Continuous frequency response

Continuous frequency response

Postby jlm1948 » Sat Mar 02, 2019 6:01 am

Hi,
Certainly a noob question, but how can I produce a Bode plot using a frequency sweep? I can set the generator to produce the desired sweep but I can't find how to plot the amplitude vs. frequency plot. I see onlly the oscilloscope and the spectrum analyser.
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Re: Continuous frequency response

Postby VirtinsTech » Wed Mar 06, 2019 10:21 pm

Magnitude frequency response can be measured using the spectrum analyzer in Amplitude Spectrum mode. There are a few ways to do it, such as:

(1) white noise + narrow band FFT analysis
(2) linear frequency sweep + narrow band FFT analysis
(3) Log frequency sweep + octave band analysis
(4) pink noise + octave band analysis
....

Two requirements for frequency response measurement using a sweep signal:

1. The entire sweep should be captured in one oscilloscope frame from start to end. That means the oscilloscope frame width should be equal to or greater than the duration of the sweep signal. And the trigger level should be adjusted properly such that the oscilloscope is triggered right after the sweep starts.

2. FFT size should be equal to or greater than the Record Length of the oscilloscope.

If you want to measure Bode plot (gain and phase, frequency response), click the Spectrum Analyzer window and select "Transfer Function" in the middle selection box at the bottom of the screen. Multi-Instrument Pro license is required.
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