Log domain filtering for RF applications

A new second-order log filter topology, which is particularly useful for RF signal processing, is introduced with a discussion of how its features meet the needs of RF design. The design concept behind log filters is reviewed. Simulation and experimental results on a test IC are presented for an electronically tunable filter which operates beyond 400 MHz, with Q's in excess of 60, using the AT&T CBIC-V2 process.