Ka-band Theoretical Analysis And Experimental Study Of The Diffraction Radiation Oscillator Output Device

Relativistic diffraction generator (RDG) is a very important branch of high-powermillimeter wave devices. Our laboratory has successfully developped a 300MW RDGdevice in Ka-band supported by the Natural Science Foundation (60178011) ofP.R.China. This dissertation gives detailed theoretical analysis and experimentalresearch of the output structure used in the device.The main work includes research ofTM_On modal excitation in overmode circular waveguide, radiation characteristic analysisof output window, research of the effective area of an open-ended waveguide inKa-band,radiation power measurement of RDG device.The main work is the following:1.The RDG device developped in our lab introduces overmode conic horn asoutput element.For accurately measuring the output mode and power of the device,weuse a coaxial line probe to excite TM_On mode in a overmode circular waveguide.TheTM_On multi-modal excitation of the coaxial line probe-to-circular waveguide isrigorously treated using the conservation of complex power technique(CCPT). We alsoinvestigate the reflection coefficient of the coaxial line and power distribution of variousorder modes excited in circular waveguide as a function of the probe length at differentfrequencies.By theoretical analysis and computer simulation,we design and manufacturea mode converter, consisting of a coxial probe and a overmode circular waveguide. Thenumerical programme results,HFSS simulation results and experiment results agree wellThe converter can excite the TM_On mode that operating at the device,then we canquantificationally calibrate power and radiation characteristic of the device.2. We take the TM_On mode converter as a feeding source to analyze the conic hornantenna.We use a cascaded junction ladder to simulate the conic horn,also utilize CCPTto analyze the scattering characteristic of the system.The mode scale coefficient isobtained by analyzing total scattering matrix, the numerical results and HFSS resultsagree well. We obtain the antenna farfield radiation pattern by using circular calibrefarfiled radiation formula, then we measure the near-field radiation pattern of the conic horn, which offers guidance in the power density distribution testing and radiation modetesting.3.We find that the caliber utilizing coefficient of the open-ended waveguide(BJ-320) as a receiving antenna for 8mm diffraction radiation oscillator is about 1.56 bysimulation and measurement.The simulation results are in agreement with theexperiment results.4. By analyzing mode picture and spatial power density distribution of the hot testand the theoretical analysis and simulation results,we find that the results areapproximately accordant and the methods of theoretical analysis and simulation areavailable.