Digital Methods for Linearization of Phase–Frequency Characteristics of Analog Filters

It is shown that the phase–frequency characteristic (PFC) of an analog filter connected to an ADC can be linearized with the aid of a digital filter with a finite impulse response (FIR). Circuit simulation is used to show that an end-to-end PFC becomes more linear and the frequency response function (FRF) is equal to squared FRF of the analog filter. It is also shown that the PFC of bandpass complex analog filters can be linearized. Series-connected real low-pass filter and complex bandpass filter are simulated using low-frequency fifth-order Butterworth prototype with the corresponding linearizing FIR filters. It is shown that the nonuniformity of group delay time in the pass band can be decreased by a factor of greater than 100.