How to Increase Your Signal Analyzer's Dynamic Range to See Low Level Signals - What the RF (S01E04) скачать в хорошем качестве

How to Increase Your Signal Analyzer's Dynamic Range to See Low Level Signals - What the RF (S01E04)

Learn how to see low level signals by adjusting this setting. 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   Twitter: @DanielBogdanoff   / danielbogdanoff   Transcript: No matter the signal type, whether it be simple CW signals or complex digitally-modulated signals, every signal has some amount of distortion. Signal distortion is important to characterize in your system because it can result in energy at unintended frequencies. However, being able to clearly see low-level signals is difficult to do, especially if they are buried beneath the noise floor of your signal analyzer. There are several ways to improve the dynamic range of a signal analyzer. Today we’ll discuss how you can optimize your signal analyzer’s dynamic range so that you can more easily see low-level signals. In today’s episode we’re going to discuss signal analyzer resolution bandwidth. One of the most frequently asked questions we get is “How can I get more dynamic range with my signal analyzer?” One tool in your dynamic range toolkit is resolution bandwidth. So today, we’re going to talk about both the trade offs when setting resolution bandwidth on a signal analyzer and how it can help you to see low-level signals. Every signal analyzer, like this one, has a certain amount of dynamic range, depending on how you define dynamic range. But what is exactly meant by that? By definition, dynamic range is the ratio, expressed in dB, of the largest to the smallest signals simultaneously present at the input of the spectrum analyzer that allows the measurement of the smaller signal to a given degree of uncertainty. The signal of interest can either be harmonically or non harmonically related. The dynamic range specification determines whether or not low-level signals will be visible in the presence of large signals and therefore is one of the most important performance figures for a signal analyzer. Another example of dynamic range can be seen in photography. If we compare these 2 photos that I took, the details in the shadows and highlights are lot less in the photo on the left taken with my phone, versus the one on the right taken with a DSLR camera. In fact, we can see an object sitting on top of our signal analyzer in the DSLR photo! We can confidently say that the DSLR gives us a higher resolution or detail & contrast of the shadows and highlights in our image. Similarly, having more dynamic range on our signal analyzer gives us a good picture – Of low level signals, like the harmonics we’ll be looking at today. Now, when testing your signal, one of the many things you want to check for is its harmonics. However, a signal’s harmonics can be difficult to spot sometimes because they can get buried in noise … so if we can improve our system’s dynamic range and lower the noise floor then we’ll have better visibility of those low-level signals. A narrower resolution bandwidth lowers the displayed average noise level—or DANL—of the spectrum analyzer and increases the dynamic range. So, let’s see if we can use this knowledge to our advantage. In our setup here, we’re using a signal generator to play the role of our ‘DUT’ and it is transmitting a signal @ 1 GHz. Looking at our signal analyzer, we see our signal, and a bunch of noise. This is where we want to improve our dynamic range, and one of the quickest and easiest methods is to narrow the resolution bandwidth of our analyzer. To lower this noise, we can adjust the resolution bandwidth or RBW setting. The RBW setting is a fundamental analysis parameter that’s important when separating crucial spectral components from the noise floor. The RBW also determines the FFT bin size, and the smaller it is the better resolution we get of a signal and its side bands become visible. Presently the RBW is set at 100 kHz. By lowering the RBW to 1 kHz we can now clearly see the 2nd and 3rd harmonics of the signal. However, you will notice that the sweep speed has become slower. While using a narrower resolution bandwidth helps you to see low level signals it also has an important trade off—slower sweep speeds. A wider resolution bandwidth produces a much faster sweep across a given span compared to a narrower setting. So, what we effectively did by lowering the resolution bandwidth is lower the analyzer’s noise level. As a result, we’ve improved our 2nd and 3rd order dynamic range which enables us to see our signal’s low-level harmonic signals.