Frequency agile filter for image frequency rejection in an adjustable receiver frontend

Abstract

In this paper the investigation on a frequency agile filter circuit with bandpass-bandstop characteristic is presented. The filter is intended for an application in a frequency agile RF frontend. First of all, a theoretical examination of the tuning behavior for a second order tunable bandstop filter is conducted with analytic calculations and simulations. Main focus is on the constant frequency difference between passband and stopband in the whole tuning range. Subsequently, the proof of concept is established by implementing two demonstrator filter circuits using SMD components. Therefore, the lack of access to tunable inductances is solved by either switching inductances or changing the circuit topology according to the requirements.