Richard W. Ralston
Within the Japanese R&D community today there is significant activity, primarily in the two multicompany team programs listed below, aimed at development of commercially viable high temperature superconductor (HTS) microwave filter technology and its ultimate insertion into the rapidly expanding wireless communication market. In addition to technology for terrestrial base station applications, the Japanese are also investigating filters for satellite communications. The existence of these activities is in marked contrast to the nearly total absence of HTS microwave effort in Japan at the time of the original JTEC HTS report (Dresselhaus 1989).
The bulk of this chapter treats technology for terrestrial wireless applications. Launching of these teamed development programs in Japan appears to have been a delayed response to the substantial activity in the United States and Europe (primarily Germany). Although microwave activity in Japan has grown substantially and represents a commercial focus, it is still not the dominant focus of the corporate HTS activity there as it is in the United States. U.S. achievements in radio frequency (rf) and microwave HTS technology are substantially beyond those of Japan. Because of differences in investment strategy, however, that technical lead may disappear quickly should the insertion of HTS in the U.S. wireless market stall for whatever reason.