Design of a unit composite right/left-handed cell based bandpass filter with floating slot approach and suppression of spurious using defected microstrip structures

摘要

This paper presents the construction of a unit composite right/left-handed cell using hairpin microstrip coupled line circuits. To get the high coupling in comparison to conventional edge coupled microstrip line, the floating slot on the ground plane is used here. Two basic configurations named after short-open-short (SOS) the open-short-open (OSO) model are studied for the realization of band pass filter. The floating ground equalizes the even and odd mode phase velocities and solves the difficulties arises in the fabrication process as it relaxes the requirements on physical dimensions like coupled gaps between lines. The hairpin structure makes the filter structure more compact in size. Defected microstrip structure on the feed line suppresses the spurious response and provides a good stopband performance. Finally a bandpass filter having fractional bandwidth of 70.83 % for OSO model and 44.05 % for SOS model are obtained. Those filters have wide application in modern wireless communication system.