Effect Of The Surface Roughness On Electrical Properties Of High Performance Microwave Electronic Equipments

In recent years, with the high frequency, high density and high power development of theelectronic equipments, relationship of the acting on or influencing each other between theelectronic performance and the mechanical structural factors became more and moreprotruding. Among several mechanical structural factors which influencing the electronicperformance of the electronic equipments, the roughness attracted mucha attention of thescientist because of its widespread presence, random distribution and complicated influences.With strong economic support of several state key construction projects, take the waveguide,filter, reflector antenna and planar slot array antenna as the research case, this dissertation ismainly concerned with effect of roughness on the electronic equipments in the process of thedesign and analysis. The author’s major contributions as follows:1. Electromechanical coupling modeling of roughness in cavity was built. According tothe constructional feature of roghness in cavity, the value of skin depth determined by theworking frequency and material properties of the cavity structure based on the microwavesurface theory, and then the roghness scope, roghness in which has an important influence onthe flow path of the surface current, was determined. Secondly, the roughness component,which has little effect on the flow path, was filtered off from the original roughness by usingthe Gaussian function as the filter tool. Finally, the effective roughness component was gainedand the electromechanical coupling modeling of roughness was built.2. Multi-scale roughness modeling of roughness on panel was built. To the specialformation mechanism and distribution form of roghness in cavity, a concept of generalizedroughness was put forward. Roghness on the panel structure can be devided into three scalesbased on the different error sources and phase-amplitude characteristics. One was theroughness error in high frequency and low amplitude, which determined by the materialproperties and machining process; Two was the waviness error in low frequency and lowamplitude produced by the antenna assembling process; Three was the error in low frequencyand high amplitude, which by the external loads. The three scales errors together were calledas generalized rughness in the dissertation. Firstly, the frequency spectrum division was madeon the plane test data including three-scale roughness error by using the wavelet as theanalysis tool. Secondly, the wavelet base and decomposition times were determined by eachscale roughness. Based on the wavelet function, the three roghness error were separated andreconstructed, the multi-scale roughness modeling of roughness was built.3. Effect of the roughness on the electronic performance of the waveguide has beenstudied. Based on two dimensional fractal function, an electromechanical coupling modeling was built to simulate the roughness on the inner surface of the waveguide. Research showedthat effect essence of the roughness on the waveduide was prolonging the flow path of thesurface current. So, the mathmetics model of the roughness was taken as the boundarycondition, the effective conductivity was gained by the effective current path. According tothe circular and square waveguide, two effect formulas of the roughness on the power losswere given separately. In addition, also to the local roughness, the computation formula of thepower loss has been presented. Finally, a seven-step waveguide filter prototype wasconstructed to validate the feasibility of the modeling methods and the effect formulations.4. Effect of the roughness on the electronic performance of the filter has been studied.Firstly, one and two dimensional electromechanical coupling modeling were built to simulatethe roughness on the inner surface of the filter. The persistence length was introduced as acomplementary parameter for the root means quare, which is used as the only Assessmentparameter the roughness. Secondly, the impedance of the filter with roughness was gained andthe effect formulas of the roughness on the quality factor was deduced. The dissertation thenderived the calculation formulas of the S11and S21of the filter with roughness. Finally, anelectronic tuning duplex filter prototype was constructed to validate the feasibility andefficiency of the modeling methods and the effect formulations.5. Effect of the roughness on the electronic performance of the reflector antenna has beenstudied. With the consideration of actual working conditions, the multi-scale modeling wasbuilt to simulate the three scales roughness on the reflector surface of the antenna. Firstly, theroughness was converted into the optical path difference in the physical optics method, andthen it was transformed into the phase difference in the computational electromagnetism.Secondly, the effect formulas of the roughness on the radiation field was deduced based on thephase difference. In addition, effect of the different scale and amplitude of roughness on theantenna radiation patter was studied. Finally, a3.7m reflector antenna prototype is constructedto validate the feasibility and efficiency of the modeling methods and the effect formulations.6. Effect of the roughness on the electronic performance of the planar slot array antennahas been studied. On the one hand, the electromechanical coupling modeling was built tosimulate the roughness on inner surface of the radiating waveguide; Firstly, the disturbance ofincident wave in radiating waveguide caused by the roughness will originates the forward andbackscattering wave. So, the normalized admittance of the radiating slot can be gained by thereflection and transmission coefficient, and then the effect formulas of roughness on theradiating voltage can be deduced. On the other hand, the multi-scale modeling was built tosimulate the roughness on the radiation array surface of the antenna. The position and direction offset of the radiation slot were studied in consideration of the roughness. The newphase error and radiating pattern were added into the electromagnetic analysisi model of theideal antenna.So that, the effect formulas of roughness on the electronic performance can begained. Finally, a11*10cm planar slot array antenna prototype is constructed to validate thefeasibility and efficiency of the modeling methods and the effect formulations.7. Modelig and simulation of the nonideal electronic equipments has been studied. Inaccordance with the present problems of the business softwares, the nonideal electronicequipment is hard to simulate and the divorce of structural analysis from electromagneticanalysis. Firstly, the machining error is added into antenna in the process of geometricmodeling, and the error was set by the description precision. And then, when the structureanalysis of the antenna is carried out, the loading error was added, and the deformed structuremodel of the antenna is gained by the structure analysis. The assemble error is added on thedeformed model with the model modify module. Finally, the deformed structure model istranslated into the electromagnetic analysis model, and the electrical property of the antennais gained. Moreover, aiming at the large planar slot arrar antenna, which contains manysubarrays, has huge physical size and complex structure, some actual problems exsiting inprocess of simulation has been studied. Some comparative analysis experiments were madeon the choosing method of calculation, meshing of the grid, applying of the radiationboundary and the effect of mutual coupling among the subarrays. Finally, the simple andeffective modeling criterion was proposed.8. A rudimentary functional design method of electronic equipments surface was putforward. Based on the research results of the roughness modeling and effect relationshipbuiding, a functional degign flowchart was presented as follow: Firstly, on the basis ofperformance requirements, the design indexs of the electronic equipments were given, and thedesign indexs included the structural design indexs and the electronic design indexs. Secondly,the structural design indexs were implemented by choosing the good material and soundworkmanship, while the latter were implemented by choosing the appropriate coating materialand technology. Thirdly, the solid boundary was obtained by structure modeling and surfacecladding, and then the electromagnetic boundary was gained based on the solid boundary.Finally, the electronic performance of the electronic equipment was got by using theelectromagnetic boundary.