合成波導之設計與應用

Abstract

本篇論文係研究立體式(Three-dimensional)與平面式(Two-dimensional)合成波導以多層印刷電路板( Multi-layer Printed Circuit Board)製程與矽(Silicon)半導體製程之實現並提出相關應用。傳統立體式矩形波導(Rectangular Waveguide)可藉由微小化週期結構 (Periodical Structure)重新合成，並透過成熟之矩形波導轉換器(Rectangular Waveguide Transition)，設計出合成矩形波導(Synthetic Rectangular Waveguide, SRW)。經由實驗與理論相互驗証，該立體傳輸線具備慢波效應(Slow-Wave Effects)可突破傳統矩形波導之理論限制，有效縮小面積達60%以上。該微小化特性應用到5GHz積體化近全向性矩形波導天線 (Omni-directional Rectangular Waveguide Antenna)。更進一步，由於週期結構在能階止帶 (Energy Bandgap) 呈現出完美磁性金屬 (Perfect Magnetic Conductor) 特性，使該立體合成波導可傳播傳統金屬矩形波導無法存在之第一階横向磁場模(TM10 mode) 而本論文亦針對該模態提出其模態轉換器 (Mode Converter)。 除外，本論文研究互補式金屬(Complementary-Conducting Strip, CCS)合成波導在多層結構 (Multi-layer Structure) 之特性與提出相關應用。透過實驗與理論驗証，互補式金屬在多層結構實現下，除保有原多樣化特徵阻抗合成之特性，亦突破傳統夾心線 (Stripline)之理論限制，具備更高之慢波因子 (Slow-Wave Factor)。該平面式合成波導以多層印刷電路板技術，應用在以傳輸線為主 (Transmission-Line based) 之WLAN 2.4GHz微小化帶通濾波器設計。而設計出之濾波器尺寸為5.0 mm X 5.0 mm X 0.18 mm，甚接近傳統以低溫陶瓷共燒 (Low Temperature Cofired Ceramic)之濾波器體積。 本論文最後一部份提出平面式合成波導應用於改進傳統晶片繞線電感 (On-chip Spiral Inductor) 之設計困難。該設計同時以印刷電路板與標準多層CMOS 製程驗証其可行性。

This dissertation presents a new class of the transmission lines so-called synthetic waveguide, which can be realized by mass-producible technologies, such as multi-layer print-circuit-board (PCB), and silicon-based monolithic integrated circuit foundry. Meanwhile, the novel design methodologies incorporating the proposed synthetic waveguide are reported to demonstrate the impacts on the designs either in component-level or system-level for meeting the trends of modern portable devices. A new synthetic waveguide, which is the composite structure including the rectangular waveguide transitions and rectangular waveguide synthesized by the periodical electromagnetic bandgap (EBG) structures at top and bottom surfaces of the rectangular waveguide, is theoretically and experimentally verified, showing the following characteristics. First, the slow-wave factor of the synthesized rectangular waveguide (SRW) exceeds the theoretical limit of the conventional metallic rectangular waveguide in the TE10 mode, significantly increasing the size-reduction more than 60%. One example employing the TE10 mode of the proposed SRW was the design of integrated waveguide antenna in the 5 GHz ISM band, demonstrating its potential on circuit miniaturization. Second, the proposed SRW can support TM00 and TM10 mode propagation in the same SRW. Notably, no TM00 and TM10 mode can exist in the conventional rectangular waveguide with an all-metallic enclosure. Additionally, the waveguide transitions for the synthetic TE10, TM00 mode, and TM10 mode of the SRW are also presented for the further applications. The second part of the dissertation focuses on the design and application of the synthetic quasi-TEM transmission line so-called complementary conducting strip transmission line (CCS TL) in multi-layer portion. A series of experimental and theoretical verifications conclude that the stacked CCS TL not only provides a wide design solutions for the circuit requirements but also achieve a low-loss slow-wave device whose slow-wave factor (SWF) exceeding the theoretical value of the conventional stripline. Moreover, a typical multi-layer system, which includes two filters in different signal layers, is realized by the stacked CCS TL, revealing good isolation between two filters during the system design. Furthermore, the proposed two-dimensional synthetic waveguide is applied to design an transmission-line based 2.4GHz ISM-band bandpass filter for demonstrating a new filter design methodology, which can systematically reducing the size of filter based on multi-layer CCS TL. A quick estimate on the prototype filter with the size of 5.0 mm X 5.0 mm X 0.18 mm reveals that the volume of the prototype approaches that of state-of-the-art device, such as multi-layer low temperature cofired ceramic (LTCC) filters. Finally, the new spiral inductor architecture, named EBG enhanced inductor, incorporating the synthetic waveguide is presented, providing another solution for designing planar inductors on lossy substrate. The two-dimensional EBG array servers as a ground plane beneath the conventional spiral inductor, providing a shielding for inductor on the lossy substrate. The proposed approach is verified through the experiments using the conventional multi-layer PCB technology and standard 0.25um CMOS foundry, showing that the performance of a spiral inductor can be improved in almost aspects.