2-D-IIR Time-Delay-Sum Linear Aperture Arrays
TL;DR: In this paper, a uniform linear array (ULA) digital beamformer with enhanced selectivity over conventional true-time delay-sum (TTDS) beamforming is proposed for scanned aperture applications.
Abstract: A uniform linear array (ULA) digital beamformer with enhanced selectivity (interference rejection) over conventional true-time delay-sum (TTDS) beamforming is proposed for scanned aperture applications. Conventional TTDS transfer function, which contains only zero-manifolds, is modified by introducing complex pole-manifolds based on 2-D infinite impulse response (IIR) digital beam filters, thereby achieving enhanced selectivity for the same number of antennas in the ULA. For a ULA of 64 antennas, desired direction of arrival (DOA) 30° and interference DOA -60° from array broadside, a relative improvement in signal-to-interference ratio (SIR) of 7 dB is verified. For 128-element ULA, interference DOA -10°, a relative improvement in SIR of 5-10 dB is obtained for the desired DOA in the range 10°-90°. The projected improvements are independent of the weights of the conventional phased-array, TTDS, or filter-sum beamformer used because the method does not change the zero-manifolds of the original array pattern.
Citations
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TL;DR: In this paper, an observer-based dynamic output feedback H∞ controller is proposed for a class of two-dimensional (2D) uncertain discrete systems described by the Roesser model with actuator saturation, time-varying state delay and external disturbances.
Abstract: An observer-based dynamic output feedback H∞ controller is proposed for a class of two-dimensional (2D) uncertain discrete systems described by the Roesser model with actuator saturation, time-varying state delay and external disturbances. First, a delay-dependent Lyapunov stability condition is derived in linear matrix inequality (LMI) form which uses the reciprocal convex approach and H∞ disturbance attenuation performance is also analysed. Secondly, a convex hull is adopted to represent the saturation nonlinearity. The H∞ control synthesis for uncertain 2D discrete systems is described by a Roesser model subjected to actuator saturation and external disturbances using an observer-based dynamic output feedback approach. Some practical examples are provided to highlight the usefulness of the presented results.
11 citations
Cites methods from "2-D-IIR Time-Delay-Sum Linear Apert..."
...The stability conditions of digital filters with state delay have been derived (Ahn, 2013, 2014a, 2015; Chakrabarti and Mitra, 2003; Dey and Kar, 2014; Shyu et al., 2009; Kandanvli and Kar, 2009a, 2009b, 2013; Madanayake et al., 2014)....
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01 Jan 2017
TL;DR: An analog all-pass filter based transfer function synthesis method is proposed for realizing multifunctional microwave active circuits and a novel space time array processor (STAP) and a frequency and bandwidth agile multi-band filter have been simulated.
Abstract: An analog all-pass filter based transfer function synthesis method is proposed for realizing multifunctional microwave active circuits. An analog realization is obtained by replacing unit sample delays in an existing digital prototype with a second-order all-pass analog filter. A novel space time array processor (STAP) and a frequency and bandwidth agile multi-band filter have been simulated using the proposed transfer function synthesis method using measured S- parameters of a fabricated 130 nm second-order CMOS all- pass filter. Simulated array patterns of the STAP beamformer show improved side-lobe performance for better interference suppression and noise rejection. The tunability of the multi-band analog filter, in terms of the center frequency and the quality factor, is verified up to 8 GHz, which has potential applications in analog microwave front-ends.
5 citations
Cites background or methods from "2-D-IIR Time-Delay-Sum Linear Apert..."
...Here, we propose a multi-dimensional STAP beamformer in analog for microwave applications, which combines an FIR filter-sum structure with recently proposed 2-D infinite impulse response (IIR) plane-wave filters to obtain enhanced spatial selectivity [6], [7]....
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...(2) where the coefficients bpq = R+(−1)p cos θ+(−1)q sin θ R+cos θ+sin θ enable electronic tuning of passband orientation θ (thereby the direction of the far-field beam) and selectivity (thereby the halfpower beam width) [6], [9]....
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TL;DR: The presented work explores novel methods for synthesizing approximately frequency independent array factors at lower hardware complexity for wideband beamforming applications by employing 2-D infinite impulse response digital beam filters together with nested uniform linear arrays (ULAs).
Abstract: The presented work explores novel methods for synthesizing approximately frequency independent array factors at lower hardware complexity for wideband beamforming applications. The proposed approach employs 2-D infinite impulse response (IIR) digital beam filters together with nested uniform linear arrays (ULAs). The array is designed to have multiple levels of nesting. Each level of nesting consists of a ULA covering a temporal subband of the incident wideband signal. The use of nested arrays provides the required aperture size using a smaller number of elements compared to using a single ULA to capture the entire wideband signal. The use of different levels of nesting allows the operation of the digital processor for each sub-band at different clock rates. This is a hierarchical approach that saves both digital VLSI hardware and power consumption. The 2-D IIR digital beam filters that process each subband signal from each of the nested subarray achieves wideband beamforming. Simulations illustrate approximately frequency independent passbands as required in wideband beamforming.
5 citations
07 Apr 2015
TL;DR: The concept of MD network-resonant pre-filtering is described as a modification to existing phased/timed array beamforming back-ends to achieve improved side-lobe performance in the array pattern, leading to better interference rejection capabilities.
Abstract: In this review paper, recent advancements in multidimensional (MD) spatio-temporal signal processing for highly-directional radio frequency (RF) antenna array based receivers are discussed. MD network-resonant beamforming filters having infinite impulse response (IIR) and recursive spatio-temporal signal flow graphs are reviewed. The concept of MD network-resonant pre-filtering is described as a modification to existing phased/timed array beamforming back-ends to achieve improved side-lobe performance in the array pattern, leading to better interference rejection capabilities. Both digital and analog signal processing models are described in terms of their system transfer functions and signal flow graphs. Example MD frequency response and RF antenna array pattern simulations are presented.
2 citations
Cites methods from "2-D-IIR Time-Delay-Sum Linear Apert..."
...The multi-inputmulti-output SFG pertaining to (4) allows us to employ the 2-D IIR digital beam filter described by (3) as a pre-filtering stage to conventional phased/timed array beamforming backends, thereby modifying the overall phased/timed array transfer function as [12]...
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TL;DR: A digital very-large-scale integration architecture is proposed for beam-enhanced linear aperture arrays that provides better than 10 dB improvement in bit error rate versus signal-to-interference ratio performance compared to phased/timed-array beamforming.
Abstract: Beam-enhanced digital aperture arrays employ 2-D infinite-impulse-response (IIR) filters as a preprocessing stage for phased/timed-array beamformers to obtain lower side-lobe levels without compromising the array size or the main-lobe selectivity. A digital very-large-scale integration architecture is proposed for beam-enhanced linear aperture arrays. The proposed architecture consists of four subsystems: 2-D IIR prefiltering, beam steering via fast computation of filter coefficients, compensation for nonlinear phase, and phased/timed-array beamforming. Systolic-array architectures are used for first- and second-order 2-D IIR prefiltering subsystems, including fast computation of filter coefficients. The trade-off due to the nonlinear phase response of the 2-D IIR prefilter is partially compensated via fast Fourier transform-based complex phase rotations. Designs are implemented on a Xilinx Virtex-6 XC6VLX240T field-programmable gate-array device and verified using on-chip hardware cosimulation. Field-programmable gate-array designs for both 2-D IIR prefiltering and filter coefficient computation are mapped to standard-cell application-specific integrated circuits in 45 nm complementary metal-oxide semiconductor technology up to the synthesis level with supply VDC = 1.1 V. For a simulation having 64 antennas with binary phase-shift keying modulation, the beam-enhanced aperture array provides better than 10 dB improvement in bit error rate versus signal-to-interference ratio performance compared to phased/timed-array beamforming.
2 citations
Cites methods from "2-D-IIR Time-Delay-Sum Linear Apert..."
...11a as achieved by combining FIR and IIR digital systems in cascade, following the theory in [34]....
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...We recently showed that 2-D IIR beam filters can be employed as a preprocessing stage to phased/timed arrays leading to beam-enhanced digital aperture arrays [34]....
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References
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TL;DR: An overview of beamforming from a signal-processing perspective is provided, with an emphasis on recent research.
Abstract: An overview of beamforming from a signal-processing perspective is provided, with an emphasis on recent research. Data-independent, statistically optimum, adaptive, and partially adaptive beamforming are discussed. Basic notation, terminology, and concepts are included. Several beamformer implementations are briefly described. >
4,122 citations
"2-D-IIR Time-Delay-Sum Linear Apert..." refers background or methods in this paper
...Such RF AESAs achieve directional wave enhancement using beamforming algorithms [3], which are typically based on phased arrays—in the case of narrowband systems, or true-time delay-sum (TTDS) networks—for the case of wideband systems, respectively [3]–[6]....
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...Coherent summation using TTDS aperture beamforming can be realized both in the analog-RF domain using transmission lines or in the digital-RF domain using high-order finite impulse response (FIR) discrete interpolation filters or using fast Fourier transform (FFT)-based phase rotations that operate in the discrete frequency domain [3]....
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Book•
01 Dec 1950
TL;DR: In this article, Lehto and Vainikainen discuss the relationship between aperture distribution and far-field pattern and the Fourier Transform Relation between Aperture Distribution and Far-Field Pattern.
Abstract: 1 Introduction 2 Antenna Basics 3 The Antenna Family 4 Point Sources 5 Arrays of Point Sources 6 The Electric Dipole and Thin Linear Antennas 7 The Loop Antenna 8 End Fire Antennas: The Helical Beam Antenna and the Yagi-Uda Array 9 Slot, Patch and Horn Antennas 9II Slot and Horn Antennas II 10 Flat Sheet, Corner and Parabolic Reflector Antennas 11 Broadband and Frequency-Independent Antennas 12 Antenna Temperature, Remote Sensing and Radar Cross-Section 13 Self and Mutual Impedances 14 The Cylindrical Antenna and the Moment Method (MM) 15 The Fourier Transform Relation Between Aperture Distribution and Far-Field Pattern 16 Arrays of Dipoles and of Apertures 17 Lens Antennas 18 Frequency-Selective Surfaces and Periodic Structures by Ben A. Munk 19 Practical Design Considerations of Large Aperture Antennas 20 Some Examples of Large or Unique Antennas 21 Antennas for Special Applications 22 Terahertz Antennas 23 Baluns, etc. By Ben A. Munk 24 Antenna Measurements. By Arto Lehto and Pertti Vainikainen Appendix A Tables for Reference Appendix B Books and Video Tapes Appendix C Computer Programs (Codes) Appendix D Absorbing Materials Appendix E Measurement Error
1,130 citations
"2-D-IIR Time-Delay-Sum Linear Apert..." refers methods in this paper
...For a given beamforming scheme applied to a ULA, the total array pattern is obtained by following the principle of pattern multiplication [10] given by , where is the spatial angle and is the temporal frequency....
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TL;DR: The proposed robust adaptive beamformers are based on explicit modeling of uncertainties in the desired signal array response and data covariance matrix as well as worst-case performance optimization and offer a significantly improved robustness and faster convergence rates.
Abstract: The performance of adaptive beamforming methods is known to degrade severely in the presence of even small mismatches between the actual and presumed array responses to the desired signal. Such mismatches may frequently occur in practical situations because of violation of underlying assumptions on the environment, sources, or sensor array. This is especially true when the desired signal components are present in the beamformer "training" data snapshots because in this case, the adaptive array performance is very sensitive to array and model imperfections. The similar phenomenon of performance degradation can occur even when the array response to the desired signal is known exactly, but the training sample size is small. We propose a new powerful approach to robust adaptive beamforming in the presence of unknown arbitrary-type mismatches of the desired signal array response. Our approach is developed for the most general case of an arbitrary dimension of the desired signal subspace and is applicable to both the rank-one (point source) and higher rank (scattered source/fluctuating wavefront) desired signal models. The proposed robust adaptive beamformers are based on explicit modeling of uncertainties in the desired signal array response and data covariance matrix as well as worst-case performance optimization. Simple closed-form solutions to the considered robust adaptive beamforming problems are derived. Our new beamformers have a computational complexity comparable with that of the traditional adaptive beamforming algorithms, while, at the same time, offer a significantly improved robustness and faster convergence rates.
496 citations
"2-D-IIR Time-Delay-Sum Linear Apert..." refers methods in this paper
...Adaptive beamforming algorithms such as Frost’s beamforming, multiple sidelobe canceller (MSC), minimum variance distortionless response (MVDR), and linear constraint minimum variance (LCMV) are employed when the direction of the desired signal is not known [8], [9]....
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TL;DR: In this article, simple algebraic methods may be used to design three-dimensional (3D) recursive digital filters for two important applications: first, the selective enhancement of a two-dimensional signal that is moving with time along a linear trajectory at known velocity.
Abstract: It is shown that simple algebraic methods may be used to design three-dimensional (3-D) recursive digital filters for two important applications: first, the selective enhancement of a two-dimensional (2-D) signal that is moving with time along a linear trajectory at known velocity and, second, the selective enhancement of 3-D spatially planar waves. The design techniques involve first-order 3-D networks in the continuous domain and proceed by analogy with an extension of the simple circuit theoretic concepts of resonance and Q factor. A 3-D spatial straight-line filter is designed in the frequency domain as a 3-D planar filter and, conversely, a 3-D spatially planar filter is designed in the frequency domain as a 3-D straight-line filter.
187 citations
01 Dec 1983
TL;DR: In this article, it was shown that the conventional definition of BIBO stability for n-dimensional discrete systems is unnecessarily restrictive for most practical applications, and a new definition of practical-BIBO stability is introduced which is less restrictive, and more relevant for practical applications than the conventional one.
Abstract: It is shown that the conventional definition of BIBO stability for n-dimensional discrete systems is unnecessarily restrictive for most practical applications. The conventional definition permits the input signal to be unbounded in all n dimensions; however, in most practical applications the input signal is unbounded in, at most, one dimension. Based on this, a new definition of practical-BIBO stability is introduced which is less restrictive, and more relevant for practical applications than the conventional one. It is shown that the voltage transfer function of an n-D continuous network, consisting of a reactance 2-port terminated in a resistance, leads to practical-BIBO stable n-D digital filters after bilinear transformation. An example demonstrates the usefulness of the new definition.
177 citations
"2-D-IIR Time-Delay-Sum Linear Apert..." refers methods in this paper
...By employing recently proposed 2-D IIR transfer functions, which were derived based on the concept of 2-D passive network resonance [11] to implement the prefiltering stage, we ensure that the resulting array transfer function is guaranteed to be practical bounded-input–bounded-output (p-BIBO) stable [12]....
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...The coefficients , and in (2) are obtained from the first-order p-BIBO stable [12] 2-D IIR digital beam filter transfer function [7] as...
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