Over the horizon radar (OTHR) is a well developed sensor technology in established use for long-range air and surface surveillance. More detailed information about the targets can be achieved by using simultaneous ope...
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ISBN:
(纸本)0819454974
Over the horizon radar (OTHR) is a well developed sensor technology in established use for long-range air and surface surveillance. More detailed information about the targets can be achieved by using simultaneous operation of multiple OTHRs. However, a key limitation with HF radar is the conflict between selection of an appropriate operating frequency and the demand for radar waveform bandwidth commensurate with the range resolution requirement of the radar. In this paper, we consider the simultaneous operation of two over-the-horizon radar systems that use the same frequency band with different chirp waveforms to respond the advanced wide-area surveillance needs without reducing, the pulse repetitive frequency. A cross-radar interference cancellation technique is proposed and shown to be effective.
A new class of nonlinear filters for color image processing was proposed by Lucchese and Mitra. This type of color filter processes the chromatic component of images encoded in the International Commission. on Illumin...
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ISBN:
(纸本)0819454974
A new class of nonlinear filters for color image processing was proposed by Lucchese and Mitra. This type of color filter processes the chromatic component of images encoded in the International Commission. on Illumination (CIE) u'v' color space. Images processed by this filter do not show color shifts near edges between regions with different intensities. The filter uses linear convolution operations internally and is effective and efficient for denoising and regularizing color images. Image processing systems are computationally intensive and usually require a large amount of area in order to reach desirable levels of performance. The use off on-line arithmetic can decrease the area of the hardware implementation and still maintain a reasonable throughput. This work presents the design of the color filter as a network of on-line arithmetic modules. The network topology and some detail of each arithmetic module are provided. The final implementation targets FPGAs and it is compared in terms of area against an estimate of a conventional design. The throughput of this solution is capable of supporting real-time processing of common image formats.
The aim of this paper is to present a high data rate transmission system through the ionospheric channel in the HF band (3-30 MHz). The applications expected in this study are image transmission and real-time videocon...
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ISBN:
(纸本)0819454974
The aim of this paper is to present a high data rate transmission system through the ionospheric channel in the HF band (3-30 MHz). The applications expected in this study are image transmission and real-time videoconferencing. Very high rates are required compared to the standard modems (4.8 kbits/s). Therefore. an array processing performs in the multi channel receiving system. Its main originality stands in the development of a compact device of collocated antennas. the spatial responses of which are different one from each other. Besides. synchronization (Zero Crossing Detector) and spatio temporal equalization (L.M.S. algorithm) as well resort to classical and well-tested techniques involving training sequences. An experimental radio link has been under test with a range of 800 km. The corresponding results underlines the improvement of the bit transfer rate which reaches 20 kbits/s (QAM 16 in a 6 kHz bandwidth) or 30 kbits/s (QAM 16 in a 9 kHz bandwidth). Several transmitted images are presented and appear quite consistent with the original..
Sonar array systems in the highly cluttered undersea environment require new and enhanced signal-processingalgorithms and sophisticated architectures to meet the stringent real-time and reliability mission requiremen...
Sonar array systems in the highly cluttered undersea environment require new and enhanced signal-processingalgorithms and sophisticated architectures to meet the stringent real-time and reliability mission requirements. These demands present significant challenges in terms of computational complexity and dependability; and necessitate the development and use of high-performance computing techniques and advancedsignal-processingalgorithms. Our study introduces novel parallel and fault-tolerant techniques for adaptive matched-field processing (MFP) which we investigated on distributed array systems along with high-performance networking and distributed computing architectures. We developed the parallel algorithms for adaptive MFP to satisfy the computational and memory requirements not readily supported by cutting-edge, high-performance, single-processor systems. We proposed robust MFP algorithms to compensate for the performance degradation presented by sensor failures in sonar array systems. We also developed fault-tolerant parallel algorithms characterized by low overhead and fast recovery time to enhance dependability. We implemented the proposed parallel algorithms and fault-tolerant mechanisms on scalable clusters of computers. We compared their performance considering several critical factors such as parallel and fault-tolerant techniques, communication schemes, and processor architectures. Results show that these parallel and fault-tolerant algorithms can provide a feasible solution for real-time, scalable, and highly reliable beamforming implementations on distributed array systems.
A streak camera is a recording instrument in which spatial image is swept in time. creating a spatial-temporal image on a charge-coupled device (CCD). Traditional analysis for captured image data has been using unifor...
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ISBN:
(纸本)0819454974
A streak camera is a recording instrument in which spatial image is swept in time. creating a spatial-temporal image on a charge-coupled device (CCD). Traditional analysis for captured image data has been using uniform and as sampling points, in which a block of CCD pixel readouts are summed to give one reading. Equivalently simple area moving averages are applied concurrently while sampling, and high frequency content is reduced. To solve this problem. we use peak-value sampling procedure, based on the view from photoelectron statistics. After background correction. maximum values in spatial dimensions are selected to obtain time series data. A DSP filter is then applied and optimized for this time series. A Welch algorithm fast Fourier transform is applied to obtain power spectra. Segmented cumulative spectra is then calculated for global statistics and related to time domain fluctuations. Self similarity at different sweeping time-scales is used to recognize CCD pattern noise. Sinusoidal pattern noise is automatically corrected by peak-value sampling. Computational results show that time-frequency analysis using peak-value sampling algorithm and similar variants is far more effective in discovering high frequency oscillatory noise than traditional uniform binned sampling. We have applied this algorithm to analyze data produced by a 4096x4096 CCD streak camera illuminated with a macro pulse laser. High frequency oscillations in 6similar to10 GHz region were found in laser spectra. Spatial-temporal oscillations of this range are difficult to diagnose with conventional optoelectronic detectors on a per-shot basis. This work has led to improvement of laser design.
This paper collects the most recent parallel coprocessors and highlights the recent trends. It is shown that the single chip massively parallel processor implementations seem to disappear from the scientific investiga...
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This paper collects the most recent parallel coprocessors and highlights the recent trends. It is shown that the single chip massively parallel processor implementations seem to disappear from the scientific investigations (with the exception of low-level near-sensor image processing). Meanwhile, the formerly developed architectures have moved inside complex system-on-chips/microprocessors. The common aspect of the recent architectures is the advancedprocessing element and internal interconnection solutions, and the dominant mid-grain parallelism (i.e. up to a hundred processing element per chip).
This Volume 5205 of the conference proceedings contains 59 papers. Topics discussed include time frequency and time scale analysis, adaptive sensor network, wireless communication, image processing, exploitation of st...
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This Volume 5205 of the conference proceedings contains 59 papers. Topics discussed include time frequency and time scale analysis, adaptive sensor network, wireless communication, image processing, exploitation of structured in imaging and signalprocessing, matrix algorithms, signalprocessing applications, computer arithmetic and arithmetic and architectures for real time applications.
Previously, most mammalian auditory systems research has concentrated on human sensory perception whose frequencies are lower than 20 kHz. The implementations almost always used analog VLSI design. Due to the complexi...
Previously, most mammalian auditory systems research has concentrated on human sensory perception whose frequencies are lower than 20 kHz. The implementations almost always used analog VLSI design. Due to the complexity of the model, it is difficult to implement these algorithms using current digital technology. This paper introduces a simplified model of biosonic reception system in bats and its implementation in the ‘‘Chiroptera Inspired Robotic CEphaloid’’ (CIRCE) project. This model consists of bandpass filters, a half‐wave rectifier, low‐pass filters, automatic gain control, and spike generation with thresholds. Due to the real‐time requirements of the system, the system employs Butterworth filters and advanced field programmable gate array (FPGA) architectures to provide a viable solution. The ultrasonic signalprocessing is implemented on a Xilinx FPGA Virtex II device in real time. In the system, 12‐bit input echo signals from receivers are sampled at 1 M samples per second for a signal frequency range from 20 to 200 kHz. The system performs a 704‐channel per ear auditory pipeline operating in real time. The output of the system is a coded time series of threshold crossing points. Comparing hardware implementation with fixed‐point software, the system shows significant performance gains with no loss of accuracy.
Inter-symbol interference (ISI) and co-channel interference (CCI) are two major sources to signal impairment in mobile communications. To suppress both ISI and CCI, space-time adaptive processing (STAP) systems are sh...
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ISBN:
(纸本)0819450782
Inter-symbol interference (ISI) and co-channel interference (CCI) are two major sources to signal impairment in mobile communications. To suppress both ISI and CCI, space-time adaptive processing (STAP) systems are shown to be effective, leading to increased capacity and improved quality of service. The high complexity and slow convergence, however, are often the hurdles in practical implementation of the STAP systems. Several subband array implementations have been proposed for STAP over the past a few years. These methods are to provide optimal or sub-optimal steady state performance with reduced implementation complexity and improved convergence performance. The purpose of this paper is to investigate the steady state performance of subband arrays with different decimation rates and to derive analytical expressions of the minimum mean square error (MMSE). The discrete Fourier transform (DFT) based subband arrays and both unconstrained and constrained weight adaptations are considered.
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