Research On Linearization Technology Of Power Amplifier Based On Distortion Feedback Structure In Analog Domain

As a key component of wireless communication transmitter,the power amplifier will generate spectral regrowth due to the nonlinear distortion,and reduce the spectrum resource utilization.How to suppress the nonlinear distortion of the transmitter has become a key issue,which is usually solved by digital signal processing solutions represented by digital predistortion(DPD).However,in the face of large-scale array antennas scene,the traditional DPD solution needs to equip the power amplifiers with a large number of high-performance observation channels and digital signal processing units,which makes it difficult to deploy nonlinear correction.Therefore,in this thesis,in order to explore a method suitable for nonlinear suppression in array antennas scene and easy to integrate into the design of power amplifier,a method based on distortion feedback structure in analog domain is designed.The main contents are as follows.Firstly,the linearization method of the distortion feedback structure is analyzed.A one-channel distortion feedback model is constructed,which can extract and adjust the nonlinear distortion components of the power amplifier,and then feed them back to add to the input signal.The iteration of the feedback signal and its influence are analyzed from the time domain,frequency domain and S domain.Simulations are carried out under different wideband signal conditions,and the distortion suppression performance of the model under different feedback channel parameters are analyzed.Secondly,a linearization scheme with two-channel distortion feedback structure is designed.Based on the extraction of distortion components,two feedback channels with double delay relationship are constructed.The extracted distortion components are fed back through the two channels and then added to the input signal,forming a two-channel distortion feedback model.The model is analyzed from the frequency domain and the S domain,and the relationship between the distortion suppression frequency range and the feedback channel parameters is obtained.The special feature is that the distortion suppression frequency range can be flexibly adjusted by changing the parameters of the feedback channel.Finally,an experimental platform for distortion suppression is designed and built for a typical power amplifier with 1W output.Tests were performed using a 40 MHz bandwidth signal with a center frequency of 780 MHz.The results show that under the condition of hardware feedback delay of 6ns,by adjusting the parameters of the feedback channels,the ACLR improvement of 6d B can be achieved when the distortion suppression center is on the main channel.In addition,the ACLR improvement of 11.2d B can also be achieved when the distortion suppression center is on the adjacent channel.The distortion suppression frequency range of the proposed model can be adjusted flexibly,and the performance is better than that of the one-channel distortion feedback structure.In this thesis,a power amplifier linearization method using distortion feedback structure in analog domain is studied.A two-channel distortion feedback structure is designed to suppress the nonlinear distortion of the power amplifier,a hardware circuit is realized,and the performance is verified.This thesis provides an exploration development idea for the application of feedback linearization technology in array antennas scene.