Clutter suppression filters with cascade connection using offset of zeros for staggered PRF radars

摘要

When MTI (Moving Target Indicators) and AMTI (Adaptive MTI) are used in the pulse radar for searching, the staggered trigger scheme that transmits pulses at non-equal intervals in order to reduce the blind speed region is often used. As a clutter suppression process when the staggered trigger scheme is used, a method using the time variable coefficient filter is commonly chosen. However, in this method, a higher-order time-varying filter is needed in order to suppress several different clutters received at the same time. As a result, the computational effort to derive the filter coefficients for the desired characteristics increases, making real-time processing difficult. As a solution to this problem, this paper proposes a method of realizing a clutter suppression filter by means of a cascade connection of several low-order time-varying filters with their zero frequencies adjusted by zero frequency offset. First, the frequency characteristics of this filter are analyzed. It is made clear that the zero multiplicity cannot be obtained, so that the clutter suppression performance is degraded in the case of a configuration consisting of a cascade connection of several time-varying filters with the same zero frequencies. The effectiveness of zero frequency offset is presented. Next, it is shown by computer simulation that a time-varying AMTI that provides the desired clutter suppression performance can be realized by means of the proposed method, while the computation effort can be reduced.