Performance Evaluation
53
CG635 Synthesized Clock Generator
Functional Tests
Functional tests verify that basic frequency synthesis of the CG635 is operating correctly.
This is accomplished by measuring the frequency of the CG635 at several specific
frequencies from DC to 2 GHz. The SR620 time interval counter is used to measure the
frequency output from the CG635. An SR625 is required to measure frequencies from
1 GHz to 2 GHz.
SR620/SR625 Configuration
Use the following procedure to set up the SR620/SR625:
1.
With the power off hold down the ‘CLR’ button in the DISPLAY section and
turn the power on. This resets the SR620 to default settings.
2.
Press MODE
ź
button three times to switch the mode from TIME to FREQ.
3.
Press the GATE/ARM
Ÿ
button two times to switch the gate to 1 s.
4.
Press the SAMPLE SIZE
ź
button three times to set the sample size to 1.
5.
Press DISPLAY
ź
button five times to set the display to TRIG.
6.
Adjust the channel A trigger knob until the trigger level displayed for channel A
reads 0.00.
7.
Press the DISPLAY
Ÿ
button five times to set the display back to MEAN.
8.
Press the channel A ‘AC/DC’ button once to switch to AC coupling
9.
Press the channel A ‘INPUT’ button once to switch to 50
termination.
10. For frequency measurements between 100 MHz and 1 GHz, press the channel A
‘INPUT’ button once more to switch to 50
termination with UHF prescalers.
CG635 Configuration
Use the following procedure to configure the CG635 for frequency measurements:
1.
Press ‘SHIFT’, ‘INIT’, ‘Hz’ to return the CG635 to default settings.
2.
Press the Q/Q
¯
ź
button to 7 dBm output level for the Q/Q
¯ outputs.
3.
For each frequency, use the number pad to enter in the desired frequency and
complete the entry with the appropriate units button.
Frequencies 1.0 to 2.0 GHz
Measuring frequencies above 1.3 GHz with the SR620 requires the UHF divide by 10
prescalers that come with an SR625. Use the setup shown in Figure 7.
Figure 7: Setup for frequency measurements from 1.0 to 2.0 GHz.
The SR625 prescaler has a level adjustment knob. Adjust the level until the SR620
reports frequencies that are 1/10 of the set frequency. Set the frequency of the CG635 to
Q
Q
CMOS
CG635
SR620
EXT A
B REF
SR625
OUT IN
10 MHz OUT
10 MHz IN
50
Ω
terminator
