The Research And Design Of An Over-octave Power Amplifer

With the rapid development and evolution of wireless communication systems today,the signal bandwidth required for high-speed data transmission is increasing.Therefore,how to achieve high-efficiency transmission of broadband signals is an urgent problem to be solved.As an important part of the transmitter in the wireless communication system,the radio frequency power amplifier directly determines the stability of the entire communication system.Therefore,the power amplifier must also have broadband and high efficiency characteristics.At the same time,due to the increasing shortage of spectrum resources,communication frequency bands have become very crowded,and the frequency bands allocated to operators have gradually become fragmented,and the operating mode of multi-band power amplifiers has also become a research hotspot.In order to improve the utilization of the spectrum resources of the communication system,the use of a higher peak-to-average ratio modulation method will also affect the linearity of the power amplifier.Therefore,the power amplifier should be made to work in the low-power back-off area state as much as possible.The Doherty power amplifier has become the mainstream of design currently due to its own structural advantages.Aiming at the application scenarios of broadband and multi-frequency mode,this paper designs two power amplifiers based on the over-octave ultra-wideband power amplifier theory and Doherty technology.The main research contents are as follows:Firstly,starting from the impedance solution space of the traditional mixed continuous and Resistive-Reactive mixed continuous operating modes,it points out the incompleteness of the current theory of the impedance solution space of ultra-wideband power amplifiers.For the over-octave ultra-wideband power amplifier,only when the fundamental wave and each harmonic impedance solution space are exactly the same,that is,the two sides have each other,can it be ensured that the high-order harmonics at the low frequency point are designated as the fundamental wave,the corresponding power and efficiency can also be output.Secondly,in order to improve the current over-octave ultra-wideband power amplifier theory,the current source plane of the power amplifier are half-sine and square wave respectively,and the operating frequency band is one octave and two octave,saturated output power is reduced by 1d B,2d B and 3d B when the fundamental wave and each harmonic are common impedance solution space.Based on the impedance solution space theory,a 0.5-3GHz over-octave ultra-wideband power amplifier is designed.The circuit simulation design and processing test are completed on the ADS software,and finally the saturated output power measured in the entire operating frequency band is38.6-42.4d Bm,the drain efficiency is 50.1%-65.1%,and the in-band gain fluctuation range is 10.2-14.6d B.Then,combined with the traditional Doherty power amplifier theory,the working principles of the main power amplifier and peak power amplifier in saturation and backoff state are analyzed,and designed a dual-frequency Doherty power amplifier based on the theory of over-octave power amplifier impedance solution space.The operating frequency points are 1.8GHz and 3.6GHz,the fundamental impedance value of 3.6GHz is fixed to the second harmonic impedance value of 1.8GHz,the layout simulation design is completed on the ADS software,and the saturated output power of the two frequency points is 44.1d Bm,43.1d Bm respectively;saturated drain efficiencies are 67.3% and64.2%,respectively;6d B power back-off efficiencies are 49.9% and 42.2%,respectively;saturation gains are 8.1 d B and 7.1d B,respectively.Finally,summarize the research content of this paper and follow-up prospects,analyze the existing shortcomings and put forward suggestions for improvement.