HP 8340b User Manual

Swept
Mode
Single Band
Sweeps
>5
MHz.
In
swept
mode,
the
instrument phase-locks
the
YO
at
the
beginning
of
each
sweep,
undergoing
the
same sequence
of
events as
in
the
CW
mode.
The
sample
and
hold
on
the
A49
YO
loop
phase
detector
assembly
holds
the
YO
TUNE
error
signal
constant
at
its
phase-
locked
value.
In
the
hold
mode
the
YO
phase-lock loop
is
opened,
allowing
a
ramp
signal, VSWP,
to
be
summed
into
the
PRETUNE
signal
and
subsequently
applied to
the
YO
main
coil
to
sweep
the
YO.
This
sequence
is
called lock
and
roll.
The
processor
writes
the
sweep
time
and
sweep
width
numbers
to
to
the
ASS
sweep generator
assembly,
which
generates
the
voltage
ramp,
VSWP,
with the
appropri¬
ate
slope
and
duration.
The
ASS
sweep
generator
assembly
also
generates
a
0
to
10V
ramp
(MKR
RAMP),
that
has
the
same
duration
as
VSWP.
Because
of the
inherent delay
characteristics
of
the
YO
during
sweeps,
a
ramping compensation
voltage,
VCOMP,
is
summed
with
PRETUNE
in
the
ASS
YO
driver.
VCOMP is
generated
by
summing
correction
data from
the
processor
with
the
VSWP
ramp.
This
is
done
in
the
YO
Delay
Compensation
portion
of the
AS4 YO
pretune
delay
compensation assembly.
At
each
YO
sweep
retrace,
the
YO
retrace
kick
pulse
generator
(on
the
AS4
assembly)
produces
a
pulse
with
a
programmable
width
(via
the
microprocessor)
that
is
sent
to
the
ASS YO
driver.
This
signal
causes
current
drain
from
the
YO
tuning coil.
When
activated,
this
momentarily
tunes
the
YO
lower
in
frequency
(by
about
2.S
GHz)
to
remove
the
effects
of
YO
magnetic
hysteresis.
Multiband
Sweeps.
The
operation
of
the
sweep
generator/YO
loop
circuitry
in
multiband
sweeps
is
essentially
the
same
as
in
single
band
sweeps.
The
difference
is
that
at each
band
crossing,
the
YO
is
retraced
and
the lock
and
roll
sequence
is
initiated
again.
This
produces
a
pause
in
the
instrument
sweep
at
each bandcrossing
while
each loop
is
being
reset.
VSWP is
reset
to
zero
volts
between
bands,
however
the
MKR RAMP
signal
remains
fixed
at
its
end-of-band value
until
the
lock
and
roll
sequence
for
the
next
band
begins.
The
sum
of
the
durations
of
the
ramping
portions
of
MKR RAMP
will
still
equal
the
selected
instrument
sweep
time.
VSWP
has
a
sensitivity
of
+2
V/GHz
of
YO
frequency.
The
distinction
between
YO
frequency
and
instrument frequency
is
important
because
the
instrument
frequency
is
not necessarily
the
same
as
the
YO
frequency.
In
the
10
MHz
to
2.3
GHz
band
(band
0).
the
YO
output
is
heterodyned
with
a
3.7
GHz
oscillator.
Consequently,
the
YO
frequency
is
3.7
GHz
higher than
the
instrument
frequency.
In
the
higher
bands
(SYTM
multiply
bands
1
through
3
or,
in
the
case
of the
HP
8340B,
band
4),
the
instrument
frequency
is
derived
from
the
first,
second,
third,
or
fourth
multiple of
the
YO
frequency as
shown
in
Table
D-1.
Table
D-1.
RF
Output
Frequency
vs.
YO
Frequency
Band
0
1
2
3
4*
*HP 8340B
only
Multiplication
Heterodyned
(mixed)
YO
fundamental used
Multiplied
by
2
Multiplied
by
3
Multiplied
by
4
RF
Output
Frequency
0
01
to
2.3
GHz
2.3
to
7.0
GHz
7.0to13.5GHz
13.5to20.0GHz
20
0
to
26.5
GHz
YO
Frequency
3.71
to
6
2
GHz
2.3
to
70
GHz
3.5
to
6.75
GHz
4.5
to
6.67
GHz
5.0
to
6
625
GHz
HP
8340B/41B
Sweep Generator
-
YO
Loop Theory of
Operation

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English