Agilent Technologies PNA Series Service Manual page 122

Troubleshooting
Measurement System Troubleshooting
A phase lock problem is due to either:
• faulty RF signal generation (caused by the A12 source 20, A21 SOMA 50, A23 and A24
SOMA 70)
• faulty LO signal generation (caused by the A8, A10, A11, A17 or A18 board)
RF Signal Troubleshooting
To isolate a broadband RF signal generation failure, check the test port output power:
1. Connect a power meter and power sensor to Port 1 of the analyzer.
2. On the analyzer, press
to . Note the power reading displayed on the power meter.
0 Hz
NOTE In the unlocked state, the analyzer will "search" for the reference signal. The
output power, as indicated on the power meter, should be approximately
−15 dBm ±5 dB.
3. Connect the power sensor to Port 2 and set trace to measure S
reading displayed on the power meter.
• If the power level is low on both ports the problem is either A12 or A21, confirm the
failure with the following checks for the A12 board and A21 assembly on
• If the power level is low on only one of the ports the problem is either A23 (Port 1) or
A24 (Port 2), confirm the failure with the following checks for A23 or A24 on
(as required for your port's failure).
• If the output power is high on both test ports the problem is LO signal related (continue
with "LO Signal Troubleshooting").
LO Signal Troubleshooting
To isolate a broadband LO signal, refer to the data obtained from the
page 4-35:
• If the data obtained for the A10 frequency reference board is out of tolerance, confirm
the failure with the following checks for the A10 board starting on
• If the data obtained for the A10 frequency reference board is correct but the data for the
A8 fractional-N synthesizer board is out of tolerance, confirm the failure with the
following checks for the A8 board on starting on
• If the data obtained for the A8 fractional-N synthesizer board is correct—and the RF
has been checked—but there is still a phase lock problem, confirm the failure with the
following checks for the A17, A18, and A20 boards starting on
Checking the A12 Output, All Bands
1. Disconnect W1 from A12.
2. Connect a cable to A12 and measure the output power. A power level of −17 dBm ±5 dB
indicates the A12 assembly is functioning normally.
3. If the output power level is at or below the minimum power level for the power sensor,
replace the A12 assembly.
4-42
, set the
Preset Center Frequency
PNA Series Microwave Network Analyzers
to , and the
2 GHz
. Note the power
22
"Serial Bus Test" on
page
page 4-44.
page 4-45.
Service Guide E8361-90001
E8361A
Frequency Span
page 4-42.
page 4-43
4-43.