交錯型複合式左右手傳輸線之分析與設計與其在漏波天線之應用

Abstract

此論文分析一個交錯型(晶格型)複合式左右手傳輸線，利用ABCD矩陣分析在任意的電感和電容下它的色散圖與阻抗值。並提出設計的步驟和參數分析。之後將分析結果運用在漏溢波天線的設計上。此交錯式結構有幾個特點：1.輸入阻抗不受頻率所影響；2.如果是平衡的結構，此種結構有全通的特性；3.群速(group velocity)比一般複合式左右手傳輸線更快。這些特性在於漏波天線的使用上，可以讓輸入阻抗較和頻率無關，增加掃頻的範圍，並減少主輻射波束角的偏移。本論文將此種傳輸線架構分別設計成兩種單邊饋入漏溢波天線，兩種中心饋入漏溢波天線(延遲型和對稱饋入型)，並將兩種中心饋入漏溢波天線加入反射板來討論它們的場型和S參數，並且解決交叉極化過大的問題。其中單邊饋入漏溢波天線在+Z方向的主極化增益可以達5 dBi，交叉極化增益為-15 dBi。而中心饋入漏溢波天線(對稱饋入型)，其在+Z方向主極化增益可達6.5 dBi，交叉極化增益為-20 dBi。中心饋入漏溢波天線(對稱饋入型)加入反射板後，在+Z方向主極化增益可達11.5 dBi，交叉極化增益為-20 dBi。

This thesis analyzes a cross-type (X-type or lattice network) composite right/left-handed (CRLH) transmission line using ABCD matrix. The proposed model can provide the dispersion relation and the bloch impedance (input impedance) for arbitrary inductance and capacitance. Furthermore, this thesis provides design procedures and parameters analysis for the design of leaky-wave antennas using the X-type CRLH transmission line. The X-type CRLH TL has several advantages. First, input impedance is independent of frequency. Second, if this CRLH TL is built in a balanced structure, it has broadband behavior. Third, the group velocity of this structure is larger than that of traditional CRLH TL. For antenna applications, the X-type structure can provide stable input impedance, improve frequency scan range, and reduce the beam shifting. Different antenna designs are proposed, including two edge-fed leaky-wave antennas and two center-fed leaky-wave antennas with a phase delay line and a symmetry structure. These two center-fed leaky-wave antennas are then backed by a reflector to enhance the broadside gain. This thesis investigates the radiation patterns, s-parameters, and the cross polarization issue. An edge-fed LWA prototype has a co-pol gain of 5 dBi and a cross-pol gain of -15 dBi. The center-fed LWA prototype has a co-pol gain of 6.5 dBi and a cross-pol gain of -20 dBi. The center-fed LWA prototype with a reflector has an improved co-pol gain of 11.5 dBi and a cross-pol gain of -20 dBi.