Switched-capacitor filter design using bilinear element modelling

The low sensitivity of a doubly-loaded reactance ladder to element-value variations is preserved in a switched-capacitor filter with the same graph if a one-to-one replacement of branch impedances is used to derive the switched filter from the reactance ladder. This paper describes the design principles and some novel circuits based on this approach. The frequency axes of the two filters are mapped into each other by the bilinear reversible s-z transformation; this results in advantageous sensitivity and selectivity properties for the resulting switched-capacitor circuit. In addition, the number of active components is equal to the number of inductors replaced, and is hence small.