Abstract
This paper proposes a novel image formation algorithm for the bistatic synthetic aperture radar (BiSAR) with the configuration of a noncooperative transmitter and a stationary receiver in which the traditional imaging algorithm failed because the necessary imaging parameters cannot be estimated from the limited information from the noncooperative data provider. In the new algorithm, the essential parameters for imaging, such as squint angle, Doppler centroid, and Doppler chirp-rate, will be estimated by full exploration of the recorded direct signal (direct signal is the echo from satellite to stationary receiver directly) from the transmitter. The Doppler chirp-rate is retrieved by modeling the peak phase of direct signal as a quadratic polynomial. The Doppler centroid frequency and the squint angle can be derived from the image contrast optimization. Then the range focusing, the range cell migration correction (RCMC), and the azimuth focusing are implemented by secondary range compression (SRC) and the range cell migration, respectively. At last, the proposed algorithm is validated by imaging of the BiSAR experiment configured with china YAOGAN 10 SAR as the transmitter and the receiver platform located on a building at a height of 109 m in Jiangsu province. The experiment image with geometric correction shows good accordance with local Google images.
Highlights
Bistatic synthetic aperture radar has been a hot topic because of its advantage of flexible configuration, abundant information, anti-interception, anti-interference, and so forth
This paper proposes a novel image formation algorithm for the bistatic synthetic aperture radar (BiSAR) with the configuration of a noncooperative transmitter and a stationary receiver in which the traditional imaging algorithm failed because the necessary imaging parameters cannot be estimated from the limited information from the noncooperative data provider
Rocca firstly introduced Dip Move Out (DMO) method [11] into BiSAR imaging, which is derived from earthquake signal processing methods, converting bistatic echoes to monostatic echoes
Summary
Bistatic synthetic aperture radar has been a hot topic because of its advantage of flexible configuration, abundant information, anti-interception, anti-interference, and so forth. Rocca firstly introduced Dip Move Out (DMO) method [11] into BiSAR imaging, which is derived from earthquake signal processing methods, converting bistatic echoes to monostatic echoes. Some bistatic system concepts were advanced [25] Those synchronization errors could not be eliminated in the absence of accurate orbit data and some important system parameters information, including squint angle, orbit height, satellite velocity, off-nadir angle, and accurate sampling time, while all above imaging algorithms were based on the synchronized echo and could not be directly implemented to nonsynchronous echo. This paper discusses the feasibility of focusing nonsynchronous bistatic echo and introduces a novel imaging algorithm based on the direct signal. The focusing algorithm based on direct signal and image contrast optimization that will be derived in that Section 3. Y X range at azimuth time η, and t delay(η; x, y, z) is the duration time from transmitter to target to receiver at azimuth time η:
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