臺灣博碩士論文加值系統

有線通訊因其高資料頻寬及可靠性在多媒體資訊傳輸上催生了許多研究發展。在數位家庭中，電力線通訊在多通道訊號傳輸中使用正交分頻多工調變達成高資料速率。接收器在前綴訊號期間透過自動增益控制評估通道特性，在有線通訊中，此機制扮演調整接收訊號敏感度的重要角色。
本論文旨在接受器前端高線性度以及快速穩定自動增益控制之分析與設計。兩個關鍵類比電路在此提出：一個高線性度、重構基礎可變增益放大器以及一個快速穩定前饋式自動增益控制。在可變增益放大器中，藉由可適性偏壓電路改善互補式放大器之線性度；採用二進制加權切換虛指數逼近技巧達成對數線性化的增益控制；另外也採用重構式可變增益放大器以減少寄生效應及電路複雜度。在自動增益控制中，提出一個適用於正交分頻多工接收器之前饋式架構達到快速迴路反應效果，其電路架構分析以及實務考量將在本論文中詳述。
藉由90-nm互補式金氧半導體製程實作本專題。實驗結果顯示，可變增益放大器之線性度可適用於正交分頻多工解調1024 正交振幅調變；在1.2伏特電源供應下，自動增益控制消耗3.7毫瓦，收斂時間小於0.1 微秒。

The wireline communication has spawned a revival of interest in multimedia content distribution due to its high data bandwidth and reliability. Powerline communication (PLC) in digital home employs orthogonal frequency-division multiplexing (OFDM) modulation for high data rates in multi-path signal channels. The receiver estimates the channel’s characteristics during the reception of the preamble by the process of automatic gain control (AGC), which is an essential function in wireline receivers to adjust sensitivity to incoming signal strength.
This work focuses on the analysis and design of high-linearity, fast-settling AGC in receiver front-end. Two key AGC building block applications, a high-linearity reconfiguration-based programmable gain amplifier (PGA) and a fast-settling feedforward AGC, are presented. In the PGA, linearity of amplifier is improved by adopting adaptive biasing circuit in a push-pull amplifier. Binary-weighted switching pseudo-exponential approximation technique is utilized for decibel-linear gain tuning. Reconfigurable PGA architecture is also employed to reduce parasitic effect and circuit complexity. In the AGC, a novel feedforward control scheme is proposed to achieve fast loop response requirement of OFDM-based receivers. The analysis and implementation consideration of key building blocks are provided in this work.
Fabricated in 90-nm CMOS technology, the experimental results show that the linear characteristic of PGA is suitable for 1024 QAM in OFDM demodulation and 0.1 μs is used for the AGC system convergence while consuming 3.7 mW through 1.2-V supply.

Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Application of Automatic Gain Control (AGC) 3
1.3 Powerline Communication (PLC) 4
1.4 Contribution of this Thesis 7

Chapter 2 Background 9
2.1 Fundamentals of Automatic Gain Control 9
2.1.1 Feedback-Type AGC 10
2.1.2 Feedforward-Type AGC 16
2.1.3 Generalized Settling Time Constraints 19
2.2 Fundamentals of Programmable Gain Amplifier 20
2.2.1 Various Approaches of VGA/ PGA 20
2.2.2 SNR of VGAs/PGAs 23
2.2.3 Circuit Design Parameters 25
2.3 Design Methodology 33

Chapter 3 A High Linearity Programmable Gain Amplifier 35
3.1 Introduction 36
3.2 The Proposed PGA Architecture 37
3.2.1 Design of PGA Transconductance Cell 38
3.2.2 Complementary Push-Pull Differential Amplifier 43
3.2.3 PGA Cell 45
3.2.4 Pseudo-Exponential Approximation 49
3.2.5 Binary-Weighted Switching Technique 51
3.2.6 Reconfiguration Technique 53
3.2.7 Fixed Gain Amplifier 54
3.3 Experimental Results 56
3.4 Chapter Summary 60

Chapter 4 A Fast-Settling Automatic Gain Control Amplifier 61
4.1 Introduction 62
4.2 The Proposed AGC Architecture 64
4.2.1 PGA 65
4.2.2 Power Detector 66
4.2.3 Charge-Redistribution SAR ADC 68
4.2.4 AGC Algorithm 76
4.3 Experimental Results 77
4.4 Chapter Summary 81

Chapter 5 Conclusion 83

Bibliography 85

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