HP 8340B Manual page 49

4-9.
SINGLE SIDEBAND PHASE NOISE (Cont'd)
PHASE NOISE
MEASUREMENT
obtains phase noise data
for
DUT
frequencies of 2.202, 6.902,
13.402,19.502,
and,
in
the case of the HP 8340B,
26.032 GHz. These
specific frequencies typically
have the
worst
case
phase
noise for the HP
8340B/41B. The DUT
is adjusted for the test frequency
and then the LO
frequency
is
adjusted to obtain
a
1
MHz
± 0.9 Hz
IF. A
signal to
noise level
(IF
to
phase noise level at
30
Hz, 100 Hz, 1
kHz,
10
kHz,
and 100
kHz
offsets from IF) measurement
is
performed using the OFFSET and NOISE LVL
functions
of the HP 3585A and
the results are recorded
as the Measured Noise Level (MNL, measured
in dBc).
PHASE NOISE CALCULATION
takes the data obtained for
MNL
and adds and subtracts the calibra¬
tion data and
a
3 dB correction factor
to obtain the actual phase noise. The formula that
is used
is:
Actual Phase Noise
=
MNL
+
IFCD
-
CD
-
3 dB
IFCD
is the response of the
1
MHz notch filter at 1
MHz.
Since
the
filter
is
not installed during the 10 Hz,
100
Hz and
1
kHz measurements, IFCD
=
0. During the 10 kHz and 100
kHz offset measurements, the
notch filter attenuates the IF causing the power difference between the
IF
and the phase noise to be
smaller than
it
actually
is,
therefore IFCD must be added
to
MNL
to
correct this.
The system's
fre¬
quency response (LCD) causes
the difference between the
IF
level and the
phase noise
level to be
greater than
it
actually
is,
therefore CD must be subtracted from
MNL.
A
factor of
3 dB
is
subtracted
from
MNL
to correct
Tor
the LO's phase
noise contribution.
SPECTRUM ANALYZER
LOCAL OSCILLATOR
^
ADAPTER
APC-3.5(«i)
to N(m)
(B341B
ONLY)
50-75n
^
RF
OUTPUT
r"-\
AOAPTER
APC-3.5(f)
to APC-3.5(f)
(8340B ONLY)
^
ADAPTER
APC-3.5(f)
to N(ffl)
(8341B ONLY)
SEMi-RiQiO
CABLE
Figure 4-9.
Single Sideband Phase Noise
Test Setup
Performance Tests
HP 8340B/41B