Studies And Design Of Microwave Ultra-wideband Bandpass Filter

Ultra-wideband (UWB) technology, as a primary candidate of wireless personal localarea network (WPANs), has received the global attention with the development of near fieldwireless communication technology and the multimedia business. Ultra-wideband technologyhas the advantages of high rate, low power consumption, high anti-interference, and highersecurity. It has very broad application prospects and a huge market value. As a indispensablecomponent of UWB system, the characteristics of UWB filter directly affects the performanceof the system.This thesis focuses on design theory and implementation method of microwave UWBbandpass filter. The main contribution of this thesis on ultra-wideband bandpass filter includesthe following two aspects:(1) A UWB filter with notch band is proposed using complementary spur-line resonator.By study the resonant conditions of defected grounded stepped impedance resonator, theminimum value conditions of SIR, relationship between first four harmonic and impedanceratio of defective SIR are given. To eliminate the interference form WLAN band, acomplementary spurline is introduced to the DSIR and a notch band at5.2GHz is achieved.Relations between the characteristic of notched band and the position and length of spurline isstudied. The DSIR is orthogonal coupled to the microstrip feed lines and a UWB filter withnotched band is achieved. The proposed UWB is finally fabricated and measured.(2) A novel method for realizing notched band in the UWB band is introduced. Thecharacteristic of the structure to be used for producing notch band is studied. Microstripopen-loop resonators are externally coupled to a DSIR to achieve a notched band. The circuitmodel for the structure is proposed. A UWB BPF with narrow notched band is firstly realizedby using the proposed method. Furthermore, coupling between loaded microstrip open-loopresonator is introduced by change the distance between two loaded resonators. A UWB BPFwith wide notched band is realized. The proposed filters are designed and fabricated.Measured results verify the proposed method.