Doppler Synthetic Aperture Hitchhiker imaging

In this paper we consider passive airborne receivers that use backscattered signals from sources of opportunity that transmit fixed-frequency waveforms to form an image of the ground. Due to its combined passive synthetic aperture and fixed-frequency nature of the transmitted waveforms, we refer to the system under consideration as Doppler Synthetic Aperture Hitchhiker (DSAH). We present a novel image formation method for DSAH. Our method first correlates the windowed signal obtained from one receiver with the scaled and transmitted version of the received signal from another receiver and then forms the image of the scene radiance by weighted-backprojection of the correlated signal. The method is applicable with both cooperative and non-cooperative sources of opportunity, mobile and stationary sources and one or more receivers. Additionally, it is an analytic reconstruction technique which can be made computationally efficient.