Ultra-steep cut-off double mode SAW filter and its application to a PCS duplexer.

This paper describes the double mode surface acoustic wave (DMS) filter design techniques for achieving the ultra-steep cut-off characteristics and low insertion loss required for the Rx filter in the personal communications services (PCS) duplexer. Simulations demonstrate that the optimal combination of the additional common ground inductance Lg and the coupling capacitance Cc between the input and output terminals of the DMS filters drastically enhances the skirt steepness and attenuation for the lower frequency side of the passband. Based on this result, we propose a novel DMS filter structure that utilizes the parasitic reactance generated in bonding wires and interdigital transducer (IDT) busbars as Lg and Ce, respectively.

Analysis and suppression of side radiation in leaky SAW resonators.

This paper discusses side acoustic radiation in leaky surface acoustic wave (LSAW) resonators on rotated Y-cut lithium tantalite substrates. The mechanism behind side radiation, which causes a large insertion loss, is analyzed by using the scalar potential theory. This analysis reveals that side radiation occurs when the guiding condition is not satisfied, and the LSAW most strongly radiates at the frequency in which the LSAW velocities in the grating and busbar regions approximately correspond to each other.