Power-law based intercept receiver with nonorthogonal transforms

A method to set the threshold of a power-law detector that uses a nonorthogonal transform is presented. The mean, variance and skewness of the decision variable in the noise-only case are derived and these are used to find a shifted log-normal approximation to the distribution of the decision variable. The accuracy of this method is verified through simulations. Simulation results are presented for the case where the windowed fast Fourier transform (FFT) is used. The results show that the performance loss associated with windowing (windowing loss) is 0.6-1.7 dB depending on the parameters of the power-law detector and the signal to be detected.