In a frequency-domain excision system for a wide band receiver, a window
function is applied to blocks of received signal samples and a transform
function is applied to the windowed blocks. Each block of frequency-domain
coefficients from the transform function is morphologically filtered to
generate a threshold function representing an estimate of the spectrum of
the desired wide band signal, and a non-linear gain function is applied to
the coefficients. The gain function has a fixed-gain region for input
values less than a threshold value from the threshold function, an
excision region for input values greater than a multiple of the threshold
value, and a soft limiting region between the fixed-gain region and the
excision region. The inverse transform is performed on the excised blocks
of coefficients, and an overlap-eliminating central portion of the inverse
of the window function is applied to the resulting blocks of signal
samples.
