Table of Contents
Advertisement
6.3 Why the refresh rate is slow when SPAN is set to
narrow?
The spectral resolution of KC908 is tied to SPAN. The narrower the SPAN,
the smaller the resolution(RBW).
For example, when SPAN=1KHz, the resolution is 1Hz. It takes time to
measure the frequency of 1 Hz, and the period of the 1 Hz is 1 second. To
increse the frequency resolution, either add more sampling points, or narrow
the bandwidth, this is the principle of FFT. And more sampling points means
more time, in certain amout of sampling point, the narrower the bandwidth,
the longer the period, means it'll take longer to collect the same amout of
sampling point.
For sacannning spectrum, the narrower the RBW, the narrower the
bandwidth of the resolution filter, and the longer it takes for the signal to pass
through.
For example, there is a filter with a nominal bandwidth = 1Hz, if a signal
can pass through it within 0.5s, then it will pass a signal of 2Hz at least, this is
obviously contradicted with the bandwidth. Actually the response time of the
filter will be longer. At high resolution, FFT spectrum is way fatster than
scanning spectrum.
Advertisement
Table of Contents
