Limiter-Differential Detection of a Frequency-Hopped CPFSK Diversity System in Partial-Band Jamming

The error probability achieved by a differential detector with a bandpass limiter preceding the receiver is analyzed for a slow-frequency-hopped CPFSK diversity waveform transmitted over a partial-band noise jamming channel, and is compared to the system’s performance without the bandpass limiter. The system’s thermal noise is not neglected in the analysis. In principle, each bit is repeated on L different hops and for the FHlCPFSK system analyzed, these repetitions are combined to yield a soft decision. The main result of the paper is that a diversity gain for error rate improvement in worst-case partial-band jamming is realized for the differential detector preceded by a limiter, but not for the differential detector without a limiter. This important result is shown by considering the error probability for L = 2 in comparison with that for L = 1.