HP 8340b User Manual

If
the
corrected
detector voltage
is
not equal
to the
reference
voltage,
the
integrator output
voltage
changes,
and drives
an
exponential
driver
that
feeds
current
to
the
linear
modulator
in
the
mod/
splitter.
This
changes
the
RF
output
level,
changing
the
detected voltage
from
the
high
band
detector.
The
modulator driver
is
also
switched
to
the
A9
high
band
modulator
in
the
3.7
GHz
oscillator.
0
PULSE
MODULATION
Pulse
modulation
requires
special
drive
circuitry
and modulators
to
achieve
narrow
pulse widths.
The
high
band
pulse
modulator is
in
the
mod/splitter,
and
the
low band pulse modulator
is
located
just
after
the
3.7
GHz
oscillator.
The
pulse
modulator
drive
circuitry
coordinates
ALC
operation
with
the
pulse
signal.
When
the
pulse
input
is
driven low to turn
off
the
RF,
the
ALC is
triggered
to
sample
and
hold
the
current
RF
level.
During
the
time
the
pulse
is
held
low,
the
output
is
attenuated
by
more
than
80
dB.
When
the
pulse
input
is
returned
to
its
normal
high
level,
the
ALC
releases
the
hold
circuits,
and
the
instrument returns
to
the RF
level
it
had
before
the
RF
was
turned
off.
STEP RECOVERY
DIODE (SRD)
The SYTM
contains
a
step
recovery
diode
that
generates
the
harmonics
for
the
high
bands.
Power
level, frequency,
and
DC
bias
effect
the SRD's
ability
to
generate harmonics.
For
maximum
conver¬
sion
efficiency,
SRD
bias
is
varied
with
power
level
and
frequency.
In
band
1
(2.3
to
7
GHz),
the
SRD
is
biased
on
to
allow
the
fundamental
to
pass through.
The
SYTM
also
contains
a
YIG-tuned
bandpass
filter
that
can
be
tuned
over
the
high
bands
by
changing
the
magnetic
field. The
filter
passband
must
closely track
the
YO
frequency,
or
some
harmonic
of
it,
to
cover
the
high
bands.
SYTM
DRIVER
COMPENSATIONS
The
SYTM
driver
compensates
for
nonlinearities
In
the
tuning
magnet,
hysteresis,
and
magnetic
delay.
The
SYTM
pin
diode
switch
allows
the
low
band
signal
to
be switched
off
when
high
band
is
selected.
The
bias
for
this
switch
is
generated on
the
attenuator
driver/SRO bias
assembly.
A8
3.7
GHZ
OSCILLATOR
The
A8
3.7
GHz
oscillator
provides
a
fixed
3.70
GHz
RF
output.
The
A8A1
oscillator microcircuit
and
the
A8A2
oscillator bias
assembly
are
located
inside
the
A8
3.7
GHz
oscillator
housing.
This
source
is
phase-locked
to
a 100
MHz internal
standard.
A
linear
modulator,
at the
output
of
the
oscillator,
provides
amplitude
control from
nominally
+1
to
—70
dBm.
The
A8A2
bias
assembly
provides
the
necessary
circuitry
to
amplify
the
100
MHz input
signal
and
phase-lock
the
3.70
GHz
signal
to
it.
A
lock
signal is
generated
when
the
two signals
are
phase-
locked.
A8A2
also
provides
the
+20V
and
—10V
microcircuit
bias
voltages.
HP 8340B/41B
RF
Section
Theory
of
Operation
H.3

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English