Keysight Technologies N5247B, Service Manual

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Keysight N5247B Service Guide 3-49
Tests and Adjustments
Performance Tests
Equipment Used:
— Power meter
— Power sensors
— Test cables
— 10 dB attenuator
Description of the Test:
The noise receiver compression level varies from -16 dBm for the high band of
the low gain stage down to -52 dBm for the low band of the high gain stage.
This range is too wide to get an accurate source power calibration for each
gain stage using a standard power sensor. So the source power is calibrated at
a higher power level, and the analyzer’s standard receiver is used to accurately
measure the effect of the added source attenuation which is needed to bring
the source power down to the compression level.
To ensure that the match between the analyzer source and receiver is optimal
for the most accurate measurements, an external 10 dB attenuator is used.
1. The analyzer is Preset.
2. A test cable is attached to Port 1 with a 10 dB attenuator at the end of the
cable.
3. Using the low frequency power sensor, a source power calibration is
performed at the end of the cable for dozens of frequency points. The
power level is set between -9 and -18 dBm, at a multiple of 10 dB above
the specified compression level.
4. This process is repeated for each of the three gain stages since each stage
requires a different power setting.
5. Steps 3 and 4 are repeated using the high frequency power sensor.
6. The test cable and attenuator are attached to Port 2.
7. A receiver measurement is made at the calibration level and the receiver
response is normalized.
8. The Port 1 source attenuator is set such that the power level matches the
compression level and another sweep is made. The source power
calibration is adjusted for any deviation from the expected power level
change.
9. Steps 7 and 8 are repeated for each of the three gain stages.
10. The analyzer is set for a noise power density measurement using the noise
receiver and a standard receiver measurement using the B receiver.
11. The source power calibration for the appropriate gain stage is applied and
a sweep is made.
12. The source attenuator is set for an additional 10 dB and another sweep is
made.