超穎材料應用於毫米波高增益天線之設計

Abstract

本篇論文提出一種毫米波頻段的高增益天線之設計方法，利用超穎材料及多層印刷電路板的架構來實現，其中一層為超穎材料所設計之部分反射表面（Partially Reflecting Surface, PRS），另一層金屬接地面所構成，故此天線亦稱為部分反射表面天線。其中此型態的天線可讓電磁波在部分反射面及接地面之間所形成的共振腔中來回共振以達到高增益天線的特性，將可應用於即時且高傳輸速率的第五代行動通訊（5G）中。 在本論文中，首先探討超穎材料週期性結構單元的反射係數大小及相位，並依此設計天線共振腔之高度，完成原型的設計。接著以陣列方式進行激發來提高整體之增益，並採用非等能量走線的方式饋入，用以實現降低旁辦波束的表現，除此之外，在天線模組的周圍加上由金屬通孔所組成的金屬壁，除了可使共振到外圍的波再反射回來，用以增加天線增益外，亦可減少天線模組之間的互相干擾。在操作頻段37 – 40 GHz的頻率下， 陣列天線的正向輻射最大實際增益可達到19.1 dBi，SLL（Side lobe Level）在中心頻處可達到-22.5 dB。在 陣列天線的部分，正向輻射增益最高可以達到25.1 dBi，SLL在中心頻處也可達到-17.3 dB。 此外本篇論文設計了一提升部分反射表面天線頻寬的解決方案，由原本典型的結構底層加入一漸進式矩形的超穎材料，其利用五種不同大小的金屬片，藉由反射相位正向斜率的特性來達到寬頻的效果。

This thesis proposes a high-gain antenna designed in the millimeter-wave band using Metamaterials, which is implemented by multilayer printed circuit board architecture. One of the layer is made by Metamaterials designed for partially reflecting surface (PRS), the other layer is ideal metal ground plane. We call it a partially reflective surface antenna. The resonant cavity formed between the PRS layer and the ground plane allows electromagnetic waves to resonate back and forth in the resonant cavity to achieve high gain antenna characteristics. It can be applied to fifth generation (5G) communication systems with low latency and high data rate. First, we analyzed the reflection coefficient and reflection phase of each unit cell structure of Metamaterials. According to this model, we design the height of the antenna cavity and complete the preliminary design. Second we use 4 by 4 and 8 by 8 array feed excitation which use non-equal power feeding network to go in order to reduce the function of the side lobe. A metal wall composed of through via is added around the antenna module, it can not only reflect the EM wave and enhance the antenna gain but also reduce interference with each antenna modules. In our operating frequency band of 37 to 40 GHz, the maximum realized gain of the 4 by 4 antenna array can reach 19.1 dBi, the SLL (Side lobe Level) can reach -22.5 dB at center frequency. For the 8 by 8 antenna array, the maximum realized gain and SLL can also achieve 25.1 dBi and -17.3 dB respectively. Also, we proposed a solution for enhance the bandwidth of a partially reflective surface antenna. Tapered Metamaterial is added to bottom of the typical structure, which utilizes five different sizes of metal sheets, with different reflection phases. The characteristics can achieve broadband effects.