A NRI-TL metamaterial-loaded bow-tie antenna

A fully-printed and low-profile bow-tie antenna is proposed, which exhibits multi-band performance by loading a 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 transmission-line and loading parameters of each NRI-TL unit cell. Both quad-band and tri-band versions of the antenna are shown. The tri-band version of the antenna achieves a -10 dB bandwidth of 44 MHz around 1.12 GHz, a bandwidth of 820 MHz, from 2.61 GHz to 3.43 GHz, and a bandwidth of 86 MHz around 6.47 GHz. The low-frequency resonance at 1.12 GHz corresponds to a 48% reduction in the resonant frequency compared to the lowest resonant frequency of the unloaded bow-tie antenna. The antenna has a total size of 50×10×0.79 mm³ or 0.187×0.037×0.003λ₀ at 1.12 GHz, and throughout the operating bands the gain and efficiency vary from -3.08 dBi to 2.21 dBi and 52% to 96%, respectively.