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A Study on Lowpass Filter Design Using Micro-Coplanar Striplines with Defected Ground Structure
|Authors: ||Chien-Ming Chen|
|Contributors: ||NTOU:Department of Electrical Engineering|
|Issue Date: ||2011-06-22T08:52:37Z
|Abstract: ||微共面帶線除了具有共面波導之優點，如較佳之頻散特性、低功率損失、容易被應用於元件之並聯以及介質基座不需額外穿孔等，而且其結構較共面波導少了一個上接地面，可避免激發出額外的開槽模態表面波以及可以縮小電路之尺寸。此外，缺陷接地面結構不僅可以改善濾波特性，同時亦能進一步縮小電路之尺寸。因此，於本論文中我們利用具缺陷接地面結構之微共面帶線來設計低通濾波器。 於本論文中，首先分析微共面帶線之基本特性及缺陷接地面結構之影響。其次，探討微共面帶線低通濾波器之設計理論，並分析缺陷接地面結構對頻率響應之影響，進而推導出缺陷接地面結構之等效電路。最後，分別設計與製作步階阻抗型與具T字型接面之低通濾波器。此外，量測濾波器之特性，並將量測結果與模擬數值作比較。 由分析結果得知，兩種低通濾波器皆具有極佳之濾波特性。此外，步階阻抗型低通濾波器，如採用缺陷接地面結構可縮小大約16%之電路尺寸；而具T字型接面之低通濾波器，如採用缺陷接地面結構可縮小大約15%之電路尺寸。|
The micro-coplanar striplines have the same advantages of coplanar waveguides, such as the low dispersion, low power loss, easy of shunt connection, and eliminating the need of via holes. Because the micro-coplanar stripline lacks one upper ground plane as compared with the coplanar waveguide, it can avoid exciting extra slotline-mode surface wave and can reduce the size of the circuit. Furthermore, the defected ground structure not only can improve the performance of the filter, but also can furtherly reduce the size of the circuit. Therefore, in this thesis, the micro-coplanar striplines with defected ground structure are used to design the lowpass filters. In this thesis, the basic characteristics of the micro-coplanar striplines and the influence of defected ground structure are analyzed firstly. Next, the design theory of the lowpass filter using micro-coplanar striplines are studied, and the equivalent circuit of defected ground structure is derived. Finally, the lowpass filters using the stepped-impedance structures or the T-junction structures are designed and realized, respectively. In addition, the characteristics of these two filters are measured and compared with the simulation results. From the analyzed results, it is noted that both two lowpass filters have good performance. In addition, if the defected ground structures are used, the size of the circuits can be reduced about 16% and 15% for lowpass filters using the stepped-impedance and T-junction structures, respectively.
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