Research And Design Of Millimeter-wave Solid-state Power Amplifier

Recently,the millimeter-wave technology is advancing rapidly,as the core of millimeter-wave system,the solid-state power amplifier has higher requirements on its power level and bandwidth.For instance,millimeter-wave systems typically require output power levels of tens or even hundreds of watts.Due to the restriction of the semiconductor technology,solid-state devices at millimeter-wave frequencies are not capable of producing these power levels with just a single device.Therefore,it is usually necessary to combine the output power of several or,perhaps,even hundreds of devices to realize the required power level.This greatly promotes the development of power combining technology.Waveguide-based power combining technology,which is advantageous for low insertion loss,high power handling capacity,broadband,great heat dissipation,is applied to the millimeter-wave high power system widely.Based on the deep research of the N-way axially symmetric combining circuit and milti-stage power combining circuit,several novel waveguide-based power combining circuits have been presented in this thesis.A detailed analysis utilizing the circuit theory,simplified model,electromagnetic simulation,experimental measurement for the power combining circuit is also given.Furthermore,based on the actual need of the project,a broadband solid-state power amplifier at W-band is designed using the proposed combining circuits.The mainly achievements are described as follows:1.Two kinds of coaxial-radial waveguide tapered transitions,which are detailed analyzed using equivalvent circuit,is presented.In addition,a stepped-by-stepped design procodures is also developed.The proposed transitions have a smooth profile,which is advantageous for peak power handling.Moreover,it is convenient to optimize and control the impedance levels of the transition.The simulation results verify that the proposed coaxial-radial waveguide can achieve a broadband match from the coaxial waveguide to the radial waveguide.2.Based on the proposed coaxial-radial waveguide tapered transition,a radial waveguide power divider/combiner using ridge-waveguide probe coupers is presented.The ridge probe array is used for the power divider to realize a low insertion loss transition structure as well as high combining efficientcy.The probe coupling structure in favour of wide-band impedance matching.The metal character of the structure has the advantages of low loss,high power handling capacity and easy fabrication.The structure has the potential to widely apply for high power millimeter-wave system.3.Based on the impedance-controlled coaxial-raidal waveguide transition,a broadband radial waveguide power divider is presented.The structure is N-way power combining circuit that combining the N-way power in a single step.Hence,the power combiner can achieve high power-combining efficiency.The design emphasis in this structure is the radial stepped matching network,which can realize a wide-band impedance match.Finally,a Q-band twenty-way power divider/combiner has been manufactured and measured,the measured results indicate that 12-dB returned-loss bandwidth is approximately 15 GHz from 33 to 48 GHz,and insertion loss better than 0.87 dB.The amplitude imbalance and phase imbalance better than ±0.5 dB and ±4°,respectively,in the above mentioned frequency band.4.A W-band power dividing/combining network based on the overmode E-T power divider is present.The overmode waveguide is applied to break through the manufacture limit that dimensions of the traditional E-T power divider is too small at W-band.The connection between the diffierent dimension waveguides is the tapered impedance transition,which can reduce the couple of the parasitic modes,rather than the steppedimpedance transition.The simulated and measured results indicate that this novel combining network has low loss and high power combining efficiency over a wide range of frequency.