High Selectivity Filtering Power Divider Based on SAW Resonator

A high selectivity bandpass filtering power divider (FPD) based on surface acoustic wave (SAW) resonators is proposed in this article. The FPD consists of transmission lines, lumped components, and SAW resonators. It features compact physical size, higher selectivity and wider bandwidth than traditional design methodologies. Lumped inductors in parallel to the SAW resonator can decouple the resonance and anti-resonance points of the resonator. The transmission line is cascaded with the SAW resonator. The transmission lines and inductors located outside of the SAW resonators result in a bandpass FPD, which broadens the bandwidth of SAW resonators. The proposed FPD is analyzed by the Butterworth-Van Dyke (BVD) equivalent circuit model and the schematic of the power divider component. The conditions for generating two symmetric transmission zeros f_a1 and f_a2 are obtained through analysis. To verify the proposed concept, a bandpass FPD is designed with a center frequency of 803MHz, featuring a 3dB bandwidth of 14MHz, isolation better than 18.8dB, minimum insertion loss less than (3+1.2)dB, and return loss better than 15.1dB over a range of 795 to 809MHz.