A radio circuit includes a mixing module, a first adjustable resonant circuit and a second adjustable resonant circuit. The mixing module is coupled to mix a first signal having a first carrier frequency with a second signal having a second carrier frequency to produce a mixed signal having a frequency sum component and a frequency difference component. The first adjustable resonant circuit is tuned to resonant at a frequency corresponding to one of the frequency sum component and the frequency difference component. The second adjustable resonant circuit is tuned to resonant at a frequency corresponding to another one of the frequency sum component and the frequency difference component, wherein the first and second adjustable resonant circuits alter the mixed signal to produce a converted signal.