單晶片電感模型研發及射頻積體電路模擬與設計方面之應用

Abstract

近十年來，深次微米 CMOS 製程技術帶動了系統晶片的快速演進。由於CMOS技術其本身的優勢為高整合性，低成本，高速度以低功率等，RF CMOS 已變為無線通訊系統晶片可行方案。但是，於 RF CMOS 產品發展過程中，缺乏準確和可微縮性之射頻元件模型已成為主要的障礙，射頻元件模型發展之挑戰來自於複雜的電磁耦合與半導體矽基板所引起能量損耗等效應。單晶片電感模型乃為此領域中最具挑戰的主題之一，也因此激發我們研究的動機。 本論文中，我們針對螺旋狀電感發展一個新的 T 模型之等效電路，其可以準確地模擬寬頻的特性。在寬頻的範圍下，此模型中螺旋線圈和基板之 RLC 網路電路，對導體和基板損耗之效應扮演極重要的角色。至於已存在的 □□模型則無法準確地模擬上述所提及的現象。 再者，我們已成功地將簡單的 T 模型延伸至 2T 模型，以適用於對稱型和差動型電感，其於關鍵射頻電路如混頻器、壓控振盪器及低雜訊放大器應用方面相當地受歡迎，此模型的準確性於頻率高達 20 GHz 的頻寬下已與量測的S參數，輸入阻抗之實部及品質因素驗証，均有相當好的匹配，除了在寬頻下，其所有模型參數對圈數的變化已被驗証呈現線性的函數。透過等效電路分析，我們建立了一套參數汲取流程，可以進行參數自動作汲取與最佳化。此可微縮性電感模型可成功輔助單晶片電感設計，並進行最佳化的動作，及其準確性可高達 20GHz 的頻寬，依寬頻電路設計需求可以改善射頻電路模擬之準確性。

In recent decade, the fast progress of deep submicron CMOS technology is driving the realization of system-on-a-chip (SoC). RF CMOS has become an viable solution for communication SoC due to the intrinsic advantages of high integration, low cost, high speed, and low power, etc. However, for the development of RF CMOS products, lack of accurate and scalable RF device models has been a major roadblock. The challenges of RF CMOS device model development come from the complicated electromagnetic coupling and energy loss effects originated from the semi-conducting substrate of bulk Si. On-chip inductor model is among the most challenging topics in the area and stimulates our motivation of this work. In this work, a new equivalent circuit model named as T-model has been developed for single-end spiral inductor to accurately simulate broadband characteristics. The spiral coil and substrate RLC networks built in this model play a key role responsible for conductor loss and substrate loss effects in the wideband regime. The mentioned phenomena cannot be accurately simulated by the existing inductor models such as□□-model. The simple T-model has been successfully extended to 2-T model for symmetric and differential inductors, which become very popular in key RF circuits such as mixer, VCO, and LNA, etc. The model accuracy has been proven by good match with measured S-parameters, Re(Zin(□□), and Q(□) over broadband of frequencies up to 20 GHz. Besides the broadband feature, scalability is justified by the good agreement with a linear function of coil numbers for all model parameters. A parameter extraction flow has been established through equivalent circuit analysis to enable automatic parameter extraction and optimization. This scalable inductor model can facilitate optimization design of on-chip inductor and the accuracy proven up to 20 GHz can improve RF circuit simulation accuracy demanded by broadband design.