Compact Triband Patch Antenna With Large Scale of Frequency Ratio Using CRLH-TL Structures

This letter presents a novel compact triband patch antenna filled with composite right/left-handed transmission line (CRLH-TL) structures. The CRLH-TL structures enhance left-handed (LH) characteristics and lower the operating frequency, which enable size reduction and large scale of frequency ratio from 1.5 up to 4. The upper two operating frequencies are realized by the outer patch of the proposed antenna, and the lowest operating frequency is controlled by CRLH-TL structures. The large scale of frequency ratio can be arbitrarily chosen by adjusting the dimensions of the patch and CRLH-TL structures.