| 摘要 |
Communications systems, and particularly portable personal communications systems, such as portable phones, are becoming increasingly digital. The tendency towards digital systems has come about, in part, because digital systems may operate on less power than their analog counterparts. One area that has remained largely analog, however, is the modulation and RF amplifier circuits. To produce a RF frequency waveform a class D switching type amplifier is used. The output of the class D amplifier is coupled to an integrator, to create an analog signal. The analog signal coupled to a resonant circuit, to shape the output waveform into a sinusoidal RF broadcast signal. The waveform of the class D amplifier is duty cycle modulated by a combination signal representing the combination of desired amplitude modulation of the broadcast signal and the desired average power level desired. In addition the disclosure gives examples of digital modulation using a Digital Sigma Delta Modulator, and a Digital Programmable Divide Modulator. The disclosure further discloses using the digital modulation techniques and class D amplification techniques together to broadcast a PSK signal that has been decomposed into amplitude and phase components.
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