Sinusoidal and pulse responses of FIR-median hybrid filters

Amplitude and phase responses of several types of FIR-median hybrid (FMH) filters are analyzed using sinusoids and rectangular pulses as input signals. It is shown that the linear substructures used in FMH filters limit the overall filter to behave like a lowpass filter, as opposed to the standard median (SM) filter which has some spurious high-gain areas in the otherwise attenuated frequency range. It is shown that the sinewave response of the averaging FMH filter can exceed the response of the FIR subfilter by a factor of >4/π. The effect of the phase of the input signal is analyzed. It is found that the phase changes the sinewave responses only at some discrete frequencies. The pulse discrimination responses of several FMH filters are computed. They show that, in noisy conditions, the filter is able to retain pulses longer than the root length and to eliminate those shorter than the root length