| In recent years, wireless communication systems, such as smart mobile and PDA, are more and more popular. On the other hand, wireless communication systems meet more and more demands, such as low power consumption, high transmission speed, small device volume and etc. Now the IC process is reaching 65nm, most RF circuit’s devices, such as resistor, capacitors and transmission lines, can be integrated in a single chip. However antenna linking the device and free space can’t be integrated in the chip, so the whole system volume is largely dependent of the size of antenna. The performance of the antenna has a significant influence on the system performance: power consumption, transmission quality, and etc. At the same time, wireless communication frequency is now moving to millimeter-wave and sub-millimeter-wave band because the communication channel is becoming more and more crowded. In millimeter-wave band, the wavelength is only several millimeters, so the accuracy of fabrication process is most critical. Traditional precise machining can’t meet the requirements of the high precision of millimeter-wave fabrication. As a result, researchers have paid more and more attention to the design and fabrication of integrated antenna.Based on semiconductor process, MEMS (Micro-Electro-Mechanical Systems) micro-fabrication technology is compatible with IC process. In addition, MEMS micro-fabrication technology has an accuracy of 1μm, so it can be used for the fabrication of millimeter-wave antenna. According to antenna theory, combining with features of MEMS fabrication process, this article gives several designs of millimeter-wave antennas. And the numerical simulation is performed for each design using Ansoft HFSS, which is a simulation software based on Finite Element Method (FEM).The first design introduces a circularly polarized microstrip antenna fed by coplanar coupling microstrips. Through the coupling method the radiation efficiency and impedance matching are improved, while the coupling efficiency is not affected. The circular polarization is implemented by the 3dB microstrip bridge.The second design introduces a broadband unidirectional coplanar waveguide (CPW) fed rectangular slot millimeter wave antenna based on MEMS micro-fabrication technology. A wide impedance bandwidth of 75% (S11<-10dB) was obtained. A special method based on MEMS process for CPW-fed slot antennas to obtain unidirectional radiation and higher gain is introduced. By adding 3 layers of wave cut-off slots and a guiding slot, the antenna achieves unidirectional radiation, and the max gain of the antenna increases from 3.8dB to 6.8dB.In the third design a novel MEMS-based CPW-fed millimeter wave slot antenna for broadband circularly polarized and unidirectional radiation with multilayer 3D structures is proposed. Through a special short-circuiting stub perturbation method, the circular ring slot antenna generates circularly polarized radiation and achieves a broad impedance bandwidth of 20%. To obtain unidirectional radiation and relatively higher gain, a special method based on MEMS micro-fabrication technology is introduced. By adding special wave guiding slot structure and wave cut-off slot structure, a novel approximate perfect magnetic conductor (PMC) surface, the antenna radiates unidirectionally and the peak gain increases about 3dB.Antenna arrays prevail in radar and microwave communications because of their high gain, good directivity and extensive coverage area. In this paper, two kinds of 1×4 and 2×2 antenna arrays composed of CPW-fed circularly polarized slot elements is discussed. |
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