Present Status and Future Prospects of High-temperature Superconducting Cryogenic Receiver Front-ends for Mobile Base Stations

摘要

An experimental 2-GHz band Cryogeic Receiver Front-End (CRFE) has been newly developed for IMT-2000 cellular radio base stations. It uses a high-Q high-temperature superconducting filter (HTSF), a cryogenic low-noise amplifier (CLNA), and a highly reliable cooler that is very compact. TRhe ideal frequency selectivity realized with the HTSF and the virtually noise-free receiver performance made possible by the cryogenic operation are expected to achieve various sysem improvements that are not available with any existing normal temperature receiver frontend. First, the basic radio zone design for a nationwide cellular system is introduced as well as fundamental radio base station construction. It is shown that existing superconducting devices are most effective when applied to the receiver front end of the base station. Next, the basic circuit configuration of the CRFE is considered, and fundamental characteristics of the developed CRFE are measured to confirm that ultralow noise and high selectivity can be achieved. Moreover, the influence of antenna noise, including ground thermal noise and man-made noise, on CRFE is experimentally estimated. Finally, the system merits obtained by applying CRFE to IMT-2000 are predicted, and expectations of future developments in superconducting devices are discussed.