The design and investigation of a wideband common-mode rejection filter using slot line structure

• Main Authors: You-min Hou, 侯佑民
• Other Authors: Chu-yu Chen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/82685450792311567788

碩士 === 國立臺南大學 === 電機工程學系碩士班 === 101 === Two new defected ground structures (DGSs) are proposed to realize a high performance filter for suppressing common-mode noise in high-speed circuit design. One common-mode rejection filter is designed and fabricated based on the meander slot line structure (MSLS). The phi-shaped slot line structure which consists of three kinds of resonators is implemented and integrated into another filter design. The diverse parameters and coupling effects of these two common-mode rejection filters are required to be analyzed and investigated for creating the equivalent circuit model. To reduce the area of the traditional DGS structure, the resonator is further modified. With the wavelength fixed, the slower the phase velocity, the lower the resonant frequency. By increasing the coupling strength between two resonators, the occupied area and suppression bandwidth of the conventional common-mode suppression filter are improved. Compared with the equivalent circuit model, both simulation and measurement results are in good agreement. The insertion loss is of less than -15dB ranged from 2.6GHz to 7.4GHz and the overall size is 0.52λg * 0.43λg in the meander slot line structure. The stop-band bandwidth ratio of 96% is obtained. The insertion loss is of less than -15dB ranged from 2.8GHz to 8.8GHz and the overall size is 0.21λg * 0.23λg in the phi-shaped slot line structure. The stop-band bandwidth ratio of 103% is obtained. Furthermore, it is observed that the proposed two common-mode rejection filters reached more than 87% and 82% in the suppression of common-mode voltage in the time domain analysis, respectively. The phi-shaped type filter can provide better size reduction of 78% than the meander type filter.