HP 8340B Manual page 440

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).
AT2J2
A45J3 RF OUTPUT
(TO A16J2
VIA W51 AND
W3)
AT2
15dB ATTENUATOR
(TO
A46 VIA
W43)
AT2J1
A4&12
A45J1
(TO
A44 YO J2 VIA
W42)
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
AT215 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
HP 8340B/41B