Abstract
In any mobile communications system, there are poorly covered areas where radio waves are weak or cut-off because of transmission obstacles. These obstacles can be effectively eliminated by using economical relay systems, called “boosters”, between the base and mobile stations. To incorporate a booster in a W-CDMA system, high sensitivity (low noise) and high selectivity performance are required to expand the coverage and resolve or reduce problems such as interference caused by other systems working at adjacent frequencies or a reduction in user capacity that could be caused by booster transmission noise. To eliminate areas of weak or even no coverage, we found that an open-area relay "booster" system using a cryogenic superconductor front-end is indispensable. This paper presents the feasibility of practical application of a cryogenic front-end for an open-area booster. In our experiment, we made a cryogenic front-end with a pinched-off vacuum vessel and 2-W cryocooler. We used a 17-pole high-temperature superconducting filter (HTSF) and, -achieved 20-dB attenuation only 200 kHz from the band edge, for up-link and down-link input filters.
