Keysight Technologies N5511A, Руководство пользователя

Страница: 182 / 369

182 N5511A Phase Noise Test System User’s Guide
Residual and Additive Noise Measurement Fundamentals
Calibrating the Measurement
Double-Sided Spur
This calibration option has the following requirements:
— One of the input frequency sources must be capable of being phase
modulated.
— The resultant sideband spurs from the phase modulation must have
amplitudes that are -100 dB and -20 dB relative to the carrier amplitude.
— The offset frequency or modulation frequency must be between 10 Hz and
maximum (See the "Measured beat note" section on page 87 ).
Advantages
— Requires only one RF source.
— Calibration is done under actual measurement conditions so all
non-linearities and harmonics of the phase detector are calibrated out.
Disadvantages
— Requires RF source used to have modulation capabilities else a phase
modulator which operates at the desired carrier frequency.
— Requires audio calibration source.
— Requires RF spectrum analyzer for manual measurement of
Φ
M sidebands
or preferably a modulation analyzer.
For a dual-sided spur cal, turn on phase modulation on the stimulus to create a
narrowband sideband at a known amplitude and offset relative to the carrier.
Enter the offset and level in the Known Spur Parameters section in the Cal tab
of the Define Measurement menu.
Figure 7-12 Known Spur Parameters
Because the calibration is performed under actual measurement conditions, the Double-sided
Spur Method and the Single-sided Spur Method are the two most accurate calibration methods.
Most phase modulators are typically narrow-band devices; therefore, a wide range of test
frequencies may require multiple phase modulator.