自動車電話システムの超広帯域化に対応した高性能,低損失SAWフィルタ

抄録

SAW filters offer advantages in that they are small, do not need adjustment, and are highly reproducible and reliable. However, their applications to the radio communication equipments have been limited due to the large insertion losses. The transceivers used in mobile radios require not only high-performance but also miniature devices. System constructions of 800-MHz cellular-mobile telephones are determined by the original designs of each country in the world. The increase of the frequency bandwidth used in mobile telephones has been proposed in almost all countries to achieve more numbers of telephone channels.
In this paper, several new technologies are reported to realize high-performance and low-loss SAW filters used in ultra-wideband mobile telephone systems. New configurations for wideband SAW band-pass filters which were used as the receiver filters and the transmitter pre-filters were invented. They had low-loss and sharp-cutoff frequency characteristics. New configurations for wideband SAW band-rejection filters which were used as the transmitter final stage filters were also invented. They had low-loss and high-power characteristics. The frequency responses of the miniature antenna duplexer module which includes the above SAW filters as well as the receiver low noise amplifier are also presented.