Bandwidth enhancement of planar monopole antenna by loading metamaterial based via-less CRLH unit cells

Abstract

A novel compact via-less composite right hand left hand transmission line (CRLH TL) loaded ultra-wide band (UWB) CPW fed monopole antenna has been designed and tested. Initially basic planar monopole has been designed which has narrow bandwidth, but after loading CRLH unit cells in that monopole good amount of bandwidth improvement is observed. The series capacitance and parallel inductance combination realizes CRLH unit cell. The capacitance and inductance have been realized with gap capacitance and single turn inductance respectively. The single turn inductance is grounded using metallic via in first design which has multiple resonances. To eliminate this metallic vias CPW feed has been introduced in present work where grounding can be done on same plane without drilling of substrate. The proposed antenna is constructed by loading two unit cells in monopole antenna with CPW feed. The additional quarter wave transformer has been eliminated by using optimum feed location offset l of = 0.6 mm. The antenna dimension is 25 × 15 × 1.6 mm3 or 0.13λ 0 × 0.08λ 0 × 0.0085λ 0 , where λ 0 at 1.6 GHz. The S 11 curve shows that fractional bandwidth of 158% from 1.6 GHz to 13.5 GHz with corresponding impedance bandwidth of 11.9 GHz. The peak gain of antenna is 4.4 dBi at 11.2 GHz and 3.3 dBi at 10 GHz respectively, and it has suitable gain for ultra-wideband applications. The CST microwave studio has been used for parametric study of antenna. Proposed antenna is fabricated with FR4 substrate and successfully tested. Good agreement has been observed between simulated and measured results.