METHOD AND APPARATUS FOR ADAPTIVE DIGITAL PREDISTORTION IN A RADIO TRANSMITTER

摘要

An adaptive digital predistortion apparatus and method for transmitting broadband digital signals from a wireless transmitter to a transmitting channel are provided. In the adaptive digital predistortion process, a non-linearity conversion opposite to the transmitting channel characteristic is performed by a digital predistorter for input baseband signals. The predistorted signals are amplified by a power amplifier via an up conversion channel. A part of the signals outputted from the power amplifier are fed back to an adaptive controller via a coupler. The feedback signals are processed by the adaptive controller to obtain out-of-band emission energy of the feedback signals. Using the out-of-band emission energy as a target function, the predistortion parameters are updated by employing a multi-parameter optimum seeking module. Accordingly, broadband signals to be transmitted are predistorted by the digital predistortion system to cancel out the non-linear characteristic of the transmitting channels, and to suppress the out-of-band emission energy of the outputting signals. Meanwhile, by using a multi-parameter optimization seeking module, the predistortion parameters are adjusted adaptively by the digital predistortion system based on the slow variation of non-linearity of the transmitting channels.