<p>A technique of demodulating an ASK modulated signal whose modulation ratio is low is provided. A modulation ratio enhancement circuit (21) increases the modulation ratio of a current signal in which the amplitude shift keying modulation is performed by signal data. A branch section (22), an average value detecting section (23), a comparison section (24) and a buffer (25) constitute a demodulation section, which demodulates the signal data from the current signal whose modulation ratio is increased by the modulation ratio enhancement circuit (21).</p>
