Synthesis of delay equalized time-varying butterworth filters

One of the important problems of analog signal processing is to design a filter which ensures a linear phase response, and at the same time possesses sharp and fast response in the time domain. This paper presents theoretical concept of time-varying Butterworth filters with equalized group delay response. The concept consists in the introduction of time-varying coefficients 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, optimal values of the parameters of the functions of litter coefficients, solution of the undershoot problem, and comparison with the classic circuits.