Keysight Technologies N5511A, User Manual

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58 N5511A Phase Noise Test System User’s Guide
Absolute Measurement Fundamentals
The Phase-Lock-Loop Technique
Dual Channel
N5511A has the option for a second phase detector module, which allows for
dual-channel cross correlation. In a dual channel setup, the DUT signal is split
to provide the input signal to each of the phase detector modules. Two
separate reference sources are required to provide a reference to each of the
phase detectors. The result of this setup is having two separate single channel
measurements with a common DUT signal, allowing for uncorrelated noise of
the two references as well as the noise contributions from the detectors to be
removed by cross-correlation.
Figure 5-3 Dual Channel Phase Lock Loop
A closer look:
Figure 5-4 shows a high-level walk-through of the theory behind the dual
channel PLL measurement technique.
Figure 5-4 Dual Channel PLL Theory