Research And Design Of The Novel Ultra-wideband Bandpass Fliters

The Federal Communications Commission (FCC) authorized the unlicensed use of frequencyband from3.1to10.6GHz for wireless communication application in February2002. Becaues of itslow transmit power, high data rate, and simple error control capability, the ultra-wideband (UWB)radio technology has attracted more and more attention of various industries. As one of the mostimportant components of an UWB system, the UWB filter has a wide bandwidth not only with lowinsertion loss and flat group-delay response in the pass band, but also with good selectivity.Four UWB bandpass filters (BPFs) are designed in this thesis. The main work of this thesis canbe summarized as follows:1. An UWB BPF based on microstrip/coplanar-waveguide (CPW) structure is proposed. Thecharacteristics of the microstrip line and CPW structure are analyzed. Then, a novel UWB BPF withfour transmission poles, which are located in the pass band, is presented. Moreover, this filter isfabricated and measured, and good agreement between the simulated and measured responses ofthis filter is demonstrated.2. By suitably introducing a T-shape defected ground structure (DGS), the upper stopbandrejection of the UWB BPF, which is described in the first point, is improved.3. In order to produce a narrow notched band at5.8GHz for the rejection of WLAN, a/4open stub is proposed on the basis of the UWB filter which based on microstrip/CPW structure.4. A novel UWB BPF using cascading design method is presented. A low-pass filter and ahigh-pass filter are designed respectively. Then, by cascading these two filters, an UWB BPF isconstructed. The insertion loss of this filter is low, and the group-delay response is flat.