Keysight Technologies N9040B UXA Signal Analyzer Service Guide 143
RF Section Troubleshooting (RF/Microwave Analyzers)
RF Section Description
A11 Low Band Switch
This assembly operates across the entire frequency range of the analyzer. The
switch has 3 main functions:
— Switch RF input frequencies from 3 Hz to 3.59 GHz RF Output to A13 RF
Front End Assembly.
— Switch input frequencies from 3.6 GHz to 26.5 GHz Microwave RF Output to
A12, YTF Preselector.
— Contains optional high band preamplifier, which has a typical gain of 30 dB
and a noise figure from 9 to 12 dB up to 18 GHz.
— Contains protective limiter circuitry.
A12 YTF Preselector
The YTF Preselector is used for input frequencies greater than 3.6 GHz. Signals
less than 3.6 GHz bypass the YTF assembly and are routed to the low band
input of the A13 RF Front End Assembly. The YTF Preselector is a YIG tunable
bandpass filter whose main purpose is to track the input signal and to filter out
unwanted spurious or image response signals. The YTF Preselector has a 3 dB
bandwidth greater than 40 MHz and an insertion loss of ~ 6.5 dB.
The preselector requires centering for optimum amplitude accuracy. The Auto
Align routine will perform a rough centering during the preselector two point
tuning algorithm. However, when troubleshooting, press Amplitude,
Preselector Center to manually center the preselector.
A20 YTO Assembly
Provides the 1st LO signal that is required for the A13 RF Front End Assembly.
The 1st LO has a frequency range from 3.50 to 9 GHz. The output power is +13
to +18 dBm. In order to maximize the conversion efficiency and avoid LO
unlock, sufficient LO power must be supplied.
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