Tunable RC-active filters using periodically switched conductances

The realization of electronically tunable RC-active filters is achieved by the use of periodically switched conductances within the filter. A method of analysis of RC networks containing periodically switched conductances is given, which is based on the impulse response of the network at a capacitance. The use of periodically switched conductances to tune RC-active filters has several practical advantages, such as eliminating the need to carefully match independently adjustable network elements and being able to control a transfer function with one timing waveform. This method of electronically tuning RC-active filters is illustrated by several designs.