This paper describes a generalized approach to complex polyphase filter designs based on open loop active elements such as operational transconductance amplifiers or current conveyors. The low pass to band pass linear frequency transformation is performed on capacitors at circuit level, allowing a high degree of generality regardless of the employed synthesis method, voltage or current mode operation and the type of the fundamental open-loop building block. The equations and the corresponding implementations are determined for grounded and for floating capacitors, identified as the two connections typically used in high frequency integrated filters. The presented circuits support all-pole approximations and arbitrary transmission zeros of any order.
- open loop active elements
- complex filter design