Design Of Microstrip Multi-Passband Filters

Multi-band multi-standard wireless communication systems have been gaining muchattention in recent years due to the rapid development of telecom industry in our country. Inmulti-band transceivers, multi-band bandpass filters are important building blocks and thusheavily demand. This thesis mainly research on the design of microstrip multi-bandbandpass filters. Several dual-band and triple-band bandpass filters with good performancehave been designed by introducing novel coupling structure and resonators. The author’smain contribution as follows:1. A novel filter coupling structure has been introduced in this thesis. By adding someextra resonators, the traditional single filter circuit is changed into dual filter circuit. Thisstructure improves design freedom to fit easily the specific coupling coefficients at twopassbands simultaneously and the locations of two passband can also be tuned in a largeregion without enlarging the size of filter obviously. Examples of filters with a dual-bandChebyshev and quasi-elliptic response were designed and fabricated with goodperformance.2. Above novel coupling structure can be used in the design of triple-band bandpassfilter by adding another independent filter circuit. The triple–band bandpass filter fit easilythe specific coupling coefficients at three passbands simultaneously and the locations ofthree passbands can be also tuned in a large region especially the second passbands.3. Novel structure called λ/4resonator pairs with shared via-hole ground has beenintroduced in this thesis. The property of this λ/4resonator pairs has been analyzed in thethesis. This λ/4resonator pairs is very suitable to be used in the design of multi-bandbandpass filter when it takes the asymmetric structure. Multi-band bandpass filter with thisstructure have the advantages of higher design freedom, more convenient in simulation andsmaller size comparing to the filters which is designed by using SIR resonators. Examplesof multi-band bandpass filters with Chebyshev response were designed and fabricated.Especially the dual-band bandpass filter using asymmetric λ/4resonator pairs realize closedual-band performance.