Papers by Keyword: Radio Frequency (RF)

Abstract: This research aims to study the growth and the effect of annealing temperature on the structural properties of Platinum/YSZ/Platinum thin film. The thin films were prepared by RF and DC magnetron sputtering method utilized platinum as electrodes (anode and cathode) and YSZ as electrolyte. Two temperatures of annealing (400 and 600 °C) were conducted onto Platinum/YSZ/Platinum thin film for comparison in this study. Crystalline phase, microstructure and thickness of thin films were evaluated using X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FE-SEM) technique. Results show that Pt/YSZ/Pt thin film without post-annealing gives a better morphology and crystal phase.

Abstract: Custom orthopedic and dental implants may be fabricated by additive manufacturing (AM), for example using electron beam melting technology. This study is focused on the modification of the surface of Ti6Al4V alloy coin-like scaffolds fabricated via AM technology (EBM®) by radio frequency (RF) magnetron sputter deposition of hydroxyapatite (HA) coating. The scaffolds with HA coating were characterized by Scanning Electron microscopy, X-ray diffraction. HA coating showed a nanocrystalline structure with the crystallites of an average size of 32±9 nm. The ability of the surface to support adhesion and the proliferation of human mesenchymal stem cells was studied using biological short-term tests in vitro. In according to in vitro assessment, thin HA coating stimulated the attachment and proliferation of cells. Human mesenchymal stem cells cultured on the HA-coated scaffold also formed mineralized nodules.

Abstract: A new type of fully self-aligned technology for graphene field-effect transistors was presented, in which a PVD SiO₂ layer was taken as mask for the deposition of self-aligned source, drain and gate contacts. In this key process, the dielectric edge-sides exposure phenomenon during metal thermal evaporation was exploited. In the prepared self-aligned GFETs, both parasitic capacitance of the gate overlapped source and drain areas and series resistance of the spacing areas between gate and source and drain contacts were eliminated. The DC characterization and on-chip microwave measurement of the fabricated GFETs with channel length of 1give a maximum transconductanceof 2.32,field-effect mobilities of electrons and holes of 6924and 7035, and intrinsic cutoff frequencyof 0.5GHz, respectively, showing a significant improvement of both DC and RF performance.

Abstract: RF technology is widely used in wireless communication. Due to the small size, high density and high frequency, RF IC testing based on ATE faces many challenges. This paper took a LNA chip fabricated by a GaAs process as an example, simulated the test circuit and studied two methods of RF impedance matching by using the software of Agilent ADS. The results show that it solves the impedance mismatch of the input and output ports in RF test, providing the theoretical support to the design and production of RF test board.

Abstract: RF characteristics of metal-insulator-metal (MIM) capacitors with SiO2/HfO2/SiO2 (SHS) were investigated using an equivalent circuit model that is associated with the main impedance ZMIM.cap and the substrate-related conductance Ysub. However, the parasitic capacitance in Ysub was lower than that of another element component in ZMIM.cap, which makes difficult for accurate RF modeling because the parasitic component was dominant at high frequency regions. As low parasitic component is eliminated from the modeling, the extracted capacitance for SHS MIM capacitor was stable up to 20 GHz. The Q-factor and resonant frequency (fr) point of SHS structure are 23.9 at 1 GHz and 9.76 GHz, respectively.

Abstract: A new isolation optimization method of radio frequency (RF) microelectromechanical systems (MEMS) capacitive switches is carried out in this paper. We simplified the coplanar waveguide and the top movable electrode as two-port network. The existence of the maximum isolation of single switch is proved theoretically based on circuit model and S-parameters model. The isolation of the distributed switches with lossless transfer lines, which is the function of the transfer lines length and the impedance of metal beams, is described by mathematic expressions and simulated in a numerical method. We find that the isolation varies periodically with θ and f, which are the electrical length between metal beams of the distributed switches and the signal frequency. It achieves the maximum value 83dB at θ=π/2 for 2-beams switch. However, different from single beam switches, the distributed switches maximum isolation is near but not precisely at the resonance frequency f0. The bandwidth of RF signal can be widened to about 200% for 5-beams switch by using the proposed design method. The results will be useful for Resistance-Inductance- Capacitance parameters optimization of RF MEMS Capacitive switches.