Low-sidelobe Antenna Research Articles

Low-Sidelobe Dual-Beam Antenna Based on Metasurface With Independently Regulated Amplitude/Phase

A method to design low-sidelobe dual-beam antennas is proposed based on metasurface with independently regulated amplitude/phase. This method includes the following steps. Firstly, a standard horn antenna is modeled and the amplitude and phase of the radiation field at the interface are obtained. Next, the phase compensation technology based on the actual radiation phase of the feed is employed to control directions of the main lobe. Finally, the reflection amplitude of metasurface is controlled by combining Schelkunoff polynomials and actual radiation amplitude of the feed. Specifically, by mapping the angles of the dual beams to the complex coordinate system, the sidelobe level (SLL) of the dual-beam antenna is reduced. Meanwhile, a compensation factor is introduced to offset the gain loss caused by amplitude modulation.

Double-layer broadband transmission metasurface and its application in low sidelobe antenna

This study proposes a double-layer metasurface which is capable of conducting independent amplitude and phase modulation for transmitting x-polarized waves under y-polarized incidence. The phase modulation is controlled by regulating the opening angle of the middle metal ring. Meanwhile, amplitude modulation is achieved by adjusting the rotation angle of the opening ring structure. The cross-polarized transmission response achieves complete phase and amplitude coverage and exhibits wideband characteristic with which a 3 dB gain bandwidth of 54.6% (5.4–9.5 GHz). The polarization isolation level is lower than −20 dB. In the wideband frequency range, the average sidelobe level of phase-only modulated metalens antenna is less than −20 dB with the lowest value of −22.5 dB, and the intermediate sidelobe level of amplitude-phase independent modulated metalens antenna is less than −25 dB with the lowest value of −27.4 dB. Both numerical simulated and experimental results verify that the proposed metalens antenna realizes a 4.8 dB averages of the sidelobe level suppression compared with the phase-only modulation metalens antenna. Holding strong anti-interference performance due to its superiority in polarization isolation level and side lobe level, the proposed antenna embraces broad application prospects in point-to-point communication systems in jamming environments.

Low-Sidelobe Antenna Array Based on Evanescent Mode of Cutoff Waveguide

Low-sidelobe antenna arrays are widely used in the wireless systems for the anti-interference receiving. To achieve low sidelobe, the amplitudes of each array element follow a tapered distribution, which is provided by properly designed feeding networks. In this article, as a different feeding approach for low-sidelobe antenna array, the evanescent mode of a cutoff waveguide is engineered to generate a symmetric and exponential-decay distribution for array elements. To verify this strategy, an array of slots is transversely etched with equal spacing on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.67\lambda _{0}$ </tex-math></inline-formula> -length cutoff waveguide operating at its evanescent mode, achieving a sidelobe level (SLL) lower than −18.8 dB with a gain of 13.7 dBi through measurement, agreeing well with the simulations. Moreover, by optimizing the element spacing on the same cutoff waveguide, the antenna array achieves an extremely low SLL of −24.1 dB and a gain of 13.1 dBi. The proposed evanescent-mode waveguide enables low-sidelobe antenna arrays with the merits of simple structure, compact dimensions, and high aperture efficiency for potential applications in radar and communication systems.

Amplitude and Phase Independently Adjustable Transmitarray Aperture and Its Applications to High Gain and Low Sidelobe Antenna

This article introduces an amplitude and phase independently adjustable transmitarray aperture with a thin profile and low cost to fabrication characteristics, and a transmitarray antenna (TA) featuring the high gain and low sidelobe level (SLL) is realized based on it. The TA is made up of a standard feed horn and a transmitarray aperture, each of which comprises a three-layer metasurface that is well-designed to tune the transmitted phase and amplitude on its own. As a result, the transmitarray aperture can cover the 360° phase range required for phase compensation while also realizing the amplitude distribution calculated by the Taylor design, contributing to the low SLLs. The advantage of independently controlling the amplitude and phase not only enables the proposed TA to be easy to realize and less cost on optimization but also improves the performance of high gain and low SLLs with a low profile and easy fabrication. Theoretical analyses and simulations are carried out, and a prototype is fabricated and measured. At 10 GHz, the measured peak gain is 21.16 dBi, with SLLs of −31.21 and −29.93 dB in the H- and E-planes, respectively. As a result, the tight agreements between measurement and simulation validate the design concept.

High‐gain side‐fed reflectarray antenna based on metasurface using sidelobe reduction optimization

This article proposes and designs a low-sidelobe planar reflectarray antenna based on particle swarm optimization (PSO). It is composed of a feed antenna and a plane reflectarray based on metasurface, and the center frequency is 5.8 GHz. The operating frequency range of the feed antenna is 5.4–6.3 GHz, and the maximum gain is 6.3 dB. The planar reflectarray based on PSO is composed of reflector elements of different sizes. The planar reflectarray antenna optimized by the PSO achieves the optimization goal of sidelobe level less than −30 dB, and the sidelobe level can be further reduced as the number of iterations increases. The antenna array adopts a side-fed feed mode to achieve a maximum gain of 22.6 dB, and 1 dB gain relative to the bandwidth accounted for 15.8%. It has great application value in scanning and multi-beam radiation for wireless communication.

Wideband Low-Sidelobe Slot Array Antenna With Compact Tapering Feeding Network for E-Band Wireless Communications

In this work, a wideband low-sidelobe slot array antenna for wireless communication system at E-band is presented. The slots are excited by a parallel feeding network where the Taylor distribution is applied. Two types of wideband unequal power divider with compact structures are designed for various output ratios to fit the limited feeding network space. One is integrated vertically inside a 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 1 elements subarray using a set of pins with asymmetrical offset. The other type is designed inside an E-plane T-junction with unbalance impedance at two output ports. To avoid main lobe tilt and asymmetrical radiation patterns, the feeding network is designed to be biaxially symmetrical, and the feed port is placed in the center of the back. A prototype is fabricated with brass and measured in an anechoic chamber. It achieves a peak gain of 25.8 dBi and a fractional impedance bandwidth of 19.2% with the reflection coefficient below −10 dB. The measured radiation patterns agree with the simulated patterns very well, and the sidelobe level (SLL) is lower than −21 dB.

Unequally Spaced Antenna Array Synthesis Using Accelerating Gaussian Mutated Cat Swarm Optimization

Low peak sidelobe level (PSLL) and antenna arrays with high directivity are needed nowadays for reliable wireless communication systems. Controlling the PSLL is a major issue in designing effective antenna array systems. In this paper, a nature inspired technique, namely accelerating Gaussian mutated cat swarm optimization (AGMCSO) that attributes global search abilities, is proposed to control PSLL in the radiation pattern. In AGM-SCO, Gaussian mutation with an acceleration parameter is used in the position-updated equation, which allows the algorithm to search in a systematic way to prevent premature convergence and to enhance the speed of convergence. Experiments concerning several benchmark multimodal problems have been conducted and the obtained results illustrate that AGMCSO shows excellent performance concerning evolutionary speed and accuracy. To validate the overall efficacy of the algorithm, a sensitivity analysis was performed for different AGMCSO parameters. AGMCSO was researched on numerous linear, unequally spaced antenna arrays and the results show that in terms of generating low PSLL with a narrow first null beamwidth (FNBW), AGMCSO outperforms conventional algorithms.

Design of Low Sidelobe Antenna Array for 24GHz Vehicular Radar

ABSTRACT A novel design method of a low sidelobe antenna array is proposed in this paper. By combining the Chebyshev array synthesis theory and the sparse array synthesis theory, the sidelobe level (SLL) of the antenna array is greatly reduced. Compared with the traditional Chebyshev array synthesis theory, the proposed method is effective to reduce the SLL of the antenna array (SLL reduced by 6.8 dB at Phi = 0° and SLL reduced by 4.5 dB at Phi = 90°). According to the method proposed above, an antenna array applies for 24 GHz vehicle radar is designed and simulated. The measured results show that the antenna has wide bandwidth (23.6 GHz~25.07 GHz, 1.47 GHz), high gain (20.7 dBi), and extremely low sidelobe level (−28.8 dB at Phi = 0° and −25 dB at Phi = 90°). In summary, the antenna with good performance and simple structure is easy to be integrated, which can provide some reference for the design of the 24 GHz vehicle radar antenna.

A Cross-Mode Universal Digital Pre-Distortion Technology for Low-Sidelobe Active Antenna Arrays in 5G and Satellite Communications

A cross-mode universal digital pre-distortion (CMUDPD) technology is proposed here to linearize low-sidelobe active antenna arrays with non-uniform fixed power levels for each branch, which are desired in satellite communications with stringent requirements to minimize interference. In low-sidelobe arrays formed by nonuniform amplitude excitation, conventional digital pre-distortion (DPD) techniques require multiple feedback paths for either one-to-one or average linearization of the PAs, which increases system complexity and is infeasible for large-scale arrays. This is because the power amplifiers (PAs) usually operate in different modes where the supply voltages, bias voltages, and input power levels are different. The proposed CMUDPD method aims at solving this issue by intentionally arranging the PAs to work in different modes but with shared nonlinear characteristics. Based on the nonlinear correlation established among the PAs’ different operating modes, a single feedback path is sufficient to capture the common nonlinearity of all the PAs and determine the parameters of the CMUDPD module. The concept is explained in theory and validated by simulations and experiments using GaN PAs operating with three significantly different output power levels and two orthogonal frequency division multiplexing (OFDM) signal bandwidths.

Non-Contact Monitoring of Human Vital Signs Using FMCW Millimeter Wave Radar in the 120 GHz Band.

A non-contact heartbeat/respiratory rate monitoring system was designed using narrow beam millimeter wave radar. Equipped with a special low sidelobe and small-sized antenna lens at the front end of the receiving and transmitting antennas in the 120 GHz band of frequency-modulated continuous-wave (FMCW) system, this sensor system realizes the narrow beam control of radar, reduces the interference caused by the reflection of other objects in the measurement background, improves the signal-to-clutter ratio (SCR) of the intermediate frequency signal (IF), and reduces the complexity of the subsequent signal processing. In order to solve the problem that the accuracy of heart rate is easy to be interfered with by respiratory harmonics, an adaptive notch filter was applied to filter respiratory harmonics. Meanwhile, the heart rate obtained by fast Fourier transform (FFT) was modified by using the ratio of adjacent elements, which helped to improve the accuracy of heart rate detection. The experimental results show that when the monitoring system is 1 m away from the human body, the probability of respiratory rate detection error within ±2 times for eight volunteers can reach 90.48%, and the detection accuracy of the heart rate can reach 90.54%. Finally, short-term heart rate measurement was realized by means of improved empirical mode decomposition and fast independent component analysis algorithm.

Low-Sidelobe Cavity-Backed Slot Antenna Array With Simplified Feeding Structure for Vehicular Communications

In this article, low-sidelobe cavity-backed slot antenna array with simplified feeding structure for vehicular communication is proposed. Conventional low-sidelobe antennas were realized using power dividing network to obtain the in-phase and nonuniform-amplitude excitation, which causes complicated antenna's structure and design. To tackle these challenges, a simplified feeding method without using power dividing network is introduced to design the low-sidelobe slot antenna array. The slots at the top walls serve as the radiation elements, and the slots are directly fed by the electric field of the cavity mode. Nonuniform amplitude is obtained by simply modifying the slots' sizes and positions, while the in-phase excitation of the elements is remained. The nonuse of power dividers brings out a simpler antenna structure than conventional full-metal waveguide-based antennas. Besides, the full-metal structure introduces a high power-handling capacity. Then, two linear arrays with 1 × 4, 1 × 7 elements and a planar array with 5×4 elements are presented to show the design feasibility. Finally, the 5 × 4 antenna array is fabricated and measured, which can achieve 18.2 dBi gain, -20 dB sidelobe level, 94% radiation efficiency, and -42 dB cross-polarization. Good agreement between measurement and simulation verifies the feasibility of the proposed design concept.

Design and realization of 4 way Chebyshev Wilkinson power divider at 3 GHz frequency for 3 dimensional radar application

In the radar system, detection of objects with high accuracy is needed. Therefore, a low sidelobe antenna is needed to avoid interference from other detected targets. One method to suppress sidelobe antenna is by using unequal power divider with Chebyshev polynomial excitation coefficients. In this paper, we will discuss about the design and fabrication of Chebyshev Wilkinson power divider for 3 dimensional radar application. This research was conducted through 4 stages, namely design, simulation, fabrication and measurement. This power divider is realized in the form of a microstrip using Rogers R0-4003C (lossy) substrate with a thickness of 1,524 mm and a dielectric constant of 3.55. The simulation and measurement results are met the desired specifications, the operating frequency is at 3 GHz with a bandwidth of 200 MHz, the return loss is less than -10 dB, the insertion loss value is in accordance with Chebyshev, the isolation value of the port is less than -10 dB, and the unbalance phase is smaller than 2.5°.

W‐band low‐sidelobe series‐fed microstrip antenna array based on impedance matching section weighting method

A W-band low-sidelobe series-fed microstrip antenna array is proposed here. Impedance matching section weighting method is used in element series-fed weighting. This feeding method can effectively realise the desired amplitude distribution and sidelobe level of −30.1 dB is obtained in this design. The designed low-sidelobe antenna has great practical value in antenna of W-band portable radar.

Ka-Band 8 × 8 Low-Sidelobe Slot Antenna Array Using a 1-to-64 High-Efficiency Network Designed by New Printed RGW Technology

This letter proposes an 8 × 8 high-efficiency low-sidelobe slot antenna array operating at Ka -band frequencies with a feeding network designed by a new printed ridge gap waveguide (PRGW). The device consists of a slot antenna element, a PRGW unequal feeding network, and a stripline-to-PRGW transition. The substrate integrated waveguide slot antenna element fed by the PRGW through a coupling aperture has a wide bandwidth, and the isolation is also increased by adding metallized holes to the array. Compared with other gap waveguide antenna arrays, our work realizes an antenna element fed separately due to the use of a PRGW with a compact mushroom cell size, which helps improve the properties of the unequal feeding network. In addition, the transition between the PRGW and stripline is also designed with a wide band and low insertion loss. The measured reflection coefficient is less than –10 dB over a 6 GHz bandwidth (16%), the gain is more than 23.5 dBi in the working band, and the sidelobe level is –18 dB. In addition, the measured radiation efficiency of the array with a two-dimensional Taylor distribution is 41.69%.

On Alternative Approaches to Design of Corporate Feeds for Low-Sidelobe Microstrip Linear Arrays

Two design approaches, illustrated by simulations and measurements, aiming at a systematic computer-aided design of printed circuit feeds for low-sidelobe microstrip antenna arrays are described. The novelty of these approaches resides in identification of the optimal feed architectures with subsequent simulation-based optimization of the feed and array aperture dimensions. In this communication, we consider microstrip corporate feeds (CFs) realizing nonuniform amplitude excitation of linear arrays of microstrip patch antennas. Two types of the microstrip CFs are considered: with equal power split junctions and with unequal power split junctions. For each feed type, we identify candidate prototypes of feed architectures using numerical optimization of the corresponding fast feed models. Subsequently, the architectures are implemented as microstrip subcircuits within the antenna array electromagnetic (EM) models. For the sake of comparison, the antenna array circuits are defined with the same linear array of microstrip patch antennas featuring the half-wavelength element spacing, and implemented on the same microstrip substrates. Finally, the EM models are tuned—using simulation-based optimization techniques—to ensure an appropriate input reflection coefficient and minimum sidelobe levels. Selected optimal designs of antenna array circuits with 12 microstrip patches and different feeds are manufactured and measured.

A Balanced Feed Filtering Antenna With Novel Coupling Structure for Low-Sidelobe Radar Applications

A fourth-order filtering patch antenna with a novel coupling structure is presented in this paper. Using the proposed coupling structure, both the balanced coupling feed and cross-coupling are realized. Two identical slots etched on the ground plane are utilized to excite the radiating patch with the reduced cross-polarization level. A short slot etched on the ground plane is employed for cross-coupling, which introduces two controllable radiation nulls with a steep roll-off rate. In addition, owing to the split-ring resonators and hairpin resonators, the improved impedance bandwidth is achieved with the fourth-order filtering response. To demonstrate the proposed design techniques, both the filtering antenna element and the low-sidelobe array are designed, fabricated, and measured. The measured results show that the proposed antenna has the impedance bandwidth of 12% (4.78–5.39 GHz) with the total height of $0.06\lambda _{0}$ , the cross-polarization level lower than −31 dB, and two radiation nulls with the suppression higher than 31 dB. For the low-sidelobe antenna array, wide impedance bandwidth is also obtained with the sidelobe level below −28.7 dB, the cross-polarization level below −34 dB, and the out-of-band suppression better than 25 dB.

Fractal-based design and fabrication of low-sidelobe antenna array

The aim of this work is to design and fabricate a compact four-element linear array of microstrip patch antennas to be operated at dedicated short range communication service (DSRCS) band. The array is designed in such a manner to direct most of the power in a particular direction by reducing the peak sidelobe level (peak SLL) in its beam pattern. In order to reduce the array size and also to increase its gain, a modified-Cantor square-fractal based design has been employed as an element of the array. The problem of reducing the peak SLL is formulated as an optimization problem with arguments as the inter-elemental spacing and elements excitation. Optimum values are obtained using Differential Evolution (DE) algorithm. The corporate feed network of the array is designed using the optimum values of the parameters. Finally, using those optimum values, the array is fabricated and the beam pattern of the fabricated array is compared with the simulated structure. The experimental characterization of the fabricated array closely resembles with the simulated structure.

Enhancing the Radiation Performance of a Pyramidal Horn Antenna by Loading a Subwavelength Metasurface

We present the detailed design and experimental demonstration of a low-sidelobe horn antenna based on controlling the amplitude and the phase distribution of the electromagnetic fields over the aperture of the horn antenna using a thin single-layer metasurface lens. The lens is composed of two identical subwavelength metallic square-ring arrays printed on the two sides of a single dielectric layer. By placing the metasurface lens inside a standard pyramidal horn, the electromagnetic fields over the horn aperture can be manipulated, resulting in low sidelobe radiation in both $E$ - and $H$ -planes. Both simulated and measured results demonstrate the tapered field distribution over the horn aperture and the significant reduction of sidelobes in the $E$ -plane as well as the reduction of the backlobes.

Suppressing side-lobe radiations of horn antenna by loading metamaterial lens.

We propose a new approach to control the amplitude and phase distributions of electromagnetic fields over the aperture of a horn antenna. By loading a metamaterial lens inside the horn antenna, a tapered amplitude distribution of the aperture field is achieved, which can suppress the side-lobe radiations of the antenna. The metamaterial is further manipulated to achieve a flat phase distribution on the horn aperture to avoid the gain reduction that usually suffers in the conventional low-sidelobe antenna designs. A prototype of the metamaterial-loaded horn antenna is designed and fabricated. Both numerical simulations and measured results demonstrate the tapered aperture-field distribution and significant reduction of side-lobe and back-lobe radiations in the operating frequency band.

Investigations of SIW Leaky-Wave Antenna for Endfire-Radiation With Narrow Beam and Sidelobe Suppression

A new substrate integrated waveguide (SIW) leaky-wave antenna is investigated for endfire-radiation with a narrow beam and sidelobe suppression. Maximum directivity conditions for endfire-radiation from line sources with different amplitude distributions are theoretically discussed as a design aid. Interestingly, for endfire beams it is seen that designs that have a lower sidelobe level can also have a higher directivity, contrary to what is normally encountered for broadside beams. An SIW leaky-wave antenna with tapered transverse slots on only the top and bottom planes is presented. Compared with a previous leaky-wave antenna having uniform transverse slots on the top plane, the presented leaky-wave antenna has a main beam that can radiate exactly at endfire and also has a lower sidelobe level. The design of the low sidelobe antenna is based on the leaky mode, which loses physical significance as the beam is scanned to the endfire direction. Nevertheless, the antenna retains a good beam shape and a low sidelobe level when it radiates at endfire. A prototype is made, and measured results are consistent with theoretical and simulated results.