A novel miniaturized composite right/left-handed (CRLH) transmission line based on the structure of spiral inter-digital is proposed and analyzed in this article. Compared with the conventional inter-digital CRLH, the proposed CRLH realizes a 25% resonace frequency shift, and the miniaturization is realized. Then, a compact bandpass filter centered at 1.00 GHz with minimum insertion loss 0.42 dB was designed, fabricated and measured. The measured results show that the band width is 61.6% and that the sharpness at the two edges of passband is 212.5 dB/GHz and 607.1 dB/GHz. This designed filter has very high selectivity. Besides, the whole size of the designed filter is 0.114λ×0.054λ. The filter realizes the miniaturization effectively, and this designed bandpass filter has good performances and smaller size than the same works in references.
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