SWITCHED-MODE HIGH-LINEARITY TRANSMITTER USING PULSE WIDTH MODULATION

摘要

A QAM transmitter is disclosed that may reduce the frequency of local clock signals and/or reduce the switching frequency of driver circuits when generating a QAM output signal for transmission. The QAM transmitter may generate a number of PWM signals indicative of in-phase (I) and quadrature (Q) signal components, and then use one or more selected even-order harmonics of the PWM signals to generate the QAM output signal. Odd-order harmonics of the PWM signals may be suppressed by selectively combining the PWM signals, and any remaining unwanted even-order harmonics may be suppressed using filters.

主权项

1. A quadrature amplitude modulation (QAM) transmitter, comprising:
a baseband circuit to generate an in-phase (I) signal and a quadrature (Q) signal; a first circuit, having inputs to receive the I signal and a first clock signal, to generate a first pulse-width modulated (PWM) signal; a second circuit, having inputs to receive an inverted I signal and the first clock signal, to generate a second PWM signal; a third circuit, having inputs to receive the Q signal and a second clock signal, to generate a third PWM signal; a fourth circuit, having inputs to receive an inverted Q signal and the second clock signal, to generate a fourth PWM signal; a first signal combiner, coupled to the first and second circuits, to generate an output I signal in response to one or more even-ordered harmonics of the first and second PWM signals; a second signal combiner, coupled to the third and fourth circuits, to generate an output Q signal in response to one or more even-ordered harmonics of the third and fourth PWM signals; and a summing node to generate a QAM output signal in response to a summing of the output I signal and the output Q signal.