Study Of Theory, Model, Simulation And Characteristic Of RF-MEMS Antennas

In recent years, Micro-electro-mechanical System (MEMS) has been developed drastically. MEMS technology applied in radio frequency communication field, which is known as RF-MEMS (Radio Frequency Micro-electro-mechanical System), has great potentials. RF-MEMS research has become very important in application of radio frequency, and drawn attention of academe and governments greatly. Micromachined RF-MEMS antenna, one of the key devices in RF-MEMS, has small size, light weight, stable quality and other merits; it can be integrated with other circuit element.Rest on present research status of RF-MEMS antenna, systematically theoretical analysis and profoundly experimental research on electromagnetic radiation and coupling, mathematical modeling and numerical simulation, parameter optimization, machining and measuring of micromachined antenna in micro-scale have been presented in this thesis. Several types of micromachined antennas have been fabricated successfully. Innovation and breakthrough have been obtained in theory, numerical simulation, parameter optimization and fabrication.The main contents of the thesis are shown as follow: analysis on electromagnetic radiation and coupling mechanics, quasi-static characteristic parameter of RF-MEMS antenna, discuss on the related electromagnetic character of dispersion and surfacewave effect; optimization of Finite-Difference-Time-Domain (FDTD), numerical simulation of micromachined antenna using optimized FDTD, and related parameter calculation; parameter optimization by theoretical analysis associated with experimental research, realization downsize and broadband by novel structure and hybrid substrate, resolution of calculations on relative dielectric constant and input impedance, realization of a quarter wavelength antenna by shorted wall. Material selection standard and fabrication process of micromachined antenna are presented. The antenna measurement fields are introduced, then error analysis of parameters developed. We applied the micromachined antennas in Bluetooth computer Demo devices and Motorola G18 wireless communication system, both can communicate with other devices. In the end some research plan such as micromachined array and multi-chip module are put forward.Following are the important achievement and innovation:To model and simulate micromachined antenna in micro-scale using TLM, cavity model and FDTD. To simulate micromachined antenna by optimized FDTD, and(1) verify it by experiment. It indicates that the optimized method is rational, and the optimized FDTD can be used to design micromachined antenna.(2) By theoretical analysis and experimental research of shorting stubs between patch and ground, it indicates that the shorting stub could lower frequency of microstrip antenna. Shorting wall in place of shorting stub, which can turn the antenna to a quarter wavelength antenna, has been put forward. The antenna dimensions will be downsized further if C folded structure is used; the length of the antenna is only 1/12 wavelength in free space.(3) According to deficiency of high index substrate to antenna, some of the substrate beneath the patch should be partially removed, or some low index substrate should be sandwiched between the ground and the high index substrate, so the surfacewave would be suppressed greatly, then the efficiency and bandwidth would be increased.(4) By using parasitic patch and additive microstrip vibrator, the coupling effect with drive patch could enlarge bandwidth of the antenna.The research of electromagnetic radiation, miniaturization and broadband of micromachined antenna in micro-scale has benefits, and found theoretical and technical base for improvement of electromagnetic field theory in micro-scale and antenna integrated fabrication.