Integrated Circuits (ICs) can emit undesired electromagnetic energy 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 electromagnetic energy from an IC may interfere with the operation of/sometimes destroy nearby devices, this phenomenon is commonly known as electromagnetic interference (EMI).

Measurement of conducted and radiated emissions from an IC can offer valuable information for enhancing an IC's functionality and EMC performance.

Understanding IEC 61967-6:

IEC 61967-6 is an EMC standard that deals with the measurement of conducted emissions from integrated circuits (ICs) by using the magnetic probe method. It is the 6th part of the IEC 61967 series. Currently, the first edition of this standard (IEC 61967-6:2002, published in 2002) is available and valid. The title of the standard is “Integrated circuits - Measurement of electromagnetic emissions, 150 kHz to 1 GHz - Part 6: Measurement of conducted emissions - Magnetic probe method”.  

IEC 61967-6 document specifies a method or test procedure for evaluating RF currents on the pins of an integrated circuit (IC) by means of non-contact current measurement using a miniature magnetic probe. The document also specifies test conditions, test equipment, test set-up, test report details, and other content related to this measurement method. The method provided in this document is capable of measuring the RF currents generated by the IC over a frequency range of 0.15 MHz to 1 000 MHz. This method applies to the measurement of a single IC or a chip set of ICs on the standardized test board for characterization and comparison purposes. It is also a usable method to evaluate the electromagnetic characteristics of an IC or group of ICs on an actual application PCB. 

Additional information on IEC 61967-6:2002:

Measurement philosophy and Measurement principle:

Figure: Mechanism of EMI coupling

RF current may be generated by an onboard IC while working. This RF current drives PCB traces, PCB ground and supply planes, and cables connected to the PCB. The PCB traces, PCB ground and supply planes, and the cables connected to the PCB can act as RF antennas to radiate the emissions. The radiated emission may affect the operation of nearby devices/components. The emission level is proportional to the RF driving current and is also significantly affected by PCB design, radiation effectiveness of the pseudo-antennas, and noise coupling path coefficients from the IC to the pseudo-antennas.  A magnetic probe can be used to measure the RF current on the power supply pins and I/O pins of an IC under test. The magnetic probe is a device/equipment designed to perform magnetic measurements. 

By using the conducted emission measurement method specified in the IEC 61967-6 standard, the RF current on the power supply pins and I/O pins of an IC under test can be measured using a miniature triple-structured magnetic probe. The magnetic probe is positioned near the I/O pins of an IC or its associated circuitry to capture the magnetic field component of the emitted radiation. According to the IEC 61967-6 standard, this probe is used to measure the magnetic field at a specified height over a power supply or I/O strip conductor on the standardized test board in a controlled manner. 

Figure: Schematic of IEC 61967-6 magnetic probe method

The probe works by detecting changes in magnetic flux density caused by the electromagnetic fields generated by the IC’s RF current. The probe detects changes in magnetic flux and then converts it into an electrical signal (voltage signal), which can be analyzed using equipment such as a spectrum analyzer. The output voltage of the probe depends on the distance between the probe tip and the strip conductor under measurement.

The RF current is calculated from the measured magnetic field using the formula described in 8.2 of the IEC 61967-6 document. This method provides a high degree of repeatability, with accurate mechanical placement of the magnetic probe.  With accurate mechanical placement of the magnetic probe, this method offers a high degree of repeatability. In addition, it is possible to extend the frequency range of this method, subject to the limitations described in 5.2. The RF current estimation over the power supply or I/O strip conductor is an easy and handy way of characterizing and comparing the ICs.

Measurement of RF currents allows for the identification and characterization of potential sources of electromagnetic interference within the IC or its surrounding circuitry. The data obtained from magnetic probe measurements can help identify areas for improvement in the IC's design to mitigate EMI issues and enhance overall EMC performance.

IEC 61967-6 document details: