Design of Conformal Multiband Antenna and its Gain Enhancement using Metamaterial Lens

This paper presents the design of quad band antenna operating at the frequencies of 3.12 GHz, 3.68 GHz, 4.57 GHz and 5.11 GHz respectively. The simulation and optimization are carried out using HFSS software. The antenna is designed and fabricated using commercially available FR4 substrate. The gain values obtained through simulation are 3.47 dB, 1.76 dB, 0.26 dB and 6.02 dB respectively at quad band frequencies mentioned above. The average gain for the antenna is 3.41dB. Further, to improve the quad band antenna gain, a three layered $2 \times 2$ metamaterial lens array is placed at a optimized height of 19 cm above the quad band antenna and average gain enhancement of 2.14dB is observed. The experimental result of a quad band antenna is presented. The measured return loss and radiation pattern are in acceptable limits. To evaluate the performance of a quad band antenna on different substrates, simulation study of quad band antenna is carried out using RT duroid substrate. The average gain obtained is 5.55dB, which is 2.14dB higher compared to the gain obtained when FR4 substrate is employed. A single layer metamaterial lens is placed at a height of 30 cm, and a gain enhancement of 3.4dB is observed. Further, the quad band antenna is made conformed to a cylindrical surface. The average gain of 5.27 dB is observed. A conformal metamaterial lens is placed at the height of 20 cm and average gain enhancement of 3.4 dB is observed.