隨著積體電路技術的進步以及市場需求的增加，近年來通訊產業蓬勃地發展。壓控震盪器提供了升頻與降頻所需的震盪訊號，在射頻收發機中扮演著重要的角色。在升降頻的過程中，我們通常將訊號分成I/Q兩通道以利調變與解調變。由於本地震盪器的品質將影響整個通訊系統的表現，因此設計一個壓控震盪器能夠提供兩個完全相同並擁有精確正交關係的訊號是必要的。

本論文提出了一個新型正交壓控震盪器。我們利用兩個相同的弛張震盪器配合著可調史密特觸發器來建立交叉耦合架構。此震盪器擁有精確( <1°)和穩定的正交輸出而不受操作頻率和製程變異的影響。本震盪器電路由國家晶片系統設計中心所提供的TSMC 0.35μm CMOS Mixed-Signal 製程製作。我們的設計經由模擬與量測的結果所驗證。

Because of IC technology evolution and the increase of market demand, the communication industry grows vigorously in recent years. The voltage-controlled oscillator plays a key role in the RF transceiver and provides oscillation signals needed for upconversin and downconvertion. Usually, we separate the signals into I/Q channels for modulation and demodulation in upconversin and downconvertion. Because the quality of the local oscillator influences the performance of communication system, designing a voltage-controlled oscillator that can provide two identical signals in accurate quadrature is necessary.

In this thesis, a new quadrature voltage-controlled oscillator is presented. We use two identical relaxation oscillators with adjustable Schmitt triggers to construct the cross-coupled architecture. This oscillator has accurate ( <1°) and stable quadrature outputs which are independent of operating frequency and process variations. This oscillator circuit is fabricated in TSMC 0.35μm CMOS Mixed-Signal process provided by National Chip Implementation Center (CIC). Our design is verified by simulation and measurement results.

ABSTRACT (CHINESE)……………………………………………i
ABSTRACT (ENGLISH)……………………………………………ii
CONTENTS…………………………………………………………iii
LIST OF FIGURES…………………………………………………v
LIST OF TABLES…………………………………………………vii

CHAPTER1 INTRODUCTION…………………………………………1
1.1 BACKGROUND…………………………………………………1
1.1.1 SUPERHETERODYNE RECEIVERS……………………………1
1.1.2 IMAGE-REJECT RECEIVERS………………………………2
1.1.3 I/Q MISMATCH……………………………………………4
1.2 ORGANIZATION OF THE THESIS……………………………6

CHAPTER2 VCO CONCEPTS AND QUADRATUR TECHNIQUES………7
2.1 VCO CONCEPTS………………………………………………7
2.1.1 OSCILLATOR THEORY………………………………………7
2.1.2 RELAXATION OSCILLATORS………………………………8
2.2 CONVENTIONAL QUADRATURE TECHNIQUES…………………10
2.2.1 RC-CR NETWORK…………………………………………10
2.2.2 HAVENS' TECHNIQUE……………………………………11
2.2.3 FREQUENCY DIVISION…………………………………14
2.2.4 CROSS-COUPLED PAIR…………………………………14

CHAPTER3 THE PROPOSED QUADRATURE RELAXATION OSCILLATOR…17
3.1 VOLTAGE-CONTROLLED RELAXATION OSCILLATOR…………17
3.2 THE CROSS-COUPLED RELAXATION OSCILLATOR…………19
3.3 ADJUSTABLE SCHMITT TRIGGERS…………………………27
3.4 VOLTAGE-TO-CURRENT CONVERTERS………………………31

CHAPTER4 SIMULATION AND MEASUREMENT……………………33
4.1 SIMULATION RESULTS……………………………………33
4.2 MEASUREMENT RESULTS……………………………………38
4.3 COMPARISON……………………………………………… 42

CHAPTER5 CONCLUTIONS………………………………………44

REFERENCE………………………………………………………45

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