Analysis of slow-frequency-hop satellite communications using ambiguity functions

Factors that designers of future satellite systems must consider include the spacing of channels, the shaping of the transmitted pulse, and the resilience of the system to errors in estimating the timing and frequency of the received signal. In this paper it is demonstrated that each of these concerns can be addressed by using an analysis based on the ambiguity function. The relationship between the system performance and the ambiguity function is derived for a slow-frequency-hop satellite link that employs QPSK modulation. To allow for closer spacing of adjacent channels a window function is applied to each transmitted signal. For a number of different pulse shapes and window functions the amount of adjacent channel interference and intersymbol interference is determined, and the effects of timing errors are demonstrated.