HP 8753D - Page 153

Conversion Compression
Using the
Frequency Oset
Mode
Conversion
compression
is
a
measure of
the maximum
RF input
signal level,
where the
mixer
provides
linear
operation.
The
conversion
loss
is the
ratio of
the IF
output level
to the
RF input
level.
This
value
remains
constant
over
a specied
input power
range.
When the
input power
level
exceeds
a
certain
maximum,
the
constant ratio
between IF
and RF
power levels
will begin
to
change
.
The
point at
which the
ratio has
decreased 1
dB
is
called
the
1
dB
compression
point.
See
Figure
3-19
.
Figure
3-19.
Conversion
Loss
and
Output
P
ower
as
a
Function
of
Input
P
ower
Level
Example
Notice
that
the
IF
output
power
increases
linearly
with
the
increasing
RF
signal,
until
mixer
compression
begins
and
the
mixer
saturates
.
The
following
example
uses
a
ratio
of
mixer
output
to
input
power
and
a
marker
search
function
to
locate
a
mixer's
1
dB
compression
point.
1.
Set
the
LO
source
to
the
desired CW
frequency and
power
level.
CW
frequency
=
600
MHz
P
ower
=
13
dBm
2.
Initialize the
analyzer by
pressing 4
PRESET
5
.
3.
To
set the
desired CW
frequency
and
power
sweep
range
,
press:
4
MENU
5
N
NN
N
N
N
N
N
N
N
N
N
N
N
NN
N
N
N
N
N
N
N
N
N
N
NN
N
N
N
N
N
N
N
N
N
N
N
NN
N
N
N
N
N
N
SWEEP TYPE MENU
N
NN
N
N
N
N
N
N
N
N
N
N
N
NN
N
N
N
N
N
N
N
N
N
N
NN
N
N
N
N
N
N
N
POWER SWEEP
N
NN
N
N
N
N
N
N
N
N
N
N
N
NN
N
N
N
N
RETURN
NNNNNNNNNNNNNNNN
NNNNNNN
CW FREQ
4
800
54
M/ 
5
NNNNNNNNNNNNNNNNN
POWER
NNNNNNNNNNNNNNNNNNNN
NNNNNNNNNNNNNNNNNNNNN
PWR RANGE MAN
NNNNNNNNNNNNNN
NNNNNNNNNNNNNNNNNNNNNNNN
POWER RANGES
NNNNNNNNNNNNNN
NNNNNNNNN
RANGE 0
4
START
54
0 10
54
x1
5
4
STOP
54
10
54
x1
5
4. Make the connections, as shown in Figure 3-20.
3-28 Making Mixer Measurements