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HP
8350B
Sweep Chcilliltor
o
HP 11664A
Detector
HP
5344S
Microw8vI
Source Synchroniur
MODE
Switch
to
"SUBHMNC"
F,gure 5.
Transmission
measurement using
SUBHA
RMONIC/
OFFSET Lock. The
co
unter
sa mples the
rear panel
AUX
OUTPUT.
samples the AUX OUTPUT of the plug-in, which
is
the
plug-in
'
s
fundamental
YIG
tuned
oscillator (YTO) output.
The frequency of
this output
is simply related to the RF
output
in one of two ways.
1.
Offset
locking
-
For HP 83590
series
RF plug-ins tha
t
operate
in
the
low
frequency range (10 MHz to 2
.
4 GHz
for
the
HP 83592A)
,
the
sweeper
employs
a
heterodyne
technique
.
The YTO frequency, sampled
on
the
AUX OUTPUT, is mixed with a
fixed
cavity oscillator (3.8
GHz for all
HP
83590
series
plug-ins
that
operate in this range), to
obtain
a signal in the range from 10 MHz to
2
.
4 GHz.
The back panel AUX OUTPUT
is therefore offset from the front
pa
n
el
RF
by
this
fixed
cavity
oscillator
frequency
.
This
offset
must be entered manually
on
the
counter, so
it can display
the
RF
output
frequency
instead
of
the
fundamental YTO frequency.
2. Subharmonic locking
-
When higher
frequencies are used the HP 83590
ser ies or HP 86290 ser ies RF plug":'in
uses a frequency multiplier
,
and
the YTO frequency
on
the
AUX
OU
TPUT
is
harmonically
related
to
the
front
panel output
by an
integer
multiple.
The
HP
53445
can
automaticall
y
calculate
these fre-
quency
multipliers
for
integer
values from
1
to 4,
and
the counter
displays
the
multi
plied
RF
frequency.
Higher
values can be
entered
manually
.
Instructions
for using the
subhar-
monic
/of
fset locking are included
at the end
of
this section
.
Subharmonic/
offset lock-
ing
is
strongly recommended
for the HP
83590
series
and the HP 86290 series
RF
plug
-
ins
because
of these advantages:
1.
The
sweeper
plug-
i
n
I
s
AUX
OUTPUT
is
sampled
,
so there is no need t
o
take
costly power from the front panel RF
with a
coupler
or power splitter.
2. The range
of
frequencies that
can
be
phase locked by the HP
53445
can
be
extended
beyond
the range
of
the
counter, because the counter always
counts
the
fundamental
YTO
fre-
quency
and
adjusts
its
display
according to the offset or harmonic
nu mber
.
The range becomes the
same
as t
h
e range of the RF plug-in
.
3
.
The internal 27.8 kHz square wave
modulation function
of the
HP 8350B
can be used, so there is no need for
an
external
modulator.
(Normal
mode requires external modulation,
since
the
counter must sample an
unmodulated signal from the
front
panel.
)
OSING
5OBBARMONIC/OPPSBT
LOCKI NG
If you are using any
of the sweeper
plug-ins l
i
sted
in
table 1,
you can take
advantage of the
subharmonic/o
ffset locking
function of the HP
53445
.
This
enables
you
to use a much simpler RF configuration like
the one shown in figure 5.
TABLE
1
P£m-INS
wrm
NlX aJ'm1r
PUR
SI:JIlIlAIM:N[C/OPl'SKr
UXXIH:;
!\OX 00l'PUT
RilNSE OF
RilNSE OF
FR&;UfN:Y
FR&;UfN:Y
OFFSE:r
SUB~IC
RilNSE
RilNSE
LCCKIN:i
LCCKIN:i
PWG-IN
(GHz)
(GHz)
(GHz)
(GHz)
HP 83570A
18.0 - 26
.
5
9-13.25
None
18-26
.
5
HP 83590A
2 - 20
2
- 7
lble
2 -
20
HP 83592A
0
.
01 - 20
2.3
- 7
0
.
01
-
2.3
2.3 - 20
HP 83592B
0
.
01 - 20
2.3
-
7
0
.
01 - 2.3
2.3
- 20
HP 83592C
0
.
01 - 20
2.3 -
7
0.01
-
2.3
2
.
3
- 20
HP 83594A
2 -
26
.
5
2 - 7
None
2
- 26
.
5
HP 83595A
0
.
01 - 26
.
5
2.3
-
7
.
01
-
2
.
3
2
.
3
- 26.5
HP 86251A
7
.
5 - 18
.
6
2.5 -
6.2
lble
7.5 - 18
.
6
HP 86290A
2 -
18
2 - 6.2
None
2
-
18
HP 862908
2 - 18.6
2 - 6.2
None
2
- 18.6
HP 86290C
2 - 18.6
2
- 6
.
2
None
2
-
18.6
8
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