The Design and Fabrication of Low Insertion Loss and High Selectivity UWB Filters

• Main Authors: Kun-Yen Tu, 杜昆諺
• Other Authors: Chu-Yu Chen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/8d43sy

碩士 === 國立臺南大學 === 電機工程學系碩博士班 === 102 === In this thesis, the high selectivity lowpass filter with interdigital capacitors embedded is firstly designed. Then, the distributed highpass filter is designed. By cascading both lowpass filter and highpass filter together, the ultra-wide band filter operated from 3GHz to 10GHz can be achieved. Such a filter has the characteristics of low insertion loss and high selectivity. To isolate the effect from the standard 802.11a, the transmission zero which can provide the reject band from 5 GHz to 6 GHz has to be designed. The quarter-wavelength open stub can produce the transmission zero at 5.5 GHz and provide the rejection band of about 1GHz. Dual ultra wide passbands are created. The high selectivity highpass filter based on the radial stub structure is designed instead of the conventional distributed highpass filter. Compared to the short circuited stub structure, the radial stub structure without making via hole to ground is much easier to realize. Also, the radial stubs can provide extra transmission zeros in the lower stop band and enhance the selectivity of the highpass filter. In this thesis, the transmission zeros at the 1.95GHz and the 2.45GHz are designed for this purpose. The novel section by connecting the radial stub structure with a short microstrip line is proposed and designed. The short microstrip line with low and high impedances is equivalent to a series capacitor-inductor resonator and provides the reject band. This section is implemented into the designed ultra wide passband filter to realize the dual ultra-wide bandpass filter.