Agilent Technologies E1420B, Руководство пользователя

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Residual Measurement Fundamentals
7
Agilent E5505A User’s Guide 223
3 Measure the carrier-to-single-sided-spur ratio out of the coupler at the
phase detector’s modulated port and the offset frequency with the RF
spectrum analyzer (
Figure 160 ). The RF calibration source should be
adjusted such that the sidebands are between –30 and –60 dB below the
carrier and the frequency offset of the spur between 10 Hz and 50 MHz.
4 Measure the carrier-to-spur ratio of the non-modulated side of the phase
detector (
Figure 161 on page 224). It must be at least 20 dB less than the
spur ratio of the modulated port. This level is necessary to prevent
cancellation of the modulation in the phase detector. Cancellation would
result in a smaller phase detector constant, or a measured noise level that is
worse than the actual performance. The isolation level is set by the
port-to-port isolation of the power splitter and the isolation of the –20 dB
coupler. This isolation can be improved at the expense of signal level by
adding an attenuator between the coupler and the power splitter.
Table 35 Acceptable Amplitude Ranges for the Phase Detectors
Phase Detector
50 kHz to 1.6 GHz 1.2 to 26.5 GHz
1
1 Phase noise test set options 001 and 201
Ref Input (L Port) Signal Input (R Port) Ref Input (L Port) Signal Input (R Port)
+
15 dBm
to
+
23 dBm
0 dBm
to
+
23 dBm
+
7 dBm
to
+
10 dBm
0 dBm
to
+
5 dBm
Figure 160 Carrier-to-spur ratio of modulated signal
Power
splitter Phase
detector
Source
Calibration
source
-10 dB
attenuator
E5505a_carrier_spur_ratio
01 Mar 04 rev 1
Optional line
stretcher
-20 dB
coupler
Test set
Signal
input
Ref input
output
Coupler
port
input