Power Measurement Tips (Part 9): EMI Debugging and Pre-Compliance Testing

    This article will focus on EMI and RFI testing. This stage is often overlooked due to the difficulty and cost of testing. However, with design deadlines approaching, neglecting this step can lead to unexpected events and delays. We strongly recommend testing for EMC issues early in the design process to avoid unnecessary board respins and delays.

    Therefore, you can use a spectrum analyzer and pre-determined EMI compliance test templates to find these nasty EMI problems before going to the test house for compliance testing.

    The Tektronix RSA306B spectrum analyzer is an excellent option. This economical USB-based instrument provides real-time spectrum analysis capabilities while identifying EMI bursts of very short duration. The long record time of this instrument can also capture infrequent bursts.

    Example of a pre-compliance EMI scan using the RSA306B real-time spectrum analyzer.

    To quickly find the source of EMI, we recommend using a mixed domain oscilloscope (MDO), which has a spectrum analyzer and near-field probe built in. With a trusted MDO and a schematic diagram, you can easily measure the spectrum peaks to find the root cause.

    When evaluating MDOs, it’s hard to beat the MDO4000C because it lets you view both the time and frequency domain performance of your design on a single instrument. The MDO4000C is equipped with powerful trigger, search, and analysis tools to find analog and digital anomalies. With this instrument, you can decode serial buses and waveforms and view the RF spectrum at any time. Finally, the SignalVu-PC software that comes standard with the instrument allows for comprehensive analysis and debugging of Wi-Fi and Bluetooth wireless signals.

    Example of EMI debugging using the synchronized trace and spectrum trace on the MDO4000C oscilloscope.