小型化洩漏波天線與雙頻圓極化槽狀單極天線

Abstract

本論文主要包含二大部份：1. 利用開放式環形諧振器來抑制洩漏波天線的旁波瓣；2. 利用槽狀結構使單極天線產生雙頻帶且具有圓極化。在第一部分中，提出二種可以有效抑制旁波瓣的架構，第一種架構是將開放式環形諧振器放在天線主體的開路端，利用開放式環形諧振器所產生的截止頻帶效果，使得反射波在此截止頻帶內得以被抑制；而第二種則是將開放式環形諧振器放在接地金屬的部分，利用此架構將反射波耦合至開放式環形諧振器，透過此時環形諧振器所產生的截止頻帶，進而抑制洩漏波天線的反射波。由此可發現，利用開放式環形諧振器所產生的截止頻帶，不僅僅可以有效地抑制旁波瓣，更可以減少洩漏波天線的長度，達到縮小化的目的。 在第二部分中，介紹利用槽孔結構產生雙頻帶且圓極化的單極天線，天線主要架構為螺旋結構，並在其後端接一個圓形的金屬架構；而在接地金屬中，蝕刻出一個L型的槽狀孔，此L形的槽孔扮演著非常重要的角色，不僅可使單極天線能在低頻與高頻的部分產生雙頻圓極化的效果，更可以調整L形的長寬比來選擇雙頻圓極化所要操作的頻帶。另外，在天線的主體上也再蝕刻二個槽孔結構，此二個槽孔結構是調整高頻段圓極化操作頻帶的主要因素之一。由此可知，利用簡單的槽狀結構，亦可使得單極天線產生圓極化的效果。

This thesis consists of two parts：1. Using split ring resonators to suppress the side-lobe level of the tapered compact leaky wave antenna. And 2. Using the structures of slots to excite dual-band circularly polarization in monopole antenna. In the first part, we demonstrate two types of suppressing the reflection wave of the leaky wave antenna. The first structure is to put the split ring resonators at the open end of the leaky wave antenna, and the split ring resonators can generate stop-band to suppress the side-lobe level efficiently. The second structure is to etch the split ring resonators in the ground plane, and the reflected wave will couple to the split ring resonators and be trapped. Thus it can be seen that we can use split ring resonators not only to suppress the side-lobe but also to reduce the length of the leaky wave antenna. In the second part, a dual-band circularly polarized monopole antenna using structures of slots will be introduced. The main structure of the monopole antenna is a circular strip and we add a circular patch at the end of the strip. In the ground plane, we etch a L-shaped slot, and this slot play an important role of exciting the circular polarization not only at the lower band but also at the upper band. The most important is that we can choose the different length of the L-shaped slot to operate on the frequency band what we want. On the other hand, we also add two notches at the antenna, and these two notches can adjust the operating frequency band of circular polarization at the upper band. From the above, we can use these simple structures to get circular polarizations.