Time filter

Source Type

Huang J.-W.,CAS Institute of Electronics | Huang J.-W.,University of Chinese Academy of Sciences | Qi H.-M.,CAS Institute of Electronics | Qi H.-M.,The National Key Laboratory of Microwave Imaging Technology | And 3 more authors.
Dianzi Yu Xinxi Xuebao/Journal of Electronics and Information Technology | Year: 2011

Considering the issue of huge data rate in DBF-SAR system, the feasibility of one-bit quantization under low signal-to-noise ratio condition is analyzed by two methods. In the first method, each sample of echo is quantized into one bit, while in the second, samples of both echo and range matched filter are quantized into one bit. Theoretical analysis and numerical experiments indicate that, both methods can correctly get the positions and scattering characteristic of targets, and keep the spatial resolutions. However, false targets and high side lobe are generated, and false targets become more obvious with higher SNR. Therefore, one-bit quantization is feasible when single channel echo's SNR is lower than-5 dB. Source

Huang J.-W.,CAS Institute of Electronics | Huang J.-W.,University of Chinese Academy of Sciences | Qi H.-M.,CAS Institute of Electronics | Qi H.-M.,The National Key Laboratory of Microwave Imaging Technology | And 3 more authors.
Yuhang Xuebao/Journal of Astronautics | Year: 2011

In order to deal with the issue of huge data rate and complicated onboard processing in digital beamforming synthetic aperture radar (DBF-SAR) system, an one-bit quantization for both echoes and range matched filters is proposed. First, the feasibility of the one-bit quantization that the amplitude information on the signal is included in the sign of the echo under the low signal-to-noise ratio (SNR) condition is confirmed. The digital beamforming technique used coherently to combine the signals in all receiver channels improves the system's SNR. Then the processing architecture and the resource consumption are discussed. Finally, simulation results verify the effectiveness of the method. This method simplifies the electrical design of the system and reduces data rate while the image quality is slightly degraded, and it is valuable for implementation of DBF-SAR. Source

Zhang Y.-T.,University of Chinese Academy of Sciences | Zhang Y.-T.,CAS Institute of Electronics | Zhang Y.-T.,Chinese Academy of Sciences | Chen H.-Z.,University of Chinese Academy of Sciences | And 6 more authors.
Hongwai Yu Haomibo Xuebao/Journal of Infrared and Millimeter Waves | Year: 2012

Combining scattering theory and principle of SAR, a novel prediction model is proposed based on the multi-path scattering characteristics in the SAR image of cylinder tanks, for both the fixed and the floating top styles. The model can provide the relationship between the geometry parameters of the tank, the SAR parameters, the approximated position, and the scatting strength of the bright region in the SAR image. The validity of this model is proved by analyzing the Terra-SAR data and simulation experiments. Furthermore, geometry extraction is successfully implemented on the Terra-SAR data. The results show that the model is better than traditional methods in precision and stability. Source

Guan X.,CAS Institute of Electronics | Guan X.,Chinese Academy of Sciences | Guan X.,University of Chinese Academy of Sciences | Hu D.-H.,CAS Institute of Electronics | And 6 more authors.
Dianzi Yu Xinxi Xuebao/Journal of Electronics and Information Technology | Year: 2013

For passive radar, the computation cost of traditional 2-dimentional coherent integration (ambiguity function) is high, which makes it hard to perform in real-time processing. And range migration may occur during the integration time, leading to a Signal-to-Noise ratio (SNR) decrease. The migration may cause a detection ability loss. A migration compensation algorithm is proposed with keystone transform based on a real-time integration method in this article to realize real-time processing of 2-dimational integration. The real-time integration includes: 1-dimentional signal is divided into segments, match filtering is applied to each segment, and FFT is applied across segments. An improved segment method is introduced for application demand. Based on this method, an effective method to rectify range migration is proposed using keystone transform in this article, enhancing the detection ability of weak targets. The algorithm can improve computation efficiency with less energy loss, and is easier to perform in real-time then other algorithms. So it's a real-time and efficient target detection method. In this article the real-time processing ability of integration and migration compensation is analyzed. Experiments based on simulated signal and real-life signal show that the algorithm can realize real-time processing with effective processing gain. Source

Yan W.,Northwestern University | Xu J.-D.,Northwestern University | Li N.-J.,Northwestern University | Li N.-J.,National University of Defense Technology | Tan W.-X.,The National Key Laboratory of Microwave Imaging Technology
Progress in Electromagnetics Research | Year: 2011

A fast method for electromagnetic imaging from monos- tatic full rotational near-field scattering is proposed in this paper. It is based on circular spectrum theory which exploits the Fourier decom- position of the targets distribution instead of point by point imaging in earlier works. The novelty of the proposed method is that it sim- plifies the relationship between the spatial frequency domain and the scattering field. The near-field scattering is analyzed by expanding the distance to Taylor series at the centre of the targets zone. The near- field focus function is then transformed to spatial frequency domain and evaluated by the method of stationary phase. The imaging result is given by two-dimensional inverse Fourier transformation from spa- tial frequency domain of targets. The proposed method is validated by comparing the simulation results of distributed targets with the tomo- graphic imaging. The dynamic range of imaging result is derived by distributed targets with different reflection coefficient. Furthermore, the experiment is also conducted in microwave chamber at Ku band with target placed on the turntable. Source

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