578 Chapter11
Synthesizer Section
Sampler and Sampler IF
• If adjusting the sampler match does not bring the signal at
A15TP101 within specification when the signal at A15TP201 is
correct, the A15U100 sampler is defective.
8. The sampler IF signal at A15J101 is 60 MHz to 96 MHz at −10 dBm
to +5 dBm. If the signal at A15TP101 is correct, but the signal at
A15J101 is wrong, the fault lies in the sampler IF circuitry. Continue
with the following steps.
9. Set the spectrum analyzer to the following settings:
Center frequency .................................................. 300MHz
Span ..............................................................................0Hz
10.Set a microwave source to the following settings:
Frequency ......................................................... 4.2107GHz
Amplitude ................................................................−5dBm
11.Connect the microwave source to A15U100J1.
12.Measure the signal at U103 pin 1 using an active probe/spectrum
analyzer combination.
13.If a 94.7 MHz signal, approximately −14 dBm, is present, but the
signal at A15J101 is low, suspect U103.
14.When U104 pin 3 is at TTL low, U104 pin 6 should near −15 Vdc and
PIN diodes CR101, CR102, and CR103 should be reverse-biased.
15.Set the spectrum analyzer under test to the following settings:
Center frequency ................................................. 89.3MHz
Span ..............................................................................0Hz
16.Check that U104 pin 3 is at a TTL high and U104 pin 6 is greater
than +7 V. PIN diodes CR101, CR102, and CR103 should all be
turned on with about 7 mA of forward current.
17.Disconnect the power splitter and reconnect W32 to A15J101.
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