半寬微帶洩漏波天線應用於寬頻及低旁波瓣之設計

Abstract

本論文設計天線皆使用半寬的天線架構來取代傳統結構較為複雜具180度相位差激發電路之全寬結構。半寬電路結構利用週期性鉚釘結構使基板上下層金屬導通，以此視為一等效電牆，其優點為：(Ⅰ)簡單的饋入結構，僅利用微帶線饋入即可；(Ⅱ)可以準確地激發出純正的第一高階模，而不需要抑制掉零階模；(Ⅲ)相較於全寬電路，大幅縮減其天線尺寸。 根據微帶線第一高階洩漏波特性，本論文使用數值設計流程與全波仿真模擬軟體來設計提出天線。第一支提出天線為寬頻緩變洩漏波天線，頻寬由7 GHz到13 GHz 反射損失皆小於-10 dB，且操作頻帶內，主波束指向角度大約一致；另一提出天線利用變化的週期性鉚釘結構控制傳播特性，其頻寬於9 GHz 到12.5 GHz，且具降低旁波辦約4dB之特性及主波束增益集中之效果。

In this thesis, we use half-width structure instead of conventional full-width structure which has the complex feeding structure to design leaky-wave antenna. In the half-width structure, we take the periodic via holes connecting between top and bottom metallic layers as the PEC wall. So, we can figure out the advantages of the half-width structure are shown below: (I) simple feeding structure just using microstrip line (II) pure the first-higher-order leaky-mode excitation and no need to suppress EH0 mode (III) reduced antenna size compared to the full-width structure . Based on the characteristics of the first higher leaky-mode for the microstrip antenna, this thesis proposes a design flow of broadband tapered half-width microstrip leaky-wave antenna by numerical analysis and simulation software. The simulated bandwidth of the antenna is from 7 GHz to 13 GHz and the angle of main beam is not changed with the varied frequency in operation bandwidth. On the other hand, we also propose a design flow that use varied periodic via holes to control propagation characteristics to make the pattern of proposed antenna impoved. The simulated bandwidth of the antenna is from 9 GHz to 12.5 GHz and the peak side lobe level is reduced 4 dB.