Keysight Technologies N9040B UXA Signal Analyzer Service Guide 141
RF Section Troubleshooting (RF/Microwave Analyzers)
RF Section Description
The RF section is comprised of the following major assemblies:
— A9 Input Attenuator A
— A10 Input Attenuator B
— A11 Low Band Switch Assembly
— A12 YTF Preselector
— A20 Yig Tuned Oscillator
— A13 RF Front End Assembly - shown on the block diagram as A13A1 and
A13A2. A13A1 and A13A2 cannot be replaced individually, the entire A13
assembly must be replaced.
— A15 Front End Control Assembly
— Option LNP - Low Noise Path (standard on UXA)
— Option MPB - Microwave Preselector Bypass (standard on UXA)
1. RF input frequencies < 3600 MHz route through the low band path. Refer
to the RF Lowband Path Block Diagram in Chapter 12 for details.
The RF input signal level can be optimized by Input Attenuator A and/or
Input Attenuator B. The low band switch assembly contains a limiter that
offers added protection for the mixer, and routes the input signal to the
low band input of the A13 RF Front End assembly. There are (3) different
signal paths on the input of the RF Front End assembly that the signal can
be routed through depending on installed options and front panel settings.
— Electronic Attenuator path, 0-24 dB (Option EA3)
— Low Band Preamplifier path, 20 dB nominal gain
— Direct to Mixer #1
The RF input signal is then mixed with the 1st LO from the A20 YTO
assembly to a 1st intermediate frequency of 5122.5 MHz. Since the RF
input signal is < 3600 MHz for low band, this RF input signal is
upconverted in Mixer #1 to the 1st IF. This 1st IF signal is then
downconverted in Mixer #2 using the 4800 MHz 2nd LO generated on the
A16 Reference assembly to a 2nd intermediate frequency of 322.5 MHz
(5122.5 MHz (1st IF) − 4800 MHz (2nd LO)). The 2nd IF output is at
A13A1J7. This signal path is used for all frequency range options when the
RF input frequencies are < 3600 MHz. The control voltages and biasing for
these assemblies come from the A15 Front End Control assembly.
The RF input signal can route through the Electronic Attenuator section or the Preamplifier, but
not both. All RF input frequencies < 3600 MHz go to Mixer #1.
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