Chip-rate hopping counters chip-rate detection of direct sequence spread spectrum signals

The novel technique of chip-rate hopping (CRH) has been developed to counter chip-rate detection of direct sequence (DS) spread spectrum communications signals below noise. A laboratory proof-of-concept BPSK DS communications transmitter was designed and implemented. The signal presence was detected with a chip-rate detector examining a number of spectra in order to capture the elusive hops. The best the interceptor can do, with optimum detection bandwidth, is to detect a signal with input SNR of ⩾-11 dB. On the other hand, the receiver can use a matched filter despreader to detect CRH data bits at an input SNR of -15 dB