Detection of frequency hopping signals using a sweeping channelized radiometer

The paper presents a novel performance analysis of a frequency sweeping channelized radiometer when the signal to be detected is a frequency hopping signal. Often technology limits the instantaneous bandwidth that can be used. When frequency sweeping (search strategy) is used, the center (carrier) frequency of the receiver is changed rapidly to increase the probability of intercept (POI). Conventional logical OR, sum and maximum based methods are used to combine the channelized radiometer outputs. Exact results are derived for the sum based channelized radiometer. A novel accurate approximation of the performance of the sweeping maximum based channelized radiometer is presented. An efficient method is presented for accurately calculating the likelihood ratio used in optimal detection. The effects of fading are analyzed. Numerical results show that although sweeping increases POI, the final probability of detection is not increased if the number of hops observed is large. When the number of hops observed is small, sweeping can increase performance in the case of fading channel.