Research On Millimeter Wave Ultra-wideband Radial Power Combination

Recently,a millimeter-wave waveguide-based spatial power combining technique using MMIC PAs(Monolithic Microwave Integrated Circuit Power Amplifiers)has gradually become a hot point in millimeter-wave solid-state high power electronic field.In these researching works,the realization of millimeter-wave broadband power combining has been cumbered by problems about maintaining a high efficiency and a broad bandwidth under a large number of combining ways.These problems are mainly studied in this thesis.This thesis describes the design of K~Ka band ultra-wideband radial power combiner based on three kinds of power combining structures.This thesis has analysed the development of the solid power combination technique and the power distribution network,which is widely used in millimeter-wave bands.Three structures,including coaxial waveguide-radial waveguide transition,ridged waveguide-microstrip double probe transition and transition structure with ridged waveguide are simulated,optimized,fabricated and measured respectively.The main results are as follows.1.Based on the theory of coaxial-radial waveguide transmission,coaxial-radial waveguide transition structure has been designed in K~Ka band.This structure has the advantages of well symmetry,low-loss and not easily affected by processing and assembly factors,thus it is appropriate for ultra-wideband application in K~Ka band.In 18~40GHz,the reflection coefficient at coxial port is less than-15 dB,the insertion loss at every radial port is less than 0.3dB,the VSWR in band is less than 1.25.2.Based on the theory of the E-plane waveguide-microstrip probe transition,the waveguide-microstrip double probe has been designed,manufactured and measured.This structure is appropriate for ultra-wideband application in K~Ka band.The reflection coefficients at two port are less than-13 dB,the insertion loss at every port is less than 2dB,taking out of the transmission line loss,the insertion loss of this transition is about 1.5dB.3.Based on the theory of Chebyshev impedance converter,the step transition structure with ridged waveguide has been designed.The simulation result of this structure and coaxial-radial waveguide transition structure shows that in 18-40 GHz,the reflection coefficient at coxial port is less than-16 dB,the insertion loss of mixed structure is less than 0.2d B.And then based on this structure,the improved multiple disk Matching transition structure has been designed,it made the reflection coefficient at coxial port is less than-19 dB,the insertion loss of improved mixed structure is less than 0.1dB.4.Based on the combination of all of the above structures,the coxial-radial-ridged waveguide-microstrip double probe 24-road power combiner's back-to-back structure has been designed,manufactured and measured.In 24~40GHz,the reflection coefficient at coxial port is less than-10 dB,the insertion loss of back-to-back structure in band is less than 1.25 dB,the combined efficiency of single-ended back-to-back structure is about 75%.