| At3mm wave band, the output power of an individual solid-state power device isquite limited. Therefore, realizing the multi-way high efficiency high power combing at3mm wave band is significant to promote the development of the system, and also thekey problem of3mm wave research. Based on the low transmission loss of waveguide,the thesis has mainly studied on the waveguide-microstrip multi-way integrated powercombing technique, and made outstanding achievements on aspects of workingfrequency band, power combing efficiency and the maximum output power. The mainwork of this thesis is as follow.1. The waveguide-microstrip E-plane multi-way probe transition has been studiedintensively. Based on the research of the waveguide-microstrip single probe coupling,the waveguide-microstrip anti-phase dual-probe power combing network has beenmanufactured at3mm wave band. In90-100GHz, the measured insertion loss is about2.2dB. The corresponding power combing efficiency is about86.3%. Besides, in thisthesis, a novel in-phase waveguide-microstrip dual probe transition available at3mmwave band has also been proposed. The two microstrip lines in the novel structure sharethe same metal ground. Each has an individual cavity which is quite convenient for theinstallation of solid-state devices. The simulation result shows that, in75-110GHz, thereturn loss of the input port is better than29dB, and the amplitude difference betweenthe outputs is less than0.1dB. Based on the simulated model, a2-way power combingnetwork has been fabricated. But, because of the fabricating error, the metal grounds ofthe two microstrip lines are not connected tightly. An air gap exists between the twogrounds. This is different from the simulation model and also the main reason of thegreat difference between the measured result and the simulation one. In90-100GHz, themeasured transmission factor is less than-2.6dB.2. The H-plane waveguide branch coupler has been studied and realized at3mm waveband. By changing the step style impedance transition to continuous style transition, thefrequency band of the H-plane branch coupler is widened. Besides, the rectangularmetal joint in the coupling region is changed to ladder-shaped. This improvement not only broadens the frequency band, but also reduces the difficulty of fabrication. In85-100GHz, the measured return loss of the input port is better than15dB, and theamplitude difference between the outputs is less than0.3dB.3. The thesis has studied the theory of the4-port rat-race coupler and derived therelationship between the admittance of the branches and the power dividing/combingproperty of the coupler. To reduce the transmission loss, waveguide is used to designthe coupler. Based on the study of the4-port rat-race coupler, the5-port symmetricwaveguide rat-race coupler is proposed and fabricated. This coupler has properties ofbroadband, low loss and highly symmetric outputs. In80-98GHz, the measured returnloss of the input port is better than14dB. The two outputs are in phase and theamplitude difference is less than0.35dB.4. A4-way power combiner working at3mm wave band has been fabricated. The2stage waveguide rat-race couplers are used to realize4-way power combing and thesingle probe to realize the transition between waveguide and microstrip. The measuredmaximum output power is more than450mW in88.5—93.5GHz, and the largest551.9mW is at90.5GHz. The achieved power combing efficiency is more than75%in89.5-95GHz, and the highest84.2%is at93.5GHz. |
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