dc.description.abstract | 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. | en_US |