Loran-C Receiver Performance in the Presence of Carrier-Wave Interference

Abstract

Carrier Wave Interference (CWI) has been shown to be a serious problem which affects the operation of all Loran-C receivers in Europe, and aviation and land mobile receivers in the US and Canada. The designers of Loran-C systems for use in Europe have been obliged to pay considerable attention to CWI in predicting their coverage. This paper contains a unified analysis of the effects of the phase-coding of the signals and integration in receivers on CWI ,and it provides a quantitative assessment of receiver performance under CWI conditions. The analysis includes synchronous, near- synchronous and asynchronous interference. It shows that synchronous and near-synchronous CWI, in contrast to asynchronous, are attenuated by phase-decoding and integration within periods of 2GRI and that longer periods of integration do not improve performance. Front-end filtering is incorporated into the analysis by considering not only the attenuation of interference which it provides. but also the delay and distortion it causes to Loran-C signals. Both the phase- tracking and the cycle-selection functions of receivers are examined and their relative sensitivities to interference are compared. The results of the analysis, which have also been confirmed by computer simulation, are presented in a form that will be of direct use to the designers of both receivers and systems.

Keywords

Signal crossing carrier wave interference signal analysis phase tracking.

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