Digital tuning of an analog tunable bandpass BAW-filter at GHz frequency

A master/slave technique which allows to digitally tune the center frequency of BAW RF band-pass filters is proposed to correct the process dispersions and temperature drifts affecting BAW resonators. The proposed scheme relies on detecting the error between the targeted frequency and the actual one by using an envelope detection technique and can be applied to all types of lattice filters. A successive approximation register (SAR) allows reducing the locking time by its dichotomy function. A one stage-lattice BAW SMR (solidly mounted resonators) filter and the proposed tuning circuit have been implemented in a 0.25 mum BiCMOS process and measured. It ensures a less than 0.2% error. The tuning circuitry core´s chip area is 0.15 mm² and its power consumption is less than 9 mW.