高分辨率SAR定標(biāo)參考目標(biāo)輻射特性的校正方法
doi: 10.11999/JEIT150570
基金項(xiàng)目:
對地觀測系統(tǒng)國家科技重大專項(xiàng)(GFZX0403220402, GFZX04032204)
Correction Methods of Calibration Reference Targets RadiometricCharacteristic in High-resolution SAR Systems
Funds:
National Science and Technology Major Project on Earth Observation System (GFZX0403220402, GFZX04032204)
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摘要: 定標(biāo)參考目標(biāo)雷達(dá)截面積(RCS)的頻率、入射角相關(guān)性是一個(gè)固有性質(zhì)，對于常規(guī)SAR系統(tǒng)，在小帶寬/窄方位波束條件下通常近似認(rèn)為目標(biāo)具有恒定的后向散射特性，即RCS為一常數(shù)；然而，對于高分辨率SAR系統(tǒng)，繼續(xù)用中心頻點(diǎn)、方位角處的RCS表示大信號(hào)帶寬/寬方位波束條件下的RCS，將會(huì)直接影響輻射定標(biāo)的準(zhǔn)確性。鑒于此，該文提出基于標(biāo)準(zhǔn)數(shù)據(jù)或參考定標(biāo)體的目標(biāo)輻射特性校正方法，暗室地基SAR系統(tǒng)仿真結(jié)果表明，在目標(biāo)輻射特性校正前后，點(diǎn)目標(biāo)積分能量相差1.2 dB；實(shí)測數(shù)據(jù)處理結(jié)果顯示，經(jīng)過參考目標(biāo)輻射特性校正，SAR圖像中點(diǎn)目標(biāo)旁瓣更加對稱，且方位向主瓣寬度變窄，在時(shí)域更接近理想點(diǎn)目標(biāo)沖激響應(yīng)，從而驗(yàn)證了校正算法的有效性。
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關(guān)鍵詞:
- 高分辨率SAR系統(tǒng) /
- 輻射定標(biāo) /
- 雷達(dá)截面積 /
- 參考目標(biāo)輻射特性校正 /
- 地基SAR系統(tǒng)
Abstract: The calibration reference point targets Radar Cross Section (RCS) is a inherent property depending on frequency and incidence angle, for traditional SAR systems, which can be approximately regarded as a constant under the condition of narrowband and narrow beam. However, for high-resolution SAR systems, replacing the RCS in the case of wideband and wide beam by the RCS of central frequency and azimuth aspect, will result in an inaccurate radiometric calibration output. In this paper, correction methods of reference point targets in the echo domain or in the complex image domain are presented. From the experimental result of simulation and ground-based SAR, it can be seen that the absolute calibration factor varies over 1.2 dB before and after the reference point target correction. The results of real data show that point targets in the SAR image are more symmetric after correction of reference targets radiometric characteristic, and the main lobe in azimuth becomes narrower, which is more close to ideal point target impulse response in time domain, thus validating the effectiveness of the correction algorithm. -
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