Abstract
We have developed pulse tube cryocoolers for high temperature superconducting (HTS) filter subsystems used in the base stations of mobile telecommunication systems. The demands for a smaller-sized cryocooler with higher efficiency and with 5-year reliability prompted us to develop such a cryocooler with U-type expanders and flexure-bearing-supported linear compressor opposed pistons. We have developed an HTS filter and a long-life Stirling pulse tube cryocooler to cool the filter whose cooling capacity is 1W at 80K class. For a compressor input power of 60W at an operating frequency of 50 Hz, this cryocooler achieved a cooling capacity of 1.05W at 80K (0.63W at 70K), 5.5% Carnot (3.9% Carnot at 70K), with a minimum temperature of 57K in an ambient 23℃. The HTS filter has a fractional bandwidth below 1.2% at 2GHz and has a minimum insertion loss at 0.3dB. We integrated them with the cryocooler into a subsystem and the external dimensions of this system are a total volume of 8.7L.
