Direct-Sequence Interceptor Performance Gains Due to a Partial-Band Receiver Approach

In this study, an interception receiver is attempting to determine whether or not a direct-sequence spread-spectrum signal is present during some measurement time interval. The interceptor bases this decision on an energy measurement. This study shows that if the interceptor knows the bandwidth of the possibly present direct-sequence signal, then an improved detection probability may be achieved if the interceptor has a receiver bandwidth adjusted to some fraction of the signal bandwidth. Here the signal bandwidth is defined as the frequency increment between the two zeros of the signal spectral density that are closest to the center frequency. The fraction of the signal bandwidth that optimizes the interceptor´s detection probability performance is evaluated as a function of signal and receiver parameters. The rather modest performance gain due to this partial-band receiver approach is easily achieved, and is especially useful in interception systems where the detection probability is in the vicinity of one-half. The approach taken and the results also apply to the detection of PSK sinusoids and time-limited sinusoids.