超寬頻毫米波之先進印刷式電路及對數週期天線之設計

Abstract

本論文旨在設計超寬頻電路耦合器與平衡器及對數週期天線，用以整合成超寬頻線性極化天線。方向耦合器可以產生90度之相位差，可使線性極化轉成圓極化，或搭配180度之相差產生序列旋轉（sequential rotation）。電路平衡器用來將不平衡饋入轉為平衡輸出，可以減少場型偏移，使系統增益穩定。對數週期天線是常用的超寬頻天線，在超寬頻的設計中具有穩定的增益與線性極化特性，此類天線需額外設計饋入端，以連接不平衡之輸入。 在耦合器部分，設計耦合線，並用奇偶模態分析，調整耦合係數使其大小平衡性在0 dB正負6 dB以內，可操作頻帶模擬值落在3 GHz - 38 GHz，量測後其可用頻帶則從3 GHz - 30 GHz。在超寬頻平衡器部份，分析marchand balun之架構，並將其對應到等效傳輸線模型上，設計各段傳輸線之阻抗，拓展其頻寬，可操作頻帶之模擬值從3 GHz - 40 GHz。 為能良好將電路與對數週期天線做整合，我們採用印刷式電路板技術，不僅能將設計簡單化，還有縮小體積之優點。對數週期天線整合後，頻帶落在5 GHz – 40 GHz，其峰值增益模擬值約從2 dBi 到 6 dBi，而峰值增益量測值從2 dBi 至 6 dBi，但其起始頻點為12 GHz。毫米波對數週期天線整合，頻帶在11 GHz – 35 GHz，其模擬之峰值增益約從2 dBi 到 4 dBi。

This thesis aims to design ultra-wideband baluns, couplers and log periodic antennas. Used to integrate into an ultra-wideband linearly polarized antenna. The directional coupler can produce a phase difference of 90 degrees, which can be converted to circular polarization. Or with a phase difference of 180 degrees to produce a sequential rotation. The balun circuit is used to convert the unbalanced feed into a balanced output, which reduces the field offset and stabilizes the system gain. Log periodic antennas are commonly used ultra-wideband antennas with stable gain and linear polarization in ultra-wideband designs. Such antennas require an additional design to connect the unbalanced feed. In the coupler section, design the coupled line and use the even/odd mode analysis to adjust the coupling coefficient so that the magnitude imbalance is within 0 dB plus or minus 6 dB. The simulated frequency band falls between 3 GHz and 38 GHz, and the measured frequency band is from 3 GHz to 30 GHz. In the ultra-wideband balun section, analyze the architecture of the marchand balun and map it to the equivalent transmission line model. Design the impedance of each segment of the transmission line and expand its bandwidth. The simulated frequency band is from 3 GHz to 40 GHz. In order to integrate the circuit with the log periodic antenna, we use printed circuit board technology. Not only can the design be simplified, but also the advantages of reducing the size. After the log periodic antenna is integrated, the frequency band falls between 5 GHz and 40 GHz, and the simulated peak gain is about 2 dBi to 6 dBi. The measured peak gain is from 2 dBi to 6 dBi, but its starting frequency is 12 GHz. The millimeter-wave log periodic antenna integration has a frequency band of 11 GHz – 35 GHz and the simulated peak gain of approximately 2 dBi to 4 dBi.