A single sideband mixer circuit includes a voltage controlled oscillator operable a tunable frequency f1. The mixer circuit outputs a frequency signal at a frequency f1±f2. A tracking filter operates to filter the frequency signal and generate a first output signal at the frequency f1±f2. A resonance frequency fr of the tracking filter is tunable to substantially match the frequency f1±f2 of the frequency signal. The output signal of the tracking filter may be processed by a phase lock loop circuit to generate a control signal for controlling the setting of the tunable frequency f1 and resonance frequency fr. Alternatively, the output signal of the tracking filter may be divided and the divided signal processed by a phase lock loop circuit to generate the control signal for controlling setting of the tunable frequency f1 and resonance frequency fr.