Keysight Technologies N5511A, User Manual

Page: 95 / 369

N5511A Phase Noise Test System User’s Guide 95
Absolute Measurement Fundamentals
Calibration
Double-sided Spur
The double-sided spur method, along with single-side spur is the most
accurate user calibration. This calibration method conveniently needs no extra
RF source, if the DUT is capable of being phase or amplitude modulated at the
carrier frequency. When performing a double-sided spur user calibration, the
calibration is done under actual measurement conditions so all non-linearities
and harmonics of the phase detector are calibrated out. The offset frequency or
modulation frequency must be between 10 Hz and the maximum (See the
table from the “Measured Beat Note” section on page 87 . The resultant
sideband spurs from the phase modulation must have amplitudes that are
-100 dB and -20 dB relative to the carrier amplitude.
Advantages
— Calibration is done under actual measurement conditions so all
non-linearities and harmonics of the phase detector are calibrated out.
— No additional RF source is needed
Disadvantages
— Requires a phase modulator which operates at the desired carrier
frequency.
— Requires RF spectrum analyzer for manual measurement of Φ M sidebands
or preferably a modulation analyzer.
The double-sided spur user calibration method connection setup is the
standard absolute measurement setup shown in Figure 5-1 on page 56 and in
Figure 5-3 on page 58 . Figure 5-32 shows an example of a phase modulated
carrier with the upper side band measuring -40 dBc at a 10 kHz offset.