Distribution of the sum of clutter and thermal noise

The results of an approximate method for calculating the probability density function of the amplitude of the sum of Weibull-distributed radar clutter and thermal noise are compared with the exact distributions and found to be inaccurate except in one special case. It is shown how the assumption that the in-phase (I) and quadrature (Q) components of clutter have a joint circular-symmetric density function can be used to compute the density functions of the I- and Q-components themselves from the hypothesized distribution of the amplitude.