Phase-Compensated Time-Varying Butterworth Filters

One of the important problems of signal processing is to design the filters which possess linear phase characteristics. This paper presents the concept of time-varying Butterworth filters with linear phase. The compensation of the phase characteristics is carried out with the aid of phase shifter which is cascade-connected to the structure of the original Butterworth filter given by the transfer function. The parameters of the phase shifter were calculated in this way that the group delay of the designed filter is possible constant in the filter pass–band. Time varying coefficients were introduced to the phase–compensated filter structure for the purpose of minimization of the filter transient state. This paper contains simulation results of proposed filters and comparison with classic circuits.