Tunable surface acoustic wave resonators and filters

摘要

Filters and oscillators are important components for electronic systems especially those for communications. For many portable units operating at 2 GHz or less, surface acoustic wave resonators are used as filters or oscillators, the resonant frequency is determined by the electrode pitch and velocity of the surface acoustic waves. Because of the large number of frequency bands for communications, it is important to have SAW resonators where the resonant frequencies are tunable and adjustable. This invention provides tunable surface acoustic wave resonators utilizing semiconducting piezoelectric layers having embedded or elevated electrode doped regions. Both metallization ratio and loading mass are changed by varying a DC biasing voltage to effect a change in the resonant frequency. A plurality of the present tunable SAW devices may be connected into a tunable and selectable microwave filter for selecting and adjusting of the bandpass frequency or an tunable oscillator by varying the DC biasing voltages.

主权项

1. A frequency tunable SAW inter digital transducer IDT structure with embedded electrode doped regions for surface acoustic devices comprising
a support substrate with a support substrate thickness; a first piezoelectric layer with a first piezoelectric layer thickness on said support substrate; a plurality of positive electrode doped regions embedded in said first piezoelectric layer, said positive electrode doped regions are piezoelectric semiconductors having a first doping type; a plurality of negative electrode doped regions embedded in said first piezoelectric layer, said negative electrode doped regions are piezoelectric semiconductors having a second doping type, wherein each said negative electrode doped region is between two adjacent positive electrode doped regions; a plurality of metallic positive electrode fingers connected to a positive electrode pad, each said metallic positive electrode fingers on one of respective embedded positive electrode doped regions; a plurality of metallic negative electrode fingers connected to a negative electrode pad, each said metallic negative electrode fingers on one of respective embedded negative electrode doped regions; and a DC biasing voltage is connected to said IDT through blocking inductors to tune and adjust frequency of surface acoustic waves to be excited or to be received by said IDT through tuning and adjusting loading mass and metallization ratio associated with said positive electrode fingers and negative electrode fingers,wherein a center-to-center distance between adjacent said positive electrode finger and said negative electrode finger or between adjacent said positive electrode doped region and said negative electrode doped region is controlled to a pitch b, whereas said positive electrode pad and negative electrode pad are connected to an electrical signal source or to a signal receiver to excite or receive surface acoustic waves.