Experimental Evaluation of Range Disambiguation Methods Using Slow‐Time Coding for Moving Target Indication

ABSTRACT Conventional pulse‐Doppler radar processing suffers from range and velocity ambiguities due to the periodic nature of pulse repetition intervals (PRIs). Traditional disambiguation using the coincidence algorithm requires multiple coherent intervals with varying PRIs to resolve range and velocity ambiguities, leading to extended search timelines and inefficient use of transmitted energy. Slow‐time coding (STC) is a well‐established range disambiguation technique that applies a complex scalar to each pulse, enabling separation of scattering from different range intervals through decorrelation. This work evaluates both random and optimised STC sequences. A phase‐only STC optimisation framework is introduced that reduces the sidelobe energy of range‐folded scattering within a desired Doppler notch bandwidth when applying the Doppler matched filter. The design is found to be effective if the Doppler notch is small compared to the unambiguous Doppler extent. To address the short‐comings of conventional STC Doppler processing, an adaptive method called MR‐RISR is also developed. When combined with STC, it iteratively estimates and isolates scattering from multiple range intervals by suppressing both range‐folded and range‐coincident sidelobe energy. MR‐RISR operates on a single slow‐time data snapshot, eliminating the need for training data or knowledge of the clutter + noise covariance, and achieves SINR performance comparable to that of the clairvoyant max‐SINR filter. An open‐air experiment was conducted to evaluate MR‐RISR against conventional and max‐SINR processing using both random and optimised STCs, with the latter shown to be necessary for Doppler matched filter processing to effectively suppress folded clutter energy. MR‐RISR and max‐SINR processing yield comparable performance for both random and optimised STC sequences, with MR‐RISR providing enhanced sidelobe suppression of targets and exhibiting modest Doppler super‐resolution.