Measure sine wave bandwidth on spectrum analyser
I have a basic question.
Can you measure a bandwidth of a sine wave on a spectrum analyzer?
Does it make sense since, the theoretical value should be zero.
Kind regards
Depends on what you mean with bandwidth.
First: No, it wouldn't make sense unless you are looking to find some kind of jitter or so in the signal.
Second: (probably stating the obvious) The frequency of the sine wave could be a measure to indicate the bandwidth of your signal. Applying a sine at the worst-case frequency could let you evaluate the results.
One could also have to report the resolution bandwidth settings of the measurement device. If you cannot set it to zero, the RBW would be the highest possible bandwidth of the sine wave (if there is jitter or so involved).
First thank you for the reply.
By bandwidth I literally mean for example the 3-dB or what ever you specify as bandwidth and I dont look for jitter either.
If you have a small RBW, lets say 1Hz, then what do you see? I would guess the sweeping filter which could be Gaussian.
But basically my question is: if you put a sine wave from a signal generator into a spectrum analyser, would it make sense to measure the 3-dB bandwidth for example? And what would you measure if you for example used 1 Hz RBW?
Kind regards
If you look at a pure sine wave with a spectrum analyzer, the curve that you see is the filter bandwidth of the analyzer.
Do you mean to measure e.g. a 3-dB bandwidth of a not pure sine wave (with harmonics and other distortions)?
I would say they are decoupled. Given what you explain, you just want to know what frequency the generator/analyzer can produce/detect/measure? Yes, in that case, looking for the frequency at which the sinusoid lost 3dB would make sense.
OK but if I produce a sine I would expect it to have a 3-dB bandwidth of nearly nothing. So I could use a 1 Hz resolution bandwidth and I would expect, as volker@muehlhaus also say you simply measure/see the RBW filter characteristics.
Yes, that should be the case.