Ultrawideband (UWB) SAR images often contain clutter and other types of spatially correlated noise. To reduce these effects, we have developed a complex, multichannel, autoregressive image- modeling and inverse-filter...
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ISBN:
(纸本)0819415340
Ultrawideband (UWB) SAR images often contain clutter and other types of spatially correlated noise. To reduce these effects, we have developed a complex, multichannel, autoregressive image- modeling and inverse-filtering algorithm. Our algorithm extends a previously reported technique to include complex image data and a solution to the directionality problem of 2D AR models. A multichannel image pixel, represented by a vector, is modeled as an autoregressive process with a nonsymmetric half-plane (NSHP) support region. The parameters of this NSHP AR model, represented as matrices, are estimated by minimizing a squared residual. To account for possible nonstationarity in the image statistics, the estimation is performed over a series of small subwindows, which lends a degree of adaptabtility to the algorithm. Once estimates of the complex AR parameter matrices are obtained, they are used in an inverse filter. To account for the directionality inherent in the NSHP filter, we have adopted a bi-directional filtering approach, with the results of the two filters combined such that targets are enhanced and clutter is minimized. This algorithm has been applied to various UWB SAR images and shown to be an effective whitening filter. The resulting signal-to-clutter enhancement depends on a variety of factors, including clutter statistics, target size, and AR model order. A version of the whitening algorithm has been incorporated into our standard set of tools for processing UWB SAR images.
Multidimensional Synchronous Dataflow is a model of computation where functional blocks produce and consume data on a multidimensional index space. The model can express multidimensional signalprocessing systems and ...
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We describe a perceptual audio coder that employs nonuniform hierarchical filterbanks and entropy-coded lattice vector quantization. The nonuniform filterbanks present a good match to critical-band sampling, and they ...
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We describe a perceptual audio coder that employs nonuniform hierarchical filterbanks and entropy-coded lattice vector quantization. The nonuniform filterbanks present a good match to critical-band sampling, and they avoid the complications of block-size adjustment during signal transients. An entropy-coded lattice vector quantizer provides efficient quantization and coding of the filterbank samples. The coder achieves "transparent" quality at a rate of 96 kb/s, and efficient algorithms exist for the filterbank and vector quantizer subsystems.< >
Efficient techniques for speech compression are of practical interest. In this paper, a new compression algorithm based on Discrete Orthogonal Laguerre Functions (DOLFs) is proposed and analysed. Experimental results ...
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Efficient techniques for speech compression are of practical interest. In this paper, a new compression algorithm based on Discrete Orthogonal Laguerre Functions (DOLFs) is proposed and analysed. Experimental results show that a good quality of the synthesized speech with a low bit rate representation is possible with a finite number of DOLFs basis.< >
In typical MC-DCT compression algorithms, up to 90% of the available bit rate is used to encode the location and amplitude information of the nonzero quantized DCT coefficients. Therefore, efficient encoding of the lo...
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In typical MC-DCT compression algorithms, up to 90% of the available bit rate is used to encode the location and amplitude information of the nonzero quantized DCT coefficients. Therefore, efficient encoding of the location and amplitude information is extremely important for high quality video compression. In this paper we describe the position-dependent encoding (PDE) approach for encoding the DCT coefficients. This method attempts to exploit the inherent differences in statistical properties of the run-lengths and amplitudes as a function of position. This paper includes preliminary comparisons between the PDE scheme and conventional coding approaches. The PDE approach can be applied in any transform/subband filtering scheme for image or video compression.< >
The electro-optical space surveillance (EOSS) technology program at MIT/Lincoln Laboratory develops advanced electro-optical technology for space and missile surveillance. This advanced technology includes visible CCD...
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ISBN:
(纸本)081941493X
The electro-optical space surveillance (EOSS) technology program at MIT/Lincoln Laboratory develops advanced electro-optical technology for space and missile surveillance. This advanced technology includes visible CCD focal plane arrays and cameras, mid-wave IR (MWIR) Shottky barrier focal planes and cameras, and the detection processingalgorithms and processors to optimize the use of these focal plane arrays. Some of these EOSS technologies are highly suited to the detection of faint near earth objects. A near-earth asteroid surveillance system has been designed to utilize recently developed technology and existing telescopes to meet the performance requirements outlined in the NASA SPACEGUARD Study (Morrison, 1992). A detailed model was developed to evaluate the expected detection performance of this system and the proposed Spaceguard system. The components of the designed system have been tested as part of routine device evaluation and field measurements. Results indicate that the proposed system can meet the performance objectives spelled out in the spaceguard study at lower cost and risk than the proposed spaceguard system and with existing technology.
Multipath fading is one of the major practical concerns in wireless communications. Multipath problem always exists in the mobile environment, especially for a mobile unit which is often embedded in its surroundings. ...
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ISBN:
(纸本)0780317750
Multipath fading is one of the major practical concerns in wireless communications. Multipath problem always exists in the mobile environment, especially for a mobile unit which is often embedded in its surroundings. The RAKE receiver has been used to reduce the multipath fading in a wideband spread spectrum mobile system. However, the tap weights of the multipath channel model need to be estimated. We explore the possibility of using advancedsignalprocessingalgorithms to estimate the multipath channels and propose a least-squares approach to tap weight estimation based on chip rate channel estimates to investigate the performance of the RAKE receiver in a realistic mobile environment. Simulations show that the new approach outperforms the existing approaches.< >
The paper describes a parallel architecture for universal digital signalprocessing. This architecture uses not only multiply-accumulate but also nonlinear operations, such as reciprocal, squareroot, exponential, sine...
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The paper describes a parallel architecture for universal digital signalprocessing. This architecture uses not only multiply-accumulate but also nonlinear operations, such as reciprocal, squareroot, exponential, sine/cosine, etc. Several advancedalgorithms can thus be mapped to this array architecture. Specifically, the paper focuses attention on two very diverse algorithms, namely the fast Fourier transform and the matrix LU decomposition. Only two types of cells are used in the architecture; these are the Universal Multiply-Subtract-Add cell (UMSA) and the Universal Nonlinear cell (UNL). Both MA and nonlinear operations are performed in hardware, so that the operation times are on the order of chip-clock cycle times. The use of only two types of cells makes the architecture highly suitable for wafer scale integration. It is interesting to note that the same resources on the wafer are used for configuring it to either the FFT algorithm or the LU decomposition algorithm.< >
This paper provides a description of a simulation being developed as a testbed for the development and performance evaluation of multiple Multi-Sensor Correlation (MSC) algorithms. The selected application platform is...
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This paper provides a description of a simulation being developed as a testbed for the development and performance evaluation of multiple Multi-Sensor Correlation (MSC) algorithms. The selected application platform is the U.S. Navy LAMPS MK III Helicopter Avionics System. This system will undergo a major modification, the Block II Upgrade, which includes enhanced sensor subsystem and processing capabilities that will ultimately incorporate advanced operator assistance algorithms, with an emphasis on MSC.< >
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