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Technical Tidbit - October 2014
Direct RF Injection for Circuit Debugging
(A Video Presentation)

Test Setup for RF injection

Figure 1.
Test Setup for Direct Injection of RF Energy into Circuits

Abstract: Tracking down radiated and conducted immunity problems in electronic equipment can be difficult. Since the official standards based tests illuminate the whole system, information about the exact cause of the problem can be impossible to determine from test results in many cases. Direct injection of an RF signal into a circuit can narrow down the problem, often in minutes, to the root cause. A video presentation of the principle is offered including using the technique on an operating PCB.

Figure 1 shows the test setup to demonstrate the principle. My March-April 2014 Technical Tidbit describes the method, but the video shown in Figure 2 includes applying the method to an operating circuit. The applied stress in the video simulates fields of ~100 V/m, far higher than commercial circuits need to withstand (and in this case a protoboard, for which there is no requirement), but is useful in illustrating application of this method.

Details of the methodology, including signal levels, strategy, and other details are not covered in this video and are included in my seminars. They may be the subject of a future Technical Tidbit. These details and care may be needed with this method so as not to spend time chasing problems that don't exist in the circuit.
link to YouTube video

Figure 2.
Application of Direct RF Injection Video

You are welcome to copy this video, use it in training, or distribute it as long as it is unedited and shown it its entirety.

Summary: Direct injection of RF energy can be useful in tracking down radiated and conducted immunity problems. The video presented shows both the principle and its use demonstrated on a live circuit. Details of the methodology, including signal levels, strategy, and other details are not covered in this video and are included in my seminars and may be the subject of a future Technical Tidbit.

Technical Tidbit on this site related to this article:
Equipment used in this Technical Tidbit:

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Copyright 2014 Douglas C. Smith