Design of HTS microstrip filters for mobile communications application

The low-loss and high-selective high-temperature superconducting (HTS) bandpass filters can enhance performance of mobile communications systems. This paper illustrates the design technique of high-order filter and presents a HTS bandpass filter for Code Division Multiple Access (CDMA). The structure consists of a parallel array of folded half-wavelength resonators. Aimed at the application in the front-end receiver of a CDMA base station, a 13-pole HTS bandpass filter with 1.2% fractional bandwidth at 830 MHz was designed. The filter shows an insertion loss of 0.8 dB, and a return loss of 15dB in the passband. Two transmission zeroes are introduced for the deepened skirt steepness of 40 dB/MHz near-by the cut-off frequencies.