Keysight N9912A Service Guide 5-9
Theory of Operation
Measurement Group
Pre-Amp
The pre-amp that follows the RF In attenuator may be in or out during the SA
mode. Option 235 is required for the firmware to enable use of this pre-amp.
The pre-amp is always bypassed in CAT and NA modes.
Typical gain of the pre-amp is 22 dB. It has two sections, high-band and
low-band. The low-band section covers up to 2.7 GHz.
Converters
Three stages of conversion produce the 37.5 MHz SA IF signal that goes to the
A5 system board.
The first converter stage mixes the incoming signal with the LO output. Input
signals below 2.7 GHz are up converted and input signals above 2.7 GHz are
downconverted.
Spur avoidance is accomplished by slightly shifting the output frequency of the
first converter stage. When the output frequency of the first converter is
shifted, the second converter compensates for the shift.
The third converter output frequency is fixed at all times.
SA Frequency Bands
The frequency bands for the SA function are as listed below:
Up to 2.7 GHz (bands 1-4) are considered LOW bands and above 2.7 GHz
(bands 5-11) are considered HIGH bands. Different hardware is used for each
type.
Band Analyzer
Start Frequency
(MHz)
Analyzer
Stop Frequency
(MHz)
1 0.000 10.000
2 30.000 715.000
3 715.000 1665.000
4 1665.000 2700.000
5 2700.000 3313.500
6 3313.500 3500.000
7 3500.000 4263.500
8 4263.500 4300.000
9 4300.000 5200.000
10 5200.000 5936.500
11 5936.500 6000.000
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