Propagation effects on noise-modulated randomly polarized ultrawideband communication system

A noise-modulated ultrawideband covert communication system has been developed in order to conceal data sent over wireless channels. The modulated signal containing the coherent carrier is mixed with a sample of an ultrawideband (UWB) random noise signal. The frequency range of the UWB noise signal is chosen such that the lower sideband of the mixing process falls over its own frequency range. The -frequency-converted -noise-like signal and the noise key are simultaneously transmitted over orthogonal -horizontal (H) and -vertical (V) polarizations. At the receiver, both orthogonally polarized signals are -amplified, mixed together in an -upper sideband up-converter and demodulated. The H and the V polarized signals are affected differently due to the differential attenuation and phase shift in the propagation channel. Results of simulations to -assess the impact of various propagation factors, such as frequency-selective fading and -absorption, multipath, and differential attenuation on polarization channels on bit error rate (BER) -performance, are presented. The -primary cause of degradation in error performance is high multipath reflection.