Electrical properties of an input-output cable for Josephson applications

The electrical properties of an 80 signal line microstrip cable for transmitting signals between room-temperature electronics and cryogenic electronics were calculated and verified. The impedance, propagation velocity, skin effect losses, dielectric losses, forward wave cross talk, and backward wave cross talk were investigated for a copper and polyimide microstrip cable. An effective method of reducing forward wave cross talk was discovered. The microstrip cable has a high signal line density, 19.7 lines/cm, and a high bandwidth, dc-1 GHz.