Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide 191
RF Assembly
A3 RF Assembly Overview
There are four different output bands contained within the RF Output section to
cover the instrument frequency range, as seen in Table 10-2.
For information on how frequencies 3.2 GHz and above are generated in
microwave instruments see Chapter 11, “Micro-Deck Assembly”
There are several adjustments related to the RF Output section found in the
performance verification and adjustment software for these instruments, which
will be covered later in this chapter.
Pulse Modulator (Option UNW)
The Pulse Modulator block is only used in instruments with option UNW,
Narrow Pulse Modulation.
The Pulse Modulator block on the A3 RF assembly is used for all frequencies in
RF instruments, but only below 3.2 GHz in microwave instruments. There is an
additional pulse modulator on the A7 Micro-Deck assembly for frequencies 3.2
GHz and above for microwave instruments.
The Pulse Modulator is made up of two electronic switches in series. The
modulator control circuitry can be driven by either the internal function
generator or an external pulse applied to the PULSE input on the rear panel.
The Pulse Modulator output is switched to either the input of the High Band or
Low Band block. It is not routed to either the Het Band or the Op-Amp band.
The Het Band block gets its input from the Low Band, and the Op-Amp band
gets its input from the Function Generator / Trigger Control section, which
controls any pulse modulation when that band is used.
High Band
The High Band block is only in the RF instruments, the microwave instruments
do not have it.
The High Band block contains amplifiers, ALC modulators, filtering, and ALC
detection for frequencies greater than 3 GHz in RF instruments.
Low Band
The Low Band block contains amplifiers, ALC modulators, filtering, and ALC
detection for frequencies of 250 MHz to 3 GHz in RF instruments. In microwave
instruments it is used from 250 MHz to just below 3.2 GHz.
Table 10-2 A3 RF Output Frequency Bands
RF Output Band RF Instruments Microwave Instruments
High Band >3.0 GHz to 6.0 GHz n/a
Low Band 250 MHz to 3.0 GHz 250 MHz to <3.2 GHz
Het Band 5 MHz to <250 MHz 5 MHz to <250 MHz
Op-Amp Band 9 kHz to <5 MHz 9 kHz to <5 MHz
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