Why Use Vector Mode - Agilent Technologies 89410A Operator's Manual

Choosing an Instrument Mode

Why Use Vector Mode?

The Vector Mode provides extremely fast measurements of magnitude and phase.
It can also easily change between the frequency and time domains. These
capabilities are especially useful in characterizing transient or non-stationary
signals.
If you've used a swept-tuned spectrum analyzer before, you already know that
narrow resolution bandwidth measurements of small frequency spans are very
time-consuming. Traditionally, swept-tuned analyzers have required very long
sweep times for narrow resolution bandwidths due to the sweep rate of the narrow
filters. The narrower the resolution bandwidth, the more time it takes for the
resolution bandwidth filters to settle. In fact, a swept-tuned analyzer's sweep time
is inversely proportional to the square of the resolution bandwidth. As you choose
increasingly narrower resolution bandwidths (for example, when trying to resolve
close-in sidebands) the time it takes to make a measurement increases
exponentially. This characteristic is common to all conventional swept-tuned
analyzers.
However, this analyzer can make narrow band measurements very quickly in
Vector Mode. This lets you make measurements for spans from 1Hz to 10 MHz
(with resolution bandwidths from 9.6 mHz to 3 MHz) much faster than you can with
a swept spectrum measurement. For vector measurements, the analyzer uses the
FFT (Fast Fourier Transform) to convert the input signal from the time domain to
the frequency domain. The result is measurement capability up to 1000 times faster
than conventional swept spectrum analyzers.
If you have previously used FFT or dynamic signal analyzers, Vector measurements
will seem familiar to you. However, with most FFT analyzers you are restricted to
low frequency measurements, often to less than 100 kHz. But in this analyzer,
Vector Mode lets you perform FFT measurements up to 10 MHz for the Agilent
89410A and beyond 1 GHz for the Agilent 89441A.
Use Vector Mode when you need:
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Time selective (gated) frequency domain measurements
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Time data display
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Phase information
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Time capture/playback
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Narrow span with high speed
Specific examples of applications for which you would use Vector Mode include:
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Characterizing spurious response of an oscillator
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Characterizing a burst signal in both the time and frequency domain
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