Highly Efficient Multimode RF Transmitter Using the Hybrid Quadrature Polar Modulation Scheme

This research first presents a hybrid quadrature polar modulator to drive the power amplifier (PA) highly efficiently in a wireless RF transmitter required for multi-mode operation. The proposed modulator consists of a quadrature modulator for processing the RF modulated carrier and a class-S modulator for processing the envelope signal. Since both quadrature and class-S modulators deliver signals with envelope variation, the double amplitude modulation distorts the RF modulated signal at the PA output. Therefore, a digital predistorter is required in front of the hybrid quadrature polar modulator for compensation. The use of such predistorted drive signals can help reducing the average DC and input RF drive powers and the output feed-through levels so as to enhance the power added efficiency and adjacent channel power rejection remarkably