S-band High Efficiency Power Amplifier Based On Harmonic Control

The continuous development of modern wireless communications, directly or indirectly, promotes the progress on RF technology. The development and progress of RF power amplifier(PA) means great significance for wireless communications. After years of development, the type and structure of the RF PA has a variety of different forms. In all of forms, the high-efficiency PA realized by harmonic control can achieve excellent performance which becomes one of the most cited PAs.This thesis aims to study and research how to improve the performance of RF PAs by harmonics control method. Harmonics control method is also used in broadband high efficiency PA design. And the research of the combining of Doherty structure and continuous class F is carried out. Specific contents are as follows:Firstly, this thesis describes the design method of Class F PA in detail. This thesis analyzes the impact of the input second harmonic on the performance of class-F PA. The circuit area is reduced by making the second harmonic tuning line and DC bias line share one microstrip. Microstrip radial stub is used to instead of the short-circuit capacitance because of the limitations of short-circuit capacitance. A class F PA with input second harmonic tuning has designed by using a 10 W GaN transistor. The test results show good performance.Secondly, in this thesis, a novel approach for the design of Broadband High-Efficiency Power Amplifiers(BHPAs) is proposed. The method is to simplify the process of synthesizing a wideband output matching network by realizing harmonic tuning and fundamental matching separately. First, the fundamental and second harmonic impedances are calculated based on the theory of Continuous Class-F Mode. Then, a novel wideband harmonic-suppressing network is obtained by using four microstrip radial stubs(MRSs). This structure achieves a good performance about harmonic tuning and fundamental matching. Test results show that this proposed PA achieves 60.9-81.6% drain efficiency(DE), 60-79.9% PAE and 39.7-41.7dBm output power from 1.95-2.6GHz. A 5MHz WCDMA signal was used as excitation to the PA to test linearity and ACPR characteristics at 2.14 GHz. It exhibits an average DE of 32.1% and output power of 35.34 dBm with an acceptable ACPR of-32.85 and-32.66 dBc at ±5 MHz offset, whereas-50.49 and-50.89 dBc at 10 MHz offset were obtained.Thirdly, this thesis describes the work principle of Doherty amplifier. The narrowband characteristic of λ/4 impedance transformation line is analyzed. And an improved parallel structure is used to replace it for getting wideband performance. A more appropriate characteristic impedance value of quarter-wavelength line in this parallel structure is selected by simulation and optimization. The performance of wideband is significantly improved. Finally, the Continuous Class-F amplifier is used to replace the class AB and class C of Doherty for designing a broadband high efficiency Doherty PA.From the measured results of the three different power amplifier, the test performance and simulation design are consistent which indicating that the research program of this thesis is reasonable and the theoretical analysis is correct. This thesis provides a reference for how to improve RF amplifier performance with harmonic control method.