Several technologies are developed to achieve broader band surface-acoustic-wave (SAW) filters for portable telephones used in an 800-MHz wideband (25-MHz) cellular radio system. The design and realization of a transmitter final stage filter (high-power filter) and a prefilter (high-performance filter) are examined from initial specification to final device operation. An insertion loss of less than 2 dB and a rejection level of more than 20 dB are achieved for the final stage filter, and less than 5 dB and more than 50 dB, respectively, are achieved for the prefilter. Two integrated SAW modules, an antenna duplexer and a high-power amplifier, that include the above SAW filters and satisfy almost all requirements for wideband cellular radio have been developed. Their physical dimensions are the same as those of previously developed 20-MHz models. New SAW electrode materials (Al+Ni, Al+Cu+Ni) have also been investigated to improve the power-handling characteristics of the transmitter final stage filter.
SAW integrated modules for 800-MHz cellular radio portable telephones with new frequency allocations. Publishing Authors By Initials
