Maximum Sidelobe Research Articles

A Novel Window Function Yielding Suppressed Mainlobe Width and Minimum Sidelobe Peak

In many applications like FIR filters, FFT, signal processing and measurements, we are required (~45 dB) or less side lobes amplitudes. However, the problem is usual window based FIR filter design lies in its side lobes amplitudes that are higher than the requirement of application. We propose a window function, which has better performance like narrower main lobe width, minimum side lobe peak compared to the several commonly used windows. The proposed window has slightly larger main lobe width of the commonly used Hamming window, while featuring 6.2\ sim 22.62 dB smaller side lobe peak. The proposed window maintains its maximum side lobe peak about -58.4 \sim -52.6 dB compared to -35.8 \sim -38.8 dB of Hamming window for M=10~14, while offering roughly equal main lobe width. Our simulated results also show significant performance upgrading of the proposed window compared to the Kaiser, Gaussian, and Lanczos windows. The proposed window also shows better performance than Dolph-Chebyshev window. Finally, the example of designed low pass FIR filter confirms the efficiency of the proposed window.

Investigations on the synthesis of uniform linear antenna array using biogeography-based optimisation techniques

This paper presents the use of biogeography-based optimisation (BBO) algorithm for uniform linear antenna array (ULA) synthesis using amplitude only control method. BBO is a new evolutionary algorithm (EA) proposed by Dan Simon in the year 2008. The first objective of this paper is to optimise the excitation magnitude of array elements to minimise the maximum side lobe levels. Second objective is to place nulls at specific directions for the optimised pattern by optimising a weight parameter. We review classic BBO and modified biogeography-based optimisation (M-BBO) with two migration models namely linear and sinusoidal. Several simulation experiments are conducted on ULA using BBO techniques to minimise the maximum side lobe level (SLL) imposed with broad nulls. We compare the results of simulation case studies of classic BBO and M-BBO with other EAs such as ACO, GA and StudGA. Best performance is achieved using BBO techniques compared to other EAs for our design problem. The major aim of our investigation is to expose BBO to the EM community and demonstrate its great potential in antenna array design optimisation problem.

A MULTI-OBJECTIVE MEMETIC OPTIMIZATION APPROACH TO THE CIRCULAR ANTENNA ARRAY DESIGN PROBLEM

The paper provides a novel approach to the design of non- uniform planar circular antenna arrays for achieving maximal side lobe level suppression and directivity. The current excitation amplitudes and phase perturbations of the array elements are determined using an Adaptive Memetic algorithm resulting from a synergy of Difierential Evolution (DE) and Learning Automata that is able to signiflcantly outperform existing state-of-the-art approaches to the design problem. Moreover, existing literature considers the design problem as a single- objective optimization task that is formulated as a linear sum of all the performance metrics. Due to the con∞icting nature of the various design objectives, improvements in a certain design measure causes deterioration of the other measures. Following this observation, the single-objective design problem is reformulated as a constrained multi-objective optimization task. The proposed memetic algorithm is extended to the multi-objective framework to generate a set of non-dominated solutions from which the best compromising solution is selected employing a fuzzy membership based approach. An instantiation of the design problem clearly depicts that the multi- objective approach provides simultaneous side lobe level suppression and directivity maximization in comparison to the single-objective scenario.

Gradient Index Lens Antennas with Controllable Aperture Field Distributions

This report focuses on a design method for gradient index (GRIN) lens antennas with controllable aperture field distributions. First, we derive differential equations representing optical paths in a gradient index medium with two optical surfaces by using geometrical optics, and then we formulate a novel design method for GRIN lens antennas based on these equations. The Levenberg-Marquardt algorithm is applied as a nonlinear least squares method to satisfy two conditions-focusing and shaping the aperture field distribution-thus realizing a prescribed radiation pattern. The conditions can be fulfilled by optimizing only the index (or permittivity) distribution, whereas the shapes of the optical surfaces remain as free parameters that can be utilized for other purposes, such as reducing reflection losses that occur on the surfaces, as illustrated in this report. A plano-concave GRIN lens is designed as an example, applying the proposed method, to realize a sidelobe level of -30dB pseudo Taylor distribution, and a maximum sidelobe level of -29.1dB was observed, indicating it is sufficiently accurate for practical use. In addition, we discuss the convergence of this method considering the relationship between the number of the initial conditions and the differential order of the design equations, factoring in scale invariance of the design equations.

Non-uniform Concentric Circular Antenna Array Design using IPSO Technique for Side Lobe Reduction

In this paper the optimal design for maximum sidelobe level (SLL) reduction of three-ring Concentric Circular Antenna Array (CCAA) is determined using a novel Particle Swarm Optimization (PSO) technique namely Improved Particle Swarm Optimization (IPSO) algorithm. Standard PSO is also adopted for the comparative optimization. The present text assumes non-uniformly excited and non-uniform inter-element spacing array with a design goal of maximizing SLL reduction using the above two evolutionary optimization techniques. It is shown that among all the designs, the three-ring structure containing (N1=4, N2=6, N3=8) elements proves to be the optimal design owing to the highest SLL reduction achieved by each technique. IPSO yields grand minimum SLL (-31.86dB) for the above optimal set.

Synthesis of Reactively Controlled Antenna Arrays Using Characteristic Modes and DE Algorithm

A simple yet efficient procedure for the synthesis of reactively controlled antenna arrays is proposed by applying the theory of characteristic modes (CM) to the differential evolution (DE) algorithm. A characteristic-mode analysis of an antenna array consisting of N elements is first carried out to identify its different radiating modes. Based on these characteristic modes, the DE algorithm is then employed to seek the optimal mode excitation coefficients according to the specific requirements on radiation pattern, loading schemes, and/or other specifications. Several circular antenna arrays are successfully synthesized according to main beam direction and maximum sidelobe level. The benefits brought by the theory of CM are finally concluded in terms of the quality of the optimal design, the convergence rate, and the computational complexity.

Coherence, Compressive Sensing, and Random Sensor Arrays

Random sensor arrays are examined from a compressive-sensing (CS) perspective, particularly in terms of the coherence of compressive-sensing matrices. It is demonstrated that the maximum sidelobe level of an array corresponds to the coherence of interest for compressive sensing. This understanding is employed to explicitly quantify the accuracy of array source localization as a function of the number of sources and the noise level. The analysis demonstrates that the compressive-sensing theory is applicable to arrays in vacuum, as well as in the presence of a surrounding linear medium. Furthermore, the presence of a surrounding media with known properties may be used to improve array performance, with this related to phase conjugation and time reversal. Several numerical results are presented to demonstrate the theory.

Optimized radii and excitations with concentric circular antenna array for maximum sidelobe level reduction using wavelet mutation based particle swarm optimization techniques

In this paper, a Particle Swarm Optimization with Constriction Factor and Inertia Weight Approach with Wavelet Mutation (PSOCFIWA-WM) is applied to the process of synthesizing three-ring Concentric Circular Antenna Arrays (CCAA) without and with central element feeding, focused on maximum sidelobe level reductions. Sidelobe level (SLL) is a critical radiation pattern parameter in the task of reducing background noise and interference in the most recent wireless communication systems. To improve the radiation pattern with maximum SLL reduction, an optimum set of antenna element parameters as excitation weights and radii of the rings are to be developed. The extensive computational results show that the method of PSOCFIWA-WM provides a maximum sidelobe level reduction of 96.06% with respect to the uniformly excited case for the particular CCAA containing 4, 6, and 8 numbers of elements in the three successive rings along with central element feeding.

Design of FIR Filter Based on Adaptive Window

There are several windows used for truncated the impulse response in order to fixed the filter size. Kaiser window is the most important type and from it is possible to generate other types of windows depending on the value of ?. The proposed adaptive Finite Impulse Response (FIR) Filter is designed and implemented to merge many filter parameters. The results are obtained in different window sizes and different attenuations. These results indicate good performances during the implementation of the filter. This filter is stable and linear phase when implement in non-recursive form, and the ample hardware support that exists for them among other reasons. The Kaiser window provides a simple to calculate set of window coefficients, whose parameters can be adjusted to produce the desired maximum side lobe levels for the near minimal filter length.

Hilbert-shaped complementary ring resonator and application to enhanced-performance low pass filter with high selectivity

In this article, a novel single negative metamaterial (MTM) transmission line (TL) consisting of a Hilbert-shaped complementary ring resonator (H-CRR) on the ground plane is initially presented and studied in depth. Then based on the proposed MTM TL, a novel six-section Hi-Lo microstrip low-pass filter (LPF) with a cut-off frequency 2.5 GHz is developed, fabricated, and measured. Measurement results indicate that: by integrating H-CRR, the selectivity has been significantly improved which is 77.3 dB/GHz due to the single negative permittivity; by etching a crown square on low-impedance section, the bandwidth characterized by 20 dB return loss was obviously enhanced by 26.2% and the maximal sidelobe level of in-band return loss was reduced from 22 to 24.6 dB. What' more, the developed LPF achieved a 36.3% size reduction with respect to its conventional counterpart. The design concept, which was confirmed by the measurement data, is of practical value and can be popularized in other microwave devices where high selectivity is requested. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Identification of multiple characteristic components with high accuracy and resolution using the zoom interpolated discrete Fourier transform

Complex systems can significantly benefit from condition monitoring and diagnosis to optimize operational availability and safety. However, for most complex systems, multi-fault diagnosis is a challenging issue, as fault-related components are often too close in the frequency domain to be easily identified. In this paper, the interpolated discrete Fourier transform (IpDFT) with maximum sidelobe decay windows is investigated for machinery fault feature identification. A novel identification method called the zoom IpDFT is proposed, which combines the idea of local frequency band zooming-in with the IpDFT and demonstrates high accuracy and frequency resolution in signal parameter estimation when different characteristic frequencies are very close. Simulation and a case study on rolling element bearing vibration data indicate that the proposed zoom IpDFT based on multiple modulations has better capability to identify characteristic components than do traditional methods, including fast Fourier transform (FFT) and zoom FFT.

Design of non-uniform circular antenna arrays using biogeography-based optimisation

Biogeography-based optimisation (BBO) is employed for the optimisation of non-uniform circular antenna arrays. In BBO, the problem solutions are represented as islands and the sharing of features between solutions corresponds to immigration and emigration between the islands. The scheme of BBO is employed to find out an optimal set of weights and antenna element separations to provide a radiation pattern with maximum side lobe level (SLL) reduction with the constraint of a fixed major lobe beam width. The capability of BBO is demonstrated by taking different sizes of antennas. The results show that the design of non-uniform circular antenna arrays using the BBO algorithm offers a SLL reduction better than that obtained using genetic algorithms, particle swarm optimisation and simulated annealing.

Finite impulse response-filter-based RF-beamforming network for wideband and ultra-wideband antenna arrays

In this study, a wideband electronic beamforming concept applicable for ultra-wideband short pulse systems is derived and experimentally demonstrated. In particular, a finite impulse response (FIR)-filter-based beamforming network is configured such that an antenna array yields a desired radiation pattern within a predefined frequency range. An experimental verification of a wideband transmission system is presented for the frequency range from 1.5 to 2.0 GHz. The transmit system consists of a wideband power divider feeding a matrix of analogue FIR-filters. These FIR-filters control a circular antenna array of four elements. The receiver consists of a single antenna element. Measurements are performed in frequency domain using a vector network analyser. The results show an almost frequency independent radiation pattern with a half power beamwidth of 72 and a maximum sidelobe level of 10 dB.

Cooperative Beamforming with Mobile Wireless Sensor Nodes: Performance Analysis and Optimal Node Locations

In this paper, cooperative beamforming in the context of wireless sensor networks with random mobile nodes is analyzed. In the first part, we use two dimensional Brownian motion to model mobile nodes, which are assumed to follow Gaussian distribution at every time. The concept of overall outage probability is introduced, and its lower and upper bounds are derived theoretically. In the second part, we extend the Brownian motion to any form and prove the beampattern with minimum mainlobe as well as maximum three-dB sidelobe region can be got simultaneously, then we design a low complexity algorithm to arrange sensor node locations to produce this optimum beampattern. Simulation results show that the overall outage probability and its lower and upper bounds are in good agreement, and compared with uniform and Gaussian distribution, the beampattern produced by the algorithm has sharpest mainbeam and significantly small sidelobe peaks.

Accuracy of Sine Wave Frequency Estimation by Multipoint Interpolated DFT Approach

This paper focuses on the frequency-domain estimation of the normalized frequency of a sine wave corrupted by a stationary white noise. The weighted multipoint interpolated discrete Fourier transform method is considered, and its effect on both the spectral interference due to the image component and the additive wideband noise is taken into account. In particular, the expression of the combined standard uncertainty of the estimator is derived in the case when the H-term maximum sidelobe decay window (H ≥ 2) is used, and the number of interpolation points is 2J + 1 (J ≥ 1). Based on this expression, the number of interpolation points that minimize the estimator-combined uncertainty can be determined. The derived results are validated by means of computer simulations and applied to experimental data.

Application of evolutionary optimization techniques for finding the optimal set of concentric circular antenna array

In this paper the maximum sidelobe level (SLL) reductions, optimal beam patterns and optimal beam widths of various designs of three-ring planar concentric circular antenna arrays (PCCAA) are examined using three different classes of evolutionary optimization techniques to finally determine the global optimal three-ring PCCAA design and then establish some sort of ranking among the techniques. Apart from physical construction of a PCCAA, one may broadly classify its design into two major categories: uniformly excited arrays and non-uniformly excited arrays. The present paper assumes non-uniform excitations and uniform spacing of excitation elements in each three-ring PCCAA design and a design goal of maximizing SLL reduction associated with optimal beam patterns and beam widths. The design problem is modeled as an optimization problem for each PCCAA design and solved using different evolutionary optimization techniques to determine an optimum set of normalized excitation weights for PCCAA elements, which, when incorporated, results in a radiation pattern with optimal (maximum) SLL reduction. Among the various PCCAA designs, one which yields the global minimum SLL with global minimum first null beamwidth is the global optimal design. In this work the three-ring PCCAA containing ( N 1 = 4, N 2 = 6, N 3 = 8) elements proves to be such global optimal design. The optimization techniques employed are real coded GA (RGA), canonical PSO (CPSO), craziness based PSO (CRPSO), evolutionary programming (BEP), hybrid evolutionary programming (HEP). While ranking the techniques after 30 total runs for each design, HEP, CRPSO, RGA, CPSO, BGA hold the first five ranks in order of optimization capability. HEP yields global minimum SLL (−32.86 dB) and global minimum BWFN (77.0°) for the optimal design. BEP often changes the rank from second to fifth depending on the design set. Further, when compared to a uniformly excited PCCAA having equal number of elements and same radii a reduction of major lobe beamwidth is also observed in the optimal non-uniformly excited case.

NLFM waveform generation using tunable integrated optical ring resonators: simulation and proof of concept experiment

The NLFM waveform resulting from a tunable integrated optical ring resonator is simulated. The metrics of interest are the first sidelobe levels and FWHM times of the autocorrelation, as these directly relate to the long-range performance and fine range resolution of a LADAR system, and should ideally be as small as possible. Through simulation, the maximum sidelobe level of the autocorrelation of an NLFM waveform generated by a series of tunable integrated optical ring resonators is shown to be -20 to -30 dB or lower. A proof of concept experiment employing an off-the-shelf thermally tunable silicon-nitride optical ring resonator is shown to generate NLFM chirped waveforms with a bandwidth of 28 kHz.

Accurate Amplitude Estimation of Harmonic Components of Incoherently Sampled Signals in the Frequency Domain

This paper focuses on estimating the amplitude of harmonic components of a harmonically distorted sine wave by the interpolated discrete Fourier transform (IpDFT) method with maximum sidelobe decay windows. The expression of the maximum of the interference error caused by the fundamental sine-wave component on the amplitude estimation of harmonic components is derived. In addition, for a signal corrupted by stationary white noise, the statistical efficiency of the IpDFT method is investigated with respect to the single-tone unbiased Crame¿r-Rao lower bound (CRLB). Based on the derived expressions, a constraint is derived ensuring that interference from the fundamental component could practically be neglected. Finally, the performance of the IpDFT method is compared with that of the energy-based method on the basis of theoretical, simulation, and experimental results and with that of a state-of-the-art method according to simulation and experimental results.

Design of Concentric Circular Antenna Array with Central Element Feeding Using Particle Swarm Optimization with Constriction Factor and Inertia Weight Approach and Evolutionary Programing Technique

In this paper the maximum sidelobe level (SLL) reductions without and with central element feeding in various designs of three-ring concentric circular antenna arrays (CCAA) are examined using a real-coded Evolutionary Programming (EP) to finally determine the global optimal three-ring CCAA design. Standard real-coded Particle Swarm Optimization (PSO) and real-coded Particle Swarm Optimization with Constriction Factor and Inertia Weight Approach (PSOCFIWA) are also employed for comparative optimization but both prove to be suboptimal. This paper assumes non-uniform excitation weights and uniform spacing of excitation elements in each three-ring CCAA design. Among the various CCAA designs, the design containing central element and 4, 6 and 8 elements in three successive concentric rings proves to be such global optimal design set with global minimum SLL (−39.66 dB) as determined by Evolutionary Programming.

Optimal Design of Concentric Circular Antenna Array Using Particle Swarm Optimization with Constriction Factor Approach

In this paper the maximum sidelobe level (SLL) reductions without and with central element feeding in various designs of three-ring concentric circular antenna arrays (CCAA) are examined using Particle Swarm Optimization with Constriction Factor Approach (PSOCFA) to finally determine the global optimal CCAA design. Binary coded Genetic Algorithm (BGA) is also employed for comparative optimization but it proves to be suboptimal. The present paper assumes non-uniform excitations and uniform spacing of excitation elements in each three-ring CCAA design. Among the various CCAA designs, the three-ring CCAA containing central element and 4, 6 and 8 elements in three successive concentric rings proves to be such global optimal design with global minimum SLL (-17.42dB) determined by PSOCFA.