Digitising the signals from a phased array at the element level is becoming more practicable through advances in technology. Adaptive beamforming schemes such as a sample matrix inversion involve inverting a covarianc...
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ISBN:
(纸本)0819429163
Digitising the signals from a phased array at the element level is becoming more practicable through advances in technology. Adaptive beamforming schemes such as a sample matrix inversion involve inverting a covariance matrix of dimension equal to the number of spatial channels. Since with an element digitised system there can be several thousand elements it becomes impractical to invert such large matrices. This paper presents a weight computation scheme for a fully digitised system. The clutter returns are firstly range gated and then the adaptive process is broken down into a smaller cascade of stages, or domains. Attenuation of the clutter is then achieved using a spatial Wiener filter in each domain. From a simulation of an airborne radar at a high pulse repetition frequency, examples are given of adapted beampatterns and clutter output doppler spectra within each domain. By choosing alias free domains, a clutter-free output is obtained for the sidelobe clutter scenario investigated. A comparison is then given with the performance of a 32 sub-array system. The sub-array system does not have the necessary control of the small scale order of the array weights to spatially null the clutter.
In certain applications, the discretization of two-dimensional integral equations can lead to systems involving matrices with block Toeplitz-Toeplitz block structure. Iterative Krylov subspace methods are sometimes em...
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ISBN:
(纸本)0819429163
In certain applications, the discretization of two-dimensional integral equations can lead to systems involving matrices with block Toeplitz-Toeplitz block structure. Iterative Krylov subspace methods are sometimes employed to find regularized solutions to the related 2D discrete ill-posed problems;however, preconditioners which filter noise are needed to speed convergence to regularized solutions. We describe a preconditioning technique based on the Toeplitz-type structure of the matrix which generalizes the approaches in [1] and [2] to take advantage of symmetry and real arithmetic operations. We use fast sine transforms to transform the original system to a system whose matrix has partially reconstructible Cauchy-like blocks. The preconditioner is a block diagonal, rank m approximation to this matrix, with Cauchy-like blocks each augmented by an identity of appropriate dimension. We note that the initialization cost is in general less than that for the similar 2D preconditioner in [2] which does not take advantage of symmetry. Several examples are given which illustrate the success of our preconditioned methods.
The problem of blind equalization of MIMO (multiple-input nultiple-output) communications channels is considered using the second-order statistics of the data. Such models arise when a single receiver data from multip...
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ISBN:
(纸本)0819429163
The problem of blind equalization of MIMO (multiple-input nultiple-output) communications channels is considered using the second-order statistics of the data. Such models arise when a single receiver data from multiple sources is fractionally sampled (assuming that there is excess bandwidth), or when an antenna array is used with or without fractional sampling. We focus on direct design of finite-length MMSE (minimum mean-square error) blind equalizers. We allow infinite impulse response (IIR) channels. Our approaches also work when the "subchannel" transfer functions have common zeros so long as the common zeros are minimum-phase zeros. We only require that the there exist a causal, stable left inverse (not necessarily unique) to the MIMO transfer function and that the leading coefficient matrix of the MIMO channel impulse response have its rank equal to the number of sources. The channel length or model orders need not be known. The sources are recovered up to a unitary mixing matrix and are further 'unmixed' using higher-order statistics of the data. An illustrative simulation example is provided.
An innovative approach is being used to implement and simulate the infrared (IR) and laser radar signalprocessingalgorithms for the advanced Sensor Technology Program (ASTP) and the Discrimination Interceptor Techno...
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ISBN:
(纸本)0819428221
An innovative approach is being used to implement and simulate the infrared (IR) and laser radar signalprocessingalgorithms for the advanced Sensor Technology Program (ASTP) and the Discrimination Interceptor Technology Program (DITP). Although the algorithms will run on four different computer architectures, they will use the same source code for all implementations. The initial development and testing will occur in Mathcad on a Windows 95/NT personal computer, then move to simulation on a Silicon Graphics (SGI) workstation, then to scaled real-time simulation on a parallel high performance computer (HPC), and finally to the actual flight processor, the miniaturized parallel Wafer Scale signal Processor (WSSP) with a MIMD (multiple-instruction and multiple data) architecture. This flexibility is accomplished with code wrappers that implement interchangeable interface layers for the code modules, one wrapper for Mathcad matrices, one for C++ objects on the workstation, one for message passing with static routing on the HPC, and one for dynamically routed message passing on the WSSP. With this approach, developers can move modules back and forth from the workstation simulation environment to the implementation hardware. This will eliminate the need to maintain different versions of the same algorithm. The signalprocessingalgorithms will be modified to work in a massively parallel architecture, with a message passing interface, which is simulated on the Silicon Graphics workstation, emulated on the HPC, and implemented on the WSSP. This approach will allow for pipeline processing as well as multiple, concurrently running instances of modules. In addition, innovative algorithms will fuse active laser radar detections and passive multicolor IR sensor measurements to improve target state estimation.
Recently, there has been a great deal of interest in the application of wavelet transforms to signalprocessing applications. Fundamentally, the wavelet transform of a signal is the correlation of the signal with a ba...
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ISBN:
(纸本)081942840X
Recently, there has been a great deal of interest in the application of wavelet transforms to signalprocessing applications. Fundamentally, the wavelet transform of a signal is the correlation of the signal with a basis function derived from a mother wavelet and its scaled versions called daughter wavelets. Thus any real-time correlator can be used for the implementation of the wavelet transform. Since a one-dimensional input signal produces a two-dimensional wavelet transform, optical correlators provide a natural advantage over conventional electronic implementations. Examples of optical correlation architectures include the vanderLugt correlator, the joint transform correlator and its derivative, the quasi-Fourier transform joint transform correlator. Any optical correlator architecture can be used to implement the wavelet transform provided a suitable spatial light modulator is used to convert the electrical input signal into an appropriate optical signal. The concept of the smart pixel is to integrate both electronic circuitry and individual optical devices on a common integrated circuit to take advantage of the complexity and programmability of electronic processing circuits and the switching speed of optical devices. Arrays of these smart pixels would then bring with them the advantage of parallelism that optics provides. Smart pixel arrays can function as spatial light modulators providing additional electronic processing features at each individual pixel and therefore are naturally well-suited to realize the wavelet transform.
Object-Based Media refers to the representation of audiovisual information as a collection of objects - the result of scene-analysis algorithms - and a script describing how they are to be rendered for display. Such m...
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Object-Based Media refers to the representation of audiovisual information as a collection of objects - the result of scene-analysis algorithms - and a script describing how they are to be rendered for display. Such multimedia presentations can adapt to viewing circumstances (e.g. size and aspect ratio of display) as well as to viewer preferences and behavior, and can provide a richer link between content creator and consumer. With faster networks and processors, such ideas become applicable to live interpersonal communications as well, creating a more natural and productive alternative to traditional videoconferencing. I outline an example of object-based media algorithms and applications developed by my group, and present new hardware architectures and software methods that we have developed to enable meeting the computational requirements of object-based and other advanced media representations. In particular I will describe stream-based processing, which enables automatic run-time parallelization of multidimensional signalprocessing tasks even given heterogeneous computational resources.
The capabilities of switched networks for parallel and distributed computers are evolving rapidly towards networks with various forms of intelligence in support of parallel execution of programs. This paper presents a...
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ISBN:
(纸本)081868433X
The capabilities of switched networks for parallel and distributed computers are evolving rapidly towards networks with various forms of intelligence in support of parallel execution of programs. This paper presents a perspective on intelligent networks, including reconfiguration of the network to adapt to the needs of successive computational algorithms being performed as part of an overall problem, for clusters containing a modest number of digital signal processors (DSPs), Scalability of the overall parallel DSP-based computer is achieved by adding these cluster nodes. It is suggested that there are many operating system functions which might be directly integrated into such an intelligent network, including adapting those operating system functions according to the needs of the specific tasks being performed. The viewpoint presented here is based on a reconfigurable system using FPGAs and being constructed for image processing applications to study opportunities for integration of such intelligent networks into future silicon vLSI components, including advanced packaging such as multi-chip modules (MCMs), The packaging limitations present the greatest barrier to aggressive development of such networks, with active substrate MCMs implementing the network function providing the greatest flexibility and performance.
The capabilities of switched networks for parallel and distributed computers are evolving rapidly towards networks with various forms of intelligence in support of parallel execution of programs. This paper presents a...
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The capabilities of switched networks for parallel and distributed computers are evolving rapidly towards networks with various forms of intelligence in support of parallel execution of programs. This paper presents a perspective on intelligent networks, including reconfiguration of the network to adapt to the needs of successive computational algorithms being performed as part of an overall problem, for clusters containing a modest number of digital signal processors (DSPs). Scalability of the overall parallel DSP-based computer is achieved by adding these cluster nodes. It is suggested that there are many operating system functions which might be directly integrated into such an intelligent network, including adapting those operating system functions according to the needs of the specific tasks being performed. The viewpoint presented here is based on a reconfigurable system using FPGAs and being constructed for image processing applications to study opportunities for integration of such intelligent networks into future silicon vLSI components, including advanced packaging such as multichip modules (MCMs). The packaging limitations present the greatest barrier to aggressive development of such networks, with active substrate MCM implementation of the network function providing the greatest flexibility and performance.
System developers have found that exploiting parallel architectures for control systems is challenging and often the resulting implementations do not provide the expected performance advantages over traditional unipro...
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The proceeding contains 53 papers from the conference of SPIE advancedvIII signalprocessing: algorithms, architectures, and implementations. The topics:include pattern recognition under translation and scale changes...
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The proceeding contains 53 papers from the conference of SPIE advancedvIII signalprocessing: algorithms, architectures, and implementations. The topics:include pattern recognition under translation and scale changes, instanteous frequency of a propagating pulse;data-driven time-frequency and time-scale detectors;time-varying frequencies of a signal;circulant preconditioners from B-splines;extensions to total variation denoising and Jacobi method for signal subspace computation.
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