Bandwidth enhancement of ZOR antenna by loading novel via-Less CRLH-TL unit cells

Novel via-less CRLH-TL unit cells loaded compact and bandwidth-enhanced zeroth-order resonant (ZOR) antennas have been designed and experimentally verified. Two CRLH-TL unit cells are designed and loaded in monopole antennas to enhance the bandwidth. The series capacitance of CRLH-TL unit cell is implemented with both interdigital capacitance/gap capacitance and shunt inductance is implemented with meander line inductance. The dispersion characteristics of the proposed unit cells are numerically calculated which follows CRLH-TL properties. Further, the conventional CRLH-TL unit cell metallic vias have been eliminated by using two novel techniques, which increases the fabrication flexibility. The compactness has been achieved by realizing ZOR mode and the resulting four open-ended ZOR antenna's bandwidth is increased by realizing small shunt capacitance and large shunt inductance. Further, to increase its bandwidth, merging of ZOR mode to the higher and lower order modes into a single passband by realizing proper CRLH-TL unit cells has been done. The each proposed antenna has a compact dimension of 25 × 15 × 1.6 mm3 and S11 < −10 dB impedance bandwidths of 9.6 GHz, 9.7 GHz, 10 GHz and 9.6 GHz respectively. The optimum gain, good efficiency and desired radiation characteristics have been achieved for proposed antennas, which are most suitable for ultra-wideband applications. The CST-MWS has been used for the parametric study of the proposed antennas. A good agreement has been achieved between simulated and measured results.