Isolated ground circuit board apparatus

Abstract

A circuit board apparatus for terminating shielded conductors having multiple different ground potential values is disclosed. In a signal interconnection region, a multi-layer laminated circuit board comprises a shield termination layer that is capacitively coupled to a separate ground reference layer by a dielectric layer. A signal layer is electrically isolated from both the ground reference layer and shield termination layer by a substrate. A shield of a shielded cable terminates at the shield termination layer of the interconnect region, and a signal conductor of the cable terminates at the signal layer. Buried capacitance is developed between the shield termination layer and the ground reference layer. As a result, RF emissions are minimized and an electrically safe termination of multiple ground sources is provided, without enlarging the surface area of an interconnection. In the specific context of E1/E3 equipment, buried capacitance may be incorporated into the back plane printed circuit board of a unit of telecommunications equipment. As a result, port density may be increased, while maintaining simplicity. The value of the capacitance can be varied by increasing or decreasing the physical area of the plane referenced to the shield of the cable through the connector.