A Concurrent Dual-Band Uneven Doherty Power Amplifier with Frequency-Dependent Input Power Division

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Abstract
A concurrent dual-band uneven GaN Doherty power amplifier (PA) for two wide-spacing frequencies application is proposed in this paper. To avoid an early load modulation-drop caused by the soft turn-on characteristic of the peaking device, an adaptive power division is realized by a frequency-dependent uneven power divider as well as the input matching nonlinearities of the two cells in Doherty PA. Due to the adaptive power division, the proposed dual-band uneven Doherty PA achieves a power-added efficiency of 45% and 41% at the 6 dB backoff from the saturation at 850 MHz and 2330 MHz, respectively, the gain of the proposed Doherty PA is also enhanced to 19 dB and 13 dB in the dual bands. Furthermore, a more accurate two-dimensional joint digital predistortion model (2D-JDPD) is applied to linearize the PA and compensate for the in-phase and quadrature (I/Q) imbalance simultaneously. With this new model, the adjacent channel power ratio (ACPR) is improved to better than -47.1 dBc and -49.4 dBc in the lower and upper bands at an average output power of 31.75 dBm, and a drain efficiency of 26.7% is obtained at the same time.

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