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225 |
RAO Yun-Hua, ZHU Feng-Yuan, ZHANG Xiu-Zhi, WAN Xian-Rong, GONG Zi-Ping |
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Ambiguity Function Analysis and Side Peaks Suppression of WiFi Signal for Passive Radar Hot! |
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WiFi (Wireless Fidelity) is widely deployed all the world. When it is utilized as external illuminaor in Passive Radar, its broadband singal make the high resolution of detection be obtained in both the range and Doppler domains. In this paper, the typical WiFi signal format and its characters are analyzed, then the theoretical signal model is setup. Based on the theory of bistatic passive radar, the relationship between typical IEEE 802.11 signals format and the characters of its Ambiguity Function (AF) is analyzed. Moreover, the position and amplitude of side peaks in time and frequency domain is analyzed and its causes from the signal structure is also discussed. In this paper, a method for suppressing the side peaks based on the correction of direct-path reference signal is proposed, therefore to avoid the false alarm brought in target detection caused by side peak interference. Experimental results valid the proposed signal processing method.
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2012 Vol. 1 (3): 225-231
[Abstract]
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2478
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[PDF 2050KB]
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3422
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246 |
Li Wei, Wang Xing-liang, Zou Kun, Xu Yi-meng, Zhang Qun |
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Anti Deceptive Jamming for MIMO Radar Based on Data Fusion and Notch Filtering (in English) |
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Deceptive jamming can get vivid jamming effect on Multiple-Input Multiple-Output (MIMO) radar with very low power. In order to remove those deceptive targets, one method based on signal jittering, data fusion and fake target notch filtering is proposed in this paper. Multiple orthogonal binary phase codes are used as transmitted signals, before each time of transmission each transmitter will choose one signal from all the orthogonal codes, images of echoes of all kinds of codes are detected with constant false alarm rate. Targets detected in images of echoes of all different signals are fused to determine to be real or not, fake targets will be nulled by notch filtering in the image, therefore, weak real targets can be detected in the next round of detection, in this way fusion and notch filtering are implemented again and again until no fake targets exist. The effect of deceptive jamming on radar will be removed completely. Simulation result testifies that the method based on signal jittering, data fusion and notch filtering can help MIMO radar remove deceptive jamming completely.
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2012 Vol. 1 (3): 246-252
[Abstract]
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1597
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[PDF 1739KB]
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3116
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277 |
Li Gao-sheng, Jia Lei, Ming Yong-jin, Cao Qun-sheng |
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Study of Power Coefficient and Insertion Phase Shift for Organic Magnetic Slab |
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In this paper, theories of electromagnetic reflection and transmission as well as transmission line are adopted, a simulation method is designed to calculate power transmission coefficient and insertion phase shift, and also the mathematical formulas are deduced that the electromagnetic parameters of material used in radomes must be satisfied to remove the depolarization phenomenon, a single magnetic slab is used to discuss and verify the formulas. A special A sandwich radome, as a example, is calculated to analysis the effects of the magnetic and dielectric materials on the power transmission coefficient and the insertion phase shift. It is found that the phenomenon of depolarization can be avoided for A sandwich radome structure once when r r ε = μ (the relative complex permittivity of the magnetic material equals its relative complex permeability), and the power of transmission coefficient for magnetic material is better, the insertion phase shift is smoother, and the property of transmission performance is better than those of the electric material. Finally, the commercial software HFSS further verifies the correctness of the conclusions and validity of the method.
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2012 Vol. 1 (3): 277-282
[Abstract]
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1810
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[PDF 1374KB]
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3158
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| Special Topic Papers：Synthetic Aperture Radar (SAR) |
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301 |
Li Guang-ting, Yang Liang, Huang Ping-ping, Yu Wei-dong |
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The Pixel-similarity Measurement in SAR Image Despeckling |
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The Pixel Relativity (PR) measurement of SAR image, which is the key of the despeckling techniques based on weighted average, is researched in three aspects. Firstly, the rationality of ratio PR model is expounded, and two new ratio PR models, which are the LOG-domain Gaussian model and the pixel similarity probability model, are proposed. Meanwhile, the Probability Density Function (PDF) of SAR image and the PDF of the ratio between pixels are transformed into ratio PR models. Then, in order to evaluate the four ratio PR models, the weighted maximum likelihood filters are designed using the PR. Finally, a novel method, performed by calibrating the maximum location of the PR model, is introduced to improve the radiation preservation of those models whose maximum do not locate at 1. The effectiveness of the two proposed PR models and the approach to calibrate the maximum location of the PR model, are indicated by the theoretical analysis and experimental comparison.
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2012 Vol. 1 (3): 301-308
[Abstract]
(
1990
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[PDF 3600KB]
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3337
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309 |
Llin Shi-bin, Li Yue-li, Yan Shao-shi, Zhou Zhi-min |
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Study of Effects of Flat Surface Assumption to Synthetic Aperture Radar Time-domain Algorithms Imaging Quality |
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Time-domain algorithms have great application prospect in Ultra Wide Band Synthetic Aperture Radar (UWB SAR) imaging for its advantages such as perfect focusing and perfect motion compensation. We could adopt the flat surface assumption to simplify the imaging geometric model, when undulating terrain is imaged using time-domain algorithms. Nevertheless, the flat surface assumption leads to geometric errors, thereby affecting the imaging results. This paper studies the effects of this assumption on time-domain imaging algorithms, points out that it leads to position offset problem in the case of linear aperture, and it even leads to target defocusing problem in the case of non-linear aperture. The expression of position offset is given in this paper, as well as the restriction of the maximal offset of the non-linear aperture and the maximum elevation of the area in order to focus the targets. The conclusions are validated by simulated data, which is processed by one kind of time-domain algorithms, namely Back Projection (BP) algorithm.
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2012 Vol. 1 (3): 309-313
[Abstract]
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1452
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[PDF 585KB]
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2585
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314 |
Wang Bing-nan, Xiang Mao-sheng |
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Three-dimensional Resolution Analysis for Geosynchronous Circular SAR |
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GEOsynchronous Circular SAR (GEOCSAR), having a high orbit, operating in a slant ellipse, and imaging in spherical surface, should be newly modeled to assess the resolution performance. In this paper, starting from modeling geometry, a function of slant range difference and orientation angle is deduced. Then we can obtain the three dimensional point spread function and make a conclusion of resolution affected by both sinc function and bessel function of first kind. Lastly, resolution with the variation of location of target, bandwidth, radius of orbit, and integral time is analyzed detailedly. Finally raw signal simulations show the validity of theoretical model.
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2012 Vol. 1 (3): 314-322
[Abstract]
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2249
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[PDF 4423KB]
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3074
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