Side Lobe Level Reduction Research Articles

Experimental investigation of the unit circle minimum variance distortionless response adaptive beamformer

Source masking occurs when loud interferers produce high side lobes in the conventional beamformer (CBF) scanned response, obscuring the true direction-of-arrival of the desired signal. The minimum variance distortionless response (MVDR) adaptive beamformer (ABF) places deep beampattern notches near interferer directions to suppress their power in the ABF output while maintaining unity gain in the look direction. In practice, the sample matrix inversion (SMI) MVDR ABF replaces the ensemble covariance matrix with the sample covariance matrix (SCM) when computing the array weights. Estimation of the SCM in snapshot-limited and snapshot-deficient scenarios causes perturbations of the array polynomial zeros from the unit circle. The unit circle (UC) MVDR ABF projects the array polynomial zeros radially back to the unit circle, producing deeper notches and reduced sidelobe levels [Tuladhar and Buck, ICASSP 2015]. Preliminary experiments in an outdoor, free-field environment with a 21-microphone uniform linear array at a design frequency of 2.3 kHz found the UC MVDR ABF consistently outperformed both the conventional and SMI MVDR beamformers in interferer suppression when limited to 21 snapshots (one snapshot/sensor). Additionally, the UC MVDR beamformer averaged 18 dB better white noise gain than the SMI beamformer across six independent trials. [Research funded by ONR.]

Beamforming in Smart Antenna using Some Variants of Least Mean Square Algorithm

Beamforming and side lobe level reduction of smart antenna are important tasks in mobile network. Adaptive signal processing algorithms are used for beam forming in smart antenna. In this paper, variable step-size sign least mean square (VS-SLMS) algorithm is used for beam forming of smart antenna with linear antenna array. The results are compared with the results obtained using sign least mean square (SLMS) algorithm. Variable step-size algorithm shows good results for beam forming compared to ordinary constant step-size algorithm.

Performance Evaluation of Elliptical-Cylindrical Antenna Array using SaDE Optimized Hyper Beam

<p>For high performance communication systems, Side Lobe Level (SLL) reduction and improved directivity are the goal of antenna designers. In the recent years, many optimization techniques of antenna design are occupying demanding place over the analytical techniques. Though they have contributed attractive solutions, it is often obvious to select one that meets the particular design need at hand. In this paper, an optimization technique called Self-adaptive Differential Evolution (SaDE) that can be able to learn and behave intelligently along with hyper beam forming is integrated to determine an optimal set of excitation weights in the design of EcAA. Non-uniform excitation weights of the individual array elements of EcAA are performed to obtain reduced SLL, high directivity and flexible radiation pattern. To evaluate the improved performance of the proposed SaDE optimized hyper beam, comparison are done with uniformly excited, SaDE without hyper beam and Genetic Algorithm (GA). In general, the proposed work of pattern synthesis has resulted in much better reduction of SLL and FNBW than both the uniformly excited and thinned EcAA. The results of this study clearly reveal that the SLL highly reduced at a very directive beamwidth.</p>

Backward to Forward Scanning Periodic Leaky-Wave Antenna With Wide Scanning Range

A new type of circularly polarized printed periodic leaky-wave antenna (LWA) structure with a wide scanning range and reduced sidelobe level (SLL) is presented. Fifteen matched unit cells (UCs) are cascaded along the direction of propagation to provide seamless frequency scanning from 20 to 29 GHz with a scanning range of 95° from backward to forward quadrant. The open-stopband has been suppressed around the broadside region by matching the input impedance of the UC to the characteristic impedance of the transmission line. Two empirical transmission line models are presented to describe the behavior of the periodic LWA. Parametric study using full-wave simulation is used to improve the SLL and minimize the axial ratio of the circular polarization leading to a fully optimized periodic leaky LWA.

A Comparative study on Linear Array Antenna pattern synthesis using Evolutionary Algorithms

Antenna array is defined as a collection of multiple radiating elements (antennas) which are placed in space in uniform or non-uniform manner to get a directional radiation pattern that a single antenna generally not adequate to achieve it. In antenna array pattern side lobe level and deep nulls are major problems which cause wastage of energy. This paper presents a brief survey on previous work on optimization of the linear antenna array to achieve a radiation pattern with maximum side lobe level (SLL) reduction along with control null placement in the specified directions. To get superior ability from antenna array it is requisite to modify or synthesize its geometric configurations (as linear, circular, and rectangular etc) or its electrical parameters such as excitation amplitude, phase or distance between array elements. Modern communication system demands compact array designs with high directivity and low side lobe levels. Aimed at this problem several optimization evolutionary algorithms are presented and compared in this paper, are genetic algorithm, ant colony algorithm (ACO), modified invasive weeds optimization algorithm (MIWO), Ant Lion Optimization (ACO), Gravitational Search Algorithm (GSA) and so on.

Enhanced radiation characteristics for antipodal Vivaldi antenna using high permittivity dielectric director

In this paper, we investigate the influence of higher permittivity dielectric director on the radiation performances of an antipodal Vivaldi antenna. An elliptical dielectric director with high permittivity is inserted in an antipodal Vivaldi antenna aperture in order to ameliorate the radiation characteristics of the antenna. Due to the capacity of elevated permittivity dielectric to confine and guide energy in the desired direction, an increment of 4[Formula: see text]dB in the gain of the antenna is obtained. This antenna, which covers an ultra-wide frequency band of 146.8% from 2.3[Formula: see text]GHz to 15[Formula: see text]GHz, has approximately regular radiation patterns with reduced side lobe level and narrower beamwidth. In the interest to achieve radar application necessities, the proposed antenna is exploited to develop an antenna array which consists of four connected elements. Adding dielectric directors can significantly enhance the radiations characteristics of the antenna and reduce the mutual coupling inter-elements. So using four elements with dielectric director in the antenna array can achieve the same results obtained with eight elements without directors. This can decrease the used number of elements that form the antenna array.

High Aperture Efficiency Wide Corrugations Bull’s-Eye Antenna Working at 60 GHz

A full metallic Bull’s-eye antenna operating at 60 GHz is numerically and experimentally analyzed. The antenna presents wide grooves, rather than narrow ones, which support higher order resonances that lead to a large gain enhancement with just a pair of corrugations, achieving an overall miniaturization and increase of its aperture efficiency. In addition, an annular soft surface (SS) of five grooves is placed on the edge of the antenna, giving rise to a slight increase of the gain, reduced sidelobe level as well as reduced end-fire and backward radiation, when compared with an antenna without SS and another antenna with narrow corrugations. A narrow beam antenna with a gain of 19 dBi and nearly −16 dB sidelobe level and 10.8° beamwidth is numerically obtained at the operating frequency. Measurements and numerical results show overall good agreement, with an experimental gain of 20.2 dBi, −13.2 dB sidelobe level, 10.4° beamwidth, and 32% of aperture efficiency.

Non-uniform single-ring antenna array design using wavelet mutation based novel particle swarm optimization technique

Side lobe level (SLL) reduction is the key challenge in antenna array synthesis. In order to achieve low SLL in array pattern, many conventional optimization methods are proposed to handle complex, nonlinear and non-differentiable array factor of antenna array. In this article, we present an improved optimization scheme; Wavelet Mutation based Novel Particle Swarm Optimization (NPSOWM) for the synthesis of various single-ring planar arrays of isotropic antenna elements. The primary objective is to achieve the radiation pattern with minimum SLL and maximum directivity for the non-uniform, planar circular array (CA), hexagonal array (HA) and elliptical array (EA) antenna. The array pattern synthesis is done based on two parameters of the array; namely, excitation amplitude and element spacing. Two design examples are presented which illustrate the effectiveness of the NPSOWM algorithm. As compared with conventional optimization techniques like genetic algorithm (GA), simulated annealing (SA), particle swarm optimization (PSO) and its variant NPSO, NPSOWM outperforms with the goal of maximum SLL suppression.

In brief

PAGE 741 A low-loss hollow-core photonic crystal fibre (HV-PCF) which operates in the terahertz (THz) frequency range is proposed by researchers from Bangladesh. The HV-PCF has a total diameter of 2.75 mm and consists of a regular hexagonal lattice structure with four air-hole rings and a larger central air-hole. The fibre has an extremely low effective material loss of 0.0122 cm−1 obtained at 2.125 THz with 94% of air-core power fraction. PAGE 704 French and Canadian researchers present an air-filled substrate integrated waveguide (AFSIW) slot array antenna, for use in high-performance substrate integrated millimetre-wave systems. When compared with the conventional dielectric-filled SIW, the AFSIW design displays a narrower beam (44% and 18% narrower H- and E-plane half-power beamwidth), and enhanced efficiency (improved by 1.6%). Cross-section of hexagonal lattice structure of crystal fibre able to operate in THz range. PAGE 726 A balanced ring hybrid with arbitrary power division ratio was fabricated by embedding four half-wavelength microstrip lines in the single-ended ring hybrid. The design from China, displays arbitrary differential-mode power division, good common-mode suppression and low insertion loss and high realisable maximum k2. Air-filled substrate integrated waveguide slot array antenna. PAGE 717 An image-compressive sensing preprocessing algorithm is proposed by researchers from China. The collaboration reduced rank (CRR) algorithm is based on nonlocal sparsity and a nonlocal low-rank regularisation reconstruction algorithm (NLR-CS). The method outperforms current compressive sensing reconstruction methods in peak-signal-to-noise and visual perception. Photograph of balanced ring hybrid with arbitrary power division. PAGE 702 Researchers from Korea present a method for supressing surface waves on a microstrip antenna array at the millimetre-wave frequency. Complimentary split ring resonator (CSRR) structures are etched on the ground plane of a 10×2 microstrip array. Measured results show a gain improvement of 2.5 dB and a side lobe level reduction of 3.5 dB. Its light weight, low volume and thin profile make it suitable for radar applications. Image compressive sensing preprocessing algorithm proposed. Microstrip array antenna with etched on CSRR structures for supressing side waves.

Adaptive Beam Formation in Smart Antenna Using VSLMS and VSNLMS Algorithms for Side Lobe Level Reduction

In mobile communication using smart antenna, the capacity of a cellular network can be enhanced significantly. Adaptive beamforming is one of the critical issues in smart antenna. A comparative study of beamforming algorithms by using their variable step size parameter like, variable step size least mean square algorithm (VSLMS) and variable step size normalized least mean square algorithm (VSNLMS) are presented in this paper. Smart antennas of 8 elements and 10 elements linear array are considered here. It is found that using VSNLMS algorithm a lower side lobe level is achieved compared to VSLMS algorithm for various angles of desired user and undesired interferer.

Design of planar concentric circular antenna arrays with reduced side lobe level using symbiotic organisms search

This paper investigates the design of concentric circular antenna arrays (CCAAs) with optimum side lobe level reduction using the Symbiotic Organisms Search (SOS) algorithm. Both thinned and full CCAAs are considered. SOS represents a rather new evolutionary algorithm for antenna array optimization. SOS is inspired by the symbiotic interaction strategies between different organisms in an ecosystem. SOS uses simple expressions to model the three common types of symbiotic relationships: mutualism, commensalism, and parasitism. These expressions are used to find the global minimum of the fitness function. Unlike other methods, SOS is free of tuning parameters, which makes it an attractive optimization method. The results obtained using SOS are compared to those obtained using several optimization methods, like Biogeography-Based Optimization (BBO), Teaching-Learning-Based Optimization (TLBO), and Evolutionary Programming (EP). It is shown that the SOS is a robust straightforward evolutionary algorithm that competes with other known methods.

Blocked Elements in 1-D and 2-D Arrays-Part II: Compensation Methods as Applied to Large Coherent Apertures.

In Part I of this paper, we detected elements blocked by ribs during simulated and in vivo transcostal liver scans, and we turned those elements OFF to compensate for the loss in visibility of liver vasculature. Here, we apply blocked-element detection and adaptive compensation to large synthetic-aperture (SA) data collected through rib samples ex vivo, in order to reduce near-field clutter and to recover lateral resolution. To construct large synthetic transmit and receive apertures, we collected the individual-channel signals from a fully sampled matrix array at multiple and known array locations across the tissue samples. The blocked elements in SAs were detected using the method presented in Part I and retroactively turned OFF, while the subapertures covering intercostal spaces were either compounded, or coherently summed using uniform and adaptive element-weighting schemes. Turning OFF the blocked elements reduced the reverberation clutter by 5 dB on average. Adaptive weighing of the nonblocked elements to rescale the attenuated spatial frequencies reduced sidelobe levels by up to 5 dB for the transcostal acquisitions, and demonstrated a potential to restore lateral resolution to the nonblocked levels. In addition, the arrival-time surfaces were reconstructed to estimate the aberration from intercostal spaces and to offer further means to compensate for the loss of focus quality in transthoracic imaging.

A Wide-Angle Scanning Planar Phased Array with Pattern Reconfigurable Magnetic Current Element

A wide-angle scanning planar phased array with magnetic current elements is proposed. A pattern reconfigurable technique is used to design the element that enhances scanning gain and decreases the sidelobe level throughout the entire scanning range. The array is comprised of eight elements in a $2 \times 4$ arrangement with uniform spacing. The proposed phased array operates at 5.8 GHz and can scan with 3 dB beamwidth the entire upper ground elevation plane from −90° to +90° enabled by a two-step pattern reconfigurability mechanism consisting of: 1) coarse-angle scanning and 2) fine-angle scanning. Significant outcomes also include the reduced sidelobe level (less than 7.8 dB) and the particularly small fluctuation (±0.75 dB) of the gain during scanning over a scanning range of 150° (from −75° to +75° in the elevation plane). With the absence of any structure above the ground level, the high efficiency, and the coverage of the entire upper half-space, this proposed antenna array is very attractive for a variety of phased array applications, particularly those that require a flush-mounted structure.

Design of Filtering Microstrip Antenna Array With Reduced Sidelobe Level

For the requirements of efficient integration and simple fabrication, a new codesign approach for a microstrip filter with an antenna array with reduced sidelobe level is introduced in this communication. The microstrip patch antennas and the stub-loaded resonators are used to illustrate the synthesis of a bandpass filtering antenna array. By controlling the coupling strength between the resonators, a uniform or nonuniform power divider network can be obtained. A nonuniform power division is used to reduce the sidelobe level. The equivalent lumped circuit model is developed and analyzed in detail. Two types of eight-element filtering antenna array with uniform and tapered power-distribution among the elements have been designed. Simulated and measured results provide a good verification for the theoretical concepts.

Phase correction of the electric field for a dielectric loaded substrate integrated waveguide H‐plane horn antenna

ABSTRACTThis article presents a simple graphical method for introducing phase correction in the electric field for a dielectric loaded substrate integrated waveguide H‐plane sectorial horn antenna. An additional pair of rectangular patches with the dielectric loading to the horn antenna provides significant reduction of sidelobe level while maintaining similar gains and beamwidths. Phase plots generated by CAD help explaining the phase correction mechanism and designing. Our studies demonstrated that the reduction of the sidelobe bandwidth is up to 20% of the center frequency. The fabricated antenna operates at 22.7 GHz, and the measured radiation patterns are in good agreement with the simulation results. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:584–588, 2017

Beam pattern synthesis based on improved biogeography-based optimization for reducing sidelobe level

This study deals with a design problem of linear and circular antenna arrays (LAAs and CAAs, respectively) for suppressing the sidelobe levels (SLLs). By adding a new local search strategy and a selection operator into the normal biogeography-based optimization, this work develops a biogeography-based optimization based on local search (BBOLS) algorithm to determine an optimal set of excitation current values for LAAs and an optimal set of excitation current as well as spacing values for CAAs. Various simulations are performed to examine the effectiveness of the proposed BBOLS algorithm in optimizing the radiation beam patterns of LAAs and CAAs, and the results show that BBOLS algorithm has a better performance in reducing the maximum SLL compared with other algorithms such as firefly algorithm.

Solution and Design Technique for Beam Waveguide Antenna System by Using a Parallel Hybrid-Dimensional FDTD Method

This letter presents a novel technique to accurately solve the radiation problems of a beam waveguide (BWG) antenna system aiming to achieve high gain and low sidelobe level (SLL). In order to rapidly obtain the radiation field of the antenna system, a hybrid method using three-dimensional (3-D) nonuniform meshing finite-difference time domain (FDTD) with symmetric boundary condition and body-of-revolution FDTD has been employed. In this method, a parallel algorithm with MPI is applied to enhance computational efficiency, and several approaches are adopted to reduce the errors of simulation. Numerical examinations demonstrate that both the computer memory and run time can be greatly saved by performing this 3-D–2-D hybrid FDTD simulation instead of a complete 3-D one. Furthermore, the accuracy of this method has been validated with a scaled model. Finally, the hybrid method combined with an optimization algorithm has been applied to design an X-band BWG antenna system. Numerical results show a 2.02-dB gain improvement and a 3.46-dB SLL reduction after optimization.

An Effective Approach for the Synthesis of Unequally Spaced Antenna Array by Estimating Optimum Elements Density on the Aperture

In this letter, a simple, effective, and computationally efficient approach for the synthesis of uniformly excited unequally spaced linear antenna (USLA) arrays is proposed. The proposed approach deals with determination of optimum elements' density on the aperture, which empowers the synthesis technique with flexibility and increased search competency in attaining maximum possible reduction in peak sidelobe level (PSLL). In the present study, an inertia-weight particle swarm optimization (IW-PSO) algorithm is employed for the synthesis of USLA arrays. Numerical analysis on 16- and 32-element linear arrays is carried out to evidence the effectiveness of the proposed approach. The numerical results obtained through our technique are compared to those employing other techniques available in the literature, which reveals that the proposed scheme outperforms other schemes and offers great flexibility as well as enhances the global search ability of the IW-PSO algorithm in achieving the lowest possible PSLL at reduced computational effort.

Hardware implementation of antenna array system for maximum SLL reduction

Side lobe level (SLL) reduction has a great importance in recent communication systems. It is considered as one of the most important applications of digital beamforming since it reduces the effect of interference arriving outside the main lobe. This interference reduction increases the capacity of the communication systems. In this paper, the hardware implementation of an antenna array system for SLL reduction is introduced using microstrip technology. The proposed antenna array system consists of two main parts, the antenna array, and its feeding network. Power dividers play a vital role in various radio frequency and communication applications. A power divider can be utilized as a feeding network of an antenna array. For the synthesis of a radiation pattern, an unequal-split power divider is required. A new design for a four ports unequal circular sector power divider and its application to antenna array SLL reduction is introduced. The amplitude and phase of the signals emerging from each power divider branch are adjusted using stub and inset matching techniques. These matching techniques are used to adjust the branches impedances according to the desired power ratio. The design of the antenna array and the power divider are made using the software package CST MICROWAVE STUDIO. The power divider is realized on Rogers R03010 substrate with dielectric constant εr=10.2, loss tangent of 0.0035, and height h=1.28mm. In addition, a design for ultra-wide band (UWB) antenna element and array are introduced. The antenna elements and the array are realized on the FR4 (lossy) substrate with dielectric constant εr=4.5, loss tangent of 0.025, and height h=1.5mm. The fabrication is done using thin film technology and photolithographic technique. The experimental measurements are done using the vector network analyzer (VNA HP8719Es). Good agreement is found between the measurements and the simulation results.

A Sibelobe Suppressing Beamformer for Coherent Plane Wave Compounding

Contrast degradation is a critical problem in ultrasound plane wave imaging (PWI) resulting from signals leakage from the sidelobes. An ideal sidelobe reduction method may enhance the contrast without remarkably increasing computational load. To this end, we introduce a new singular value decomposition (SVD) sidelobe reduction beamformer for coherent plane wave compounding (CPWC) based on a previous work. The SVD takes advantage of the benefits of the different features of the mainlobe and sibelobe in terms of spatio-angular coherence and removes the sidelobes before the final coherent summation. This SVD-based method provides a three-dimensional approach (2D in the space and 1D in the angle) while the computation load is kept satisfactory by a dimension-reduced operation before the SVD. To directly observe the sidelobe level, we demonstrate the performance of our SVD method with a point spread function (PSF) simulation. Compared to CPWC, our method shows a 6.2 dB reduction in the peak sidelobe level (PSL). We also applied our method to the anechoic cyst inside the speckle for the imaging contrast. Both in the simulation and phantom studies, our method enhances the contrast-to-noise ratio (CNR) by more than 10%. Therefore, this new beamformer can be an efficient way to suppress sidelobes in PWI.