I wrote my diploma thesis about phase noise measurement near the carrier. Even more than a decade later the topic is still actual and critical, because phase noise influences the accuracy of our communication systems. It makes a difference in how good your smartphone works in the high frequency range e.g. Wi-Fi and cellular communication. This gets even more important when applied in critical system devices.
The diploma thesis was written in German, but with frequent requests in the past years, I decided to re-publish on my new site. Please feel free to reference, but do not place copies on websites.
The phase noise of voltage-controlled quartz oscillators is created by its fluctuations in the phase and causes a spreading of the spectrum.
The basics of noise, oscillators, PLL, and four-diode ring mixers as phase detectors are explained in this diploma thesis.
All of the following concepts of measuring phase noise have been evaluated:
- simplest method: measurement with the spectrum analyzer.
- frequency discriminator method
- frequency discriminator method with cross-correlation
- phase detector method
- phase detector method with cross-correlation
- phase detector method with PLL (phase locked loop)
- phase detector method with cross-correlation and PLL and one reference oscillator
- phase detector method with cross-correlation and PLL and two reference oscillators
The conclusion of this diploma thesis is, that phase noise measurements are possible from 3 Hz down to a noise floor of -132 dBm, based on available components in 2008.