FIR-median hybrid filters

This paper introduces a new generalized class of median-type filters which we call FIR-median hybrid (FMH) filters. The input signal x(n) is filtered with M linear phase FIR filters, and the output of the FMH filter is the median of the outputs of the FIR filters. The statistical properties of the FMH filters are analyzed for input signals with Gaussian, double exponential, and uniform density functions. It is shown that FMH filters have essentially the same statistical properties and same type of root signals as the standard median (SM) filters. FMH filters preserve corner points and ramps and attenuate impulsive-type noise components effectively. An interesting subclass of the FMH filters requiring only one scaling multiplier, two additions, and three compare/swap operations irrespective of the filter length is introduced. In the examples, speed improvement by a factor of 450 is obtained over an otherwise approximately equivalent SM filter.