Research On Broadband High Efficiency Power Amplifiers For Wireless Communication Systerms

In modern communication systems,to achieve high-speed data transmission,the required signal bandwidth is getting larger and larger,and how to efficiently transmit broadband signals is an urgent problem.Power amplifier(PA)as one of the most important components in the transmission systems,its performance directly affects the signal transmission quality of the communication systems,so the PA must also have broadband and high efficiency characteristics to meet the requirement of modern communication systems.For the required broadband applications,the techniques of performance improvement for PAs are studied.Firstly,the continuous working modes of PAs are researched,a high order extended hybrid continuous working mode is proposed,and for the design problem of the matching network of broadband PAs,a matching methodology using real frequency technique with finite transmission zero is proposed.Secondly,the frequency characteristics of Doherty PA are analyzed,and design method of wideband Doherty PA and the dual-band Doherty PA based on impedance control are proposed.Finally,load network parameters of generalized Class-E PAs are studied,impedance solution spaces of class-E PA with shunt filter and parallel-circuit Class-E/F₃PA are expanded with generalized structures,and generalized parallel-circuit Class-E/F₃structures is applied to the design of radio frequency wideband class E PA.The main contents and innovations of this dissertation are describedas followed:(1)The impedance space of the hybrid continuous mode is extended,a high order extended hybrid continuous working mode is proposed for designing broadband PAs.Compared with the hybrid continuous working mode,by introducing a higher-order resistive term(1+?cos(n?))to the voltage waveform formula,impedance solutions of the continuous working mode can be further enriched,which provides wider impedance solution spaces for the design of broadband PAs.A broadband PA is fabricated to verify the theory.Experimental results show that the fabricated PA can deliver a saturation output power of 41-43.3 d Bm d Bm with a gain of 12-14.3 d B over 0.5-3.1 GHz.Meanwhile,the saturated drain efficiency of the designed PA is 56.3%-76.6%.(2)Harmonic impedances have great impacts on the performance of continuous working mode PAs,PAs can work in high efficiency modes only by matching the harmonic load impedances to the corresponding impedance solution spaces.A matching methodology using real frequency technique(RFT)with finite transmission zero is proposed to design a broadband continuous class-F PA,the proposed matching method extends the traditional RFT,the second harmonic impedance of the PA can be more conveniently controlled by introducing the finite transmission zero,which can improve the bandwidth and efficiency of the PA.To verify the validity of proposed method,a broadband continuous class-F PA working from 1.15 to 2.2 GHz is designed.Experimental results show that the fabricated PA achieves 11.3-13.7 d B power gain and 40.5-43.2 d Bm output power in the operation band.And the PA has also achieved a high-efficiency characteristic of 70%-83%saturated drain efficiency.(3)In the design of broadband Doherty PAs,noninfinity output impedance of the OFF-state peaking stage will affect the performance of the broadband Doherty PAs.After analyzing the frequency characteristics of the broadband Doherty PAs,a broadband Doherty PA topology using noninfinity output impedance of the OFF-state peaking stage and complex combining load is proposed,this topology can improve the efficiency of the Doherty PA at both the saturated power level and the output back-off level,which can extend the bandwidth and efficiency of the Doherty PA.Based on the proposed theory,a Doherty PA working over the frequency band of 1.1-2.4 GHz is designed and fabricated.Experimental results exhibit 6d B output back-off drain efficiencies of 43.8%-54.9%and saturated drain efficiencies of 55.4%-68%can be obtained.The saturated output power of the Doherty PA is 43.3-45.4 d Bm.(4)Based on continuous operation mode,a novel methodology for designing dual-band continuous class-B/J Doherty power PA is proposed.noninfinity output impedance of the OFF-state peaking stage and harmonic tuning postmatching network are used to control the fundamental and harmonics impedances of the carrier PA,reseparately,which can make sure the PA works in continuous class-B/J mode,thus improves the performance of the dual-band Doherty PA at output back-off level.The fabricated dual-band Doherty PA can achieve 68.5%and 75%drain efficiencies for saturated power level,64%and 63%drain efficiencies for 6d B back-off level at two operation frequencies 1.8 and 2.6 GHz,respectively.(5)To solve the problem of single load network parameter of class-E PA,a generalized class-E PA with shunt filter is investigated comprehensively.The generalized class-E PA with shunt filter is realized with connecting a reactance element in series before the load resistance,the generalized structure can extend the impedance solution space of class-E PA with shunt filter.The effects of sub-normal conditions and arbitrary duty ratios on the performance of generalized class-E PA with shunt filter are analyzed in detail.The generalized sub-normal class-E PA with shunt filter can achieve different performances with properly selecting generalized parameter variable and signal duty ratio,the fabricated generalized sub-normal class-E PA has a efficiency of91.9%.(6)The generalized structure is extended to generalized parallel-circuit class-E/F₃PA,and a high-efficiency wideband generalized parallel-circuit class-E/F₃ PA based on impedance space expanding of load network is proposed.The load impedance solution changes from a single value to a series of values in the generalized structure,which expands the load impedance solution space of the PA,the expanding of load impedance solution space makes the realization of wideband generalized parallel-circuit class-E/F₃PA possible.The generalized parallel-circuit class-E/F₃ PA structure is applied to the microwave frequency band,a broadband high-efficiency generalized parallel-circuit class-E/F₃ PA is designed based on the obtained expanded impedance solution space and broadband matching network design method.Experimental results illustrate the fabricated PA achieves a drain efficiency of 68.5%-81%in the frequency band of 1.7-2.6 GHz.