> Network analyzer is a spectrum analyzer with signal source to measure
> the pass band characteristics.
>
Well, sort of.
A spectrum analyzer displays an amplitude versus frequency plot, using a
sweep tuned narrow band (relative to a network analyzer) receiver with
an AM detector. Some spectrum analyzers also have a tracking generator
option, which is a sweep oscillator which tracks along with the sweeping
receiver. Amongst other uses, this allows the spectrum analyzer to be
used as a network analyzer.
A network analyzer is displays amplitude versus frequency plot, using a
sweep generator and a wide band detector.
A network analyzer's detector generally does not "know" what frequency a
signal is on, just it's amplitude, and in order to give an amplitude
versus frequency plot, it assumes that the signal it is plotting is
coming from it's own sweep generator. Network analyzers often have two
detectors plotting two separate amplitudes, such as transmission loss
and return (reflected) loss.
A spectrum analyzer can plot the amplitudes and frequencies of many
signals. It does not require a tracking generator to do this (other than
the internal local oscillator used in the sweeping superheterodyne
receiver). It's detector is part of a sweep tuned superheterodyne
receiver, and it "knows" what frequency the signals are on as it plots
their amplitudes. Spectrum analyzers have only one detector and a single
plot, unless they are also equipped with a tracking generator, in which
case they may have a second detector (probably a wideband one like in a
network analyzer) and can give two plots.
DE N6KB
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