How to Make Spectrum Emissions Mask (SEM) Measurements

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Transcript: Spread spectrum signals such as wireless LAN, LTE, and W-CDMA all have strict emissions standards. So how do you know whether or not your device is compliant? Today, we’ll be looking at how to use a spectrum emission mask to do a quick check to see if your device meets these standards.

Hi, I’m Ally, and welcome to Keysight’s Rapid Measurement Series. Communication standards stipulate the maximum power a device can generate in adjacent channels. A quick way to see if your device is compliant with these standards is to use a spectrum emissions mask, or SEM.

A SEM helps you to visualize these limits and determine if your device is compliant.

Unlike an ACP, or adjacent channel power, measurement, an SEM looks at the power at specific frequencies instead of integrating across the entire band. It also tells you how close you are to violating the communication standard.

If you’re using an analyzer with SEM capabilities, all you have to do is select the communication standard you are working with and it will automatically set up a predefined mask. Your signal is in yellow. And once your mask is set up, the absolute power mask is in blue and relative power mask is in pink. The measured absolute power values are reported in dBm while the relative power values are not affected by the units specified.

It’ll then give you a quick idea of if your signal is compliant or not, based on if it passed or failed.

Additionally, a table for the selected frequency offset bands is provided. This table provides the absolute power in dBm and the delta value, or how close you are to failing, in dB for both the upper and lower limits of each band.

If you are failing, you need to identify what frequency components are failing by making a spurious emissions measurement.

#spuriousemissions #spectrumanalyzer #signalanalyzer #signalanalysis #rf #electricalengineering #electronics #spectrumemissions #sem ... https://www.youtube.com/watch?v=1NUcMfwXuE8