Design of a Novel Negative Group Delay Circuit for Phase-Sensitive Radar System

To address the degradation in he ranging accuracy of phase-sensitive radar systems caused by RF front-end group delay mismatch, this paper establishes a nonlinear group delay interference model. Using Monte Carlo simulations, we derive the group delay constraints required to achieve millimeter-level ranging accuracy, and, based on these constraints, we propose a novel negative group delay circuit (NGDC). The proposed NGDC attains a figure of merit (FoM) of 0.063, outperforming related designs while offering low insertion loss and high tuning flexibility. After cascading the NGDC, the group delay of a 200–400 MHz bandpass filter (BPF) was improved from 3.015±1.135 ns to 2.53±0.54 ns. When incorporated into the radar system, the NGDC reduces the root mean square (RMS) ranging error from 17.17 mm to 9.25 mm at SNR=16 dB, approaching the theoretical limit of 5.07 mm. These results demonstrate that the proposed hardware provides effective support for high-precision phase linearization in radar systems and offers substantial engineering value.