Estimation of receiver frequency error in a TDOA-based direction-finding system

Direction-finding of radio transmitters is considered and in particular correlation-based time-difference-of-arrival (TDOA) estimation between a pair of intercept receivers. In the target application, the received and down-converted signals are corrupted by a frequency error due to a receiver frequency tuning offset which degrades the performance of the TDOA estimation. Traditionally, the cross-ambiguity function (CAF) is used in a 2D scheme for joint TDOA and frequency error estimation. In this paper, sequential 1D frequency error and TDOA estimators are introduced and compared to the 2D method. The 2D method attains the CRLB for both the TDOA and frequency error estimates, but have high computational and memory complexity. The proposed frequency error estimator is outperformed by the 2D method. However, the main objective is to estimate the TDOA and the proposed TDOA estimator have a performance similar to that of the 2D method. The main advantage of the proposed method is a reduction in both computational and memory complexity.