Research On Key Technologies Of Microwave Ultrawideband Power Synthesis

With the rapid development of current radar system,satellite communication,remote sensing measurement and control technology,the demand for high power and ultrawideband as two most important indicators of microwave system application is increasing.The emergence of the vacuum tube solves the need of high power,but compared with power amplifier chips,vacuum tubes are limited in practical application due to their large size and high cost.The output power of a single power amplifier chip is very limited,and power synthesis technology can synthesize the output power of multiple chips to produce higher power,which can be better applied in design.Therefore,based on this application background,the key technologies of microwave ultra-wideband power synthesis are studied as follows:(1)The broadband matching technology and the factors influencing the power synthesis efficiency are studied.First,the broadband matching technology of impedance converter based on one-fourth wavelength is analyzed.Then,the key factors influencing the power synthesis efficiency are analyzed.The effects of insertion loss of each port output and the phase consistency of each port output on the power synthesis efficiency are analyzed.(2)The passive network of UWB power synthesis is studied.It includes the structure design of extended coaxial and fin line.Through the analysis of broadband matching technology and the factors affecting the efficiency of power synthesis,the extended coaxial and fin line are selected as the main structure of the design.There are many kinds of fin line functions to choose.Finally,it is decided to use cosine square function to calculate the curve of design fin line.In this paper,a 2-18 GHz power divider / combiner and a 2-18 GHz power combiner are designed based on the extended coaxial and fin line.Both designs change from standard coaxial to extended coaxial,and the energy is transmitted to the standard coaxial output after passing through the fin line.The simulation results show that the return loss of the two designs is more than 15 dB in the whole frequency band,the insertion loss is less than 0.3dB,and the amplitude and phase consistency of the output port is good.The test results show that the VSWR of the power divider / combiner is better than 1.7,the insertion loss is less than 1.5dB in most frequency bands,the VSWR of the power combiner is better than 1.7,the phase difference of the output port is less than 5 ° and the insertion loss is less than 1.5dB in most frequency bands.(3)The design theory of the coupler is analyzed.A 2-18 GHz coupler is designed based on the analysis of odd and even mode.The coupler is fully symmetrical and cascaded with a coupler with a two-stage coupling of 8.34 dB to reach a coupling of3 dB.To achieve the purpose of rapid coupler design,the even mode numerical table of Chebyshev is used,and the structural parameters of the coupler are calculated using MATLAB programming for the comprehensive formula of the interlaced coupling stripline.Based on this parameter,a coupler is designed.The test results show that the return loss of the coupler is greater than 20 dB,the isolation is greater than 20 dB,and the coupling degree of the coupling port is about 3dB in the whole frequency band.However,the coupling degree of the straight-end does not achieve the simulation effect.The reason is analyzed later.