使用超穎材料之微波平面功率整合放大器

Abstract

N路功率分配/整合器為了達到低損失的特性，其電路結構普遍使用非直線排列之多埠，使得主動元件的整合於平面電路上極具困難性。本論文旨在提出使用超穎材料設計新型平面式功率分配/整合器，並整合微波功率放大器，研製新型微波平面功率整合放大器，內容理論與實驗並重。 此功率分配/整合器以超穎材料實現之微波透鏡為基礎架構，並由右手單元構成的正折射率材料及左手單元構成的零折射率材料所組成，正折射率與零折射率材料的界面則使用半圓形曲面。功率分配/整合器的輸入埠及輸出埠在正折射率材料內，分別位於零折射率材料製成之雙凹透鏡的兩個焦點上。當電磁波於零折射率材料內傳播，波長因係無窮大，使其呈現等大小及等相位的分佈，藉由此特性，適當地連接共線性排列的放大器，進而設計平面功率整合放大器。 首先，第二章敘述右手單元和左手單元的結構及公式推導，以及設計一正折射率/負折射率/正折射率夾層結構，並分別於焦點上放置一放大器及振盪器，以有效加強顯示電磁波於超穎材料內波前反向及聚焦現象。第三章則敘述新型平面九路功率分配/整合器之結構及電路分析，其中於電路分析上，使用2N埠傳輸矩陣法來分析此九路結構，求得其解析式，並以實驗驗證。透過電路散射參數量測，顯示此九路功率分配/整合器的整合效率可達到88%，並且經由量測洩漏電場，證實零折射材料的無窮波長現象，功率分配/整合器結構上其電壓分配與整合現象亦清楚顯見，量測結果與理論相吻合。 最後，第四章則進一步敘述新型平面九路功率整合放大器，使用第三章所提出之功率分配/整合器架構整合九只1 W放大器，此九路功率整合放大器操作於頻率1.008 GHz。功率量測結果顯示其輸出功率為7.64 W，整合效率為85%，並且透過量測洩漏電場，進一步驗證電壓分配與整合現象，量測結果與理論相吻合。此九路功率整合放大器之優雅遞減的特性，亦透過散射參數、功率、以及洩漏電場的量測所驗證。

The problem of noncollinearly aligned ports in N-way power divider/combiners makes their integration with active devices in a planar structure difficult. This dissertation develops a novel planar metamaterial power-dividing/combining structure with the integration of power amplifiers (PAs) as a power-combined amplifier for PA application. Both the theoretical analysis and the experimental implement are emphasized. The presented planar power divider/combiner is based on the metamaterial lens structure. Specifically, it is composed of positive refractive index (PRI) material with right-handed (RH) unit cells and zero refractive index (ZRI) material with left-handed (LH) unit cells. A semi-circular interface is between PRI and ZRI materials. The input and output ports are within the PRI materials and at the two focal points of a double-concave ZRI lens. The infinite wavelength phenomenon in the ZRI material attains an equal magnitude and phase distribution to have an interconnection with the collinearly aligned amplifiers as a planar power-combined amplifier. Firstly, Chapter 2 describes the basic design principle of RH and LH unit cells and a planar PRI-NRI-PRI slab. Two planar PRI-NRI-PRI slab structures embedded with an amplifier and an oscillator, respectively, to effectively enhance the wavefront reversal and focusing phenomenon are presented and experimentally verified. Chapter 3 presents a novel planar nine-way metamaterial power divider/combiner, along with its design principle and circuit analysis. A 2N-port transmission matrix approach is used to analyze this nine-way power-divider/combiner structure and derive the analytical formulation. Through the circuit scattering-parameter (S-parameter) measurement, the nine-way power divider/combiner shows an average combining efficiency of 88%. Through the field measurement to each cell, it not only demonstrates the infinite wavelength phenomenon of the ZRI material, but also clearly indicates the dividing/combining phenomenon within the power-divider/combiner circuit. Measured results are shown in good agreements with analytical results. Finally, Chapter 4 presents a novel planar nine-way power-combined amplifier based on the metamaterial power-dividing/combining structure in Chapter 3. The power combining of nine 1-W amplifiers gives an output power of 7.64 W with a combining efficiency of 85% at 1.008 GHz. The dividing/combining phenomenon is further demonstrated via the field measurement to each cell of the power divider/combiner and is shown in good agreement with analytical results. Furthermore, the graceful degradation characteristic of this power-combined amplifier is experimentally demonstrated through S-parameter, power, and field measurements.