New concept of phase-compensated butterworth filters

This paper presents theoretical concept of timevarying Butterworth filters with compensated group delay 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 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 the proposed filters and comparison with the classic circuits.