應用於WiMAX之電感式多頻段切換壓控振盪器設計與實作

Design and Implementation of A Multi-Band Voltage-Controlled Oscillator Switched by Inductors for WiMAX Applications

翁仲連(Chung-Lien Wong)

指導教授 ： 鄭士康

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.10402

摘要

此論文提出了一個使用於WiMAX 2.5G及3.5G頻段的切換電感式壓控振盪器，最終並以PCB板實現。一般使用切換電容設計壓控振盪器時，通常會面臨如何取捨KVCO及可調頻率範圍的考量；前者與相位雜訊有關，後者則與涵蓋可用的頻帶範圍有關。

壓控振盪器需經由控制變容器(Varactor)之電壓，亦即改變振盪器諧振腔總電容，達成控制輸出振盪頻率的目的。使用傳統切換電容方式製做之壓控振盪器，當電容與變容器並聯後，會使諧振腔之整體電容值變大，而同時由變容器所影響的KVCO值卻隨之變小，在實際應用時將會造成輸出頻率涵蓋範圍變小之限制。在本論文中將對此一問題進行探討。

本論文最終提出之架構可改善傳統使用切換電容式壓控振盪器的問題：選擇主頻帶時以切換電感方式進行，再以切換電容切割小頻帶；主要目的為減少並聯電容的使用，換取更穩定的KVCO值。透過模擬及實驗，可證實此種架構之優良特性。

關鍵字

WiMAX ； 壓控振盪器 ； 切換電感式壓控振盪器 ； 多頻帶壓控振盪器

並列摘要

This thesis presents a multi-band voltage-controlled oscillator, which is switched by inductors and used for WiMAX applications. At the end of the thesis, we use simulations and PCB implementations to achieve the design of the oscillator. If an oscillator is switched by capacitors, it will usually face the problem of how to balance KVCO and the tuning range of the frequency. In general, KVCO has great impacts on phase noise and tuning range.

To achieve the purpose of controlling the output frequency, we usually control the voltage of varactors and change the total capacitance of the oscillator cavity. If we use the traditional way making the voltage-controlled oscillator by switching capacitors, the capacitors will be in parallel with the varactors, and the system gets a larger cavity capacitance. At the same time, KVCO will be decreased because the change of overall capacitors. In other words, we will have a VCO with smaller output frequency limitation. We will also discuss this issue in this thesis.

This thesis suggests that we can use the architecture that switches inductors while selecting the wide range frequency band needed by the system, and selects the precise frequency by switching capacitors. Experiment results show that our new design has better performance.

並列關鍵字

WiMAX ； Voltage-Controlled Oscillator ； VCO ； multi-band VCO ； switch inductors ； switch capacitors

參考文獻

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