What is Spectrum and Spurious Emissions – What the RF S01E03

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Learn what spectrum and spurious emissions are • Click to subscribe: http://bit.ly/Labs_Sub • Learn more in the Spectrum Analysis Basics application note ↓ • ► http://bit.ly/SpecAnBasics ◄ • Like our Facebook page for more exciting RF content: • / keysightrf • Check out our blog: • http://bit.ly/RFTestBlog • Learn more about using oscilloscopes: http://oscilloscopelearningcenter.com • Check out the EEs Talk Tech electrical engineering podcast: • https://eestalktech.com • Like our digital counterpart’s Facebook page: • / keysightbench • In this episode of What the RF (WTRF) Nick discusses what spectrum and undesired, out of band spurs are. • Transcript: • In today’s episode, we’ll discuss in more detail what exactly a signal analyzer measures and the very important spurious emissions measurement that many of us will be making post R D. • Alright, so from the previous episodes we know that signal analyzers are great tools to use for a holistic picture of our device’s signal. • But what exactly are we measuring on our signal analyzer? • We’re measuring spectra. Spectrum is comprised of a collection of sinusoidal waves and with a signal analyzer, we can measure the power of the spectrum of known and unknown signals. • Now with our signal analyzers, we can measure the frequency, power, distortion, and out of band emissions. • One such important out of band measurement is the spurious emissions measurement. This measurement helps you detect non-harmonic, low-level spurs that are most commonly generated by oscillators and transmitters of your system. Signal analyzers with low-level noise floors are sensitive to very low signals like spurs. This sensitivity is good because that means that we can actually see any spurs caused by our device and they’re not buried in the noise. • With the spurious emissions measurement, we can validate that our device is not emitting its remnant signal power into channels in which it’s not assigned to operate in. • Regulatory bodies like the FCC in the US and ETSI in Europe place strict limits on spurious emissions. • To give you an idea of what issues spurious emissions can cause let’s look at our signal analyzer here where we’ve now set the center frequency to 100 MHz and the span to 10 MHz. By connecting this antenna to the RF input of my signal analyzer we can see these distinct signals. We can safely assume that these signals are local radio stations, but let’s confirm that. • With this portable speaker, I’m going to connect it to the analog jack here and use the analog-demodulation app on our signal analyzer to see if we can confirm what signal this is. • Oh wow! Would you look at that, looks like it is a local radio station after all. • Let’s look at a real situation where a spur can be problematic is with this setup that I now have here. • I’ve connected two antennas, one to the RF output of the signal generator and another to the RF input of the signal analyzer. • Let’s use the signal generator to emulate a device that hasn’t been checked for spurious emissions, and as a result, will emit in a bandwidth where it shouldn’t be. With the signal generator, I can create an “artificial spur,” or rather a signal, at the same frequency that we heard that local radio station on earlier – 96.9 FM. • Now that I’ve created this signal we should hear the tone interfering with the radio station. • This demonstrates that if you have spurs from your device, in our case the signal generator, it will interrupt signals of other devices operating in another channel, in this case, the 96.9 FM radio station. • Finding spurious emissions manually can be a time-consuming task that can potentially take days to complete. • Fortunately, if you have a signal analyzer with a built-in spurious emissions measurement, finding spurs is quick. • Now on my signal analyzer, we can identify 4 spurs and we also have a limit line for the maximum emissions according to any standard that we’re trying to meet. With this measurement table, we can also see any spurs that fail with this indicator right here. • Identifying spurious emissions from your device will help you determine any potential design or regulatory issues which can save you tons of time and money. • • The signal analyzer we used: http://bit.ly/MXASignalAnalyzer • (The Keysight X-Series MXA Signal Analyzer) • The X-Series signal analyzers allow you to visualize across the spectrum to see known and unknown signals. Choose from frequencies of 3 Hz – 110 GHz and 1 MHz – 1 GHz analysis bandwidth. • What the RF is hosted by Nick Ben. The video series covers when and how to use analyzers to make various RF measurements. You’ll gain familiarity with features that will help you save time in your measurement, further your analysis, and deepen your insight. • #RF #SpectrumAnalyzer #SignalAnalyzer #SpuriousEmissions #spectra #electricalengineering #rfengineering #electronics

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