Prediction of system-level emissions performance via equipment shelf primary power bus frequency response characteristics
This paper reports an interesting extension of the frequency response testing technique to characterize real-world EMC conditions as encountered in the Product Realization cycle. It is demonstrated that the behavior of the Primary Power Bus of a system Equipment Shelf is a reliable predictor of the system’s EMC performance. In particular, the Conducted and Radiated Emissions characteristics of the system are anticipated before the system is fully assembled, and long before System-Level formal compliance testing is done. The frequency pass-bands and resonances of the Primary Power Bus are identified and these outcomes are closely correlated with independently obtained Conducted and Radiated Emissions spectra for the populated system Equipment Shelf.
Sensitivity of frequency-swept shielding effectiveness measurements to reflecting surfaces and EMI noise in the test area
This paper reports and compares empirical outcomes of frequency-swept Shielding Effectiveness (ES) measurements for several types of metallic enclosures, performed under two extreme conditions. In one case, the test is done in an area with numerous metallic surfaces and objects, while in the other case reflecting surfaces or objects are practically nonexistent. It is demonstrated that the frequency-swept data obtained from the two cases are well correlated, and that the existence of reflecting surfaces in the test area does not appear to be a significant source of error. These outcomes suggests that the frequency-swept method offers a quick and inexpensive method of measuring the effective SE of enclosures even in the presence of reflecting surfaces, large metal objects and EM noise from other equipment.
A pulse method for measuring the minimum shielding effectiveness of enclosures
This paper reports a pulse technique for measuring the shielding effectiveness (SE) of enclosures, without the use of an anechoic chamber or an open area test site (OATS). Experimental results are presented and compared to those of the conventional frequency domain method using an anechoic chamber. The results obtained from the pulse method are in good agreement with those of the frequency domain method. The pulse method is demonstrated to be a practical means of measuring enclosure SE, as well as an independent means for cross-checking outcomes from other measurement schemes, because it does not require site calibration.