Method of and arrangement for demodulating a frequency-modulated input signal

Abstract From the Canadian patent

23, ABSTRACT:, For determining the half-cycle durations of the input signal which is presented as a sequence of sampled values, its zero crossings are approximated too by lines which interconnect the from sampled values of different sign on both sides of the zero crossing. The half-cycle duration is derived from the number of sampled values within a period, i.e. between two consecutive zero crossings, and from the time intervals at the beginning and end of each half-cycle determined by the intersection of the approximation line with the axis. The time intervals at the beginning and end of each period are corrected for a more accurate determination of the duration and the time intervals …