High Performance, Low Cost Loran-C Cycle Identification and ECD Estimation

Abstract

A Loran-C system is a hyperbolic navigation system which works based on time difference of arrival (TDOA). Cycle identification is the task of finding time of arrival of the incoming signal. Finding time of arrival of the signal needs choosing a reference point which is defined to be the third zero crossing of the signal. ECD is the varied Loran-C signal’s envelope from the original pulse. Cycle identification and ECD estimation accuracies have considerable effects on the Loran-C system receivers’ localization accuracy and the error in cycle identification or ECD estimation has direct effect on each other so it is important to estimate the reference point and ECD as precise as possible. In this paper, algorithms for cycle identification and ECD estimation are proposed.Furthermore, this paper addresses the problem of the reference points existence between two samples and proposes two algorithms to estimate the reference points time of arrival between two samples which leads to reach high accuracy using low sampling frequency. The simulation results show that the proposed methods for cycle identification and ECD estimation are robust in noisy conditions and intersample cycle identification algorithms give accurate estimate of the reference points between two samples.