2-36 Keysight M937xA PXIe Service Guide
Tests, Adjustments, and Troubleshooting
Performance Tests
2-
Frequency Accuracy Test
Function of the Test
To verify the frequency accuracy and range of the analyzer’s source output.
Specification Tested
Test Port Output – CW Accuracy
Equipment Used
- Frequency counter
1
-Test cable
-Any necessary adapters
Description of the Test
This test is performed at key frequencies over the frequency range of the
source voltage controlled oscillator (VCO), not the full frequency range of the
analyzer. To generate the higher frequencies, the analyzer passes the signal
through a series of frequency doublers. These doublers exactly double the
source frequency, so the deviation from a perfectly accurate frequency is
exactly doubled. The frequency accuracy is specified as the ratio parts per
million (ppm), so this ratio is unaffected by the signal doubling. Therefore, only
the frequency accuracy of the VCO needs to be tested.
1. The analyzer is Preset.
2. The analyzer is set up for a CW measurement on Port 1.
3. A test cable is connected between Port 1 and a frequency counter with any
necessary adapters.
4. The signal frequency is measured and compared with the analyzer source
frequency setting. The difference must be less than the source frequency
divided by 10
6
for a 1 part per million (ppm) specification.
5. This test is repeated at several frequencies across the range of the VCO.
If the Analyzer Fails this Test
- Verify the accuracy of the 10 MHz REF OUT by using a frequency counter. If
the 10 MHz reference is off by more than 10 Hz, perform the “10 MHz
Frequency Reference Adjustment” on page 2-45 and then repeat this test.
1. Refer to Get the Hardware Required for your GPIB Instruments.
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