Keysight Technologies, Inc.
System and method for measuring phase noise

Abstract:

A system and method are provided for measuring absolute phase noise of a test signal from a DUT using a reference source for generating an RF reference signal, a mixer for mixing the RF reference signal and an input signal, an adjustable DC voltage source for outputting a DC voltage, and a PLL for maintaining a 90 degree quadrature between the RF reference and input signals. The method includes mixing RF calibration signals and the RF reference signal to provide calibration phase signals, at least one of the RF calibration signals having one-tone AM modulation; monitoring modulation tone frequency of the one-tone AM modulation; adjusting the DC voltage output by the adjustable DC voltage source to minimize a voltage level of the tone frequency being monitored; mixing the test signal and the RF reference signal to provide a measurement phase signal for measuring absolute phase noise of the test signal.