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| Siglent SDG1032X - Sweep does steps of frequency |
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| 2N3055:
--- Quote from: gf on June 02, 2024, 07:53:34 pm --- --- Quote from: 2N3055 on June 02, 2024, 06:45:07 pm ---Create that chirp (it is not a sweep) and feed it into scope, do a FFT and tell me what you see? There is a reason when we do sweep that we actually specify dwell time at frequency to enable time for equipment to detect the frequency in full amplitude. --- End quote --- A traditional continuous Glide-Sweep is basically the same as a Chirp. However, many modern spectrum analyzers do a Step-Sweep, measuring a finite number of discrete frequency points. Since you cannot configure the number of discrete frequency points, I would expect that the SDG1000X generates a continuous Glide-Sweep. And where can you configure a dwell time in the SDG1000X? I could not find anything in the manual. IMO that's only relevant for a step-sweeping SA + TG (or for a NA). If you do a Bode Plot, then I do not think that the scope configures the SDG to sweep, but more likely it tunes the SDG to each frequency point individually. If you manage to fit the whole interval of the chirp exactly into the FFT window then you should see a Chirp Spectrum. Although the waveform has a constant peak amplitude in the time domain, the spectrum is not flat in the frequency domain, but shows Fresnel ripples. EDIT: If you would do a STFT instead, then you could see the frequency as a function of time in the spectrogram. --- End quote --- 1000X cannot do dwell. Fast continuous glide sweep will create linear chirp. In Bode Plot there are discrete frequencies stepping, you are right. IF you manage to fit whole chirp exactly into window you WILL get Chirp spectrum. You will not get same result as people expect to see with slow sweep and FFT in peak hold mode. That is why I said not to confuse chirp burst with frequency sweep. I wanted to point out that our equipment need time to detect frequency with sufficient amplitude to be actually detected, and to have enough time to achieve full amplitude for us to be able to verify the right amplitude. Which is what you do when you sweep. So it is either dwell or slow enough so window can grab enough energy in its bin to do the good job. That is if you use FFT. You can simply use long capture and look at it in time domain. Where also you need at least one full period in all frequencies in question to be able to see what was it's P-P amplitude at that frequency. And yes, on 3000xHD and 7000A by using Gated Acquisition you can traverse chirp and see how frequency changes. You can also see frequency change with track plot, but you need to sample properly... |
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