Research On Active Load Modulated Power Amplifier For 5G NR

In order to realize massive information transmission,more and more complex signal modulation methods have appeared,which put forward new requirements on the efficiency performance of power amplifiers(PAs).Because of the limitation of the structure with fixed load and passive matching network,the traditional PA using one transistor shows the defect that the efficiency drops sharply during the input power back-off.Due to the unique architecture,the active load modulated PA is one of the most effective technologies which enhance the efficiency of PA at the OBO.After studying the traditional technologies which improve the efficiency of PA at the peak output,based on the theory of active load modulation,some solutions which expand the bandwidth and power back-off range of PA are proposed and verified in this thesis.The main research contents and innovations of this dissertation are summarized as follows:1.The design method of the traditional harmonic control network is improved to decrease the design difficulty and expand the bandwidth of PA.The low-order FMN is realized using the simplified real frequency technique(SRFT).With the predesigned FMN,the harmonic control network is designed to improve efficiency by combining it into the bias circuit.A high-efficiency PA working across 6.1– 7.2 GHz is simulated and fabricated.Experimental results show that the fabricated PA delivers a saturated output power of 38.2– 39.3 d Bm with a drain efficiency(DE)of 43%–63.4% in the interested band.2.To improve the traditional Doherty PA architecture,the low-order impedance inverter is used to solve the bandwidth limitation of the quarter wavelength line.A high-order post matching network(PMN)with harmonic control for carrier PA is proposed to achieve wideband performance and better back-off performance.The equivalent parasitic network(EPN)of the transistor is constructed by using the nonlinear de-embedding technique,and the active load modulation process of the Doherty PA is given based on the extracted intrinsic impedance.A symmetrical high-efficiency Doherty PA working over 6.4-7.1 GHz is designed.The Doherty PA delivers a saturation output power(Psat)of 39.6-41.6 d Bm.Meanwhile,the drain efficiencies in the interested frequency band are 45.1%–53.2% and 34.5%–43.1% at the Psat and 6-d B OBO power levels,respectively.The high-efficiency operation of peak output and output power back-off is realized at the same time.The efficiency curves of traditional high-efficiency PA and Doherty PA based on the active load modulation theory are compared to verify the unique advantages of active load modulation PA architecture.3.A three-way asymmetric Doherty PA architecture based on PMN is adopted to extend the high-efficiency back-off range.The theory of continuous mode is integrated into the design of asymmetric Doherty PA.The carrier PA is operating in continuous class B/J mode at low power region,which effectively expands the impedance space of carrier PA and further improves the broadband performance of Doherty PA.A continuous class B/J mode asymmetric Doherty PA working over 1.35-1.8 GHz is designed.The Doherty PA delivers a saturation output power of more than 50 d Bm.Meanwhile,the drain efficiencies in the interested frequency band are 42.8%-55.6% at the 8 d B OBO power level.Compared with the traditional symmetric Doherty PA,the high-efficiency back-off range of PA is further expanded.