HP 8340B Manual page 180

A45 Directional Coupler Theory of Operation
The A45
directional
coupler divides the
RF output of the A44 YO
into
two
paths.
The output of the
coupled arm goes
to
A45J1. This signal
is
attenuated by AT2 and goes through
the
A46 7.0 GHz
low
pass
filter
to the A48
YO
loop sampler.
The sampler
mixes the coupled-off YO signal with the Nth
harmonic of the
M/N output
signal.
The result
is the
Sampler
IF signal, which goes to the A49 YO loop
phase detector.
The RF signal from
the coupler's main path
is
the YO output
signal at
A45J3.
This signal
is sent to the
A16 modulator/splitter (located
in the
RF
section).
AF2J2
AH5J3 RF OUTPUT
(TO
A16J2 VIA W51 AND
W3)
AT2
15dB ATTENUATOR
(TO
A46
VIA
WHS)
AT2J1
A4.5J2
A45J1
(TO
AW YO J2 VIA
Wt2)
Figure D-2.
A45 Directional
Coupler Assembly
Drawing
A46 7 GHz Low Pass Filter
Theory of Operation
The A46 7
GHz
low pass
filter is
connected
by coaxial
cables between
the AT2 15 dB Attenuator and
the
A48 YO loop sampler.
It filters out
the harmonics
of the coupled-back portion of the
YO
output
from the directional coupler
to prevent unwanted mixing products
in the sampler.
Sweep Generator
-
YO
Loop Theory of Operation Change
10
HP 8340B/41B