Theoretical and Experimental Analysis of the Supposed Stealthiness of Noise Radar

This paper investigates the feasibility of one of noise radar's supposed main benefits, the proposed low probablity of intercept (LPI) due to the wideband pseudorandom noise signal being undetectable. The performance of both the noise radar and the intercepting receiver are first studied theoretically through stochastic signal analysis with multi-channel cross-correlating receivers, accompanied by simulation studies with realistic noise-modulated FM-signals and OFDM noise signals. The results are confirmed by a real measurement of an operating noise radar with an intercepting two-channel receiver both from mainlobe and sidelobe directions. It is shown that the interceptor with a correlation receiver has a significant SNR benefit in detecting the signal of the noise radar compared to the noise radar's own detection, even though the radar can utilize the exact knowledge of the transmit signal. This leads to 100-fold detection ranges compared to the radar's operation range rendering the supposed undetectability invalid. The main stealth benefit of noise radars is concluded to be the interceptor's inability to accurately predict the purpose of the detected wideband noise waveform.