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EMC Question of the Week: October 22, 2018
On a digital oscilloscope or real-time spectrum analyzer, what effect does increasing the sampling rate in the time domain have on the signal displayed in the frequency domain?
- better frequency resolution
- higher bandwidth
- lower noise floor
- higher dynamic range
Answer
The correct answer is "b". For a given sample period, T, the bandwidth (i.e. frequency range) of the transformed signal will be proportional to the sampling rate. The frequency resolution is the inverse of the sample period. The main factors affecting the noise floor and dynamic range are the amplitude resolution (or quantization error) of the sampled signal and the electrical design of the receiver and its components.
One additional note: Yes, in a given application, one could argue that all four parameter choices might be affected by increasing the sampling rate (depending on what other parameters were held constant). Nevertheless, the way the question is stated, it would be difficult to make a convincing argument in favor of any choice other than b.
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