A Study on Fully Digital Phase Noise Measurement System with Reduced Number of Analog-to-Digital Converters and Reference Oscillators

In this paper, we propose a new fully digital phase noise measurement method in which the oscillation signal of the oscillator under test is sampled directly by analog-to-digital converters and the phase noise spectral density is calculated by digital numerical calculation. In precision phase noise measurement, it was necessary to prepare a reference oscillator in addition to the oscillator to be measured. This is because the phase noise measurement required comparison with the reference phase. Furthermore, the fully digital phase noise measurement, four analog-to-digital converters were required to reduce the phase noise of the analog-to-digital converter itself and the clock source for driving. We have reviewed the configuration of a fully digital phase noise measurement system and demonstrated that it is possible to measure phase noise with fewer components. As a result, our method requires only two analog-to-digital converters and does not require a reference oscillator. As an application, if four analog-to-digital converters are used as before, simultaneous measurement of the phase noise of two oscillators and simultaneous measurement of the signal of the source oscillator and the synthesized signal of the frequency synthesizer can be performed.