Systematic investigation and reduction of radiated emission from LCD monitor.
Date of Issue2013
School of Electrical and Electronic Engineering
This project investigates the feasibility of retrofitting commercial off-the-shelf liquid crystal display (LCD) monitors to meet more stringent radiated emission requirements, such as military electromagnetic compatibility (EMC) standards. For reciprocity theorem, a LCD monitor with low radiated emission also exhibits good electromagnetic immunity. Hence, the modified LCD monitors are rugged enough for a more hostile electromagnetic environment and also not causing interference to other nearby systems. The project begins with a review of the basic operating principle of a LCD monitor display and common electromagnetic interference (EMI) suppression techniques. Preliminary radiated emission profiles of the various circuit modules are measured and analysed. The EMI filter has been found to play an important role in controlling radiated emissions. Hence, the EMI filter design is carefully studied and analysed to reduce the radiated emission levels from the LCD monitor. Finally, the radiated emissions of original LCD monitor and the retrofitted LCD monitor are measured in accordance with MIL-STD-461E to demonstrate the effectiveness of the EMI suppression techniques implemented. By properly designing the EMI filter on the power card of the original LCD monitor, the radiated emission from the LCD monitor can be reduced by 10 to 20 dB from 2 MHz to 1 GHz.