Approved
Frequency Tracking Using Digital Cavities
Fredrik Zetterblom (2014)
Start
2016-01-18
Presentation
2016-09-23 13:15
Location:
E:3139
Finished:
2017-01-27
Master's thesis:
Abstract
Digital cavities are efficient algorithms for comb filters with very low computational costs. The digital cavities have been used in a previous master thesis project to precisely measure the amplitude and phase of high frequency signals (few giga samples per second) from data acquired by high speed digitizers (80 giga samples per second). However, the previous measurements were done offline as the serial processors used in the analysis cannot cope with the large data acquisition rate. In this candidate project we have implemented a measurement system based on an FPGA architecture with multiple digital cavities to measure the amplitude and phase of signals in real time. The signals from a fast photodiode, which monitored the output of a mode locked laser at the repetition rate of about 70 MHz, was digitized by a fast digitizer at the rate of 1.25 GSa/s. The data were analyzed in real time to measure the repetition rate of the laser. Moreover, we implemented multiple digital cavities that were tuned to slightly different frequencies, which processed the data in parallel. Based on the interpolation of the responses from each digital cavity, algorithms to track the change in frequency of the signal were also developed. The tests showed that the repetition rate of the laser fluctuates, vibrations in the laser table, by about few kHz. The new advances made in this project are expected to be useful a wide range of applications such as in measuring the drifts in radio and microwave frequencies that are commonly used in FM broadcasting, frequency-shift keying, power systems, laser spectroscopy, synchrotrons, particle accelerators, etc.
Supervisor: Khadga Kharki (Dept. Chemical Physics) and Liang Liu (EIT) and Rakesh Gangarajaiah (EIT) and Fredrik Edman (EIT)
Examiner: Erik Larsson (EIT)