Research On Q-Band Wideband Linearization Technology

At present,China's low orbit satellite internet project in Q / V band is vigorously carried out.As the core component of satellite,space traveling wave tube power amplifier(TWTA)has a great influence on the quality and efficiency of communication system.TWT has strong nonlinearity near the power saturation point,so it is necessary to design a linearizer to improve the nonlinearity of TWT.In this paper,based on the theoretical analysis of the nonlinearity of the amplifier and the characteristics of various linearization techniques,the analog predistortion technology is adopted to realize the linearization of TWT.And this paper analyzes the principle of schottky diode and predistortion circuit.On the basis of the above research,three kinds of microstrip structure is explored.Finally,a Q-band linearizer for TWTA used in satellite communication is designed.It is good in the instantaneous frequency band from 38 GHz to 43GHz(5GHz).The linearizer entity can achieve amplitude expansion of 5.4?6.5d B and phase expansion of 56.3°?83.8° within the input power range of-30?0d Bm.The linearizer mentioned above has poor adjustability and cannot flexibly adjust the relationship between amplitude and phase.Besides,it has a slightly less nonlinear.So a new type of double-channel structure linearizer is designed.This kind of linearizer can not only be adjusted flexibly,but also enhance the nonlinear strength.It can achieve amplitude expansion of 5.5?6.9d B and phase expansion of 57.9°?80.6°within the input power range of-25?0d Bm.Finally,connect the linearizer to the TWT and test them.The reflection-type linearizer can improve the saturation point amplitude compression of TWT to-4?-2.3d B and the phase compression to-13.1°?-7.3°.When the input power regressed by 6d B from saturation point,the improvement of third-order intermodulation(IMD3)coefficient was 8.5?19.3d B.The double-channel linearizer can improve the saturation point amplitude compression of TWT to-3.2?-0.6d B and the phase compression to-6.7°?1.5°.When the IBO is 6d B,the improvement of IMD3 was 11.9?18.2d B.Both of them have achieved good improvement effect.