Unambiguous Range Extension by Overlay Resolution in Staggered PRT Technique

Abstract

In this paper a method is presented for separating overlaid echoes in a Doppler weather radar that uses a staggered pulse repetition time (PRT) transmission scheme to mitigate the effects of range?velocity ambiguities. In the standard staggered PRT technique, the PRT alternates between two values, T1 and T2; (T1 < T2) and the unambiguous range corresponds to the shorter PRT (T1). If the weather extends up to the range corresponding to the longer of the two PRTs, some echoes from the short PRT will arrive at the receiver after the transmission of the long PRT. Therefore, echoes from the short and long PRTs that arrive at the same time but originate from range locations spaced cT1/2 apart will be overlaid. An algorithm is developed to separate the overlaid echoes and estimate the spectral moments of both the overlaid signals. This effectively increases the unambiguous range to cT2/2, corresponding to the longer PRT. Conditions for which the algorithm could be applied are described, and a strategy on how to use it in a range?velocity ambiguity mitigation scheme is outlined. The method of overlay resolution is tested on simulated time series. These tests illustrate the capability to separate the overlaid echoes and identify characteristics of weather signals for which the algorithm is expected to perform well.