The Application Of Envelope Tracking Technology In The Power Amplifier

In the current wireless communication system,the hybrid modulation is the main method which makes the signal Peak-to-Average Power Ratio(PAPR)high.The high PAPR leads to the reduction of the traditional power amplifier efficiency.For power amplifiers,how to increase bandwidth and efficiency has become a major research focus.Envelope tracking technology is one of the techniques improving the efficiency of power amplifiers.Envelope tracking technology makes the modulation signal of the input envelope signal to control the drain voltage of the power amplifier in real time which improves the efficiency of the entire power amplifier.Although the envelope tracking theory has been put forward for a long time,the envelope tracking technology is developing slowly due to the limitation of the actual hardwares such as the low withstand voltage of switchings the slow switching speed and other issues.With the continuous improvement of the hardware level,Envelope tracking technology has been paid more and more attention to improve the efficiency of power amplifier.In this thesis,the main research is that the efficiency of traditional power amplifier is improved by the envelope tracking technique.Firstly,a broadband power amplifier used for Mobile Ad Hoc Networks(MANETs)is designed with the gain of 20 dB and the maximum output power of 45 dBm.The test shows that the efficiency of the design of broadband power amplifier is relatively low(below 30%)especially when input power is form 3dBm to 17 dBm.In order to solve the problem,this paper uses the envelope tracking technique to improve the efficiency of the power amplifier.A hybrid power supply modulation circuit is designed.The output of the hybrid power supply modulation circuit controls the drain voltage of the power amplifier in real time.The power amplifier is working at the highest efficiency point.thereby the efficiency of the power amplifier is improved.In the design of the hybrid power supply modulation circuit,it makes use of PWM codes to realize the output of different amplitudes,and makes use of multilevel switching power supply modulators to achieve the envelope signals fit.Meanwhile Using the linear class improves the bandwidth of the hybrid power supply modulation circuit.The efficiency of the switching power supply modulation is about 81%,while the maximum output power is up to 26.6W.The actual design of the power amplifier and the hybrid power supply modulation circuit are co-simulated through the Simulink software and the ADS software.The linear part of the hybrid power supply modulation circuit with the broadband power amplifiers conducts a joint test.The results show that the envelope tracking technique is used in the theselfdesigned power amplifier circuit,which makes the whole PAE increase by more than 4%.In this thesis,the theory of envelope tracking technology to improve the efficiency of power amplifier is proved.