Keysight N9923A, Service Manual, Page: 47 / 138

5-6 Keysight N9923A Service Guide
Theory of Operation
Measurement Group
5-
Measurement Group
The measurement group produces a stable output signal by phase locking a
synthesized voltage-controlled oscillator (VCO).
The measurement group consists of the:
— A4 RF Board
— A5 System Board
— A6 SOM Board
— Main Battery
A simplified RF block diagram is provided in Figure 5-2 .
A simplified system block diagram is provided in Figure 5-3 .
A4 RF Board
The basic function of the A4 RF board is to provide a signal source and
receivers for the analyzer functions.
An LO synthesizer produces a single LO signal from the 30 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 30 MHz time base is also used to generate a source signal in the source
synthesizer that covers the frequency range of 2 MHz to 6 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 RF board are listed below:
Band
Start Frequency
a
(MHz)
Stop Frequency
(MHz)
Band
Start Frequency
a
(MHz)
Stop Frequency
(MHz)
1 2.000 2.732 12 99.607 100.000
2 2.732 3.125 13 100.000 199.750
3 3.125 5.875 14 199.750 399.900
4 5.875 6.250 15 399.900 800.000
5 6.250 12.107 16 800.000 1600.000
6 12.107 12.500 17 1600.000 3200.000
7 12.500 24.607 18 3200.000 3399.000
8 24.607 25.000 19 3399.000 4149.705
9 25.000 49.607 20 4149.705 5099.705