A Surface Acoustic Wave (SAW) is an acoustic wave that propagates along the surface of a substrate. This principle has been commonly employed in SAW resonators. A SAW resonator is constructed with interdigital transducers (IDT) that provide a conversion medium between electric signals and surface waves. The SAW resonator is often constructed with an input IDT that generates a SAW from an electric signal, and an output IDT that detects the SAW traveling along the surface of the substrate. The frequency of the SAW resonator is based on the physical layout of the IDT and the velocity of the acoustic wave. The velocity of the acoustic wave is a function of the substrate material.
SAW resonators are inherently high Q components, and therefore, make excellent, compact size, band pass filters for wireless communication devices. Their primary drawback, however, is their inability to be tuned by means of an external voltage variable capacitor. As a result, multi-band wireless handsets using SAW resonators typically require a separate channel for each operating band. Each channel includes transmit and receive filters coupled to a duplexer. Various switches are also needed to switch the selected channel to the antenna. As the number of desired bands increase, the cost and complexity of realizing a multi-band wireless handset with SAW resonators becomes prohibitive. Accordingly, there is a need in the art for a frequency agile SAW resonator. In wireless applications, frequency agile SAW resonators will enable wireless handsets to operate at multiple bands using a single channel. This will reduce power consumption, extend battery life, and reduce the size and cost of the wireless handset.