Concurrent Dual-Band Digital Predistortion With a Single Feedback Loop

This paper proposes a compact and low-cost architecture with only a single feedback loop to implement concurrent dual-band digital predistortion (DPD) of power amplifiers (PAs). This technique is based on a new approach, down-converted carrier co-location (DC <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ), in conjunction with a 2-D carrier co-located memory polynomial model in PA forward modeling. The concurrent dual-band DPD models for each band can then be extracted successfully according to the forward modeling results. Experimental tests have been performed for a commercial Mini Circuits amplifier and a 120-W peak power GaN base-station PA. Different signal combinations have been tested for both balanced and unbalanced output power operations in the dual bands. The results validate that the proposed method is able to achieve linearization performances comparable to those of the conventional two parallel feedback loops based technique. Even when a nonideal feedback loop with nonflat frequency responses in the two bands is used, the new method performs well when the feedback loop is calibrated in advance. This single feedback loop based concurrent dual-band DPD architecture is a strong candidate for future broadband dual-band transmitting systems.