Research Of Bandpass Filter Based On Metamaterials

Recently the metamaterials with particular electro-magnetic characteristics drew more and more attention and as one way to realize the metamaterial, composite right/left-handed TL(CRLH) that bases on transmission line theory has been widely used for its advantages like simle structure, small size, fabrication convience, low loss and wide brand.The concept of metamaterials, the study course in the international electromagnetism and its significance are briefly introduced at the beginning of the thesis, and then focusing on the analysis of the Chinese and foreign achievments of band-pass-filters using metamaterial and their advantages and shorts, then interpreted the metamaterials basic theoretical characteristics and the related theories of the CRLH and finally proposed two band-pass-filters evolving from CRLH, one was a coplanar waveguide narrow-band band-pass-filter, from the equivalent circuit aspect we validate the novel CRLH unit structure's left-handed characteristic and assembled the units into a band-pass-filter, the filter had compact structure, small size and good performance, proved by simulation and practical tests, the other was a microstrip line ultra-wideband filter, we analyzed the characteristics of the structure of the Pi-type CRLH units which compose the filter, designed a ultra-wideband filtering network on balanced status after parameters selection, then was the ultra-wideband filter. Afterwards we validated the parameter-selection from the equivalent circuit aspect and the filter also had advantages like compact structure, small size and good performance. Finally, in order to meet the needs of various applications, with the ladder network equivalent circuit configuration which achieved a uniform composite right/left -handed transmission line, and in accordance with the formula for calculating the cut-off frequency bands to determine the optimal working scope, we get the application passband scope of the band-pass filter.