| 摘要: | 現代微波傳能系統中，高效的整流天線是不可或缺的元件，由於物聯網對中長距離無線傳能的需求，促使我們研究微波整流天線。本論文主要針對天線設計、微波整流器以及微波整流天線全極化性以及全方向性的實現之研究。第二章闡述了一個超寬矩形貼片天線及其1×2陣列之分析、設計及量測結果，為了實現全極化，文章最後提出了一個雙線性極化天線，及其設計與量測結果。第三章為帶有帶止結構之微波整流器及其陣列之電路設計與量測結果。最後，第四章呈現一個具備全極化及全向性的立體整流天線。
第二章介紹矩形貼片天線結構及設計原理，並且提出超寬矩形貼片天線的設計，其天線增益為8.6 dBi，相當於1×2矩形貼片天線陣列。接著介紹天線陣列的設計原理，並以此設計1×2超寬矩形貼片天線，其天線增益為11.2 dBi，相當於2×2矩形貼片天線陣列。最後提出並設計了一個雙線性極化天線，可以在接收任意極化方向的線性極化波時，都能保持較高的接收效率。
第三章為微波整流器之設計分析，介紹其理論模型架構，引入源極牽引的概念並利用ADS軟體進行模擬分析，能夠有效率地最佳化整流器的整流效率。接著根據前文的分析方法，設計實現一個帶有帶止結構（八分之一短路傳輸線）的整流器，並利用源極牽引分析比較有無短路傳輸線之等效率圓。其具有較高整流效率以及動態範圍，整流效率在輸入功率為8 dBm，操作頻率在2.45 GHz時達到峰值72%，動態範圍為13.8 dB。最後提出並設計了一個整流器陣列，該陣列輸入端利用一個枝幹耦合器來重新分配能量給兩個子整流器，以此提高整流電路整體的整流效率、動態範圍以及頻寬，整流效率在輸入功率為11 dBm，操作頻率在2.45 GHz時達到峰值75.7%，動態範圍為17.6 dB。
第四章提出一個具有全極化與全方向性之立體整流天線，藉由多個全極化整流天線組成的多面體結構。全極化整流天線包括雙線性整流天線、枝幹耦合器及兩個整流器，相較於傳統雙線性整流天線，該設計能夠在不同的極化方向角度差，保持較高的整體效率，實現真正意義上的全極化。接著，以全極化整流天線為單元引入數學模型，以分析比較在發射端不同方位下，單面、三面體、四面體以及六面體的能量獲取表現，可以看出面數越多，直流能量大小隨方位變化越小。數學模型與實驗結果相互驗證，量測環境（待測天線平面）的功率密度能量為355 mW/cm2，方位角範圍由0°到360°，單一整流天線的輸出直流能量為0.8到2.33 mW，六面體整流天線的輸出直流能量為1.7到2.85 mW。;In modern microwave power transmitting system, a high efficient rectenna is an essential building block. Since the demand for mid- (or long-) range wireless power transmitting in IoTs, we were driven to investigate microwave rectenna. This thesis focuses on the antenna, microwave rectifier and 3D rectenna with all-polarized and omnidirectional capacity. Analysis, design and measured results for 5.8 GHz ultra-width patch antenna and array are proposed in Chapter 2, meanwhile, a 2.45 GHz dual-linear polarized antenna is present. Analysis, design and measured results for the microwave rectifier with band stop structure and array are proposed in Chapter 3. Finally, a 3D rectenna with all-polarized and omnidirectional capacity is proposed in Chapter 4.
Patch antenna theory is introduced in Chapter 2. An ultra-width patch antenna is present, features an antenna gain of 8.6 dBi, amount to the gain of 1×2 conventional patch antenna array. Antenna array theory is introduced, and an 1×2 ultra-width patch antenna array is present, features an antenna gain of 11.2 dBi, amount to the gain of 2×2 conventional patch antenna array. Finally, a dual-linear polarized antenna is present and designed. It can maintain high receiving efficiency regardless of polarization mismatching.
Design and analysis of microwave rectifier is introduced in Chapter 3, including the theoretical model, transfer functions and models using ADS (advance design system) software with source-pull analysis for optimization of efficiency. A modifier rectifier with band-stop structure (eighth length short-ended transmission line) is present, source-pull analysis is introduced for analyzing constant efficiency contour with or without short-ended transmission line. The modifier rectifier attains a peak RF-to-DC PCE (Power conversion efficiency) of 72% when the input power in 8 dBm, and a dynamic range of 13.8 dB. Finally, a rectifier array based on modified rectifier is present. A branch-line coupler is introduced for power redistribution to improve PCE, dynamic range and bandwidth. The rectifier array attains a peak RF-to-DC PCE of 75.7% when the input power in 11 dBm, and a dynamic range of 17.6 dB.
In Chapter 4, we proposed a 3D rectenna with all-polarized and omnidirectional capacity for IoT applications. The proposed rectenna is composed of six dual-linear polarized (DLP) rectennas, in a hexahedron. Each DLP cell is composed of a DLP antenna, a 90° hybrid, and a modified rectifier. The 90° hybrid, and a modified rectifier are employed to reallocate received powers between two ports of DLP antenna, and the topology can maintain high RF-to-DC PCE when the polarization of incident wave is uncertain or varying.
Mathematical equivalent model is introduced to analyze 3D rectennas in trihedron, tetrahedron and hexahedron. The 3D rectenna can harvest RF power all round efficiently. With a measured power density of 355 μW/cm2, the output dc power maintains above 1.7 mW when the tile angle varies from 0° to 360° perpendicular to the surface of rectenna, and the maximum dc power is 2.8 mW. |
