| Summary: | 碩士 === 南台科技大學 === 通訊工程研究所 === 97 === In this thesis, several radio frequency multi-mode bandpass filters are designed and fabricated based on the co-planar waveguide ( CPW ) structure. They are two ultra-wideband ( UWB ) bandpass filters and three multi-mode bandpass filters. First, in the UWB Design, the capacitive coupling mechanism between two stepped impedance resonators can produce an UWB bandpass filter with bandwidth from 3.1GHz to 10.6GHz. Four folded quarter-wavelength open stubs can provide transmission zeros outside the passband and enhance the selectivity of the designed bandpass filter. The designed bandpass filter is fabricated on an FR4 substrate. It is shown that the performance of the UWB filter implemented on FR4 substrate in higher frequency can be further improved. Additional, a dual-UWB bandpass filter with two operation bands of 3.1~5 GHz and 6~10 GHz is also implemented. The series resonators are utilized and connected with two end-ports to form a dual-UWB bandpass filter. To filter out the unwanted interference from WLAN systems, the coupled lines composed of open stubs are employed to create rejection band with operation band of 5~6 GHz.
Secondly, the planar dual-band bandpass filters are designed to operate at 2.4/5.2 GHz and 2.4/5.7 GHz, respectively. A stepped impedance module associated with hairpin resonators is constructed in this design. The magnetic coupling mechanism is employed to create dual pass-bands. A shorted half-wavelength stub is utilized to provide extra transmission zeros at lower rejection band. Additional, a conductor backed strip is integrated with CPW structure to create triple passbands of 2.4 GHz, 5.7 GHz and 3.5 GHz for WLAN/WiMAX applications. In this structure, the hairpin resonators associated with the cross coupling mechanism are employed to create dual pass-bands. The square open-loop resonators integrated on the backside of the substrate is designed to create a passband with the center frequency of 3.5GHz. Finally, the ISM triple-band bandpass filter is illustrated and measured. It is designed to operate at 900 MHz, 2.4GHz and 5.2GHz. A stepped impedance module associated with square spiral- typed half-wavelength open stubs is constructed in this design. Through the various coupling mechanisms, triple-bands and multi-transmission zeros can be produced. The hairpin-typed resonator integrated on the backside of the substrate can shift fourth transmission zeros to improve the selectivity of the proposed filter. The design and fabrication of the above multi-mode bandpass filters followed the Institute of Electrical and Electronics Engineers ( IEEE ) standards and the fabricated filters can be applied to the existing wireless communication network.
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