背接金屬共平面波導饋入槽孔天線

Abstract

背接金屬共平面波導以主模(共平面波導模態)傳播電磁波，在任何頻率下皆會激發表面波向兩側傳遞，致使印刷電路板或是封裝裡產生不必要的耦合及串擾。文章中簡短提及，我們能藉由幾種方式抑制此表面洩漏波，使背接金屬共平面波導只以共平面波導模態傳遞，形成良好的傳輸線。 利用全波分析，得知該表面波以某一角度偏離主軸傳遞。在已知偏離角度下，沿該角度射線每隔一波長蝕刻一矩形槽孔，使每個槽孔被等相位地激發。當矩形槽孔長邊遠大於寬邊，並約等於二分之ㄧ波長(共振長度)時，電磁波便能有效地朝空氣輻射能量形成天線，最後可得一集中的邊射輻射場形。 直播衛星收發天線運用在12GHz的頻段，要求高增益與高效率。本論文研究遂將天線的操作頻率設計在該頻段上，最後可得25.98dBi的輻射增益以及0.9GHz的頻寬。

Conductor-backed coplanar waveguide (CBCPW) exists two dominant modes including CPW and parallel plate modes (surface wave) with no cutoff frequency. The latter causes the power leakage into transverse direction, resulting in unexpected or even harmful coupling and crosstalk to the neighboring transmission lines or devices. By some methods, we can suppress the surface leaky wave, and the structure would become a good transmission line. It will be exhibited briefly in the article. Implementing the full wave analysis (Spectral Domain Analysis) on the CBCPW structure, we can acquire the information that the surface wave propagates along an particular angle relative to the main CPW line. So, we etch rectangular slots along the angle on the two side ground planes. Because the slots are separated one guided wavelength, they are excited in the same phase. If the long dimension of the slot is significantly longer than the wide one and approximately equals to a half of guided wavelength, the slots fed by CBCPW can radiate power efficiently. Finally, we derive a broadside radiation pattern. The antenna for direct broadcast from satellites (DBS) is operated at 12 GHz and asked for high gain and efficiency. We also make our antenna operate at this frequency. Finally, we have the measured radiation pattern with 25.98dBi and the measured bandwidth with 0.9GHz.