Compact Yagi antenna utilizing mu-negative metamaterial loading of director element

A new technique to miniaturize Yagi antennas utilizing mu-negative (MNG) metamaterial loading is presented. In this method, the director element of the printed Yagi antenna is loaded with MNG-metamaterial unit-cells to introduce a new mu-zero resonance (MZR) which is independent of the size of the antenna, and can be adjusted by changing the amount of loading capacitance. This technique enables the printed Yagi antenna to operate at lower frequencies without changing size of the substrate. As a result of the proposed design, dual band operation is achieved. Lower band of the antenna is defined by the loaded capacitance and for instance for a 3pF loaded capacitance, the antenna operates at 0.78-0.81 GHz. The upper band is controlled by the dipole resonance and depending on the loaded capacitance it operates at different wide bands between 1.15-2 GHz. The proposed method enables the size of the antenna to be reduced by more than 50% compared to existing Yagi antennas with peak gain and front-to-back ratio values of 5.5 dBi and 10 dB, respectively. A sample design of a three-element printed Yagi antenna whose director is loaded with MNG unit cells is presented as a proof-of-concept