Cao Bisong

A cryogenic front end for CDMA and UMTS wireless base stations

The design and the laboratory performance of a cryogenic front end for CDMA and UMTS wireless base stations is described together with the results of a first field test at a CDMA base station in the region of Tangshan in China. The central elements of the cryogenic front ends are the cryocooler, the cryostat and the cryogenic platform mounted with up to 6 HTS pre-selection filters of high selectivity combined with the corresponding cryogenic low noise amplifiers of high dynamic range as well as the associated control electronics. Design and performance of the UMTS and CDMA filters are described and the characteristic parameters of the cryogenic low noise preamplifier are given. An analysis of the results of the first field test is discussed.

Effects of DC magnetic field upon the properties of a HTS microstrip antenna at 4.2 K

Abstract A circular polarized microstrip antenna with a working frequency of 6.26 GHz was fabricated from YBCO HTS films. The transmission coefficient and circular polarization ratio of the antenna at different external magnetic field B were measured at 4.2 K. The experimental results showed that its transmission coefficient and circular polarization ratio hardly changed with B up to 1 T. It is concluded that the field-induced increase of surface resistance of YBCO films would not influence the microwave properties of this antenna at B ⩽ 1T and T = 4.2 K.

Influence of the surface gold thin film on HTS filter performance

A four-pole high temperature superconducting (HTS) filter was designed and fabricated to investigate the influence of gold (Au) thin film on the HTS filter performance, including the bandwidth, insertion loss and return loss. Due to the resistance of the Au, dissipative loss is an important issue. Simulation showed that the insertion loss was reduced with the Au film being gradually thinner. The experimental results of 0.2 dB insertion loss, -22 dB return loss were achieved and the bandwidth met the design need when the gold film was thinner than 90 nm. Furthermore, a thin Au layer is in favor of the stability for HTS material as well as for the HTS filter.