Interference detection and suppression in Loran-C receivers

With the expansion of the Loran-C radionavigation system in Europe, serious research into interference rejection techniques for Loran-C receivers is necessary. This is because the LF-spectrum is heavily used in Europe, and many signals in this frequency band can adversely affect Loran-C receiver performance. Previous analysis of interference signals has shown that the most important parameter determining the influence of an interference signals on receiver performance is its frequency. Conventional Loran-C receivers employ hardware filters to get rid of interference signals; a method for obtaining an optimum filter configuration in a specific area is described in the paper. New receiver designs can incorporate software rejection techniques and some kind of spectrum analysis to determine the frequencies of interference signals and therefore their influence on receiver performance. Such receivers can adapt themselves to changes in the interference spectrum. In the paper, a receiver architecture is presented which is optimally suited for spectral analysis. It makes heavy use of signal processing techniques.