Agilent Technologies FieldFox MW N9913A, Service Manual

Page: 61 / 156

N9927-90003 5-11
FieldFox Analyzer Theory of Operation
Measurement Group
SA RF Section
An external RF input signal can be analyzed when connected to the Port 2 SA RF Input connector.
Before the input signal is mixed, the signal will go through the input attenuator and optional internal
preamplifier.
The input attenuator default setting from the factory is 10 dB. The input attenuator is used to control the
amount of power at the input of the 1st converter. Changing the input attenuator value can improve the
dynamic range of the instrument and reduce internally generated distortion products.
When the optional internal preamplifier is turned on, the displayed average noise level of the instrument
is improved. This occurs because the noise figure of the overall system is improved. Improving the
displayed average noise level of the system enables the user to analyze low level input signals.
The 1st, 2nd and 3rd converters are used to downconvert the input signal to a final I.F. of 33.75 MHz.
That I.F. is fed to the ADC on the A5, System board. This final I.F. on the output of the ADC can be
measured at the IF Out SMB (m) connector on the side of the instrument. Refer to
“Verifying the 33.75
MHz I.F. Output” on page 4-11 .
The frequency bands for the SA circuitry on the RF board are listed below:
Band Instrument
Start Stop
1 0.030 15.000
2 15.000 500.000
3 500.000 1366.250
4 1366.250 2600.000
5 2600.000 3900.000
6 3900.000 7500.000
7 7500.000 9500.000
8 9500.000 12300.000
9 12300.000 15700.000
10 15700.000 16300.000
11 16300.000 19500.000
12 19500.000 23000.000
13 23000.000 23734.000
14 23734.000 25500.000
15 25500.000 26500.000