Atten AT6011 Посібник користувача - Сторінка 11
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configuration is use for making selective and
Sensitive precise measurement of frequency,
by tuning to the signal and switching to zero
scan.
In the closed-loop configuration, the tracking
generator signal is fed into the device under
test and the output of the device under test is
connected to the analyzer input.
In this configuration, the spectrum analyzer/
tracking generator becomes a self-contained,
complete (source, detector, and display)
swept frequency measurement system. An
internal leveling loop in the tracking
generator ensures a leveled output over the
entire frequency range. The specific swept
measurements that can be made with this
system are frequency response (amplitude vs.
frequency), magnitude only reflection
coefficient, and return loss. From return loss
or reflection coefficient, the SWR can be
calculated. Swept phase and group delay
measurements cannot be made with this
system; however, it does make some unique
contributions not made by other swept
systems, such as a sweeper/network analyzer,
a sweeper/spectrum analyzer, or a sweeper/
detector oscilloscope.
Precision tracking means a every instant of
time the generator fundamental frequency is
in the center of the analyzer passband, and all
generator harmonics, whether they are
generated in the analyzer or are produced in
the tracking generator itself, are outside the
analyzer passband. Thus only the tracking
generator fundamental frequency is displayed
on the analyzer's CRT. Second and third order
harmonics and intermodulation products are
clearly out of the analyzer's CRT. Second and
third order harmonics and intermodulation
products are clearly out of the analyzer tuning
and, therefore, they are not seen. Thus, while
these distortion products may exist in the
measurement set-up, they are completely
eliminated from the CRT display.
The 1dB gain compression level is a point of
convenience, but it is nonetheless considered
the upper limit of the dynamic range. The
lower limit, on the other hand, is dictated by
the analyzer sensitivity which, as we know, is
bandwidth dependent. The narrowest usable
bandwidth in turn is limited by the tracking
generator residual FM and any tracking drift
between the analyzer tuning and the tracking
generator signal.
Mainly Performance
and Calibration of
AT6010/AT6011 Series
Spectrum Analyzer
1. Structural integrity
No obvious impairment and gilding damage,
all outside components are well installation,
reliable fasten and flexible operability. Warm
up for one hour to inspect the performances.
2. Inspection of Y-POS
Adjust Y-POS knob, occurs hand feeling by
obvious locating point, Failures in adjusting
the locating point will lead to all measured
amplitudes are invalid.
3. Accuracy of frequency readout
Not exceed 2% spectrum width +sweep span
-3
+5*10 *center frequency +10kHz.
4. Inspection of frequency range
Output 0.15MHz~1050MHz frequency signal
from a signal generator, screen should display
the complete signals.
Inspect frequency range of tracking signal
generator: connect output port with frequency
counter, both output attenuation and
bandwidth are zero, adjust CF knob, to check
the signal generator could output 0.15MHz to
1050MHz signal or not.
5. Inspection of reference level
2dB at 500MHz
Output 500MHz frequency and -27dBm level
signal, from signal generator to spectrum
analyzer. Set spectrum analyzer CF at
500MHz, scanwidth 20MHz/DIV, center
frequency 400kHz, with zero input
attenuation. And signal amplitude should up to
top line.
Inspect the output level of tracking generator:
connect input to output with a coaxial cable,
with attenuation 30dB, maximum output, then
amplitude should lower the top line than one
Gratitude.
6. Frequency Response
It means signal response of spectrum analyzer
in measuring equal level and different
frequency. Since the primary function of the
spectrum analyzer is to compare signal levels
at different frequencies, a lack of flatness can
seriously limit its usefulness.
7. Inspection of attenuators
(0~40dB)4*10dB 2dB step,
2dB(40dB).
8. Residual response and
interference immunity
Short circuit the input by connect a 50
terminal load to input port, then signal
response should not appears in screen.
Otherwise, it may seriously affect the ability
of spectrum analyzer in analyzing small
signals.
Replace the 50
terminal load off input port,
noise base line should not raise, especially the
tracking source cannot affect the instrument.
In a common room, no signal response
appears in screen.
9. Inspection of sensibility
Sensibility should better than -90dB.
Output a -90dBm signal with a standard signal
generator, set CF in the frequency, with IF
20kHz, 1MHz/DIV scanwidth, video filter on.
Spectrum analyzer is able to measure the
signal.
10. Grass level
The typical value is 15dB when IF bandwidth
is 400kHz, otherwise, the sensibility of he
unit is too inferior to analyze smaller signal.