Keysight FieldFox Handheld Analyzers Service Guide 61
Theory of Operation
Measurement Group
NA RF Section
An LO synthesizer produces a single LO signal from the 90 MHz time base
located on the A5 System board. The LO output is delivered to the NA mixers of
both ports. The LO frequency is always above the measured frequency. The IF
is 390 kHz.
The LO output is switched between the NA mixers and the SA first converter
depending on the function being used. At any instant in time, either the NA
receivers or the SA receiver may be active, but not both at the same time.
The 90 MHz time base is also used to generate a source signal in the source
synthesizer that covers the frequency range of 10 MHz to 26.5 GHz. The source
signal is generally rich in harmonic content. This is acceptable because the
signal is used with tuned receivers.
The frequency bands for the NA circuitry on the RF board are listed below:
Table 5-1 Frequency Bands - NA RF Section
N991xA, N992xA, N993xA
Band Instrument
Start Stop
P1 0.030 2.035
2 2.035 2.425
3 2.425 4.500
4 4.500 4.850
5 4.850 9.350
6 9.350 9.700
7 9.700 19.100
8 19.100 19.500
9 19.500 38.800
10 38.800 78.000
11 78.000 156.250
12 156.250 312.500
13 312.500 625.000
14 625.000 1250.000
15 1250.000 2500.000
16 2500.000 5000.000
17 5000.000 10000.000
18 10000.000 15000.000
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