In wireless communication channels fading phenomenon imposes serious limitations upon the system performance. Diversity combining is a well known fading compensation technique. In this paper we propose a diversity combining technique based on a nonlinear Hammerstein type filter to mitigate the destructive fading effect. In the present work, frequency selective Rayleigh fading channels in presence of additive white gaussian noise are considered and m-ary PAM modulation is employed. We first present a theoretical analysis to justify our proposed system. Then the system performance for different power delay profiles and different m-ary PAM modulations are investigated. Comparison of simulation results based on our proposed technique with the results obtained when linear equalizing filters are employed, shows that our technique leads to a considerably higher BER performance at higher SNRs. We also show that our method has a lower complexity than the linear structure. Also, a relative reliability factor for the system is defined and investigated.