Research And Implementation Of Broadband High Efficiency Power Amplifier

To achieve high-speed data transmission and improve spectrum utilization,the mobile communication system uses high-order modulated signals with high peak-to-average power ratio,and the signal bandwidth is further increased.At the same time,the coexistence of multiple signals and wireless standards leads to the coexistence of multiple frequency bands in mobile communication.The above characteristics put forward an urgent demand for high back-off efficiency and wide bandwidth of power amplifier.Therefore,to meet the requirements of mobile communication system for high back-off efficiency,high linearity and bandwidth extension of power amplifier,this paper studies active load modulation technology and bandwidth extension technology,and designs two broadband high efficiency amplifiers.The main work and innovations of this paper are as follows:(1)A broadband Doherty power amplifier(DPA)based on the linear frequency-dependent complex combining load is proposed.Firstly,the linear frequency-dependent complex combining load expression composed of normalized frequency f,expansion factor k and the optimal impedance Ropt of Class-B power amplifier is given,and the appropriate k value is determined by analyzing the dual-state matching of DPA,so as to obtain the specific value of the linear frequency-dependent complex combining load.In the design process of DPA,the band-pass matching network is used as the post-matching network to realize the linear frequency-dependent complex combining load.Finally,based on the above method,a broadband DPA is designed and implemented.The measurement results show that the drain efficiency is 47.9-62%at peaking output power and 40-51.4%at 6 dB output power back-off over the frequency band of 2.45-3.55 GHz.The maximum output power is 42-43.1 dBm.(2)A RF-input load modulated balanced amplifier is designed based on dual transmission line band-pass matching network.In consideration of insufficient harmonic optimization of band-pass matching network,an equivalent substitution of band-pass matching network is proposed by using dual transmission lines and stepped transmission lines.In this way,it is possible to insert transmission zeros in harmonic bands and make it have the effect of harmonic suppression.A RFinput load modulated balanced amplifier is designed and implemented by taking the dual transmission line band-pass matching network as the output matching network of the balanced amplifier.The simulation results show that in the working frequency band of 2.3-3.6 GHz,the S21 of the RF-input load modulated balanced amplifier is rapidly compressed in the second and third harmonic frequency ranges,which has the effect of harmonic suppression.The measurement results show that in the working frequency band of 2.4-3.5 GHz,the maximum output power is 43.24-45.85 dBm with the saturated drain efficiency of 48.53-63.67%.The drain efficiency of 41.16-63.16%and 39.65-53.29%is achieved at 6.17-7.07 dB and 7.36-8.39 dB output power back-off,which can ensure that the drain efficiency of 7 dB output power back-off is higher than 40%.Two broadband high-efficiency power amplifiers designed in this paper have good performance and have positive significance in reducing the complexity of mobile communication system equipment and base station energy consumption.