Research Of6.835Ghz Microwave Devices In Miniaturized Rubidium Atomic Clock

Because of the simple structure, small shape, light weight and excellent stability, Rubidium standard has been widely used in many feields. Due to the rapid development of MEMS technology, to miniaturize the rubidium atomic frequency standard has been a major research in many countries. As the quantum part in the rubidium atomic clock needs a6.835GHz microwave signal, this paper research the microwave cavity and MEMS coil to launching the microwave signal. Electroplating technology in the MEMS coil manufacturing process is also researched in this paper. The thesis is mainly divided into the following three parts.Firstly, The6.83GHz microwave cavity in miniaturized rubidium atomic frequency Standard is designed and analyzed. Electromagnetic fields in the microwave cavity are analyzed, relationship of the resonance frequency and the size of the field excitation probe are studied. The Ansoft HFSS software is used to simulate the electromagnetic distributions in microwave cavity. Based on these, the microwave cavity is manufactured. By using the vector network analyzer, the S11parameters for the microwave cavity filled with different thickness of aluminum oxide ceramics are acquired. Tested results demonstrate that the electromagnetic field mode is TE101when the resonance frequency reaches6.83GHz, and the size of cavity is12mm×15mm×18mm with the thickness of filled aluminum oxide ceramics (96%) of5.66mm. The volume of the developed6.83GHz microwave cavity is3.24cm3, about1/3of the volume of the conventional unfilled cavity. It fits very well for loading the MEMS-based rubidium filter cell and absorption cell for miniaturized rubidium atomic frequency standards.Secondly, the MEMS coil is researched to replace the microwave cavity in the rubidium atomic clock. Coil value is calculated using three simplified formula of the inductance (Wheeler’s formula, approximate formula of current, fitting formula of numerical value). Then, the structure parameters of the designed MEMS exciting inductance is simulated By HFSS. Based on the parameters, MEMS coil is manufactured using MEMS technology and the fabrication processes. It can be shown that Q value reaches its maximum value at the frequence of3.308GHz with a relative error of3.2%to the designed frequency3.417GHz. Finally, Electroplating technology in the MEMS coil manufacturing process is researched. The principle of the electrocoppering is introduced, and the effect of the plating parameters including temperature, PH value, current density, complexing agent and the time is invastigated. The structure and electroconductibility are charaterized by XRD, SEM and four-probe arrangement. Based on the parameters (temperature is40℃, time is27.2mA, current density is1A·dm-2), the planar inductor is successfully fabricated, and the quality of cladding material is fine.