Reducing EMI in CRT based display systems through grounding and shielding

The effect of the interference on the display can be in the forms of momentary flicker or jitter, continuous disturbance in the display, loss of genlocking, blanking of display or damage due to spikes. Mainly the grounding problems are due to common mode coupling, which can be reduced by ground impedance reduction, ground loop reduction. The need of shielding arises in display systems as noise source couple into wires by nearby high current, high bandwidth amplifier, and induction or by capacitive coupling because of nearby power lines, computer equipments, motorized equipments and many other electrical equipments present in the vicinity. Hence, influencing factors for the design includes separation of analog and digital grounds, grounding of circuits to equipment cases, safety grounding of equipment cases, grounding of cables shields, single point and multipoint grounding, ground loops, etc. This paper deals with the common EMI problems encountered in CRT based display systems and its reduction through grounding and shielding techniques on circuit/modules and finally at the system level.