The Effects of Repeater Hard-Limiting, Filter Distortion, and Noise on a Pseudo-Noise, Time-Of-Arrival Estimation System

Employment of a repeater in a communication system may lead to the introduction of several sources of potential performance degradation. They are hard-limiting, IF filter group delay distrotion and center frequency offset, and additional noise in the links from transmitter-to-repeater and repeater-to-receiver. Specifically, the hardlimiter and IF filter may introduce signal waveform distortion while the former may also introduce signal-to-noise ratio suppression. In this paper the impact of the above on a pseudo-noise (PN) time-of-arrival (TOA) estimation system is considered. The assumed modulation scheme is differential phase shift keying (DPSK) and realistic nonconstant envelope signals are considered; the performance criterion is TOA estimate standard deviation. One surprising result is that the presence ot the limiter tends to degrade performance; this is contrary to corresponding results that have been derived for data detection. It was also found that performance degrades quite gradually with increasing IF filter differential group delay over the signal bandwidth. Finally, although analytical results presented here pertain specifically to the hard-limiter, they may be straightforwardly extended to determine the effects of repeater th law devices.