First-Order Observation Modeling of Reference--Background Residuals in Single-Snapshot FDA-MIMO-GPR
This paper develops a first-order observation model for reference--background mismatch in single-snapshot frequency-diverse array multiple-input multiple-output ground-penetrating radar (FDA-MIMO-GPR) over complex media. The model separates the shared background residual from the local anomaly and maps it through a fixed-reference distorted Born approximation into the joint observation domain. The formulation distinguishes the physical residual source from its organization by FDA frequency states and transmit--frequency assignments. Closed-form residual moments are transferred to fixed linear task domains, yielding task-risk and discrepancy relations together with a finite reference-screening criterion. Controlled Cole--Cole ensembles reveal nonzero off-event covariance and task-dependent pseudo-anomaly patterns. Finite full-wave simulations support the predicted covariance and mismatch-dependent discrepancy trends while delimiting the first-order validity domain. These results provide a compact framework for quantifying and screening reference-induced residuals in single-snapshot FDA-MIMO-GPR.