Patent ID: 7307045

Claim:
A signal switching device including a plurality of transmission paths to an input path, said signal switching device outputting a signal from the input path through one of the transmission paths, comprising: a first variable impedance unit connected to a first transmission path in series, said first variable impedance unit including a first section formed from a superconducting material; and a second variable impedance unit provided on a second transmission path in parallel to a signal line of the second transmission path, said second variable impedance unit including a second section formed from a superconducting material, an area of a cross section of said second section being less than an area of a cross section of the signal line of the second transmission path, a length of the signal line of the second transmission path being determined in such a way that an input impedance of the second transmission path is greater than a predetermined value when the second section is in a superconducting state.