Measurement Techniques for Narrowband Interference to LORAN

摘要

The paper represents follow-on work to a previous paper, where the authors primarily considered the problems of cross-rate and skywave interference. Here they also discuss the issue of interferene to LORAN, but now specifically address the problems associated with narrow band interference such as power line carrier (PLC) and Navy FSK interference, and present theory and measurement techniques for detection. Specifically, they introduce a model that simplifies the exact calculation of the LORAN spectrum and predicts the effects of interference on observed Time Delay (TD) or Time Of Arrival (TOA). They derive equations that relate amplitudes of interference relative to LORAN signal strength to peak variations in observed TD and TOA (for synchronous or near synchronous interference), and to rms variations (for non-synchronous or wideband interference). Furthermore, they consider various techniques in detecting interfering signals within the LORAN band in the presence of strong LORAN signals, and present methods to determine if the interference is synchronous, near synchronous or non-synchronous. Finally, they give examples showing ana lysis methods for typical types of existing narrowband interference sources, including Naval communications stations, time dissemination signals, and power line carriers.