Patent ID: 6889068

Claim:
A heat cutoff signal transmission unit characterized by being comprised of a flat circuit body provided with a substrate and with a signal transmission line and a ground layer both disposed on the substrate, where the substrate is comprised of a dielectric material having a low heat conductivity and where conductor portions providing the signal transmission line and ground layer have a thin thickness enabling suppression of the flow of external heat, and the ground layer having slits for substantially reducing a sectional area of the ground layer to increase a thermal resistance through said sectional area; wherein said heat cutoff signal transmission unit has connectors respectively provided at each of a signal input end and signal output end of said flat circuit body, wherein said connectors are used for electrically connecting a center conductor and an outer conductor of a coaxial cable, each respectively connected externally to the signal transmission line and the ground layer, and wherein said heat cutoff signal transmission unit is further provided with a support having a small heat conductivity for supporting said substrate and said coaxial cable near said connectors.