Cross-polarization Level Research Articles

A low-profile, high gain, dual-port, planar array antenna for mm-wave powered 5G IoT systems

A dual-port, corporate-series fed, planar 8 × 2 rectangular patch compact antenna array with a very high gain is introduced for 28 GHz millimeter wave (mm-wave) communication in 5G Internet of Things (IoT) systems. In the proposed design, successive radiating elements are excited with the same amplitude but opposite phase through two separate feed networks associated with two different ports. To ensure the reliability of the proposed design, a prototype is fabricated and tested. Testing indicates that the measured results closely follow the simulated results, which proves the accuracy of the proposed design. The measured performance specifies that the dual-port antenna array provides impedance bandwidth of 4.3% operating from 27.6–28.8 GHz for |S11|≤−10 dB, the radiation efficiency of 78%, and gain of 18.2 dB. Measured radiation characteristics verified that the proposed array directs maximum power towards broadside with half-power beam widths (HPBWs) of 24.6°and 9.6°, side lobe levels (SLLs) <−18.3 dB and <−10 dB, as well as cross-polarization levels <−41.16 dB and <−42.51 dB in E plane and H plane, respectively. Due to the very high gain, directional radiation pattern, and low SLLs, the proposed array antenna can be used for mm-wave powered communication in IoT 5G devices.

Electric-Field-Coupled Resonator Antenna for 5G Applications.

In this paper, a compact wideband patch antenna comprising a modified electric-field-coupled resonator with parasitic elements is presented. The resonance at low frequency is achieved due to the electric field polarization along the split of the conventional LC (inductive-capacitive) structure. However, this antenna gives low bandwidth as well as low gain. Some evolutionary techniques are adopted to get a compact wideband antenna at 3GPP bands of 5G. The split width and the ground plane are modified to achieve enhanced bandwidth with good impedance matching, whereas the addition of the parasitic elements on both sides of the microstrip feed line enhances the gain with a slight reduction of bandwidth. The compact dimension of the proposed antenna is 0.26 λL × 0.26 λL × 0.017 λL, where λL is the free space wavelength at the lowest frequency. A prototype of the presented design is fabricated and measured. Measurement shows that the antenna has an operating bandwidth of 19.74% for |S11| < −10 dB where the gain of 1.15 dBi is realized. In addition, the radiation pattern is omnidirectional in the horizontal plane and dumbbell shaped in the elevation plane. The cross-polarization levels in both planes are less than −12 dB.

Pattern performance of active phased array antenna for Gaofen-3 satellite

The phased array antenna is one of the critical components of the space-borne SAR system and plays a key role in the quality of images. This paper focuses on the design of active phased array antenna for Gaofen-3 satellite, including its architecture, system design methods, key hardware, and the performance for the design implementation. The proposed phased array antenna have capabilities of beam broadening and scanning, left and right side look, polarization switching, in-orbit calibration, uploading beam-steering correction data, collecting self-checking information, and self-protection caused by over pulse width or duty cycle. The phased array antenna is mainly consisted of dual-polarized slotted waveguide antennas, TR modules, time-delay and amplifier modules and power distribution networks. Moreover, the solutions of the direct problem and inverse problem for accurately predicting the pattern and determining the states of TR modules for the required beam have been proposed. The obtained results can confirm that the cross-polarization level of both polarizations for the phased antenna array is below −35 dB. By employing the proposed antenna model, the beam steering error and dispersion error between the predicted and the measured beams in the range plane are less than 4% (100% probability) and less than 2% (95% probability). For beam steering in the azimuth plane, the beam steering error is less than 2% (90% probability), and less than 4% (100% probability). The ground and on-orbit test results have indicated that the functions and performance of the antenna meet the requirements of the SAR system.

A broadband dual‐polarized antenna with quasi‐trapezoidal patches for 5G base station application

A differential dual-polarized patch antenna with broadband, high isolation, and low cross-polarization level for 5G base station is presented. The antenna is composed of the radiating element, feeding structure, and reflector. The radiating element is designed with four identical smaller quasi-trapezoidal patches to achieve a wider bandwidth, which is capacitively driven by two trapezoidal feeding patches. Impedance matching of antennas can be adjusted by tuning the size of quasi-trapezoidal patches in the feeding portion. Finally, a prototype antenna is fabricated based on the simulated model. The measured bandwidth of the proposed antenna is about 27.8% (3.19–4.22 GHz) with VSWR<1.5, and the port isolation is better than 39.5 dB over the whole operating band. Furthermore, the proposed antenna has a stable gain of 8.55 ± 0.8 dBi and a low cross-polarization level (<−33 dB) within the operating band.

Dual circularly polarized aperture-coupled metasurface antennas with high-isolation for X-band synthetic aperture radars

ABSTRACT This paper describes a dual circularly polarized (CP) antenna with high isolation and its 2 × 2 element array for the X-band synthetic aperture radars. The antenna is an aperture-coupled metasurface of 4 × 4 periodic corner-truncated patches, which is fed by two orthogonal microstrip-lines to generate the dual-CP radiation. A novel asymmetric fence-shaped slot is utilized as the coupled aperture of the antenna to enhance the port-to-port isolation. To achieve a more robust dual-CP radiation, the 2 × 2 element array of the aperture-coupled metasurface antenna is designed, fabricated, and tested. Both simulation and measurement indicate that the array prototype achieves an excellent dual-CP radiation at 9.6 GHz, i.e., isolation of ≥ 30 dB, axial ratio ≤ 1-dB, radiation efficiency ≥ 80%, realized gain of 14.0 dBic, and cross-polarized level ≤ −20 dB at the broadside.

High-Gain Low Cross-Polarized Dual-Polarized Filtering Patch Antenna Without Extra Circuits

This letter presents a dual-polarized filtering patch antenna with high gain, low cross-polarization, and without extra filtering circuits. By etching the slots on the patch, a radiation null at the upper band edge is generated, while introducing an extra resonant mode to broaden the impedance bandwidth. In addition, four shorting pins are symmetrically loaded on the patch, which provides a radiation null at the lower band edge and the enhanced gain. Moreover, the cross-polarization level is reduced by adopting the symmetrical structure and a differential feeding scheme. For verification, a filtering antenna operating at 5G n77 band (3.3–4.2 GHz) is designed and fabricated. The measured 10 dB bandwidth is 29.7% (3.15–4.25 GHz) with a peak gain of 9.5 dBi, a cross-polarization level of less than −32 dB and an isolation of higher than 34 dB. The out-of-band suppression levels are more than 34 and 16 dB within the lower stopband (1–2.52 GHz) and the upper stopband (4.6–6.5 GHz), respectively.

Wideband Integrated Log-Periodic Antenna Array for 5G Q-Band Applications

A wideband integrated log-periodic antenna (LPA) based on multilayer printed circuit board for fifth-generation (5G) Q-band applications is presented in this letter. The LPA is fed by the broadband radial slot transition balun. The LPA has four dipoles which are separately placed on different thickness printed circuit board substrates. To enhance the gain and reduce the cross-polarization level, the symmetrical layout and differential feeding are adopted in the 4 × 4 LPA array design. The measured results show that the proposed 4 × 4 LPA array achieves the impedance bandwidth of 32.5% (32.5–45 GHz) and the peak gain of 15.5 dBi. Due to these advantages of low cost, wideband and easy for integration, the 4 × 4 LPA array will be a potential candidate scheme for 5G Q-band applications.

A New High Aperture Efficiency Transmitarray Antenna Based on Huygens Metasurfaces

In this article, a new transmitarray (TA) antenna is designed and fabricated based on Huygens metasurfaces (HMSs). An analytical method has been used to achieve the distribution of surface parameters equivalent to HMS. In this method, the required equations for computing the surface parameters are derived using ray tracing, generalized sheet transition conditions, and two conditions of local power consumption and local impedance equalization. In order to implement these surface parameters, wire and loop unit cells are utilized, which are exposed to the radiation transversely. The array of these unit cells offers high aperture efficiency broadband TA antennas in low aperture profile. The fabricated TA antenna with a low aperture thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.2\lambda $ </tex-math></inline-formula> exhibits the bandwidth, sidelobe level (SLL), and cross-polarization level of 14%, −19 dB, and −19 dB, respectively. In addition, the high aperture efficiency of 65% is reached with this TA, which shows great improvement in comparison to previous works.

Theoretical investigations on the influence of photonic crystal shapes on the performance of graphene-based terahertz photoconductive bowtie dipole antenna

Graphene-based photoconductive bowtie dipole antenna for terahertz radiation is investigated under different geometrical shapes of photonic crystal employed in the semi-conductor substrate. The antenna is designed using graphene radiator and Gallium Arsenide substrate to operate at 1.4 THz, 1.9 THz and 2.1 THz frequencies. Cylindrical, square, triangular and hexagonal shaped photonic crystal substrates are investigated. The analysis is carried out for various antenna parameters such as reflection coefficient, VSWR, directivity and radiation efficiency. Further, polarisation aspects such as axial ratio and cross-polarisation level are also discussed. Opto-electronic simulation is performed to determine the influence of photonic crystal shapes on the emission characteristics of photoconductive antenna. Simulation results indicate that hexagonal-shaped photonic crystals provide directivity of 15 dBi, axial ratio of 29 dB, efficiency of 98% and emission spectrum bandwidth of 220 GHz, which ascertain its suitability for terahertz photoconductive antenna.

High gain frequency scanning antenna using dumbbell‐shaped inclined slots and parallel plate waveguide polariser

A high gain vertically polarised travelling-wave frequency scanning array antenna fed by a meander rectangular waveguide is presented for Ku-band operation. The proposed antenna is used in a radar demonstrator setup to detect and monitor birds in direct proximity to the wind farms. The goal is to prevent collisions of birds with wind farms. The proposed antenna consists of 34 inclined dumbbell-shaped radiating slots integrated with a parallel-plate waveguide. The proposed meandered feeding structure is used to enlarge the beam scanning angle range over frequency. The dumbbell-shaped radiating slots are employed in the narrow wall of the meandered waveguide due to the space restriction of the meandering. The parallel-plate waveguide is used as a polarisation filter to reduce the cross-polarisation level of the proposed antenna owing to the inclination of the radiating slots. An E-plane horn is used to reduce the beamwidth in the elevation plane. The overall size of the antenna is 20.6λ in length and 15λ in width, where λ is the free space wavelength at 15.55 GHz. The antenna operates in the frequency range from 15.40 to 15.70 GHz. The half power beamwidth is about 4° in the azimuth plane and about 20° in the elevation plane at 15.55 GHz. The main beam of the antenna steers over frequency to cover 39° of angular range in the azimuth plane. A Taylor distribution is applied to achieve sidelobe level below −25 dB in the same plane and 26 dBi gain over the operating frequency range. The antenna array is fabricated and measured successfully to verify the proposed approach. The fabricated antenna shows an impedance matching significantly better than 10 dB in the operating frequency. The measured gain is higher than 25 dB throughout its frequency range.

Realization of Low Cross-Polarization Level for GF-3 SAR Antenna

In the polarimetric synthetic aperture radar (PolSAR) system, crosstalk error is the key parameter for polarimetric imaging. The source of crosstalk is mostly from the cross-polarization level of the SAR antenna subsystem. To meet the requirements of PolSAR observing modes, a low cross-polarization level under −35 dB is realized for the SAR antenna of the GF-3 satellite. In this paper, we will describe the principles and methods for implementation of low cross-polarization level. The two polarized RF chains are totally independent to ensure high isolation, and a dual-polarized waveguide slot antenna subarray is designed with a low cross-polarization level. Besides, the low taper efficiency of the cross-polarization pattern contributes to reduce the cross-polarization, showing the advantage of the phased array antenna in the PolSAR system. The paper also displays the measured results of cross-polarization for the GF-3 SAR antenna. The study gains a better understanding of the cross-polarization pattern for phased array antenna. The methods utilized here can be extended to other polarimetric SAR systems.

Dual-band omnidirectional coupled-fed monopolar filtering antenna

A dual-band omnidirectional coupled-fed monopolar filtering antenna is designed in this paper. The proposed filtering antenna consists of three stacked circular substrates. A via-loaded annular ring and an annular ring are fabricated on the top of bottom and middle substrates respectively. Four adjustable resonant modes are introduced by this way, which are combined in pairs to generate two independently controllable operating bands. Meanwhile, each resonant mode can produce corresponding omnidirectional radiation, making the proposed filtering antenna have omnidirectional radiation function. There are four adjustable radiation nulls (RNs) located at the both sides of two passbands realized by the coupled-fed via-loaded annular ring and the circular patch printed on the uppermost substrate. Hence, high skirt selectivity can be obtained. The proposed dual-band filtering antenna is simulated, fabricated and measured. The simulation and measurement are in excellent agreements. It is proved that the proposed filtering antenna realizes a stable omnidirectional radiation pattern in the azimuth plane with the cross-polarization level of lower than 20 dB. Additionally, the measured results display that the 10-dB impedance bandwidths are 6.3 % (2.47–2.63 GHz) and 6 % (5.38–5.71 GHz), respectively. The maximum realized gains are 2.6 and 5.2 dBi for two working bands with the out-of-band suppression of more than 15 dB.

Dual-Band, EBG-DGS Wearable Antenna for Emergency Services and Responses in WBAN

Abstract The paper introduces a compact, thin flexible textile antenna integrated with an Electromagnetic Bandgap (EBG) and Defected Ground Structure (DGS) covering the Wireless Local Area Networks (WLAN) bands (2.4-2.485 GHz and 5.1-5.9 GHz) for emergency services and responses. The geometry and configuration of the proposed antenna are made from common clothing jeans fabric, which makes the antenna more flexible, thin, and conformal. A new configuration of EBG structure is developed using Minkowski fractal geometry as base geometry and a DGS with the complementary dumbbell-shaped slot to operate in WLAN standards. The EBG structure is used to isolate the antenna from the human body, whereas the DGS is used to improve the bandwidth and polarization purity. The prototype covers the WLAN bands with gains of 3.37 dBi and 6.47 dBi, a bandwidth of 115.9 MHz, and 398.06 MHz for the specified wireless bands. The integrated antenna demonstrates a Front to Back Ratio (FBR) of 16.77 dB and 32.72 dB, the radiation efficiency of 36.9 % and 73.8 %, and a better cross-polarization level at 2.45 GHz, 5.85 GHz, respectively. The antenna shows a high gain and an efficiency of about 70 % under the various bending scenario. Thus, the anticipated antenna is the most appropriate and potential candidate for wearable applications in various domains.

Synthesizing Circularly Polarized Multi-Beam Planar Dipole Arrays With Sidelobe and Cross-Polarization Control by Two-Step Element Rotation and Phase Optimization

In this article, a novel method is presented to synthesize multi-beam circularly polarized (CP) patterns with sidelobe level (SLL) and cross-polarization level (XPL) suppression for planar dipole arrays by optimizing both element rotations and excitation phases. Multiple sets of excitation phases are adopted as optimization variables other than the determined values according to the rotation angles in the conventional sequentially rotated technique (SRT) and the random sequentially rotated technique (RSRT), so as to improve the performance of the obtained CP multi-beam patterns. This releases many more degrees of synthesis freedom but leads to a new problem of demanding excessive computation resources for a planar rotated dipole array with multiple CP patterns. Then, a two-step rotation and phase optimization strategy is proposed to effectively solve this optimization problem. In the initial step, the common element rotations and approximated excitation phases composed of the common phase parts plus the beam focusing phase parts are found for multiple desired CP patterns with different beam directions. And then, a refining step is performed to refine the excitation phases individually for each CP beam for improved pattern performance. Four representative examples of synthesizing multi-beam patterns with both SLL and XPL suppression are provided to verify the effectiveness of the proposed method. Comparisons with the conventional SRT and RSRT are also provided to show the superiority of the proposed method.

Dual-Band, Differentially-Fed Filtenna With Wide Bandwidth, High Selectivity, and Low Cross-Polarization

A compact dual-band, differentially fed filtenna with wide bandwidth, high selectivity, and low cross-polarization is presented. It is composed of a slot-loaded rectangular patch, two pairs of shorting pins, a pair of novel differential coupling feedlines, and a defected ground structure (DGS). Good broadside radiation patterns with an adjustable frequency ratio (FR) between its two bands are realized. A pair of U-shaped slots is loaded on the patch to enhance the bandwidth of the lower passband. The DGS and its compact differential feedlines produce five out-of-band radiation nulls to improve the frequency selectivity of the two passbands. Simultaneously, extra in-band resonances are introduced that broaden the impedance bandwidth while maintaining a compact <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.155\lambda _{0}^{2}$ </tex-math></inline-formula> aperture size and a relatively low profile ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.065\lambda _{0}$ </tex-math></inline-formula> height). Prototypes were fabricated, assembled, and tested. The measured results, in agreement with their simulated values, demonstrate that it exhibits −10 dB fractional impedance bandwidths of 17.5% and 8.2%, peak realized gain values of 8.4 and 9.5 dBi, and cross-polarization levels smaller than −44 and −40 dB, in its lower and upper passbands, respectively. Its dual-band quasi-elliptic responses have sharp roll-off rates and high stopband suppression levels.

Variations of Compact Rectangular Microstrip Antennas Using Defected Ground Plane Structure

The defects in the form of slots have been employed in microstrip antenna either on the patch or the ground plane to yield frequency reduction. However, the reported work does not provide any comparative study that highlight upon the frequency and cross-polar level reduction achieved using these various shape slot/defects. This paper provides a thorough comparative study for different compact variations of microstrip antennas obtained using various shape slots on the ground plane. Amongst all, the optimum results are obtained for the bowtie-shaped slot on the ground plane, which offers cross-polar level reduction by 30 dB with a frequency reduction of 21%. The study also reveals that the slot on the ground plane offers better results against the slot on the patch in terms of frequency and cross-polar reduction. This kind of comparative study is not available in the literature and thus this is the novelty in the present work. An empirical formulation for the resonant length at the fundamental mode frequency for different shapes of slot/defect is proposed. The frequency calculated using them closely matches with those obtained using the simulation.

Low-Cost Reconfigurable 1 bit Millimeter-Wave Array Antenna for Mobile Terminals

A reconfigurable 1 bit millimeter-wave array antenna for mobile terminals is investigated. The reconfigurable array antenna consists of four reconfigurable 1 bit microstrip patch antenna elements. Each patch antenna element is fed by a slot on the ground. The 1 bit patch antenna element with phase values of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-\pi $ </tex-math></inline-formula> and 0 is achieved by selecting the feeding direction of microstrip line. After analyzing the performance of the 1 bit four-element array, a fixed phase is applied to mitigate the negative effects of the 1 bit phase quantized error. The 1 bit four-element arrays with and without the fixed phases are compared in detail. The overlapped −10 dB impedance bandwidth of a prototype array at different beam directions reaches 3 GHz (25–28 GHz). Within the frequency range of 26–28 GHz, the array with the fixed phases can steer the main beam from −34° to 35° without grating lobes. Within these steering beams, the performances of good array gain, moderate sidelobe level, and low cross-polarization level are achieved.

Study on Impact of Mutual Coupling on Performance of Dual Polarized Phased Array Antenna

This study involves the determination of the impact of mutual coupling between antenna elements on the performance of a dual-polarized, wide-angle scanning, phased array antenna for weather radar applications. Weather radars require dual linearly polarized antennas with low cross-polarization, and a narrow beam phased array for wide scanning angle. For this simulation-based study, a microstrip dual linearly polarized 2x20 phased array antenna operating at S-band (2.65 to 3.0 GHz) is designed. This antenna has been designed to have a cross-polarization level less than -45 dB at both polarizations and for the scan angle range of -55o to 55o, which is better than most of the existing dual-pol phased array antennas. This antenna has been used to analyze the impact of mutual coupling on cross-polarization, beamwidth, and antenna gain at various scan angles. Mutual coupling is studied in terms of antenna active element pattern and the corresponding cross-polarization value as well as the active reflection coefficient and impedance values for inter-element spacings of 0.4λ and 0.5λ. It has been found in this study that cross-polarization levels of the whole array (at various scan angles) are affected significantly because of mutual coupling between elements.

Developing Broadband Microstrip Patch Antennas Fed by SIW Feeding Network for Spatially Low Cross-Polarization Situation.

A stacked multi-layer substrate integrated waveguide (SIW) microstrip patch antenna with broadband operating bandwidth and low cross-polarization radiation is provided. A complete study on the propagating element bandwidth and cross polarization level is presented to demonstrate the importance of the design. The proposed antenna includes three stacked printed circuit board (PCB) layers, including one layer for the radiating 2 × 2 rectangular patch elements and two SIW PCB layers for the feeding network. There are two common methods for excitation in cavity-backed patch antennas: probe feeding (PF) and aperture coupling (AC). PF can be used to increase the bandwidth of the antenna. Although this method increases the antenna’s bandwidth, it produces a strong cross-polarized field. The AC method can be used to suppress cross-polarized fields in microstrip patch antennas. As microstrip patch antennas are inherently narrowband, the AC method has little effect on their bandwidth. This paper proposes an antenna that is simultaneously fed by AC and PF. As a result of this innovation, the operating bandwidth of the antenna has increased, and cross-polarization has been reduced. Actually, the combination of probe feeding and aperture coupling schemes leads to achieving a broadband operating bandwidth. The arrangement of radiator elements and cavities implements a mirrored excitation technique while maintaining a low cross-polarization level. In both numerical and experimental solutions, a less than −30 dB cross-polarization level has been achieved for all of the main directions. A fractional impedance bandwidth of 29.8% (10.55–14.25 GHz) for < −10-dB is measured for the proposed array. Simulated and measured results illustrate good agreement. Having features like low cost, light weight, compactness, broadband, integration capabilities, and low cross-polarization level makes the designed antenna suitable for remote-sensing and satellite applications.

60-GHz Double-Layer Transmitarray Antenna Using Complementary Structure

Abstract—A novel double-layer transmitarray element is presented at 60 GHz with linearly- and circularly-polarized characteristics. A planar frequency-selective structure using the complementary design is adopted to augment the element performance for millimeter-wave applications. By integrating two different types of structure, i.e. cross and slot type, the compensation phase range is extended effectively with a satisfactory transmission magnitude. A transmitarray prototype is fabricated and tested to verify this double-layer complementary design. The measured gain at 60.5 GHz is 33.1 dBi with an aperture efficiency of 42.15%. Low side-lobe and cross-polarization levels are obtained. The proposed double-layer complementary design can reduce the structure complexity effectively and offer a high aperture efficiency at a low cost, which can be a potential candidate for the millimeter-wave transmitarray.