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|Title: ||Investigation of high-frequency performance of micro vacuum dielectric capacitors|
|Other Titles: ||Wei xing zhen kong jie zhi dian rong gao pin xing neng de yan jiu|
|Authors: ||Wong, Oi Ying (0)|
|Department: ||Department of Electronic Engineering|
|Degree: ||Master of Philosophy|
|Issue Date: ||2009|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Vacuum capacitors.|
|Notes: ||CityU Call Number: TK6565.C65 W66 2009|
ix, 69 leaves : ill. 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2009.
Includes bibliographical references (leaves -67)
|Abstract: ||The use of gigahertz electromagnetic spectrum for wireless communications results in some stringent requirements on the capacitors. The
dielectric losses of the capacitors constructed with commonly used
dielectric materials increase significantly at high frequency. Theoretically, the capacitors using vacuum as dielectric should have low
dielectric loss and can achieve stable characteristics over a wide frequency range in high frequency operations. However, vacuum capacitors were used in low frequency and high power applications instead
of high frequency applications. This is because of the limitation posed
by the bulky structure of the vacuum capacitors found in the market. To overcome this problem, a new manufacturing method for
making micro vacuum dielectric capacitor (VDC) was proposed recently. It allows vacuum or other gaseous to be used as the dielectric
for high-frequency ready capacitors. The structure consists of two
parallel-plate electrodes supported by periphery sealant at the boundary. Due to the vacuum dielectric inside and the simple structure, the
capacitors are expected to have excellent high-frequency characteristics. However, the effect of the sealant on the capacitor properties has
not been investigated.
In this work, a model is derived to characterize the capacitance and
frequency-dependent loss tangent of the VDCs. It has shown that
the capacitance of the VDCs depends on r, which is the ratio of the
width of boundary sealant layer to the capacitor side length. We have
shown by both analytical study and experimental measurement that
the smaller the r, the smaller the dissipation factor of the VDCs.
An equivalent circuit is further developed which can be used as an analytical tool to compute the high-frequency loss tangent of VDCs.
It was found that the dielectric loss of the capacitor at high frequency
mainly arises from the dielectric loss of the periphery sealant. Smaller
value of the width of boundary sealant layer to the capacitor side
length ratio will give smaller loss tangent. Meanwhile, the resonant
frequency of the VDCs also depends on the sealant. Empirical studies
of the resonant frequency of the VDCs have been shown to match well
with that derived from the proposed model.
Based on the developed analytic model, VDC with a required performance and a given value of capacitance can be designed through the
analytical derivation. Finally, the thesis is concluded with a presentation of some structures to further improve the VDC characteristics.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b3947855|
|Appears in Collections:||EE - Master of Philosophy |
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