Design of square-root domain filters by substituting the passive elements of the prototype filter by their equivalents

A novel technique for designing square-root domain (SRD) filters is introduced in this paper. The concept of the proposed method is based on the substitution of the passive elements of the corresponding prototype filter by their SRD equivalents. The signal processing performed by the proposed SRD equivalents achieves that the voltage at each terminal of the SRD equivalent is the compressed version of the voltage at the corresponding terminal of the passive element, and that the current that flows through the SRD equivalent is the same as that flows through the passive element. The main attractive characteristic of the proposed method is that a quick procedure for designing SRD filters is offered. The validity of the proposed technique was verified by studying the behaviour of a 5th-order SRD low-pass filter. In order to demonstrate the benefits offered by the proposed technique, a SRD leapfrog filter was also designed and its performance is compared with that of the active filter that topologically simulates the same prototype filter. Copyright (C) 2007 John Wiley & Sons, Ltd.