HP 8340b User Manual

The
mixing
and
multiplying
make
bandcrosslngs
necessary.
At
each
crossing,
VSWP
resets
to
zero
and the
YO
is
phase-locked
to the
appropriate
frequency
for
the
start
of the
next band.
The
result
is
that
in
a
multi-band
sweep
the
MKR RMP
is
a
ramp
that
pauses
for
bandcrossings,
and
VSWP
is
a
series
of
ramps,
each
starting
at
zero volts.
The
slope
of
any
particular
ramp
depends
on
the
YO
harmonic being
used
in
that
band.
The
MKR
RMP
is
a
0
to
-HOV
ramp
used as
the
reference
for
all
sweep
events.
In
a
single
band
sweep,
the
voltage
goes
linearly
from
0
to +10 volts
in
the
selected
sweep time.
In
a
multi-band
sweep,
the
voltage
is
a
segmented
ramp
where
the linear
ramp
portions
correspond
to
the
particular
bands
swept,
and
the
flat
portions
correspond
to
the
time
necessary
to
re-phase-lock
the
instrument
for
the
next
band.
In
the
multi-band
case
the
sum
of the times for
the
various
linear
ramp
portions
equal
the
selected instrument
sweep
time.
That
is
to
say,
the
instrument
sweep
time
is
the
time during
which
the
instrument
is
actually
sweeping
and
does
not
include
the
re-phase-lock
time
at
each
band-
crossing.
Narrow
Band
Sweep.
YO
sweep
widths
:s5
MHz
are
achieved
by
sweeping
the
20-30
synthesizer.
The
ASS
sweep
generator
assembly
produces
the
20-30
SWP
(from
inputs from
the
processor),
that
causes
the
20-30
output
to
sweep
in
frequency.
The
A49
YO
loop phase detector keeps
the
YO
phase-
locked
to
this
signal
for
the
duration
of
the
sweep.
For
narrow
band
YO
sweep
widths
between
500
kHz
and
5
MHz,
PRETUNE
is
also
swept
(VSWP
summed
in)
a
proportional
amount
so
that the
pretuned
YO
frequency
remains
within
the
capture
range
of
the
YO
phase
lock
loop.
This
is
in
addition
to
the
phase-locked
error
correction
by
YO
TUNE.
For
YO
sweep
widths
<
500
kHz,
VSWP
is
dis¬
abled,
and
YO
TUNE
alone
supplies
the
correction
to
keep
the
YO
phase-locked for
the
entire
sweep
ramp
voltage.
YO
Loop
Detailed
Theory
Of
Operation
The
assemblies (documented
in
this
functional
group)
that
comprise
the
YO
loop
are
show
below:
A44
YIG
oscillator
A45
directional
coupler
AT2
15 dB
attenuator
A46
7
GHz
low
pass
filter
A48 YO
loop
sampler
assembly
A49 YO
loop
phase
detector
assembly
A50 YO
loop
interconnect
assembly
A54 YO
pretune/delay
compensation
assembly
A55 YO
driver
assembly
In
CW
and
manual
modes,
the
YO
loop
phase-locks
the
YO
at the
appropriate
frequency.
The informa¬
tion
to
tune
the
YO
comes
from
two
sources:
PRETUNE
and
YO
TUNE,
that
combine
to form
the
YO
FM
COIL DRIVE
and
the
YO
MAIN
COIL
DRIVE.
Pretune.
The
PRETUNE
voltage
is
generated
on
the
A54
YO
pretune/delay
compensation
assembly.
It
is
the
scaled
sum
of
VDAC,
a
tune
voltage generated
from
inputs
from
the
instrument
processor,
and
VREF,
a
constant
DC
offset
voltage.
PRETUNE
has
a
sensitivity
of
—2.5V/GHz
of
YO
sweep.
VCOMP
makes
no
contribution
to PRETUNE
in
the
CW
or
Manual
modes.
LVSX
(low
voltage
sweep
disable)
is
low to shunt
out
any unwanted
noise
contribution from
the
VSWP
line.
D-6
Sweep Generator
-
YO
Loop Theory
of
Operation
HP 8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English