Reliability-Gated Monopulse Correlation for CC-OFDM MIMO Radar Angle Estimation

Beam-center angle extraction in multibeam CC-OFDM MIMO radar is limited by angular quantization, while direct adjacent-beam monopulse refinement can be unreliable under pair ambiguity, residual leakage, calibration mismatch, and boundary effects. This letter proposes a reliability-constrained digital monopulse correlation method for receiver-side angle estimation from post-correlation beam outputs. A perturbed beamspace ratio model is derived to relate ratio perturbations to angle error through the calibrated S-curve slope, leading to energy, monotonic-range, and slope-based reliability conditions. Simulations with a 101-element tapered ULA show that the method reduces the high-SNR beam-center RMSE from 0.366° to 0.038°. Robustness tests further show that leakage and calibration mismatch explain the high-SNR error floor, while the proposed gate identifies out-of-range ratio cases and prevents unsupported extrapolation.