Research On Key Technologies Of Terahertz Wideband Power Combiner

Terahertz electromagnetic wave has unique advantages in radar imaging,broadband communication and other fields due to its characteristics of wide frequency band,high resolution and strong penetration.In terahertz systems,the power source is an important component whose output power level directly affects the performance of the whole system.Among many power devices,solid-state power amplifiers have a wide range of applications due to their advantages of small size and high stability.However,the current output power of solid-state power amplifiers in terahertz band is generally low.As an effective technical means to improve the output power,power combining technologies can well address the above problem.The most widely used power combining technologies in the terahertz band are chip and circuit power combining.Due to the limited layout area and high transmission line losses,chip power combining cannot meet the power requirements of the system.Circuit power combining can combine the output power of multiple power amplifier chips to obtain greater output power.Therefore,in this thesis,we focus on circuit power combining,and the main points are as follows.To ensure the high efficiency of the combined power network,this thesis conducts theoretical analysis from four aspects: path loss,isolation degree,amplitude and phase inconsistency and heat dissipation,which lays a certain foundation for the subsequent design of power combining networks.Based on the theory of scattering matrix and impedance transformation,the threeport and four-port power dividers are theoretically analyzed.Two E-plane coplanar magic-Ts based on microstrip probe,and ridge waveguide probe,respectively,and an Eplane waveguide magic-T using two-stage rectangular matching steps are designed.Simulation results show that the above three magic-Ts have good performance in their respective operating frequency bands,with return loss greater than 21 d B,isolation greater than 15 d B and power imbalance less than 0.03 d B,which can be used to construct wideband binary power combining networks.Based on the two-stage E-plane waveguide magic T structure,Subsequently,a four-channel G15 combining power amplifier module is designed and implemented.The measured results show that in the frequency band of190-222 Ghz,the saturated output power is greater than 19.8d Bm,and the combining efficiency is greater than 68%.Using radial waveguide to realize N-way direct combining network has an incomparable advantage over binary synthesis network in path loss.Therefore,based on the electromagnetic theory,the mode and electromagnetic field distribution in the radial waveguide are analyzed theoretically.After considering the factors such as higher mode and power capacity,the coaxial line is selected as the input source of the radial waveguide,and three kinds of radial power splitters including twelve,eight and five channels are designed.In order to facilitate the subsequent testing and reduce the leakage loss,two kinds of rectangular waveguide-coaxial transition structure and choke ring structure are designed based on the coupling probe and resonant ring principle.The measured results show that the return loss of the three radial power dividers is greater than 10.5d B,16 d B and 14 d B respectively in the 180-240 GHz band.