Coaxially Fed Monopole Antenna With Choke Structure Using Left-Handed Transmission Line

A composite right/left-handed (CRLH) transmission line (TL) is proposed for a choke structure. The dispersion relation of the CRLH TL is designed with the left-handed (LH) branch at around 700 MHz. The proposed CRLH TL is applied to the choke structure. The radiation patterns and current distributions on the outer conductor of the coaxial cable are calculated to verify the operation of the choke structure. The characteristics of a conventional sleeve antenna are calculated and compared with those of the proposed antenna. To verify the simulation results, the proposed antenna is fabricated. The |S
₁₁
| characteristics, the radiation patterns, and the total antenna efficiency are measured. At 585 MHz, the length of the monopole and the choke structure using LH TL are 0.12 and 0.05 wavelength, respectively.