Correlation properties of direct broadcast signals for bistatic remote sensing

In this paper, we present a study of relevant correlation properties of signals transmitted from commercial DirecTV satellite signals with the purpose of evaluating their potential use as “signals of opportunity” for bistatic remote sensing. The ambiguity function of the DirecTV satellite signal is computed analytically from published information on the modulation schemes and bandwidth, under the assumption that the data modulation is random. This model is experimentally tested by recording the received signals from the satellites. Also, the signal to noise ratio (SNR) is computed from the published information. The coherence time of the DirecTV signal is computed using the experimental data from two direct signals that is recorded with two different clock sources. An experiment is done to record some reflected data from a river and the coherence time of the Interferometric Complex Field (ICF) from this reflected data is computed for the purposes of measuring the sea state.