Abstract

The low conductor loss of superconducting materials makes it possible to build passive microwave devices that cannot be built with normal metal conductors. For example, compact transversal filters in the form of tapped delay lines can be fabricated from superconducting niobium to operate with multi-gigahetz signal processing bandwidths [1,2]. Recent advances in the growth of thin films of the high-temperature superconductor (HTS) Y-Ba-Cu-O [3,4] have made possible the demonstration of a variety of passive microwave devices. This includes long delay lines [5], tapped delay line filters [6], and narrow-band microstrip bandpass filters using edge-coupled resonators [5]. The most notable of these demonstations has been the operation of a 2.6-GHz bandwidth stripline chirp filter with 12 ns of total delay and a Y-Ba-Cu-O patterned line length of 0.7 m. The HTS microwave components crucial to this development were long delay lines with more than 10 ns of delay, impedance transformers, and backward-wave couplers. Microstrip, coplanar, and stripline geometries were all examined during the course of this development. The stripline configuration selected for the chirp filter was developed using microwave CAD routines and superconducting niobium prototypes.

© 1991 Optical Society of America