Tektronix 1L30, Инструкция по эксплуатации

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Operating instructions— Type 1130
Fig. 2-9. 1 MHz Markers Output signal (phase lock reference) ap­
plied to the RF INPUT connector to check dispersion calibration.
of resolution is the frequency separation (in Hz) of two equal
amplitude signals when the notch or dip between these
signals is 3dB down. The resolution for a given display is
a function of sweep speed, dispersion and bandwidth of the
most selective (usually the last IF) amplifier in the signal
path.
Resolution bandwidth is approximately the — 6 d B band­
width (with Gaussian response) of the analyzer, with the
dispersion and sweep time adjusted for the minimum dis­
played bandwidth to a C W signal. Resolution and resolu­
tion bandwidth become synonymous at very long sweep
times.
As the analyzer sweep rate is increased, the amplitude of
a C W signal decreases and the bandwidth increases; which
signifies that both the sensitivity and resolution of the an­
alyzer have been degraded by the increased
sweep rate.
The loss of the analyzer sensitivity due to sweep rate and
the dispersion can be expressed mathematically as:
where S/Sc is the ratio of the effective sensitivity to the
analyzer measured sensitivity, at very slow sweep times or
with zero dispersion.
W here R/R0 is the ra tio o f the effective resolution o f the
a n alyzer to the analyzer measured resolution b a n d w id th at
very slow sweep speeds. R0 is som ewhat a rb itra ry and is
taken as the displayed w id th o f the C W signal at the .— 6
c!B point.
The best resolution fo r a given dispersion and sweep
time is expressed as:
A na lyze r definitions.
Dispersion (in Hz)
Sweep Time (in s)
S ee S p e c tru m
The resolution of the Type 1L30 Spectrum A n a ly z e r is
optim ized fo r most settings o f 1 he DISPERSION selector when
the RESOLUTION! control is in ihe coupled position. Reso­
lution however, can be varied from a p p ro xim a te ly 100 kHz
to less than 1 kHz by uncoupling the RESOLUTION control
and adjusting it as an independent function o f the DIS­
PERSION selector.
To ad eq ua te ly resolve pulsed spectrum in fo rm atio n, the
resolution band w id th o f the analyzer should be on the
ord er o f 1 /1 0 of the side lobe frequency w id th or the re­
ciprocal o f the pulse w idth. The RESOLUTION control is
usually set, after the sweep rate Lias been adjusted, for
optim um main lobe detail. See Fig. 2-10.
D is the dispersion in hertz
B is the —3dB bandwidth of the analyzer in hertz
T is the sweep time in seconds, or — is the scanning
velocity.
These same variables also determine the resolution of
the analyzer. The loss in resolution can be expressed as
follows:
Selecting the Sweep. Ra»e
The sweep rate fo r w ide resolution coupled settings is
usually set just above the visual flicker setting; however,
as the DISPERSION is decreased the sweep rate w ill begin
to a ffe ct the 'resolution and sensitivity o f the analyzer, as
described unc!er Resolution. Therefore, as the DISPERSION
settings are reduced the sweep rate should also be reduced
to m aintain sensitivity and resolution.
W ith the DISPERSION control set io 0, the analyzer func­
tions as a fixed tuned receiver. The an alyzer then displays
time dom ain characteristics of the signal m odulation w ith in
2-12
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