On the development of superconducting microstrip filters for mobile communications applications

Abstract

This paper presents recent developments of an eightpole planar high-temperature superconducting (HTS) bandpass filter with a quasi-elliptic function response. A novel planar filter configuration that allows a pair of transmission zeros to be placed at the band edges is described. The miniature HTS filter has a fraction bandwidth less than 1% and is designed for mobile communication base-station applications to increase sensitivity and selectivity. Design considerations including filter characteristics, design approach, sensitivity analysis and unloaded quality factor of resonators are addressed. The filter was fabricated using double-sided YBCO thin film on an MgO substrate of size 0.3 2 22.5 2 39 mm. Very good experimental results were obtained with the filter cooled using liquid nitrogen. The minimum passband loss was measured to be approximately 1 dB. The passband width at points 1 dB down from the minimum loss point was 12.8 MHz for a center frequency of 1738.5 MHz. High selectivity was achieved with a 30-dB rejection bandwidth of 16 MHz.

Development of a HTS transceiver sub-system for 3G mobile communication TD-SCDMA base station

“…So HTS band-pass microstrip filters have been studied widely and have very attractive performance, such as high frequency selectivity, low insertion loss, and large out-of-band rejection, etc. Filters fabricated from HTS materials have been used in base transceiver station (BTS) receivers for wireless communications [1][2][3][4][5]. However, due to the power handling limitations imposed by the nonlinear effect of the HTS materials, the use of these filters in transmitters is restricted [6].…”

A 24-pole highTcsuperconducting filter for mobile communication applications

“…Due to the larger surface resistance of normal metal films, the performance of normal filter cannot be improved simply by increasing its resonator number unboundedly. For the smaller surface resistance of HTS thin film, the resonators based on HTS thin film have very high Q factors (50 000-100 000) [3,4]. Therefore we can increase the resonator number to improve the selectivity and reduce the out-of-band rejection level.…”

Superconducting filters based on mixed resonators

“…Only recently have strong efforts been dedicated to the realization of miniaturized planar superconducting filters with a relatively high power handling capability. In particular, dual-mode and miniaturized hairpin resonators have been used to make more compact filters with considerable high power handling [2,3], and generally elliptical responses have been realized by introducing cross-coupled effects in order to increase the selectivity of the filter [3,4]. There has been a renewed interest recently in transmission applications for universal mobile telecommunications system (UMTS) technology, since transmitted power is a critical consideration in the design of mobile and satellite UMTS communication systems.…”

“…Prototype four-pole filters operating in L-band and C-band have been realized by using doublesided YBa 2 Cu 3 O 7−δ (YBCO) films grown on 0.5 mm thick MgO and LaAlO 3 substrates. The dimensions and the power handling capability of the filter are compared with filters obtained using dual-mode or hairpin resonators as reported in the literature, which are well known for the high degree of miniaturization [3][4][5][6].…”