低旁波瓣之洩漏波天線陣列設計

Abstract

本篇論文提出一種降低旁波瓣的微帶線洩漏波天線之設計，由於傳統微帶線洩漏波天線末端開路的架構，使得行進波在微帶線末端，因不連續而造成反射，此反射能量將沿著相反方向傳遞能量，同時也將此反射能量向外輻射，形成了不想要的旁波瓣。 此架構主要包含三個短洩漏波天線所組成的陣列天線，將反射波能量以再利用的方式，將輻射後剩餘的能量導引，並分別饋入其餘的兩個陣列天線中，將反射波功率再輻射利用，本天線是製作在FR-4板材上，操作頻率為4.4GHz，在場型的量測中，波束方向為~30□，3dB波束寬度為~40□，天線增益為+8.5dBi，旁波瓣位準為 -13dB。 利用此設計有效降低旁波瓣位準及波束寬度，對實際應用有助於降低干擾，同時陣列天線的結構也提高天線的方向性，應用在車輛防撞系統中可以提升系統的訊雜比。

In this paper, We propose a compact leaky-wave Antenna array to reduce side lobe level. Since the travelling wave propagating on the antenna will leak out the energy to the free space. But due to the discontinuity at the end of the antenna that will cause the reflected wave and propagate opposite direction. Then radiate unwanted side lobe. We reuse the reflected power due to the reflected power from the end of the microstrip line can reduce the side lobe level. The antenna array consist of 3 elements, each one has 1□ long. We guided the remained reflected power and split the power equally with the same phase difference into 2 paths then inject into each antenna elements. This antenna is fabricated on FR-4 PCB and operating at 4.4GHz. And the measurement results shows gain +8.5dBi, main beam angle is about 30□, beam width is about 40□ and side lobe level is -13dB. This design can reduce side lobe level effectively which may reduce the interference and utilize the array structure to improve the directivity. It is suitable for vehicles avoidance collision system, point-to-point radio communication and millimeter-wave applications.