Over the past few years, the standard RTCA/DO-160, Section 22 has undergone multiple revisions. For those who are new to the requirements, many questions are left unanswered. This article is intended to introduce the requirements of DO-160, Section 22, and to address some of those fundamental questions
This is the first in a series of articles that, instead of focusing on technical aspects of EMC design, engineering, testing, and standards which all of us enjoy reading, I am taking a different approach as a contributing editor to examine in a controversial manner who we are and where our career may possibly take us in the future.
In Chapter I, I introduced Maxwell’s Equations for the static case, that is, where charges in free space are fixed, and only direct current flows in conductors. In this chapter, I’ll make the modifications to Maxwell’s Equations necessary to encompass the “dynamic” case, that is where magnetic and electric fields are changing. Then I will try to explain why things radiate.
Do you supply products into Europe? If you supply products that come within the scope of the EMC Directive 2004/108/EC, the application of harmonized standards provides the simplest means of demonstrating conformity with the protection requirements (emission and immunity) of the Directive.
This article will provide you with essential information on the selection and use of the appropriate standards for your product.
In the world of RF and microwave testing, measurements required for EMI are among the most complex and time-consuming since they incorporate a wide array of specific tests that must be performed over an array of frequencies. They typically require not only many hours of test time but even more for configuring and reconfiguring the test set-up.
Fortunately, advances in the signal processing abilities of test equipment have reduced test time over the years. However, the real improvements are the result of enhancement measurement software, greater integration, automation of the test process, and increasing acceptance of time-domain techniques based on Fast Fourier Transform (FFT) for use in preview measurements of the disturbance spectrum, for example. Together they are slowly making the EMC measurement process faster, and more efficient and accurate.
Everyone in the EMC business is familiar with the traditional Normalized Site Attenuation test (NSA). However, in February of 2007 CISPR 16-1-4 was published complete with the new Site Voltage Standing Wave Ratio (SVSWR) test. At the time, the American National Standards Institute (ANSI) Accredited Standards Committee (ASC) C63® had developed a draft proposal for C63.4 (Draft 1 - May 20, 2005) called the Time Domain Reflectivity (TDR) measurement. The critical question addressed by this article is which method – SVSWR or TDR - more accurately provides an assessment of the test site. Given the investments companies make in test sites for EMC compatibility, this is key assessment question.
This paper describes how to remove the measurement artifacts caused by discontinuities in high frequency S-parameter data caused by the test connectors on the Printed Circuit Boards (PCBs) and cables. The frequency domain S-parameters are converted to the time domain to get the impulse response. Time domain gating is then used on this impulse response to remove reflections due to end connectors and/or other discontinuities. The gated impulse response is then transformed back to the frequency domain. The final result is a much improved S-parameter data set with unwanted resonance removed, allowing the PCB trace or cable loss to be determined.