254 N9030B PXA Signal Analyzer Service Guide
LO Synthesizer/Reference Troubleshooting
A14 LO Synthesizer and A20 YTO Troubleshooting
A14 LO Synthesizer and A20 YTO Troubleshooting
Turn on the N9030B Signal Analyzer and wait for the instrument to complete
the boot up process. There are 8 processes to perform, which will verify the
L.O. Synthesizer and YTO assemblies are functioning properly:
—Press Freq, 50 MHz, SPAN, Zero Span. LED's DS1 (yellow), DS2 (orange),
and DS3 (red) located near the top of the board next to J9 should all be off.
DS4 (green) should be on. See LED location in Figure 8-1 below. The
definition of each LED is as follows:
— DS1 (yellow) When lit, indicates the analyzer is sweeping.
— DS2 (orange) When lit, indicates that the Offset Loop integrator
exceeds its nominal range and is thus unlocked (applicable only in
dual-loop mode).
— DS3 (red) When lit, means the Main Loop Cycle Slipped Detector has
detected a cycle slipped condition and the main loop is thus
unlocked.
It is normal for DS3 to flash between sweeps when the Main Loop is
relocking. This can also occur during multiband sweeps. For example:
• sweeps which cross from one harmonic band to another such
as from 2 GHz to 8 GHz.
• dual-loop spans between 2.5 MHz and 10 MHz.
— DS4 (green) When lit, indicates that the FPGA has been configured.
—Press System, Alignments, Align Now, All. If the alignment functions
correctly with no error messages on the analyzer display, most of the
synthesizer section is working properly.
— Measure 4800 MHz 1st LO Reference frequency (from A16 Reference
Assembly)
— Measure 4800 MHz 1st LO Reference power (from A16 Reference Assembly)
— Measure 100 MHz LO Synth reference frequency (from A16 Reference
Assembly)
— Measure 100 MHz LO Synth reference power (from A16 Reference
Assembly)
— Measure 1st LO output frequency (from A20 YTO)
— Measure 1st LO output power (from A20 YTO)
These items can be checked with a functioning spectrum analyzer using cables
and connectors that function well up to 10 GHz. A directional coupler, such as
the 87300B, is also required for measuring the 1st LO output frequency and
power.
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