Dynamic Compensation of Phase Distortion in Time-Varying Butterworth Filters

One of the important problems of analog 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 response. The compensation of the phase characteristics is carried out with the aid of a phase shifter which is cascade-connected to the structure of the classic Butterworth filter. 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 passband. Time-varying coefficients were introduced to the phase-compensated filter structure for the purpose of minimization of the filter transient state in the sense of the settling time. This paper contains simulation results of the proposed filters and comparison with the classic circuits.