Research On Highly Efficient Continuous Mode RF Power Amplifier

In communication systems,how to efficiently amplify transmission signals is always a difficult but urgent problem.Power amplifier(PA)is one of the main device to amplify transmission signals.Thus,research on PAs has been attracting many relevant researchers from all over the world.Many new requirements on PAs have been put forward along with the development of the communication industry.These requirement include bandwidth,efficiency,dynamic range,linear,and so on.On the one hand,highly efficient working mode of the power amplifier constantly spring up.And the design technology of high efficiency PA is becoming mature gradually.On the other hand,digital and analog predistortion technologies can improve the linearity of PAs effectively.Therefore,the main concerns are how to implement high efficiency PAs across a wide bandwidth and how to improve the back-off efficiency of PAs over a wide bandwidth.According to the above problem,the continuous working modes of PAs are researched firstly.And two continuous working modes are proposed for implementing broadband PAs.Then,a continuous mode Doherty PA(CM-DPA)is proposed which takes the advantages of continuous working mode and Doherty architecture.The CM-DPA surmounts the back-off drain efficiency deterioration of Doherty PAs(DPAs)at two side working bands through elaborately processing the non-infinity peaking impedance.Thirdly,a method for implementing ultra-wideband or multi-band load-modulated DPAs is proposed based on a dual-input configuration(DIC).Unlike previous DPAs,each subamplifier of the dual-input Doherty configuration plays the role of carrier and peaking stages at different working frequencies.For DPAs,the PA designer should to find a solution of combiner network that could balance the bandwidth and performances of DPAs.Therefore,the parameter selection of a modified combiner network is finally explored in this dissertation.The main contents and innovations of this dissertation are described as followed:1.The impedance space of the hybrid continuous mode is extended for designing broadband PAs.Like the traditional method,for expanding the impedance space of the hybrid continuous mode,a resistive second harmonic factor is introduced into the voltage wavform formula.The impedance space of broadband PA is more abundant after extension.The extension of the hybrid continuous mode benefits the realization of broadband PAs.For velisation,a broadband PA working across 0.8-3.05 GHz is fabricated.Experimental results show that the fabricated PA can deliver a saturation output power of 40-43.2 dBm with a gain of 9.8-13.2 dB over 0.8-3.05 GHz.Meanwhile,the saturation drain efficiency of the designed PA is 57.4%-79%.2.Hybrid inverse continuous mode is proposed for implementing highly efficient broadband PAs.The hybrid inverse continuous mode is extended from inverse continuous Class-F mode.A broadband PA,which operates across 2.4-3.9 GHz,is designed based on the series of inverse continuous modes(SICMs).The experimental results show that this power amplifier achieves a saturation output power of 40.6-41.2 dBm,a drain efficiency of 62.2%-74.7% over the whole interesting band.Furthermore,the saturation gain of the designed broadband PA is 10.7-13.2 dB.3.When the output impedance of peaking path deviates from infinity,some potential effects on DPAs must be produced.After analyzing the effect of the output impedance of peaking PA on DPAs,a CM-DPA is proposed via taking advantage of the non-infinity output impedances of peaking stage.Specifically,the carrier PA of the designed DPA operates under continuous class-J mode when the peaking PA is in the off-state.The proposed method surmounts the back-off drain efficiency deterioration of DPAs at two side working bands through elaborately processing the non-infinity peaking impedance.A broadband CM-DPA working over 1.6-2.7 GHz is designed for interpreting the propsoed theories.Under continuous wave(CW)excitation,experimental results show the drain efficiency of the designed DPA is 46.5%-63.5% at 6 dB output back-off power level and 56%-75.3% at peaking power level.The maximum output power of this DPA is 43.8-45.2 dBm with a gain of 9.4-11.5 dB across the whole working band.Furthermore,a 20-MHz modulated signal with a PAPR of 7.4 dB is also applied to the fabricated CMDPA.After digital pre-distortion,the measured adjacent channel leakage ratios are-48.2,-50.1 and-49.7 dBc at 1.7,2.2 and 2.7 GHz,respectively.4.A methodology is proposed for extending the high efficiency power range(HEPR)of symmetrical DPAs.This method takes advantage of the output impedance of peaking stage.Traditional symmetrical DPAs maintain high efficiency over a 6 dB power range with an assumption of the output impedance of peaking stage being infinity.This paper reveals that the HEPR can be further enhanced by tuning the output impedance of peaking stage away from infinity and changing the phase delay of the impedance inverter after carrier PA.A 2.2 GHz DPA with a HEPR of 9 dB is fabricated to validate the proposed theory.Experimental results demonstrate that the fabricated DPA achieves a drain efficiency of 49.6% at 9 dB output power back-off level.5.A dual-input Doherty configuration with controllable load-modulation mode is proposed for ultra-wideband application.Unlike previous DPAs,Each sub-amplifier of the proposed configuration plays the role of carrier and peaking stages at different working frequencies.Detailedly,the first sub-amplifier acts as the carrier PA when the second sub-amplifier is the peaking device,and vice versa.A dual-input power amplifier working over 0.7-3.0 GHz is constructed for validating the proposed theory.Experimental results illustrate the fabricated power amplifier achieves a maximum output power of 42.2-44.7 dBm,a saturation drain efficiency of 49.8%-60.3%,and a 6 dB back-off efficiency of over 40% across 0.7-3.0 GHz.6.A modified combiner network is applied into the CM-DPA.When it comes to DPA,the combiner plays a dominating role in limiting the bandwidth.Whatever the type of the combiner is,what should the PA designer to do is to find a solution that could balance the bandwidth and performances of DPAs.A symmetrical CM-DPA prototype working over an octave bandwidth is constructed through reasonably selecting the designed parameters of the modified combiner.A broadband DPA working over 1.2-2.7 GHz is implemented for demonstrating the universality of the generalized combiner.As a demonstrator circuit,the fabricated DPA achieves drain efficiencies of 44%-75% and 40%-54% at 6 dB back-off and saturation power levels,respectively.And the maximum output power of the fabricated DPA is larger than 42.1 dBm.