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  • 學位論文

平行板電容的線性度強化結構的探討

Studies of linearity enhanced structures of the parallel plate capacitor

指導教授 : 李慶烈

摘要


論文提要內容: 在本論文中,吾人應用時域有限差分法(Finite Difference Time Domain,FDTD)計算幾種平行板電容的靜電容值,對於電容特性的研究常著重於感測器應用的線性度分析,且針對幾種平行板結構的線性度進行研究,包括:簡單平行板電容,只具guard ring型平板電容結構與加細針具guard ring型平板電容結構等。理論部份乃經由驅動方程式建立凖靜電荷的特性來研究平行電容板的結構,由凖靜電荷穩定後的電場值來計算出平行金屬板間的電壓,然後再將電荷總量除以電壓以獲得電容值,並可進一步分析平行板電容的線性度。 一般常用具Guard Ring型平行板電容(有Guard)來增加線性度,因此,本論文分析二種具guard ring型結構的電容與一般簡單平行板電容,以探究線性度,針對具Guard Ring 型平行板電容,吾人可以在上下平行板之間與上下Guard Ring板之間各加一個Source,並調整Source的振幅,使平行板電壓與guard ring板兩者為等電位(虛短路),並與一般簡單平行板電容以及無虛短的具Guard Ring型平行板電容的線性度做比較,結果証實有虛短路的電容結構的線性度比一般電容與無虛短路的具Guard ring型電容來的好。 另外,吾人也發現具guard ring型平板電容與相同金屬板面積的簡單平行板電容的線性度是相同的,可見引進guard ring並不是改善線性度的來源,只是擁有原大面積結構該有的線性度。接著,本研究提出一種插入細針於上、下金屬板的新平板結構,藉由減少外溢電荷以獲得較佳的線性度。當改變平行板的間距以探討線性變異量,模擬結果顯示其線性度依序為(由好至差):1)虛短路加細針的具Guard Ring型電容,2)虛短路的具Guard Ring型電容,3)一般平行板電容,4)無虛短路Guard Ring型電容。

並列摘要


Abstract: In this thesis, the FDTD method is employed to calculate the static capacitance of several parallel-plate capacitors. The study of the capacitor characteristics is made to emphasize on the linearity analysis for the possible sensor application. The linearity of several parallel-plate structures is examined, which include a simple parallel-plate capacitor, a parallel-plate structure with guard ring only, and a parallel-plate structure with guard ring and pins, etc. Through the use of the transparent current source, the parallel-plates can be charged such that the transient and static E fields are simulated using the FDTD updating equations. The static E field is used to calculate the voltage across the parallel-plates. The capacitance is obtained directly by dividing the charge over the voltage. In general the parallel plate capacitor with guard ring is used to increase the linearity of sensor capacitors. Thus, in this thesis, two capacitor structures with guard ring and the simple parallel-plate capacitor are studied for the emphasis on the linearity characteristics. A transparent source in between of the upper and lower central plates is utilized, while, another transparent source in between of the guard rings of upper and lower plates are employed at the same time. The amplitudes of these two sources are adjusted in order to achieve equal potential differences, of which the idea is to implement the concept of virtual short, for the two source terminals. The simulated results for the capacitors that are virtually shorted are compared to those of the simple parallel-plate capacitor and/or the capacitors with guard ring (not virtually shorted). The FDTD simulation results confirm that the linearity of the former capacitors with the guard ring, being virtually shorted, is better than that of the simple parallel-plate capacitor and/or the parallel plate capacitor with the guard ring, being not virtually shorted. On the other hand, it is found that the linearity of a parallel-plate capacitor with guard ring is actually the same as a simple parallel-plate capacitor with the same plate area. Afterwards, a new parallel-plate structure with pins inserted in between the parallel plates is proposed to reduce the linearity deviation as the separation of the parallel plates changes. The simulated results show that the performances of linearity characteristics in decent order are as follows: 1st) capacitors with guard ring and pins, 2nd)capacitors with guard ring (virtually shorted), 3rd) the simple parallel-plate capacitors, 4th) capacitors with guard ring (not virtually shorted).

並列關鍵字

FDTD transparent source capacitor sensor

參考文獻


[6] Ching-Lieh Li, Chien-Wei Lin, and Ding-kai Lin, “ Application of the FDTD method to the Capacitor Structure for Static Field Demonsation and Capacitance Calculation”. Symposium on Technology Fusion of Optoelectronics and Communications, pp. 80-81 May 2005,
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