OTH radar array calibration using disparate sources

Abstract

Errors in sensor positions, unknown mutual coupling and receiver gain/phase variations are known to degrade OTH radar array performance. Hence, for OTH radar currently being developed for coastal surveillance, which incorporate antenna arrays that can be erected quickly on unprepared sites, array calibration is essential. While gain/phase errors may be calibrated relatively easily by the injection of signals at the receiver inputs, both sensor position errors and mutual coupling require more sophisticated calibration methods. Unlike previous array calibration methods, which require a specific type or class of sources for calibrating the array, the method we propose can use all available sources for array calibration. It can use single-mode, multi-mode, or near-field sources, with either known or unknown DOAs. Further the DOA of each source may be either time-varying or time-invariant. We first describe the signal model, and then consider the case of time-varying and time-invariant DOA sources and formulate the problem for each case. We then combine these two cases into an overall cost function, and then the proposed algorithm is presented together with simulation results.