A tapped-delay-line superconductive chirp filter in shielded microstrip

A superconducting chirp filter having a dispersive time delay of 26 ns and a 3.4-GHz bandwidth centered at 4.7 GHz has been fabricated using a niobium-on-silicon shielded microstrip technology. Along a 2×1.6 m delay are, unequally spaced microstrip directional couplers ire employed as sampling devices. To achieve an improvement in dispersion and coupler directivity over conventional microstrip, the device uses a superconductive shield mounted at a distance equal to the height of the dielectric on top of the microstrip structure. Structural support of the 70-μm-thin high-resistivity dielectric is provided by a large-area bond to a glass substrate