Integrated Circuits (ICs) emit undesired electromagnetic energy while operating. The undesired electromagnetic energy from the IC is emitted in the form of radiated emission (via air) and conducted emission (unwanted RF noise current flowing through connected PCB traces, wires, or cables). This emitted unwanted electromagnetic energy from an IC may interfere with/affect the nearby devices; this phenomenon is known as electromagnetic interference (EMI).

Conducting the measurement of conducted and radiated emissions can provide valuable information for the improvement of an IC both in terms of functionality and EMC performance.

IEC 61967-2 is an EMC standard that deals with the Measurement of Radiated Emission from Integrated circuits (IC) by using a TEM cell (Transverse Electromagnetic cell) or GTEM cell (Gigahertz Transverse Electromagnetic cell). It is the second part of the IEC 61967 series. Currently, the first edition of this standard is available and valid. The IEC 61967-2 document titled “Integrated circuits - Measurement of electromagnetic emissions, 150 kHz to 1 GHz - Part 2: Measurement of radiated emissions - TEM cell and wideband TEM cell method”. This standard was published in the year 2005 by the International Electrotechnical Commission (IEC).    

The IEC 61967-2 document specifies test conditions, test equipment, test set-up, test procedure, test report details, and other content related to measurement of the electromagnetic radiation from an integrated circuit (IC) using a TEM/GTEM cell. This document covers the frequency range of 150 kHz to 1 GHz. 

Figure 1: IC test configuration by TEM cell (Side and top view shown)

While performing the radiated emission test, the IC being evaluated is mounted on an IC test printed circuit board (Test PCB or IC test board), Figure 1. The test PCB or IC test board is a specialized circuit board designed for the testing and validation of integrated circuits (ICs). The IC test board (Test PCB) is clamped to a mating port (referred to as a wall port) cut in the top or bottom of a TEM or GTEM cell. The test PCB is not inside the cell, as in conventional usage, but becomes a part of the cell wall. 

The test PCB is mounted on the wall of the TEM cell with the IC side facing into the cell. The septum  (middle flat metal plate of the TEM cell) serves as an inner conductor to receive and convert radiated emissions from the IC into electrical signals for measurement by a spectrum analyzer or EMI receiver. The method specified in the IEC 61967-2 document is applicable to any TEM or GTEM cell modified to incorporate the wall port. However, many factors will affect the measured radio frequency (RF) voltage. The primary factor affecting the measured RF voltage is the spacing between the septum and IC test board (cell wall). 

This procedure was developed using a 1 GHz TEM cell with a floor-to-septum spacing of 45 mm and a GTEM cell with an average floor-to-septum of 45 mm over the port area. Other cells may not produce identical spectral output, but they may be used for comparative measurements, subject to their frequency and sensitivity limitations. A conversion factor may be used to perform comparisons between data measured on TEM or GTEM cells with different septum-to-floor spacing.

The IC test board/test PCB controls the geometry and orientation of the operating IC relative to the cell. The test board also eliminates any connecting leads within the cell (these are on the backside of the board, which is outside the cell). TEM cell has two 50 Ω ports; one 50 Ω port is terminated with a 50 Ω load. The other 50 Ω port of the TEM cell, or the single 50 Ω port of the GTEM cell, is connected to a spectrum analyzer or EMI receiver.  The spectrum analyzer or EMI receiver measures the RF emissions emanating from the integrated circuit and impressed onto the septum of the cell. The emission measurement is critical in the EMC design of the product/device.

Additional information related to IEC 61967-2:2005