Low Frequency Tunable Metamaterial Small Antenna Structure

In this paper, we present a compact and frequency tunable antenna which consists of a transmission line, two shorting posts, and two inductors which are serially connected between the posts and the edge of the transmission line. By properly changing the inductance of two inductors, the operating frequency of the antenna can be controlled without seriously sacrificing the fractional bandwidth. To give good demonstration of the operating mechanism, the equivalent circuit of this antenna is included. The characteristics of the antenna with various inductors integrated are also investigated. The fabricated antennas show that the operating frequency can be shifted from 2.07 GHz to 1.2 GHz. By integrating two inductors of 33 nH inductance, the electric size of the antenna is only 0.07 lambda x 0.005 lambda x 0.028 lambda. The validity of this antenna is demonstrated by both experimental and simulated results. The agreement between measured and predicted results is good.