A Linearized 2–3.5 GHz Highly Efficient Harmonic-Tuned Power Amplifier Exploiting Stepped-Impedance Filtering Matching Network

This letter presents the analysis, implementation and experimental results of a broadband highly efficient power amplifier (PA) using harmonic-tuned method for long-term evolution (LTE)-advanced application. Load-pull simulation has been employed to obtain the optimal load impedances, especially the second harmonic impedances, for high efficiency and output power over wide bandwidth. A stepped-impedance low-pass matching network was then designed to achieve the desired impedance transformation. Experimental results show that the PA achieves 64%-76% efficiency and higher than 40 dBm output power over the frequency band from 2 to 3.5 GHz. When driven by a 100 MHz LTE-advanced signal at an average output power of 33.5 dBm, the average efficiency of 33.8%, 34.9%, and 37.8% was measured at 2.15, 2.55, and 3.45 GHz, respectively. The corresponding adjacent channel leakage ratio can be linearized to about -48 dBc by using digital pre-distortion technique.