Doppler sub-optimum estimates of two-tone polarimetric radar signals

The paper analyses the performance of Doppler frequency estimates of a polarimetric radar echo embedded in Gaussian additive noise, in the presence of an equal strength interfering echo, with pre-set Doppler shift and polarisation state. Some heuristic, sub-optimum estimate procedures of such a parameter, with respect to the maximum likelihood estimate are presented. The respective performances, based on computer simulations, are analysed with reference to both tone discrimination capability, and bias and standard deviation values of Doppler estimates, for high SNR values. Owing to the great number of parameters concerned, in the case of finite SNR values, only a few significant situations are considered. The exploitation of polarisation by dual-channel signal reception utilises the full echo strength: this can improve Doppler estimate performances of signals, compared with a single-channel fixed polarised receiver. Methods that utilise separate processing of two channels may offer better performance with respect to both discrimination and bias and standard deviation of estimates: this improvement becomes more significant as the tones exhibit greater polarisation diversity, matching those of the receiving channels