A multi-band NRI-TL metamaterial-loaded bow-tie antenna

A compact, fully-printed and low-profile bow-tie antenna is proposed, which exhibits multi-band performance by loading a reference bow-tie antenna with series capacitive gaps and shunt inductive strips, to form an asymmetric two unit-cell NRI-TL loaded antenna. It is demonstrated that the resonant behaviour of the antenna can be adjusted by changing its geometrical parameters, which in turn tune the transmissionline and loading parameters of each NRI-TL unit cell. Both triband and dual-band versions of the antenna are shown. The dual-band version of the antenna achieves a -10 dB bandwidth of 50 MHz around 1.91 GHz, and a bandwidth of 1.47 GHz, from 4.24 GHz to 5.71 GHz. The low-frequency resonance at 1.91 GHz corresponds to a 45% reduction in the resonant frequency compared to the lowest resonant frequency of the unloaded bowtie antenna. The antenna has a total size of 30×6×0.79 mm³ or 0.19×0.04×0.005λ₀ at 1.91 GHz, and throughout the operating bands the gain varies from 0.78 dBi to 1.78 dBi.