HP 8340b User Manual

M/N
Loop
Theory of Operation
The
M/N
loop
generates
the
177-197
MHz signal
that drives
the
A48
sampler
in
the
YIG
oscillator
(YO)
phase
lock
feedback
loop.
The
M/N
loop
uses
the
20
and
400
MHz
reference
signals
from
the
reference
loop.
The
A48
sampler down-converts
the
output
of
the
YIG
oscillator
so
the
YO
can
be
phase
locked
to
the
output
of the 20-30
loop.
The M/N
loop
consists
of
four
assemblies, shown
in
functional
order
below:
•
A32
M/N
VCO
assembly
•
ASS
M/N
output
assembly
•
A31
M/N
phase
detector assembly
•
A34
reference
loop
—
M/N
loop motherboard
The
YO
loop
sampler
drive
output
of the
M/N
loop
(after
being
divided by
2)
can
be related
to
the
M
and
N
numbers
by
the
following
equation:
fM/N
=
200
-
10
X
(M/N)
MHz
A
harmonic
of
this
signal
is
used
in
the
A48 YO
loop
sampler
to
down-convert
the
2.3
to
7.0
GHz
YO
output to
20
to
30
MHz.
For
every
increment
in
M
number,
the
YO
output
decreases
by
10
MHz,
and for
every
increment
in
N
number,
the
YO
output
increases
by
200
MHz.
This
relationship
is
given
in
the
following
equation
where
^0,30
is
the
output
of the
20
to
30
Loop:
fyo
=
200XN
-
10XM
-
f2o,3o
MHz
A32 M/N
VCO
ASSEMBLY
The
M/N
VCO is
a
cavity
resonator
that
is
varactor
tuned
from
355
to
395
MHz.
The
VCO
output
goes
to
the
A33
M/N
output assembly
A33 OUTPUT
ASSEMBLY
The
VCO
output
is
split
by
the
A33
output
assembly
and
sent
to
two
circuits:
•
The
A48
YIG
oscillator
sampler
assembly.
This
is
the
output
of the
entire
M/N
loop,
and
is
divided
by
two
before
going
to the
YO
sampler.
•
The
A31
phase
detector,
where
the
VCO
output
is
phase-locked
to
the
400
MHz
reference
loop
output.
The
M/N VCO
assembly
is
mounted to
the
A33
M/N
output
assembly.
B-4
M/N Loop
Theory
of
Operation
HP 8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English