Optimization Design of Broadband Doherty PA Using Fragment-Type Matching Network Based on Dual-State Impedance Objective Function

In this paper, an optimization design of broadband Doherty power amplifier (DPA) is presented for the extension of bandwidth. A dual-state impedance objective function is utilized in the optimization of the carrier and peaking output matching networks (OMNs) to satisfy the load impedance constraints at back-off output power and saturation, respectively. Unlike conventional method, a novel impedance constraint strategy is proposed by employing an impedance constraint circle in Smith chart, which can more fully utilize the impedance region obtained from load-pull simulations. Moreover, to increase design flexibility, a fragment-type matching circuit is employed in the OMN optimization design together with the dual-state impedance objective function. Experimental results demonstrate a 1.2 to 2.6 GHz (74% fractional bandwidth) broadband DPA with a drain efficiency of 49.7%-53.5% measured at 6 dB back-off and a saturated output power of higher than 43 dBm.