微機電變頻微帶天線之設計與分析

Design and Analyze of Micromachined Tunable Frequency Microstrip Patch Antenna

指導教授 : 黃榮堂、林信標  研究生 : 張錕能  機電整合研究所 90年


摘要

  本論文提出一種以微機電製作技術為基礎之變頻微帶天線(Micromachined Tunable Frequency Microstrip Patch Antenna)的設計。此變頻天線以操作在K頻段的微帶天線為主,而使微帶天線變頻的主要機制是於天線主體的周邊加上細長的調整片(tuning strip),並藉由微型開關(MEMS Switch)的配置來控制調整片是否與天線連接,當調整片經由微型開關的作動與天線連接時,天線的幾何尺寸會受到改變,進而影響其激發的頻率而達到變頻的目的。論文中以電磁軟體的模擬來確定此變頻天線的特性,由模擬結果中可得知,當我們設定好調整片與天線的距離後,等於決定其頻率的變動範圍,之後再經由微型開關的控制使天線與調整片連接,即可得到變頻的效果。若是於同一結構要有多頻段的變化,則可藉由多段調整片及微型開關的配置來達成。
本論文亦針對微型開關提出一種可變彈性係數的微型開關設計。此結構可以藉由階段式的設計來改變開關的彈性係數,進而使微型開關的可控作動行程範圍增加。由結果中可發現,兩段式變彈性係數的設計可以使微型開關作動行程的可控範圍從傳統的三分之一起始高度增加至二分之一起始高度以上,且其增加範圍亦隨彈性係數變化量的不同而有所增減。若是再增加彈性係數的變化段數,則可進一步獲得更大的可控範圍。此變彈性係數的設計可使以微機電技術製作的可變電容(Tunable Capacitors)獲得更大的電容值變化範圍。

ABSTRACT

  This thesis presents the design of tunable frequency microstrip patch antenna based on micromachining techniques. The design case is for a microstrip patch antenna operated in K-band. The rationale of tuning frequency for the microstrip patch antenna is by placing small tuning strip beside of the patch and by installing the corresponding MEMS switch to control the connective state between the tuning strip and the patch antenna. The dimensions of the patch antenna can be changed to obtain variable resonant frequency when the MEMS switch operates to connect the tuning strip and the patch antenna. In this thesis, an EM software package is utilized to simulate and analyze the range of the tuning frequency and the quantitative relationships among the dimensions of the tuning strips, the distance of the tuning strips away from the patch antenna. Simulation results show that to switch on or off the connective state between the tuning strip and the patch antenna can actually tune the operating frequency of the antenna. Furthermore, it can use the structure of multi-strip and multi-switch to achieve the requirements of multi-band application.
In this thesis a new design of the tunable spring constant MEMS switch is also presented. The design that includes both spring constant tuning structure and stopper can change the switch’s spring constant to increase the controllable displacement range. Simulation results show that the two-stage spring constant tuning design can increase the controllable displacement range from one third of initial gap between upper and lower electrodes to more than one half. In addition, the different spring constant tuning ratio also affects the controllable displacement range. The multi-stage spring constant tuning design can be developed to obtain a larger controllable displacement range. The application of the tunable spring constant structure in the micromachined tunable capacitor can obtain a tuning range of capacitance larger than conventional design.