Time-domain estimation of unambiguous Doppler frequency in low and medium PRF radars

Rader [3] described an algorithm to estimate the period of undersampled periodic signal. We extend this method to estimate ambiguous Doppler frequency in low and medium pulse-repetition frequency (PRF) radars. Multiple PRF´s are employed to resolve the ambiguity. The proposed method results in a constant false alarm rate detector. The performance of the algorithm in the presence of noise is presented. It is shown that in association with another detector, the proposed method resolves the Doppler ambiguity with good accuracy even at low signal-to-noise ratios. Finally, the method is a time-domain approach and does not require any spectral analyser to estimate the frequency.