Frequency Span Versus Time Record Length; Zoom Measurements - HP 3563A Operating Manual

Frequency Span Versus Time Record Length

The HP 3563A allows you to set either the frequency span or the time record length in a
measurement. The two are related by this formula:
time record length(in seconds)
For example, a frequency span of 0 to 100 kHz has a time record length of 8 milliseconds (800/100
000). Note that the two are inversely proportional; a narrow span and increased resolution result in
a slower measurement. Setting the frequency span automatically sets the time record, and vice
versa. Because record length is determined by span, the available time record lengths are also
predefined. Refer to table 3-1 for the predefined spans.

Zoom Measurements

Zooming, also known as band selectable analysis (BSA), allows you to concentrate the full
measurement power of the HP 3563A on any portion of the 100 kHz frequency span. Say you are
characterizing a filter with a resonant frequency of 15.0 kHz. With zoom, you can set the center
frequency to 15.0 kHz and then set a very narrow span. A span of 50 Hz would give you a
measurement from 14.975 Hz to 15.025 Hz and resolution of 50 Hz!800. Now you can accurately
measure and analyze around this point of interest.
To demonstrate the higher resolution zooming provides, press WINDOW and select the uniform
window by pressing UNIFRM (NONE). This sets the bandwidth equal to M. Next, press
TRACE until the state information
BW. You can see that the measurement bandwidth in this span is 125 Hz. Change the span to 50
Hz. The bandwidth is now 62.5 mHz, offering a much more precise characterization of a narrow part
of the signaL
Frequency Spans in the Linear Resolution Mode
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span In )
( z
displayed. Set the span to 100 kHz and look under FREQ:
is
Using The Linear Resolution Mode
STATE
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