Low EMI design of a microprocessor based password access control system-a case study

Abstract

For obtaining an ISO 9000 quality system, EMC is essential for today's equipment manufacturers. This paper discusses the EMI in the printed circuit board level of an "access control system" consisting mainly of a microprocessor and its logic circuits and the switched mode power supply. This paper also addresses the fact that in reality cables or PCB tracks are good transmitting and receiving antennas and hence aspects of PCB grounding and shielding are considered. The paper also deals with some aspects of EMC compliance testing at the equipment level, both for conducted and radiated emissions and results are presented graphically.