Rohde & Schwarz SMU200A - Page 46

R&S SMU200A Test Procedures
1007.9845.82 1.19
E-12
Residual FM
Test assembly
See section "
Test Assembly for SSB Phase Noise", page 1.4.
Test Method
The Residual FM is calculated from the phase noise measurement data. The
measurement setup and procedure is identical to the phase noise measurement.
Measurement
 Settings on DUT
:
- Fr
equency 1 GHz
- Level P
max
, unmodulated
 Setting on R&S FSQ analyzer:
- Coupling = DC
- FILTER-TYPE = FFT
- RBW = 10 Hz
- DETECTOR = SAMPLE
Set up measurement and calibrate as described under SSB Phase Noise
Measurement
 The Residual FM is defined as
dfffL
f
f

=

max
min
2
)(2 
with
(
)
fL

being the single side band phase noise.
Set Analyzer Start and Stop Frequency t
o
HzF
start
300= and kHzF
stop
3=
Read Trace Data
(
)
µ T with
[
]
N,1 µ and 625
=
N from R&S FSQ
analyzer and calculate the summed residual FM of the DUT and the Referenc
e
S
ignal Generator
()
()

=











+

=
N
startstop
start
startstop
dBPT
N
FF
F
N
FF
RBW
ref
1
2
10/)46(
1
1
10
2
µ
µ
µ
with
ref
P being the reference level from the SSB Phase Noise Measurement
with 40 dB reduced level with 20 kHz detuned frequency.
The sum of the residual FM of the DUT and the Reference Signal Generator
should be well below the guaranteed value of the DUT, so no correction of the
measurement result is necessary.
 Repeat measurement with a test bandwidth of 20 Hz to 23 kHz in two steps
:
F
irst sweep from 20 Hz to 1 kHz with a RBW of 3 Hz and then sweep from
1 kHz to 23 kHz with a RBW of 100 Hz. Calculate the Residual FM for both
measurements with the formula given above. The Residual FM from 20 Hz-
23 kHz is:
2
231
2
1202320 kHzkHzkHzHzkHzHz 
+= 