Range Estimation Under Low Sampling Frequency with FDA-PA System

Target localization holds a key position in autonomous driving and intelligent transportation systems, and has drawn increasing attention in recent years with the widespread use of millimeter-wave radar. To achieve large-scale, highprecision, unambiguous parameter estimation, the combination of frequency diverse arrays (FDA) and phased arrays (PA) has been proposed as FDA-PA radar. In this paper, we introduce a novel target range estimation method for the FDA-PA radar, where an initial coarse estimate is obtained from the FDA and refined by the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{P A}$</tex>. The method fully exploits the beamforming gains of the PA and the extended unambiguous range of the FDA, enabling accurate, unambiguous range estimation even at extended distances. Additionally, by mitigating range ambiguity with the FDA, the system allows the use of a low-sampling-rate ADC for sampling de-chirped signals. We derive the CramérRao Bound (CRB) for range estimation errors to identify the conditions necessary for effective unambiguous estimation. Simulation results validate the superiority of the proposed method and outline the key system constraints.