A tunable bandpass BAW-filter architecture using negative capacitance circuitry

Abstract

This paper deals with a tunable bandpass Bulk Acoustic Waves (BAW) filter architecture that uses integrated negative capacitors. In previous papers, the filter architecture was realized with inductances. The drawbacks of this solution were the generation of a second parasitic shunt resonant frequency and then the low-Q factor of the inductance that finally degrades the high-Q factor of BAW resonators. The proposed solution with a negative capacitance only tunes the shunt resonance of the BAW resonator without creating a parasitic one. The circuit consists of a flip-chip assembly of a BAW Solidly Mounted Resonator (SMR) die on the top of a BiCMOS 0.25 mum chip. The potentialities of such filter architecture has been tested for the WCDMA standard.