超寬調諧範圍之電壓控制震盪器設計

Abstract

為了增加壓控振盪器(VCO)的調諧範圍，我們通常會使用差動式主動電感來取代單端式主動電感，因為差動式主動電感使用較少的電晶體，導致寄生電容較小，因此使用差動式主動電感可達到較寬的調諧頻率。但在差動式主動電感中，增加可調頻率範圍會造成整體電路的電流降低，而VCO中的負阻元件也將因為電流不足而無法正常工作，可調頻率範圍約只能到達3GHz的頻寬，tuning range也只有約120%。本篇論文提出一個可調範圍達5GHz頻寬的VCO。此VCO使用差動式主動電感的架構，並額外加上一個回授電阻於主動式電感中，該回授電阻可限制可調電導的最小值，整體電路的電流不會因為電導值過小而不足，因此VCO的調諧範圍可大幅增加。本論文使用台積電0.18μm 1P6M製程技術實現，量測結果顯示輸出頻率為0.5GHz到5.6GHz。可調頻率達5GHz，tuning range為165%，相位雜訊在1MHz offset時為-94到-99dBc/Hz。使用此主動式電感，整體VCO的面積只有175 x 170 。

In order to increase the frequency tuning range of a voltage-controlled oscillator (VCO), single-ended active inductors are usually replaced by differential active inductors, which need less number of transistors to yield smaller parasitic capacitance. However, the differential active inductors lower the overall current and may lead VCO’s negative resistance to be out of function, which still limits the frequency tuning range. In this thesis, a feedback resistor is added to limit the minimum conductance of the active inductor to achieve an ultra-wide tuning range VCO of 5 GHz. The proposed circuit is implemented by the TSMC 0.18μm 1P6M process technology, and the measurement result of the proposed VCO can be tuned from 0.5 GHz to 5.6 GHz. Its frequency tuning range is 165%. The phase noise ranges from -94 to -99 dBc/Hz at a 1-MHz offset. The die area of the VCO is 175 x 170 .