Keysight Technologies N5511A, User Manual

Page: 179 / 369

N5511A Phase Noise Test System User’s Guide 179
Residual and Additive Noise Measurement Fundamentals
Calibrating the Measurement
A reference source is then inserted. The power level of this calibration source is
adjusted to the same output power as the measured output power of the
power splitter. The splitter is terminated at this path.
Figure 7-10 Calibration Source Beat Note Injection
At this point, the measurement can be started. Once a beat note is established
and within the system's acceptable range, the calibration constant will be
measured. The calibration source is then removed, the splitter's termination
removed, and this path of the splitter is connected directly to the LO input of
the phase detector module.
Quadrature will need to be established using the phase shifter and the
quadrature meters in the display. Quadrature is achieved when the meter on
the front panel of the phase noise interface is set to zero.
This method can be used in a dual channel setup as well, where the calibration
is performed on each of the separated phase detectors.
See the absolute measurement calibrations section on
page 86 for more
detailed theory about how beat note calibration works.