Frequency Tracking Using Digital Cavities

Abstract: Digital cavities are efficient algorithms for comb filters with very low computational costs. They have been used to precisely measure the amplitude and phase of high frequency signals (few giga samples per second) from data acquired by high speed digitizers 80 GSps. However, the previous measurements were done offline as the serial processors used in the analysis could not cope with the large data acquisition rate. In this project, we have implemented digital cavities in an FPGA architecture to measure amplitude and phase of signals in real time. Moreover, we have implemented multiple digital cavities that are tuned to slightly different frequencies, that process data in parallel. Based on the interpolation of the responses from each digital cavity, we have also developed algorithms which allows for tracking the change in frequency of the signal. These new advances are expected to be very useful 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.