Linear transmitter using predistortion

A transmitter for substantially linearly transmitting signals at a broadcast frequency, the transmitter comprising:

• a modulator for receiving digital data and mapping said digital data into an in-phase signal and a quadrature signal;
• an interpolator for increasing the sampling rate of said in-phase and said quadrature signal;
• a predistorter that modifies said in-phase and said quadrature signal into a predistorted in-phase signal and a predistorted quadrature signal, respectively;
• a digital quadrature modulator that combines said predistorted in-phase signal and said predistorted quadrature signal into a digital predistorted signal;
• a digital-to-analog converter that converts the digital predistorted signal into an analog predistorted signal;
• an analog upconverter for increasing the frequency of said analog predistorted signal to said broadcast frequency;
• a power amplifier that amplifies said analog predistorted signal from said analog upconverter;
• an antenna for broadcasting said analog predistorted signal from said power amplifier;
• a coupler for receiving a portion of said analog predistorted signal amplified by said power amplifier;
• an analog downconverter for decreasing the frequency of said analog predistorted signal received by said coupler;
• an analog-to-digital converter that converts the analog predistorted signal from the analog downconverter into a digital predistorted signal;
• a digital quadrature demodulator that converts said digital predistorted signal from said analog-to-digital converter into a feedback in-phase signal and a feedback quadrature signal;
• a trainer for comparing said feedback in-phase signal and said feedback quadrature signal with said in-phase signal and said quadrature, wherein said trainer modifies said predistorter such that the output of said power amplifier is consistent with said in-phase signal and said quadrature signal;
• and
• a controller coupled to said digital modulator, said predistorter, and said trainer, wherein said digital modulator, said predistorter, and said trainer are reconfigurable, said controller being capable of selectably providing reconfiguration signals to said digital modulator, said predistorter, and said trainer, whereby said digital modulator, said predistorter, and said trainer are selectably reconfigured.

A method for transmitting substantially linearly transmitting signals at a broadcast frequency, the method comprising:

• receiving digital data to be broadcast;
• mapping said digital data into an in-phase signal and a quadrature signal;
• predistorting said in-phase and said quadrature signal into a predistorted in-phase signal and a predistorted quadrature signal, respectively;
• modulating by digital quadrature modulation said predistorted in-phase signal and said predistorted quadrature signal to provide a digital quadrature modulated signal;
• converting said digital quadrature modulated signal into an analog predistorted signal;
• amplifying said analog predistorted signal to provide an amplified analog predistorted signal;
• broadcasting said amplified analog predistorted signal;
• receiving a portion of said amplified analog predistorted signal to provide a receive signal;
• converting said receive signal into a digital receive signal;
• demodulating by digital quadrature demodulation said digital receive signal to provide a feedback in-phase signal and a feedback quadrature signal;
• providing a trainer signal dependent on said feedback in-phase signal and said feedback quadrature signal, said in-phase signal and said quadrature signal;
• predistorting a subsequent in-phase signal and a subsequent quadrature signal into a subsequent predistorted in-phase signal and a subsequent predistorted quadrature signal, respectively, wherein said subsequent predistorted in-phase signal and said subsequent predistorted quadrature signal are dependent on said trainer signal;
• and
• receiving remotely communicated reconfiguration information and modifying said predistorting of said in-phase and said quadrature signal into said predistorted in-phase signal and said predistorted quadrature signal, respectively.