Study And Design Of Microstrip Filters For Wireless Communications

With the phenomenal development of science and technology, wireless communication has changed our lives more and more, especially for Near Field Communication. Many new wireless communication systems are proposed, verified, realized and adopted, such as GSM, WLAN, WiFi, UWB, Bluetooth and so on. Microwave filter have been spurred a tremendous development with communication industry progress, and more filter with high performance are desired. The demand on sufficient usage of frequency spectrum and compatible of different communication system has improved the multiband and wideband filter design technology. The research work presented in this dissertation focuses on the bandpass filter, multiband and wideband filter design in wireless communication. Based on the analysis of Microstrip structures, Defected Ground Structure (DGS) and so on, many bandpass filters, multiband filters and wideband filters working at the wireless communication band are designed, in which the comparison and co-simulation method are adopted. The author's works mainly consist of:(1) Systemically study on the split ring resonator (SRR), which including microstrip resonator and Defected Ground resonator, and the analysis on the resonant and coupling properties of the SRR have done. The coupling intensity between SRRs with different position is analyzed. The coupling properties between SRR microstrip and SRR DGS are firstly studied with the detail of position. The requirement of their have coupling is also given, which has prevalent meaning of filter design.(2) Systemically study on the different feed structures of SRR has been done, including detail of position. The comparison of direct feed and coupling feed are analyzed and summarized. Filters with different feed structures are design to verification of the conclusion.(3) The bandpass filters, dualband filters and multiband filters based on the folded stepped impedance Resonator are designed. These filters are employing SRR on microstrip and DGS with different feed as resonator. structure and source-load coupling structure, bandpass filters with transmission zeros are given. Dualband and multiband filter are designed based on paralleled band theory, frequency transformation. All these filters are employing the coupling between microstrip SRRs, DGS SRRs or both.(4) Based on Discrete z transform, novel compact ultra-wideband (UWB) bandpass filter employing this design method is proposed. The design begins with the adoption of digital filter prototypes and the implementation is facilitated by using both parametric modeling techniques and optimization algorithms.(5) Three coupled microstrip lines structure and its wideband properties are studied for UWB bandpass filter design with parallel short stubs. UWB bandpass filter employing Composite Right/Left-Handed (CRLH), square ring on DGS also studied and implemented. Lowpass filter and bandstop filters on high frequency are studied to improve the inhibition of UWB bandpass filter. UWB bandpass filter with notched band employing embedded open stub and SRR DGS are studied and implemented.