SYSTEM FOR ANALYSING THE FREQUENCY OF A SIGNAL, A METHOD THEREOF AND A SYSTEM FOR MEASURING THE RELATIVE PHASE BETWEEN TWO INPUT SIGNALS

摘要

There is provided a frequency analysis system, comprising: an analogue to digital converter (10) having a sampling frequency f s ; a first band pass filter (12) and a second band pass filter (13), the first band pass filter and the second band pass filter being arranged in parallel with one another; and a feedback loop from an output to an input of the system, wherein the system has an initial centre frequency equal to a nominal frequency f 0 , and a revised centre frequency dependent upon the output of the system that is fed back into the input of the system, wherein the transfer functions of the first and second band pass filters have the same poles, and wherein the system is configured such that, when the centre frequency f c equals the frequency of the signal f i , the output of the first band pass filter is in phase with the input, the output of the second band pass filter lags the output of the first band pass filter at a constant phase of À/2 and the two band pass filters have equal gain amplitude. There is also provided a method for analysing the frequency f i of a signal and a phase measurement system based on the frequency analysis system.