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HP 8340b Operating Instructions

HP 8340b
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The
amount
of
accuracy
degradation
as
the
pulses
are
narrowed
varies
with
frequency,
temperature,
and
power
level.
The
variation
with
frequency
and
temperature
is
due
to
detector
characteristics
and
RF
envelope
shape.
The
detector
has
a
finite
rise
time
determined
by
its
output
resistance
and
shunt
capacitance.
At
some
frequencies
there
is
a
slight
amount
of
overshoot
on
the
RF
envelope,
which
tends
to
charge
the
shunt
capacity
faster,
resulting
in
better
narrow
pulse
leveling
accuracy.
A
much
more
pronounced
effect
is
due
to
the
use
of
a
different
detector
for
frequencies
below
2.3
GHz.
The
low
band
detector
has
a
higher
shunt
capacity
in
order
to
make
it
function
properly
at
low
frequencies.
For
operation
below
400
MHz,
a
large
amount
of
additional
capacity
is
switched
in,
enabling
detector
operation
down
to
10
MHz.
Trace
3
in
Figure
3-34
is
representative
of
operation
above
2.3
GHz,
where
pulse
accuracy
is
within
1.5
dB
at
100
nsec.
From
0.4
to
2.3
GHz,
the
slower
rise
time
gives
a
1.5
dB
specification
at
200
nsec
width.
Operation
below
0.4
GHz
is
not
specified,
but
typically
is
within
1.5
dB
at
2
jisec
width.
The
detector's
rise
time
depends
on
its
output
resistance,
which
drops
with
increasing
temperature.
Therefore,
the
narrow
pulse
leveling
accuracy
improves
at
higher
operating
temperatures.
Narrow
pulse
accuracy
is
also
power
level
dependent.
Very
high
ALC
levels
reduce
the
detector’s
output
resistance,
improving
rise
time
and
therefore
accuracy.
The
rise
time
of
a
log
amp
is
dependent
on
signal
level,
degrading
with
small
signals.
In
low
band
(<2.3
GHz)
the
log
amp
is
faster
than
the
detector
at
any
ALC
level
above
—10
dBm,
so
there
is
no
degradation
due
to
the
log
amp
in
any
coupled
mode
operation.
In
high
band,
the
log
amp
rise
time
at
ALC
=
—10
dBm
is
slow
enough
to
be
comparable
to
the
detector
rise
time.
Therefore,
as
power
is
decreased,
the
leveling
accuracy
slightly
degrades
(narrow
pulse
amplitude
grows
relative
to
CW).
The
leveling
specifications
apply
to
coupled
operation,
with
no
AM;
in
other
words,
ALC>
—10
dBm.
Using
the
decoupled
mode
or
AM,
the
ALC
level
can
be
driven
down
to
—20
dBm
or
lower.
At
—20
dBm,
the
log
amp
slows
down
enough
that
high
band
accuracy
is
typically
1.5
dB
at
150
nsec,
3.0
dB
at
100
nsec.
Decoupled
mode
can
also
be
used
to
operate
the
ALC
at
high
levels
and
achieve
better
narrow
pulse
accuracy.
The
above
discussion
applies
to
internal
leveling
only.
Externally
leveled
pulse
performance
will,
of
course,
depend
on
the
detector,
but
even
with
a
perfect
detector
the
external
leveling
circuitry
is
not
as
fast
as
internal.
It
typically
will
level
pulses
wider
than
2
psec.
HP
8340B/41B
Operating
Information
3-111

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HP 8340b Specifications

General IconGeneral
BrandHP
Model8340b
CategoryInverter
LanguageEnglish

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