HP 8340b User Manual

RF
Source
A44
YIG
Oscillator/Bias
Assembly.
The
A44
YIG
oscillator
(YO)
provides
the
fundamental
RF
output
frequency
for the
instrument.
The
frequency
range
of
the
YO
is
2.3
to
7.0 GHz.
The
YO
uses two
tuning
coils:
•
Main
Coil
The
main
coil is
the
primary
tuning
component
of the
YO.
The
main
coil
tunes
the YO
to
within
the
capture
range
of
the
phase-locked
YO
feedback
loop
(within
±20
MHz
of
selected
frequency),
and
provides
low-frequency
(<100
Hz)
phase-error
correction.
•
FMCoil
The
FM
coil
frequency
modulates
the
YIG
oscillator
when
a
signal
is input to
the
instrument's
FM
input
BNC.
The
FM
coil
also
allows
high
frequency
(>100
Hz)
phase-error correction,
that
is
provided
by
the
A49
YO
loop
phase
detector
(described
below).
Feedback
Loop Assemblies
A45
Directional
Coupler.
The
directional
coupler
splits
the
output
of
the
YIG
oscillator.
One
output
goes
to
the
RF
Section
(and
eventually to
the
instrument's
RF output)
and
the other
goes
to the
YO
feedback
loop.
The feedback loop portion
goes
to the
AT2
15
dB
attenuator.
AT2
15
dB
Attenuator.
AT2
attenuates
the
coupled-off
portion
of
the
YIG
oscillator
output.
Signal
attenuation
is
required so
that
the
feedback signal
can
be
mixed
with
a
synthesized
reference
and
be
phase/frequency
compared.
These
processes are
described
below.
AT2
also
provides
isolation
between
the
feedback
loop assemblies and
the
YIG
oscillator.
A46
7
GHz
Low
Pass
Filter.
The
low
pass
filter
reduces harmonics from
the
coupled-off
YIG
oscillator
output
to
prevent
unwanted
mixing
products
in
the
A48
YO
loop
sampler.
A48
YO
Loop
Sampler.
The
sampler
mixes
the
coupled-off
YIG
oscillator
output
(from
the
A46
assembly)
with
the
synthesized
output
of
the
M/N
loop.
The
output
is
a
20
to
30
MHz difference
signal,
that
is
sent
to
the
A49
YO
loop
phase detector.
A49
YO
Loop Phase
Detector.
The
20-30
MHz
IF
signal
from
the
A48
assembly
is
phase/frequency
compared
to the
output
of the
20-30
synthesizer.
The
resultant
error
signal
is
integrated and
sent
to
the
sample
and
hold
circuit.
SAMPLE
MODE.
This
no-memory
mode sends
a
low
frequency error
correction
signal
(YO
TUNE)
directly
to
the
ASS
YO
driver.
This
mode
is
used
in
CW/Manual
operation,
or
in
swept mode
when
the
YIG
oscillator
(YO)
is
swept
5
MHz
or less.
This
completes
the
YO
feedback
loop
and
phase-locks
the
YO.
HOLD
MODE.
This
mode
must
be
used
when
the
YO
is
swept
>5
MHz,
Sample
mode
first
allows
the
YO
to
phase-lock
at
the
beginning
of
the
sweep.
Afterwards,
the
hold
mode
holds
the
YO
TUNE
voltage
constant
while
VSWP
is
summed
into
the PRETUNE
signal,
which
in
turn
sweeps
the
YO.
This
sequence
is
repeated
at the
beginning
of
each
sweep.
HP
8340B/41B
Sweep Generator
-
YO
Loop
Theory
of
Operation
D-3

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English