A method (300) includes selecting a first output (262, 262a) from a phased locked loop (260) and sending the first output from the phased locked loop to a first device under test (214, 214a) and a second device under test (214, 214b). The method includes adjusting a first phase rotator (226, 226a) connected to the first device under test to a first rotator phase value (228, 228a) of zero. The method includes determining a collection of phase detector values (252) of a phase detector (250) connected to the second device under test by adjusting a second phase rotator (226, 226b) connected to the second device under test to sweep through a phase range. The method includes measuring the phase detector values of the phase detector, and determining a phase detector gain (254) of the phase detector by averaging the collection of phase detector values and storing the phase detector gain.