antenna array (DFMPAA) is presented in this article. The dual-polarized DFMPAA is composed of two circular 4 × 4 butler matrixs (BMs) and a 1 × 4 dual-polarized patch antenna array. The two BMs are designed in the top and bottom layer as the feeding network of horizontal polarization (HP) and vertical polarization (VP), respectively. The patch is designed as the radiation element of the dual-polarized DFMPAA, which is fed by the slot and aperture coupling to generate the HP and VP wave, respectively. To achieve high cross-polarization discrimination (XPD), the antenna element is fed differentially. A prototype working at 5.5 GHz is fabricated and measured in order to validate the performance of the proposed dual-polarized DFMPAA. The dimension of the dual-polarized DFMPAA is 3.8 λ0 × 1.7 λ0. Measured results show that when the beam scan to the maximal pointing angle, the XPD of the dual-polarized DFMPAA in HP and VP are higher than 27 and 29 dB, respectively. Additionally, the beams of the dual-polarized DFMPAA can cover the range of ±42° in horizontal plane.

A Cross-Polarisation Discrimination Analysis of Off-Body Channels in Passenger Ferryboat Environments

There is a need for investigating radio channels for Body Area Networks considering the depolarisation phenomenon and new types of environments, since these aspects are becoming very important for systems design and deployment. This paper presents an analysis of cross-polarisation discrimination for off-body channels based on a measurement campaign performed in a passenger ferryboat, i.e., where all walls, floors and ceilings are made of metal. Firstly, the measurement campaign, including test-bench and scenarios, as well as the analysis approach, including classification of mutual antennas’ orientation and definition of parameters are described. The analysis of results includes distance, on-body antennas location and several scenarios, addressing statistical parameters. Mean values for the cross-polarisation discrimination are in the range of [3.7, 6.8] dB while the standard deviation is around 10.0 dB. There is no dependence of the cross-polarisation discrimination on distance, within the measured range (up to 16 m). It is found that there is no correlation between radio signals received by vertically and horizontally polarised receiving antennas, hence, enabling the application of polarisation diversity in Body Area Networks. The Normal Distribution is the best fit for describing cross-polarisation discrimination, as shown by the analysis of goodness of fit parameters, since it passes many of the tests.

A Foldable Tightly Coupled Crossed Rings Antenna Array of Ultrawide Bandwidth and Dual Polarization

Low-profile foldable array antennas are becoming increasingly more important for a wide range of applications such as satellite communications and wearable electronic devices. The conventional arrays formed by patch-like antennas have been extensively studied on surfaces with a curvature but they have exhibited limited bandwidth and polarization performance. This study investigates a coupling enhanced crossed rings antenna array with two typical configurations for dual polarization, which inherently produces ultrawide bandwidth, dipole-like polarization characteristics and a fully curved array (FCA) eventually. The fractional bandwidth of the array is over 100% on a planar surface and expanded to approximately 140% on the curved surface. For the bent array of slant polarization, the beamwidth increases by over 20&#x00B0; compared to the planar array and cross polarization discrimination (XPD) maintains above 15 dB. The effects of curvature on the impedance matching and polarized radiation patterns for such arrays are investigated by measuring the performance of the fabricated prototype arrays. The results revealed that the tightly coupled crossed rings antenna array on a curved surface has a potential to form multiple beams on a limited aperture size through smaller subarrays which can yield ultrawide bandwidth due to concentrated mutual coupling mechanism. This characteristic is promising in applications where traditional flat panel arrays are difficult to implement such as in mobile stations, moving platforms and for satellite communication on-the-move.