Patent ID: 7450666

Claim:
An ASK demodulation device for demodulating a modulated signal which is ASK (Amplitude Shift Keying)-modulated with a data sequence obtained by Manchester-encoding NRZ (Non-Return to Zero) data, the ASK demodulation device comprising: a delay section for delaying a detected signal obtained from the modulated signal by less than one bit time in the NRZ data, and outputting a resultant signal as a delayed signal; a subtraction section for performing subtraction between the delayed signal outputted from said delay section and the detected signal, and outputting a resultant signal as a subtracted signal; a clock extraction section for extracting, from crossing points at which the subtracted signal outputted from said subtraction section and a threshold value cross each other, crossing points whose time interval is more than or equal to (Tb−α) and less than or equal to (Tb+β) (wherein 0<α≦Tb/8, 0<β≦Tb: Tb is one bit time in the NRZ data), and outputting a synchronous signal synchronized with the extracted crossing point; a clock recovery section for synchronizing a clock signal having a same rate as a bit rate of the NRZ data to a phase of the synchronous signal outputted from said clock extraction section, and outputting a data clock signal; and a determination section for determining a polarity of the subtracted signal outputted from said subtraction section in accordance with the data clock signal outputted from said clock recovery section, and outputting a determination result as the NRZ data.