Patent ID: 7495520

Claim:
A frequency-shift modulation device, comprising: a crystal oscillator circuit that produces a periodic reference signal at its output; a phase-locked loop circuit connected to the output of the oscillating circuit at its input and which produces a clock signal with fixed frequency at its output starting from the periodic reference signal; and a digital frequency-modulation circuit connected so as to receive a binary data signal intended to be transmitted at its input, and which produces a frequency-coded RF transmission signal at its output, two binary values of the data signal being converted by the digital circuit into two components of the RF transmission signal having respective frequencies shifted by different amounts with respect to an RF transmission channel, wherein the digital frequency-modulation circuit has a clock signal input connected to the output of the phase-locked loop circuit; said digital frequency modulation circuit itself comprising a 1-bit digital sigma-delta modulator with bandpass filtering, which produces the RF transmission signal at an output of said sigma-delta modulator, based on a series of numbers received at an input of said sigma-delta modulator.