Close-In Phase Noise Measurements of Injection Locked Oscillators

Independent implementation and verification is described for a published injection locking approach to close-in phase noise measurements. Experimentation was conducted to study the sensitivity of the measured results to various parameters within the system, including oscillator-under-test power level, and the need for an isolator in the test system. The results show that the phase noise measurement is relatively robust to power level variations within the system, and that the isolator, although bandwidth limiting, does perform a necessary role for the measurement. A pair of 1.4GHz free running oscillators are used as test cases in this study. Measurements from the injection locking technique are compared to those made using the more traditional detector and discriminator methods.