Grounding architecture design for Wireless Base Stations — EMC and PS considerations

Abstract

Grounding facilitates the reduction in the electrical noise from electronic enclosures, improving the operational quality of circuits contained within the enclosures, and satisfying both the Product Safety (PS) and Electromagnetic Compatibility (EMC) requirements. An ideal PS ground of an electronic enclosure should be equipotential (near zero) with respect to the reference ground to minimize the electrical shock potential and to provide a quick drain path for fault currents. However, an EMC ground requires a potential-difference or controlled impedance between interconnected electrical components in order for noise currents to flow from one component to another and eventually should terminate on to a large, non-radiating electrically conductive surface area. To achieve the EMC emissions goal, the noise current flow should be from a smaller to a larger conductive surface area (i.e., higher to lower impedance) through controlled short interconnection ground paths. The interconnections are designed to prevent external electrical noise current from entering into the enclosure and to be as short as possible so that they do not become the radiators, noise couplers, or sources of ground loop oscillations. In this paper several EMC grounding architectures for interconnection of PCBs, backplanes, and card cages to enclosures for Wireless Base Stations are described in the form of signal flow graphs, and their potential for noise radiation and conduction is compared while still achieving the PS grounding compliance requirements.