Multi-frame fractional Fourier transform technique for moving target detection with space-based passive radar

This paper puts forward a moving target detection technique for space-based passive radar. The main drawback of satellite transmitters for radar applications is the very low power density on the ground level, which requires long integration times to adequately increase the signal to background ratio. To this aim, in this paper a new technique is proposed relying on a hybrid coherent/non-coherent integration of the received signal in the Fractional Fourier Transform (FrFT) domain. After the compensation of the range walk by Keystone reformatting, a coherent integration is performed over consecutive short time intervals (frames) such that the coherence of the scattering mechanism within each frame can be assumed. Then, a proper combination of the multiple frames is performed based on the kernel of the FrFT, allowing the reliable detection of low observable targets. The effectiveness of the proposed technique has been proved by simulated analysis considering very low EIRP satellites as opportunity transmitters.