Research Of Linearization Based On Multi-antenna Structure

Along with the development of communication technology,the multi-antenna technology has become the main communication transmission technology.For the core component power amplifiers of multi-antenna system,there are many differences between the analysis of nonlinear method and traditional method.In this thesis,with the multi-antenna technology as the background,the effect multi-antenna system on the nonlinear of power amplifier is researched,Then the relationship between the amplitude and phase of signals in each channel and the beamforming is analyzed,the model of multi-antenna system is inferred.The linearization of beamforming in multi-antenna system is realized.The main work and innovation points of this thesis is summarized as follows:?1?For the power amplifier in multi-antenna system,the non-linearity comes from many sources,which needs to be studied in the whole system.As for the non-linearity caused by the amplification of the power amplifier input spectrum caused by frequency hopping signal,the research result of this thesis is that when the frequency hopping rate is much lower than the carrier frequency,no obvious intermodulation component can be observed on the output spectrum,.The fitting NMSE of frequency hopping input and output signals is 7.3269 dB higher than that of spliced signals.The signals in different time domain near the frequency hopping point produce intermodulation distortion.For the non-linearity caused by antenna coupling,an equivalent measurement method is proposed by using a ring simulator.The third-order intermodulation coefficient caused by coupling of a certain power amplifier antenna in S-band is quantitatively measured to be about-19.14 dBc.The functional expression of antenna coupling compensation is derived.?2?When some elements of the antenna are damaged,it will affect the beamforming and the dynamic linearization modeling.In this thesis,the static linearization is first carried out,and then the compensation result of static linearization is taken as the foundation of dynamic modeling.The linearization of the difference beam and sum beam is accomplished by region search and amplitude weighting optimization for the undamaged position.Simulation results show that the scheme can reduce the zero depth of the difference pattern by 10.87 dB,and reduce the sidelobe level of the pattern by 3.25dB in the X-axis direction and 9.89 dB in the Y-axis direction.In other directions,the sidelobe level increases successively in the direction of?45 degrees from the X,Y-axis direction.?3?For the dynamic linearization of multi-antenna systems,two models are established.The first model is the single-input single-output system.The analog pre-distortion of single-input single-output system is to treat the power amplifier of each channel as the same,that is,the analog pre-distortion of the power amplifier means the linearization of the multi-antenna system.In this thesis,a special double inflection point amplifier at the end of the antenna is simulated.The analog pre-distortion adopts reflective pre-distortion structure with 6 diodes in parallel.The P_1dB of the amplifier is increased by about 2.3 dB.The nonlinear phase improvement of the center frequency point is about 14.7 degrees.A Vector synthesis model of power amplifier based on single channel power amplifier is proposed for digital pre-distortion single input single output model.Simulation results show that,when the maximum radiation direction is linearized,the ACPR of each sub-channel can be improved by more than 15 dB,and the antenna pattern distortion caused by non-linearity can be corrected.Based on the model,a linear pre-distortion structure with multiple frequency points and multiple beams is proposed.?4?The second model is a symmetric linearized structure model with multiple outputs.The model only performs function operation on one channel in the symmetric path,so that the vector synthesis of the output of the symmetric two channels is linearized.By using the linearized structure model,half of the hardware resources can be saved.Through theoretical calculation and simulation,the model can control the amplitude error within1.2%in the maximum radiation direction of beamforming,within 4%in other radiation directions,and within 2 degrees in Angle.The beamforming was carried out through the symmetrical linearization output of the actual sampling power amplifier,so that the beamforming gain of 196 antenna array elements was improved by 4.8807%in the maximum radiation direction,8.6322%in the sidelobe level of the 0-degree section,and10.0902%in the sidelobe level of the 90-degree section.In the whole radiation direction,the beam linearization effect was better.