臺灣博碩士論文加值系統

本論文針對美商思佳訊(Skyworks Inc.)生產之壓控式變容二極體(varactor diode)，建構可更精準地描述其射頻(radio frequency, RF)寬頻響應之等效電路。等效電路之建置上，以Skyworks提供的純集總式(pure lumped)等效電路為基礎架構，藉由加入有損傳輸線段(lossy transmission line section)，亦即分佈式結構(distributed structure)，描述二極體封裝(packaging)接腳之射頻效應，進而大幅提升電路所預測參數之精準度。此外二極體的品質因子(quality factor)，亦可經由等效電路與量測之散射(scattering)參數(S參數)擷取(extract)而得，並用於分析二極體於不同偏壓操作下損耗特性。
等效電路中集總元件與傳輸線參數可先經由向量網路分析儀量以自動置具效應移除(auto fixture removal)之方式測出二極體S參數，再透過曲線擬合(curve-fitting)的方式獲得。等效電路採實作驗證方式檢測其準確性，實作電路為以一端載有二極體之微帶截線為共振器所建構之中心頻可調的帶止濾波器(tunable bandstop filter)，驗證結果發現模擬與量測之濾波器S參數有極好之吻合度。所建立之等效電路可應用於預測以壓控式變容二極體設計之頻率捷變射頻電路(frequency agile RF circuits)電路參數，可大幅提升模擬精確度。

The thesis proposes a quasi-lumped equivalent circuit of the varactor diode manufactured by Skyworks Inc., and the proposed model predicts an accurate response for wideband applications. Based on the manufacture's pure lumped equivalent circuit model, a lossy transmission line section, i.e. a distributed structure, is introduced to describe packaging parasitic effects and enhance accuracy of the device characteristics. The circuit parameters are retrieved by curve-fitting the measured scattering parameters of the varactor. Besides, the quality factor of the varactor diode can be extracted from simulated scattering parameters of the device model for analyzing varactor loss under different reverse biases. The model validation is carried out by an experimental verification with a varactor-based microstrip tunable bandstop filter and good agreement is observed between the simulated and measured results. Therefore, the proposed model can be used for characterizing varactor-based frequency agile RF circuits with a high accuracy.

List of Figures vi
Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Literature Survey 2
1.3 Thesis Organization 4
Chapter 2 Theoretical Background 5
2.1 Microstrip Line 5
2.2 Varactor 7
2.3 Quality Factor 8
2.4 Tunable/Reconfigurable Filter 8
2.5 Fixture Removal 10
Chapter 3 Varactor Modeling 14
3.1 Varactor S-parameters Measurement 14
3.2 Proposed Equivalent Circuit 17
Chapter 4 Experimental Verification 27
4.1 BSF Design, Characterization, and Verification 27
Chapter 5 Conclusion 34
Reference 35

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