Investigation On Broadband High-Efficiency Power Amplifier Based On Harmonic Synthesis Technology

With the rapid development of communication technology,the power amplifier,as the core component of the transmitter,has ushered in a huge market prospect,but it also faces many design challenges.How to solve the mutual restriction between the conversion efficiency and the operating bandwidth of the power amplifier has become a key problem faced by designers.In this regard,this dissertation firstly proposes an improved hybrid continuous-mode power amplifier,which alleviates the contradiction between bandwidth expansion and efficiency degradation in its theory.On this basis,a dual-power mode three-band power amplifier design scheme is proposed to meet the transmission requirements of different base stations and special equipment.Then,the joint control method of input and output harmonic impedance is used to further improve the efficiency and bandwidth of the continuous-mode power amplifier.In addition,this dissertation constructs the circuit topology of the continuous-mode Doherty power amplifier and proposes a continuous-mode load modulation method to improve the output power back-off efficiency,bandwidth,and gain.The main contents and innovations of this dissertation are summarized as follows:1.An improved high-efficiency load impedance space is proposed for the extended version of the hybrid continuous-mode power amplifier,which alleviates the contradiction between bandwidth expansion and efficiency degradation in its theory.An improved hybrid continuous-mode power amplifier operating at 0.8-2.2 GHz is designed to verify the correctness of the theory.The output power is 38.2-42.1 d Bm,and the drain efficiency is 55%-70.3%.On this basis,a dual-power mode three-band power amplifier design scheme is proposed to meet the transmission requirements of different base stations and special equipment and to improve the energy efficiency conversion of the power amplifier.The scheme adopts the output stop-band network migration method to prevent the transmission zero of the output network from affecting the load impedance matching and improves the in-band performance.Combined with the drain power supply switching method,the power amplifier can maintain high efficiency under different output powers.The realized dual-power mode three-band power amplifier operates at 0.9/1.5/2.1 GHz and has 33.7/35.2/34.7 d Bm output power and 71.8%/58.8%/66.6% drain efficiency in low output power mode.In high output power mode,its output power is 40.0/41.4/41.2 d Bm output power and the drain efficiency is 71.2%/58.6%/68.1%.2.The influence of the second harmonic component of the input network of the hybrid continuous-mode power amplifier on its performance is explored,and an efficiency improvement method for the joint control of input harmonic impedance and fundamental impedance is proposed.First,the second harmonic component generated by the transistor’s nonlinear capacitance at the gate is added to the theoretical analysis,which improves the accuracy of the theoretical analysis.By analyzing the changes of the actual conduction angle,drain voltage waveform,and drain current waveform,the relationship between the input second harmonic component,the output power,and efficiency is established,and the reason why the joint control of input harmonic impedance and fundamental impedance improves the efficiency is expounded.Then,the efficiency improvement effect of this method is further verified by simulation control experiments.In order to improve the efficiency of the broadband power amplifier,the broadband design criteria of this method are proposed,and a broadband high-efficiency power amplifier operating at 1.7-2.8 GHz is designed.The measured drain efficiency is61.2%-72.4%.3.The bandwidth limiting factor of the Doherty power amplifier is analyzed,and based on the continuous-mode mode bandwidth expansion method,a continuous-mode impedance inversion method is proposed,which improves the output power back-off efficiency and operating bandwidth of the Doherty power amplifier.A 3.3-4.3 GHz broadband Doherty power amplifier is designed with a saturated output power of43.1-44.3 d Bm and drain efficiency of 46.3-52.3% at a 6 d B output power back-off.On this basis,the common intersection of the high-gain impedance space and the continuous-mode impedance space is explored,an equivalent parasitic parameter model of the transistor is proposed,and the circuit topology of the continuous-mode Doherty power amplifier is constructed.With the proposed post-matching auxiliary harmonic control method,the design requirements of the load modulation network are simplified,and the gain of the Doherty power amplifier is improved.The designed high-gain Doherty power amplifier operates at 3.1-3.6 GHz,its saturation power is 41.8-42.8 d Bm,the saturation gain is 13.0-15.1 d B,and the 6 d B output power back-off power added efficiency is 35.4%-41.1%.