Different from previous works that focus on the iterative clustering algorithm, a dual-stage hardware architecture that supports two kinds of moving averages for the on-line clustering algorithm is proposed. The archi...
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Different from previous works that focus on the iterative clustering algorithm, a dual-stage hardware architecture that supports two kinds of moving averages for the on-line clustering algorithm is proposed. The architecture includes a set of memories that operates in ping-pong mode, so that distance computations and centroid updating can be processed in pipeline. The high-throughput parallel divider in the moving-average engine is a new solution to reduce the overhead of divisions to only 1 clock cycle and to calculate cumulative moving averages with no precision loss. The experiments show that when the operating frequency is 400MHz, the gate count and the average power consumption are 16K and 6.02mW, respectively. The normalized power consumption of this work is the lowest among previous works.
In recording high-frequency biological signals such as neural activity, noise may be difficult to distinguish from useful signal content. Conventional noise-removal techniques such as autoregressive modeling do not pe...
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In recording high-frequency biological signals such as neural activity, noise may be difficult to distinguish from useful signal content. Conventional noise-removal techniques such as autoregressive modeling do not perform well on impulsive signals such as neural activity. Impulsive data can be more effectively extracted using p-normed error models, where p=2 corresponds to the least squares model, and p=1 corresponds to the least absolute value case. The least absolute value model is best when the model error is Laplace distributed. Thus, a judicious choice of p-normed model will allow outliers, such as the spikes from neural activity, to be passed through the algorithm while other types of noise are suppressed.< >
The nonlinear trajectory and bistatic characteristics of general bistatic synthetic aperture radar (SAR) can cause severe two-dimensional space-variance in the echo signal, and therefore it is difficult to focus the e...
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The nonlinear trajectory and bistatic characteristics of general bistatic synthetic aperture radar (SAR) can cause severe two-dimensional space-variance in the echo signal, and therefore it is difficult to focus the echo signal directly using the traditional frequency-domain imaging algorithm based on the assumption of azimuth translational invariance. At present, the state-of-the-art nonlinear trajectory imaging algorithm is based on singular value decomposition (SVD), which has the problem that SVD may be not controlled, and thus may lead to a high imaging complexity or low imaging accuracy. Therefore, this article proposes a nonlinear trajectory SAR imaging algorithm based on controlled SVD (CSVD). First, the chirp scaling algorithm is used to correct the range space-variance, and then SVD is used to decompose the remaining azimuth space-variant phase, and the first two feature components after SVD are integrated to make them be represented by a new feature component. Finally, the new feature component is used for interpolation to correct the azimuth space-variance. The simulation results show that the proposed CSVD can further improve the image quality compared with SVD-Stolt.
One reason recursive least squares (RLS) filters are not widely used in adaptive signalprocessing applications is because of instability problems resulting from finite precision implementation. This paper presents a ...
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One reason recursive least squares (RLS) filters are not widely used in adaptive signalprocessing applications is because of instability problems resulting from finite precision implementation. This paper presents a novel approach for stabilizing RLS filters, applying the approach to the conventional RLS filter (order N2 operations per iteration). The approach relies on a detailed fixed point analysis, which provides two important benefits. First, the analysis reveals a bias in the error propagation mechanism, providing an analytical basis for instability problems. Second, the analysis indicates which specific roundoff errors are causing instability. These roundoff errors are then biased in such a way that the overall filter is biased towards stable performance. Experimental results indicate that stability can be achieved with negligible loss in least squares performance.
This paper presents the development of two efficient FFT implementation algorithms which allow for more parallelization than the standard pipeline, M = 2(q) radix r parallel computational elements are allocated per co...
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This paper presents the development of two efficient FFT implementation algorithms which allow for more parallelization than the standard pipeline, M = 2(q) radix r parallel computational elements are allocated per column of the FFT flowgraph, and the constant geometry FFT is used for uniform stages. The first method solves the interstage data shuffle problem by decomposing the perfect shuffle matrix into the product of four matrices, with a memory grouping resulting in a reduction of switching from M(2) to 2M. The second method decomposes the perfect shuffle into the product of two matrices, and the memory is partitioned such that multiport elements may be used. All required switching is accomplished via addressing of the multiport elements requiring no external switching elements, Finally implementations are presented which allow for a varied amount of parallization by using uniform modules and merely modifying interconnect wiring.
This article, first, analyzes the influence of utilizing the space-time adaptive processing approaches in airborne passive radar (APR) systems on the dimension of the clutter subspace, and the signal-plus-noise ratio ...
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This article, first, analyzes the influence of utilizing the space-time adaptive processing approaches in airborne passive radar (APR) systems on the dimension of the clutter subspace, and the signal-plus-noise ratio loss of the target, and illustrates that it is necessary to propose clutter cancellation algorithms suitable for APR systems. Combined with the property of APR systems, the multistage least squares algorithm based on subband operation (MLS-S) and the MLS algorithm based on subband operation in temporal domain (MLS-ST) are proposed for the Doppler-shift clutter cancellation. The first method, in the case of the clutter with integer Doppler-shift bins, proves to be a simple solution. The second approach, at the expense of an additional stage, is suitable for more situations. Due to the use of Doppler-angle-dependence and subband operation to coarsen the range resolution, the proposed methods not only suppress effectively clutter along the clutter ridge, but also cancel the fractional-order-range clutter. In addition, the computational complexity of the proposed algorithms is low, and the clutter cancellation operations can be performed in parallel, which provide the possibility of real-time clutter suppression for APR systems. The feasibility of the proposed approaches is verified by diverse simulated scenarios.
This paper presents a study of several implementations of the Mueller and Muller symbol rate timing recovery algorithm [3] for ISDN transmission over digital subscriber loops (DSL). Implementations of this algorithm u...
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This paper presents a study of several implementations of the Mueller and Muller symbol rate timing recovery algorithm [3] for ISDN transmission over digital subscriber loops (DSL). Implementations of this algorithm using various estimates of a specified timing function are investigated. It will be shown that despite the fact that all of the estimates considered are derived based on one set of conditions, their performance varies widely in a real system. The intrinsic properties of these estimates are first analyzed, then their performance on real subscriber loops is studied through extensive simulations of a practical digital receiver. The effect of various system parameters such as channel distortion and additive noise are included. Possible sources of convergence problems are also identified and corrective action proposed.
A high performance system for communication with untethered underwater vehicles is presented. The system is centered around multiple digital processors which perform a variety of signalprocessing tasks. The processor...
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A high performance system for communication with untethered underwater vehicles is presented. The system is centered around multiple digital processors which perform a variety of signalprocessing tasks. The processors are combined into an array using a flexible architecture designed for communication processing. A basic system has been tested at 5 kbit/sec over the Rayleigh-fading multipath channel in Woods Hole harbor. To combat the deleterious effects of the fluctuating ocean channel, a series of algorithms designed to produce low error-rate communication is being implemented on the array. The processing elements are INMOS T800 transputers and the number of transputers may be selected at deployment time to meet the requirements of a particular task. The result is a powerful and flexible architecture for underwater acoustic communication.
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