Performance Analysis of DS Signal Code Acquisition Using the Matched Filter and the Median Filter

The theoretical analysis and simulation of the performance of a matched filter code acquisition structure with a median filter as the aiding device to cancel CW jamming in the AWGN channel is described. Both coherent and noncoherent structures are considered. As performance measures, the probability of detection and of a false alarm and mean acquisition times are used. Two kinds of analysis for coherent acquisition structure are presented. At first, the approximation for the pdf of the input signal to the comparator is used. Next, the probabilities are calculated directly. This is called the direct form. For the analysis of noncoherent acquisition, the pdf approximation of the coherent case is used. The performance of the median filter structure is compared to the performance of a simple linear interference cancellation method. The effect of CW jamming can be eliminated by both methods. Fixed thresholds of the comparator and the constant false alarm probability (CFAR) criteria are used. It is concluded that the median filter has a better performance, especially when fixed thresholds are used.