Research On Linearization Technology Of Ka Band Power Amplifier

Power amplifier is a very important component in modern communication system.Its performance seriously restricts the performance of the whole communication system.When the power amplifier works in the saturated region,it has high efficiency.However,the power amplifier will produce strong non-linear distortion,which greatly reduces the communication quality.Power amplifier linearization technology is a technical means to ensure that the power amplifier is in a high efficiency state and has good linearity.With the shortage of microwave band resources,millimeter-wave band will become more and more important in future communication systems.As an important part of millimeter wave,Ka-band has been in a high-speed development stage in military communication system in the past.It will also has great application in future communication system.In this paper,the linearization technology of Ka-band TWTA is studied and explored by analog predistorter based on schottky diode.The main work of this paper is as follows:Firstly,a Ka-band analog predistortion linearizer based on coplanar transmission line is developed using Schottky diode cascade structure.The predistortion linearizer uses microstrip capacitor instead of integrated capacitor.On the one hand,it reduces cost,on the other hand,it avoids parasitic influence of integrated capacitor.The results show that the linearizer can provide maximum 5 dB gain expansion compensation and 60 degrees phase expansion compensation in the target frequency range of 27 GHz to 29 GHz.Then two Ka-band predistortion linearizers are developed based on the reflective predistortion linearizer.The first linearizer improves the structure of the reflective branch to make it more adjustable.At the same time,the circuit structure is relatively simple by using the ?/4 open circuit as the AC ground.Through theoretical analysis and simulation verification,the structure can achieve phase expansion or compression by changing resistance while guaranteeing amplitude expansion.The linearizer achieves gain expansion of more than 10 dB and phase expansion of 80 dB at the central frequency point.The second linearizer is a cascade structure of reflection-type and transmissiontype.By adjusting two bias voltages,the linearizer can output compensation characteristics of TWTA.Finally,the working principle of the two-way synthetic predistortion linearizer is analyzed.On this basis,the structure of the two-way predistortion linearizer using both non-linear branches is proposed.Schottky diodes with up and down branches adopt pushpull structure,which theoretically makes the output port only have even harmonics.When the bias voltage of the upper and lower branches is different,the linearizer can still provide better predistortion signal.The results show that the linearizer has good linearization ability in the whole frequency band because of different bias voltage combinations.