Comparison of the estimation performance of coherent and non-coherent ambiguity functions for an ultrawideband multi-input-multi-output noise radar

The authors start by analysing the mean square error (MSE) of target velocity and location estimation in ultrawideband (UWB) multi-input-multi-output (MIMO) noise radar. In the authors' system architecture, transmit antennas are illuminated by UWB-independent noise waveforms to meet the requirement of MIMO spatial diversity. The ambiguity function (AF) formulation is applied to implement the estimations. Since the maximum value of the AF is attained when the time-delay and Doppler stretch of replica signals are exactly matched with the ones corresponding to the reflections, this estimation is also a peak localisation problem. When noise is added, the peak may be located in a different place causing error. In this study, the authors formulate probability density functions (pdfs) to approximate the distributions of coherent and non-coherent ambiguity functions (CAFs and NCAFs) that are then applied to analyse MSE of their estimates. The pdfs are also applied to analyse the detection performance based on different AF approaches. Based on the analyses, the authors demonstrate that the NCAF-based estimation is a better approach in spatial diversity MIMO radars.