Research On Millimeter Wave Linear Driver Module For Traveling Wave Tube Amplifier

With the continuous development and maturity of communication technology,low-frequency communication has been unable to meet the increasing demand of people.For satellite communication systems,the Ku/Ka band is currently the most commonly used,but in these two frequency bands,the signal communication bandwidth is relatively low.Narrow and low transmission rate will increase the complexity of system modulation and demodulation.In order to obtain greater channel capacity and shorten the signal transmission time,domestic experts in the field of satellite communications have conducted in-depth studies on how to use frequencies above millimeter waves.But no matter which frequency band,the most important thing for a communication system is the accuracy of signal transmission.For systems with power amplifiers as the core,when the input power is large,the non-linear characteristics of the power amplifier will seriously reduce the accuracy of signal transmission.For this phenomenon,research on millimeter wave linearization technology is urgently needed to compensate for signal distortion and reduce the impact of signal distortion on the communication system.In this paper,based on millimeter wave circuit,starting from the nonlinear phenomenon of the system and the principle of analog predistortion,the Q-band linear driver module is designed and studied.The whole module takes Schottky diode as the core device and adopts predistortion principle to design.It can adjust the nonlinear characteristics of different TWTA power amplifiers to meet the linearization requirements of specific TWTA.The module test results show that the amplitude expansion is more than 4d B,the phase expansion is more than 55 degrees and the input dynamic range is 30 d B.The input and output can be adjusted in a certain range,which ensures the matching of the input power of the whole linearized TWTA and the linear driver module provides enough driving ability for the TWTA.In practical application,the phase expansion of the module is too large,which will cause over compensation for TWTA.Therefore,he pre-distorter witnesses great Improvement in the perspective of bandwidth and adjustability.The wide band circuit structure is designed and the adjustable parameters are added.As the statistics of simulation and measurement results reveals an augment of each structure by comparison.,and the minimum phase expansion can reach 14 degrees.Taking WR19 standard waveguide as input and output ports,a U-band analog predistorter with waveguide and microstrip is designed.The test results show that in the bandwidth of 47.2 ? 51.4 GHz,the minimum amplitude expansion of the predistorter can reach 3 d B,the maximum can reach 7.2d B,the minimum phase expansion can reach 20 degrees and the maximum can reach 75 degrees.Combined with the adjustable gain amplifier module,the whole linear drive module is developed and tested,which makes the input and output power of the module have adjustable function in a certain range.The performance of the whole module: in the index frequency band,the minimum amplitude expansion can reach 4.2d B,the maximum can reach 15.4d B,the minimum phase expansion can reach 123 degrees and the maximum can reach 172 degrees.The input dynamic range is 30 d B.It has the ability of cascading with TWTA.