Extracting data from a coded signal by measuring pulse duration

The present invention demodulates a coded signal, such as a frequency modulated (FM) signal by measuring the duration of pulses of the coded signal using a high frequency logic clock signal. An edge detector (100, Fig. 2) generates an edge pulse whenever a transition in the coded signal occurs. A time counter (12, Fig. 2) counts the cycles of the high frequency logic clock between the occurrence of two subsequent edge pulses. Then a window comparator (16, Fig. 2) compares the cycle counts with predefined count ranges and generates the time result signal, e.g. 1t, 2t, 3t or >3t. A decoder state machine (20, Fig. 2) post-connected to said comparator samples the time results at every edge pulse, generates a data clock with the decoded data bit (0 or 1) and indicates a frame start signal. The present invention provides demodulation apparatus which is less expensive than a PLL.