HP 8340b User Manual

Sweep
Generator
—
YO
Loop
Theory
of
Operation
SWEEP
GENERATOR
-
YO
LOOP
OVERALL
THEORY
OF
OPERATION
Main
Tuning
Assemblies
Four
instrument assemblies
provide
coarse
tuning
for
the A44
YIG
Oscillator
(YO),
these
are:
ASS
Sweep
Generator.
This
assembly
produces
signals
required
to
sweep
the
YO
when
in
swept
instrument
modes.
A54 YO
Pretune/Oelay
Compensation Assembly.
The
A54
assembly
tunes
the
YO
close
to
the
desired
output
frequency.
The following
signals
are
summed
on
the
A54
assembly:
•
The
coarse
tuning signal
(VSWP)
from
the
ASS
sweep
generator
(during
sweeps
">5
MHz
only).
•
A
microprocessor-controlled pretune
voltage.
•
A
fixed
reference
voltage.
The
resultant
signal,
PRETUNE,
is
sent
to
the
ASS
YO
driver and
the
A28
SYTM
driver.
The
A28
assembly
is
in
the
RF
Section.
The
AS4
assembly delay
compensation
circuitry
counteracts
the
sweep
delay
inherent
in
the
YIG
oscillator.
This
circuit
is
controlled
by
the
instrument
microprocessor.
VCOMP
speeds
the
YIG
oscillator's
response
during
a
sweep.
This
compensates
for
YO
eddy
current-related
delays.
VCOMP
is
sent
to
the
ASS
YO
driver.
This
assembly
also
produces
a
kick
pulse
(LKICK)
that
eliminates
magnetic
hysteresis
in
the
YIG
oscillator.
This
kick
pulse
is
also sent
to
the
ASS
YO
driver.
ASS
YO
Driver.
The
ASS
YO
driver
sums
VSWP,
VCOMP,
and
LKICK
and
converts
them
into
a
current
signal
to
drive
the
YIG
oscillator's
main
coil.
The
ASS
assembly
is
also
in
the
phase-lock
feedback
loop.
Low
frequency phase/frequency error
voltages
are
summed
into
the
voltage-to-
current converter
with
the
VSWP,
VCOMP, and
LKICK
signals. Low
frequency
phase-error
correction
must
be
input
to the
YO
main
coil,
which
can
respond
to signals below
100
Hz.
High
frequency
phase-error
correction
is
explained
in
the
feedback
loop
description,
below.
A47
Sense
Resistor
Assembly.
The
YO
main
coil
requires
a
powerful
current
source.
The
ASS
YO
driver
can
not
supply
the
required
current,
so
its
output
is
amplified
by
the
A47
sense
resistor
assembly
and
sent
to
the
YIG
oscillator's
main
coil.
This
assembly contains
the
high
current
components
of
the
ASS
YO
driver's
voltage-to-current
converter.
The
components
are
placed
on
the
A47
assembly
for
proper
heat
dissipation.
This
assembly
also
contains
high
power
portions
of
the
A28
switched YIG-tuned
multiplier
driver
assembly (part
of
the RF
section).
This
function
is
relevant
to
the
RF
section.
D-2
Sweep Generator
-
YO
Loop Theory
of
Operation
HP 8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English