Keysight Technologies N5247B, Service Manual

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Keysight N5247B Service Guide 5-11
Theory of Operation
Synthesized Source Group Operation
— A14 Frequency Reference Board (S/N prefixes
<
6021 Only) (including
rear-panel interconnects)
— A23 Test Set Motherboard (including rear-panel interconnects)
— A70 4-Port and A75 2-Port Low Frequency Extension (LFE) Board
(including rear-panel interconnects)
Basic Operation
This section contains the following:
— “Version 6 Synthesizers Basic Operation”
— “Version 7 Synthesizers Basic Operation” on page 5-19
Version 6 Synthesizers Basic Operation
Table 5-7 on page 5-15 lists the L.O. harmonic number, the synthesizer
frequencies (A4, A15, and A17), the main source frequency (A5 and A10), and
the doubler frequencies (A7, A8, A12, and A13) within the analyzer for each
band. This table is referred to throughout this chapter and also appears on the
overall block diagram at the end of Chapter 4, “Troubleshooting.”
The A14 frequency reference board produces a constant phase locked
reference signal of 50 MHz that is sent to the A4, A15, and A17 13.5 GHz
synthesizer boards.
Refer to
the NOTE notice on page 5-1 . The A15 13.5 GHz synthesizer board
produces an LO signal that is sent through the A25 LO multiplier/amplifier 26.5
board to the A27 and A28 mixer bricks (via the A26 splitter).
1
The frequency is
synthesized such that the mixing product of this LO signal with the test signal
output is a constant IF signal. For analyzers with DSP version 4.0, the IF signal
is 7.606 MHz (at frequencies below 53 MHz the IF is 2.535 MHz). For analyzers
with DSP version 5.0, the IF is 7.438 MHz (at frequencies below 53 MHz the IF
signal is 0.826 MHz). This IF signal is sent to the A16 SPAM board for digital
processing.
The A4 13.5 GHz synthesizer board produces an incident signal that is sent
through the A5 26.5 GHz source board and then through the A7 and A8
doubler boards to the front panel outputs. Likewise, the A17 13.5 GHz
synthesizer board produces an incident signal that is sent through the A10
26.5 GHz source board and then through the A12 and A13 doubler boards to
the front panel outputs. Portions of these signals are coupled off and sent to
the A27 and A28 mixer bricks (A–D and R1–R4) where they are mixed with the
LO signal from the A26 splitter
1 to produce the IF signal. For analyzers with
DSP version 4.0, the IF signal is 7.606 MHz (or 2.535 MHz). For analyzers with
DSP version 5.0, the IF signal is 7.438 MHz (or 0.826 MHz).
1. A26 splitter only applies to PNAs with serial number prefix
<
6021.