Thanks Kirt for your answer, but does it really
depend on the instrument ?
explanation is given on
According to this, the number of points is
determined by the maximum length of the impulse
response and the bandwidth of measurement:
number of points = length of impulse response *
bandwidth of measurement
First of all I don't
understand this simple formula, secondly how do
I know the impulse response of my DUT ?
Generally, that's unknown I would say.
The necessary IF bandwidth is determined by the
desired dynamic range (SNR).
the sweep rate is calculated by the bandwidth,
number of points and group delay through the IF
BW-filter (approximately the reciprocal value of
the chosen IF BW). The sweep rate, together with
the length of the impulse response results in
the change in frequency during the impulse
response, which must be lower than the IF
bandwidth ("the sweep time is always okay if you
are properly sampling the frequency domain!").