Detectability of a Direct Sequence Emitter within a Network of Direct Sequence Emitters

摘要

This report analyzes the ability of unintended intercept receivers to isolate individual Direct Sequence (DS) emitters within a network of DS emitters. The report demonstrates that interception over 1/(R to the 4th power) propagation paths requires very large, ground-based antennas in order to achieve a usable intercept Signal-to-Noise Ration (SNR). On the other hand, free space, 1/(Sqr R) propagation paths provide intercept receivers with signal power levels well above the thermal noise power even when the intercept antenna is quite small. However, these small antennas are not able to resolve individual emitters at typical intercept ranges. Antennas large enough to resolve individual emitters are too large to put on aircraft as required to achieve the necessary free space propagation. Hence, the report finds that the beamwidth of the intercept receiver will typically contain many DS emitters. Therefore the receiver bandwidth will contain many overlapping DS signals each typically with a power level which is well above the thermal noise power in the intercept bandwidth. This is the intercept context analyzed in this report.