This paper discusses possibilities of tunable radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) filters. First, configuration of RF front-end in current wireless communication systems is surveyed, and research trends of the flexible RF front-end and software defined radio (SDR) are discussed. Second, various RF tunable filters are introduced, and we discuss how high performances are expected by the use of tunable RF SAW/BAW filters provided that above mentioned key technologies are developed. Finally, we explain what kinds of research subjects are going on in our projects for realization of the flexible RF front-end for the SDR. |