Evaluating HPA Effects on Chaotic Sequence Spread Spectrum Detectability

Digital chaotic sequence spread spectrum (CSSS) communication systems provide a number of advantages for secure communications due to the apparent bandlimited Gaussian noise-like signal characteristics and non-repeating nature underlying chipping sequence. The Rayleigh magnitude distribution represents challenge, however, transmission through linear high-power amplifiers (HPA), both high peak-to-average power ratio (PAPR) impacts selective compression on tails time-domain signals, which becomes observable by cyclostationary low probability detection (LPD) metrics. This paper first provides an analysis HPA effects single-carrier CSSS understand HPA-induced artifacts when pushed into compression. work also defines evaluates pre-distortion techniques memoryless HPAs, validating those formulations Matlab simulations live measurements predistorted signals transmitted physical HPAs. Unlike computationally expensive statistical models used predistort multi-carrier waveforms, this technique is shown be efficient method minimize increased likelihood adversarial waveforms. proposed are measured as achieving average 3.35 dB in improvements operating range, enabling waveforms at backoff 4.80 without adversely affecting kurtosis-based detectability.