HP 8340b User Manual

If
you
access
the
peaking routine
by
pressing
[SHIFT] [AMPT
MKR],
or
by
remotely
programming
"SHAK",
it
executes
immediately,
regardless
of
instrument
state,
but
only
a
fine
search
around
the
most
recent
slope
DAC
setting
is
done.
Because
the
SYTM
passband
is
not
tuned
to track
the
output
frequency
in
low
band,
the
peaking
routine does not
execute
if
the
instrument
is
in
low
band.
MOD
LVL
is
fed
to
the
A27
level
control
assembly,
where
it
becomes
one
input
to
the
ADC
input
multiplexer.
The
peak
routine
programs
the
ADC
multiplexer
to
route
the
MOD
LVL
voltage to
the
test
ADC.
By
monitoring
the
test
ADC
output
while
tuning
the
SYTM,
the
program
finds
the
peak
RF
signal
level.
When
you
select
the
peak
function from
the
front
panel,
the
instrument
does
a
full
peak (coarse
and
fine
search)
if in
CW
or
manual.
If
you leave
the
peaking function
on,
the
instrument
repeaks
every
seven minutes,
doing a
fine
search around
the
most
recent
slope
DAC
setting.
If,
while
peaking
is
on,
you
change
the
CW
or
manual
frequency
with
the
front
panel
knob,
the
instrument
performs
a
fine
search
around
the
most
recent
slope
DAC setting;
if
you
change
the
frequency
using
the
step
or
numerical
entry
keys,
the
instrument
performs
a
full
peak.
The
SYTM
passband
has
a
second, narrower
peak
200
to
300
MHz lower
in
frequency
than
the
desired
peak.
The
coarse
search routine
starts at
the
top
of the
passband
and
searches
for
a
peak
in
15
MHz
steps.
Once
a
peak
is
found,
the
coarse
search continues
for
another
150
MHz to
verify
that
it
found
the
correct
peak,
stopping before
it
reaches
the
second
peak.
The
step
size
is
15
MHz to
ensure
that
at
least
one
step
falls within
1
dB
of the
peak
(the
minimum
1
dB
bandwidth
is
24
MHz).
Once
the
coarse
search peak
is
located,
the
microprocessor reads
the
modulator
level
as
a
reference
for
the
—1
dB
points.
The level
control
DAC
is
stepped
down
1
dB,
causing
the
modulator
level
to
drop
1
dB
(because
the
ALC
loop
generates
the
1
dB
change).
Using
the
—1dB
reference,
the
micro¬
processor
steps
the
slope
DAC
until
the
modulator
level is
equal
to
or
less
than
the
—1
dB
reference
level.
The
slope
DAC
Is
stepped
down
from
the
peak
until
the
same
reference
threshold
is
reached.
If
the
slope
DAC
goes out
of
range
before
it
reaches
the
—1dB
reference level,
the
routine
searches
the
other
side
of
the
passband
to
the
same
modulator
threshold
present when
the
slope
DAC
reached
the
end
of
its
range.
The
slope
DAC
is
set
to the midpoint of
the
two
values,
and
the
original
power
is
restored.
Because
the
SYTM
passband
can
vary
with
power
level, peaking
is
done
at
the
current
ALC
power
level.
In
the
fundamental
band,
the SYTM YIG
sphere
may squeg
if
too
much
power
is
applied.
To
prevent
this
from interfering
with
peaking,
the
maximum
ALC
power
setting
(in
the
fundamental
band
only)
is
0
dBm
during
the
coarse search,
and
+10 dBm for
fine
search.
Once peaking
is
completed,
the
original
power
is
restored.
When
the
instrument
goes
unleveled,
the
current
driving
the
ALC
modulator
is
turned
off
to
give
maximum
available
power.
The
MODLVL line
still
gives
an
indication of the detected
power
out
of
the
SYTM,
with
a sensitivity
of
30
mV/dB.
The
absolute voltage
level
shifts
by
about
1V
when
the instru¬
ment
goes
unleveled,
but
the
incremental
level
remains
valid. Because
the
peaking routine
uses
incremental
changes,
the
absolute
level
shift
poses
no
problem
to
the
peaking
routine.
Initiate SYTM
tracking
by
either
pressing
[SHIFT] [PEAK]
on
the
front
panel, or
remotely
program¬
ming
"SH
RP"
over
the
HP-IB.
Each
band
is
tracked
independently.
To track
a
band,
a
single
band
sweep
is
set
and
the
sweep
is
stopped
at
several
points
across
the
band.
The
number
stored
in
the
calibration
constant
represents
the
least
squares
analysis
of the
straight
line
fit
for
the
slope
DAC
numbers
returned
from
the
peaking
routine.
If
the
least
squares
number
is
out
of
the
slope
DAC
range,
the fault
light
turns on
with
the
TRK
indicator
flashing.
In
band
1,
the
SYTM
is
peaked
at
2.3
GHz,
and at
1
GHz
steps from
3
to
7
GHz.
In
band
2,
the
SYTM is
peaked
at
6.9
GHz,
and
at
1
GHz
steps
from
7.5
to
13.5
GHz.
In
band
3,
the
SYTM
is
peaked
at
13.4
GHz,
and
at
1
GHz
steps
from
14
to
20
GHz.
In
band
4
(HP
8340B), the
SYTM
is
peaked
at
19.8
GHz,
and
at
1
GHz
steps from
20.5
to
26.5
GHz.
H-IO
RF
Section
Theory
of
Operation
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English