CFAR Detection in a Passive Coherent Location System Using FM Signals

Recently, interest in a passive coherent location (PCL) system using commercial broadcasting signals has been increased since it exploits the existing broadcasting facilities without revealing the receiver’s location. To estimate positions of multiple targets by using the PCL system, constant false alarm rate (CFAR) detection, whose input is the samples of the range-Doppler map, has to be preceded, so that the parameters of the CFAR detector are influenced by the range-Doppler map. However, the characteristics of the range-Doppler map vary with bandwidth of the used broadcasting signals and its collection time. Therefore, algorithm parameters for the CFAR detector have to be properly determined considering those characteristics. To achieve this goal, we analyze the range-Doppler map in a PCL system using commercial FM broadcasting signals and then derive mathematical descriptions for the algorithm parameters of the number of window cells and that of guard cells. We also present which axis out of the range and the Doppler axes is better for CFAR detection.