The Study Design Of High-efficiency Doherty Power Amplifier Based On Envelope Tracking

In modern wireless communication systems, the power amplifier plays an important rolethat it transforms DC power into RF power, which is sent out by the antennas. This way isallowing users to completely get rid of the constraints on the distance of space, to achieve acomplete personal mobile communications.To meet the growing Communication traffic volume, the wireless communicationsystems often use complex modulation schemes, such as QPSK modulation Mode havingPAPR10.26dB, and the OFDM modulation technology for the core of the fourth-generationtechnology, the PAPR is more than12dB. A high PAPR non-constant envelope signal requirespower amplifier with a wide linear dynamic range to amplify the signal without distortion.The conventional power amplifier module using power back-off approach to solving thelinearity, efficiency generally only ten percent, greatly sacrificing efficiency of the amplifier,resulting in a loss of energy, affecting the performance and life communication systems.Therefore, the use of the project for improving the efficiency of the power amplifier hasobvious practical significance.Currently, the efficiency enhancement techniques are used mainly, LINC Modulationtechnique, Envelope Elimination and Restoration (EE&R), envelope tracking (ET) technologyand Doherty structure. In this paper, around the efficiency of the power amplifier, there aresome brief introduction to the efficiency enhancement techniques, and theoretical analysis ofthe efficiency and working mechanism about Doherty. Considering the circuit structure, cost,efficiency and so on, the study design in this paper combines Doherty PA with envelopetracking (ET) technology. According to the size of the input signal power, the peripheralcontrol circuit will select a perfect drain bias voltage. For the practical application, the peakamplifier can’t reach saturation output, resulting in the problem of Load-Pull, so adaptive gatebias is using in circuit design, and the gate voltage will increase as the input signal powerincreases. While the input signal power reaches a certain threshold, ALC circuit starts to work,effectively protect the amplifier system.The thesis is divided into six chapters, and then the paper gives a design process of control circuit and the power amplifiers for a detailed description and explanation. In the end,further research work is prospected.