Post design EMI encounters and remedies in indegenously developed systems

Judging the EMI phenomena theoretically, implementing the EMC design and evaluating the performance after the development may not assure the total electromagnetic compatibility of the system. The post design EMI encounters may be few but are very much critical. Some times there is a large gap between theoretical concepts and practical results. Analyzing and pin pointing the problem, reaching to the problem area and solving the problem at the source is very difficult. Even after identifying the problem area, a practical difficulty is there to incorporate the EMC fixes. Judging of noise coupling inside the equipment and co-relating the noise with practical results is not an easy job. Practical experience only helps in coming out from these sort of problems. In airborne systems weight is the important criteria. We may have to think in-terms of flexibility and weight before implementing EMC fixes. Usage of shielded cables should be minimized to reduce the weight and the coupling of noise should be eliminated. In these areas judging of common mode noise and differential mode noise becomes tough and eliminating at the source is not an easy task. The noise in the form of conducted may become radiated and vice versa. In this paper the authors mainly expressed their views about controlling the post designed EMI problems with analysis and techniques used.