Size reduction of composite right/left handed transmission line and its application to the design of dual-band bandpass filter

This article presents a method that chooses appropriate phase size to reduce the size of a composite right/left-handed (CRLH) transmission line. A reduced-size dual-band bandpass filter was designed and fabricated to demonstrate the proposed CRLH line, and the wide dual-passband characteristics are obtained by implementing a dual-band J-inverter as the coupling between 2 CRLH-resonators. A defected ground structure is adopted to obtain the line with a high characteristic impedance for the J-inverter. The designed dual-wideband bandpass is validated by conducting experiments and obtaining measures of its performance. The results show that the 2 passbands are centered at 2.4 GHz and 5.2 GHz, with a 3-dB fractional bandwidth of 33.75% and 38.46%, respectively. In addition, this filter has low insertion losses of 0.21 dB and 0.5 dB for each passband.