24-GHz車輛前視防撞警示雷達之高增益透鏡天線開發

Abstract

本論文中設計一個可以應用在24-GHz前視防撞警示雷達上之高增益透鏡天線，操作頻段為24.025GHz~24.225GHz，本論文使用架構為將接收與發射饋入天線放在透鏡天線焦點之兩側，接收與發射天線其主波束輻射場形會有小角度往主軸兩側偏移，而收發天線輻射場形之交集維持在主軸上，其優點為使用面積與單天線相同，並且無使用單天線時，混波器造成之6dB 損失。當實際系統應用上時，微波主被動元件被包覆在金屬牆遮蔽內，因此饋入天線周圍會存在金屬牆遮蔽，適當設計金屬牆與天線間之距離，可以提高接收與發射端之隔離度。在不同的傳送與接收饋入天線之間距時，探討對於收發天線輻射場形與接收與發射端隔離度之影響。最後為了得知天線應用時的可偵測範圍，實際量測車輛之雷達反射強度對角度的關係，帶入雷達方程式，評估實際應用時雷達可偵測範圍。

In this thesis, a 24GHz forward-looking collision warning antenna operating at 24.025GHz~24.225GHz has been developed. In order to separate transmitted and received signal at reality application, we generally use two kinds of structures. First one is double antenna structure but the drawback is using double area. Another type is single antenna structure, which uses the quadrature hybrid to separate transmitting and receiving signals. The cost is extra 6dB loss. When feed antenna is located lens focal point radiating energy through lens, the main lobe is located at axis. We introduce a new antenna structure putting transmitting and receiving feed antenna at focal point two sides. The main lobes of the transmitting and receiving signal diverge from axis, but the intersectional region of the transmitting and receiving signals is still locate at axis. In practical application, RF active and passive components are surrounded by metal shield. We treat the effect when antenna surrounded by metal wall. We can enhance the isolation between transmitting and receiving port when we properly design the metal wall. We discuss about different space among transmitting and receiving antenna impact on radiation pattern and the isolation between transmitting and receiving port. In the end, we measure the radar cross section of vehicle at different angles. Then we calculate the radar detection region by the radar equation.