Patent ID: 8027408

Claim:
An ASK modulator comprising: a Manchester encoder that generates Manchester-encoded signals by applying Manchester encoding to an input signal sequence; a waveform shaping unit that generates shaped signals from the Manchester-encoded signals, the shaped signals are band-limited encoded signals and minimum values of waveforms of the band-limited encoded signals are limited; and a modulating unit that modulates carrier waves based on the shaped signals, wherein the waveform shaping unit comprises a band-limiting unit that limits frequency bands of the Manchester-encoded signals, and a signal-limiting unit that detects and limits the minimum values of the waveforms of the band-limited encoded signals generated by the band-limiting unit, and wherein the signal limiting unit comprises a control signal generating unit that generates a control signal responsive to the Manchester-encoded signals, a minimum value detector that detects a value of the waveform of the band-limited encoded signals responsive to the control signal, and that generates a bottom signal indicative of the detected value of the waveform, and a clipper unit that limits the waveforms of the band-limited encoded signals to be greater than the detected value of the waveform responsive to the bottom signal, to provide the shaped signals.