Saw filters for high‐power use in cellular radio portable phones

Before a SAW filter is applied to the high‐power section of a cellular radio portable phone, it is necessary to develop a higher‐performance filter with a high‐power capability and a small, nonlinear effect. In this paper, as a new type of filter, a SAW resonator coupled filter of an extended type is proposed which uses two types of piezoelectric substrates. A design method considering the impedance matching between the substrates is presented as well as the results of the experimental duplexer satisfying the specifications of the cellular radio portable phone for the United States. This filter has a third‐order nonlinearity effect that results in the spurious response sensitivity much smaller than the conventional transversal type. These characteristics are almost identical to those for the present dielectric resonator duplexer for the forementioned use.