| Millimeter wave is defined as electromagnetic wave whose wavelength falls in the range of 1 centimeter to 1 millimeter, and the frequency is from 30GHz to 300GHz. Wireless communication applications working in the millimeter wave band can utilized its broadband advantages to achieve high speed data transmission. Millimeter wave transmitters and receivers are easy to be integrated with monolithic microwave circuits, which make the Miniaturization and compactibility of RF integrated circuit into possible. Millimeter waves can travel through severe weather much more readily than infrared or optical waves, which make itself a more suitable candidate for wireless communication. Antenna is the corn component of wireless communication applications. Millimeter wave antennas have merits of small size and compact configuration, meanwhile, its high directivity make itself to be used for high-resolution radar and compact guidance systems. Coplanar waveguide (CPW) fed slot antennas are preferable candidates for millimeter wave application, owing to their light weight, low profile and compatibility with monolithic integrated circuits and active solid-state devices. Due to its feature size comparable with wavelength, millimeter wave antenna has a high request for fabrication precision, besides, in order to achieve high performance in bandwidth, complicated configuration in two dimension plane has been introduced in antenna design, and also some low profile 3 dimension structures. Traditional precise machining can't meet the requirements of the high precision integration of millimeter-wave fabrication. We must explore integrated fabrication process which is more suitable.MEMS technology has got the advantage of planar integrated fabrication which also belongs to the IC technology, furthermore, it compatible with three dimensions micromachining process which has the accuracy of 1 micron, or even nano scale, and it can integrate the process of multi-materials. It provides a method to satisfy the requirement of precisely integrated multicomponent fabrication.Based on the advantage of three dimensions micromachining technology, we intend to explore the proper way to apply the MEMS fabrication technology to the millimeter wave antenna focusing on the design of low profile planar slot antenna array. In this article, three designs of millimeter-wave broadband antenna arrays with CPW-based feeding network are presented. The Ansoft-HFSS, a kind of numerical simulation software, is performed for each design to conduct analysis and optimization. After exploring a serier of integrated fabrication process we fabricated a kind of design under the process of MEMS technology, did some tests and reached the expected target.In the first design, a 2×2 antenna array fed by CPW-based parallel feeding network is proposed, air bridges is used to suppress the unwanted odd mode excited in the T-junctions of CPW-based feeding network, which can guarantee low loss of the transmission network, a cutting tuning stub is introduced to achieve impedance matching, the measured operating bandwidth is 30GHz-39.6GHz with S11<-10dB, considering that the center frequency is 35GHz, the relative bandwidth is 27.4%, the measured result and the simulated one match well, and the simulated antenna gain is in the range of 8.5dB and 10dB among the whole operating band.Based on the design of bi-directional radiation, antenna array with metal reflecting structure which has a circular slot in the center is given. The performance of antenna gain which is effected by the reflection patch is discussed, the simulated result shows that the antenna array radiate unidirectionally and the antenna gain is 12.2dB in the point of 35GHz, the impedance bandwidth is from 34.4GHz to 35.9GHz with S11<-10dB.The third design has achieved the performance of broad band as well as the unidirectional radiation. The impedance bandwidth is from 31.6GHz to 39.2GHz with S11<-10dB, the relative bandwidth is 27.4%, and the simulated antenna gain is 11.6dB. |
PDF Full Text Request