Compact Low-Profile Dual Band Metamaterial Antenna for Body Centric Communications

A compact low profile dual band metamaterial antenna is presented for wireless body centric communications. It is composed of a zeroth-order loop loaded periodically with mu-negative transmission line (MNG-TL) for a lower frequency band and a circular patch located in the center of loop for an upper frequency band. The MNG-TL loop based on the fundamental infinite wavelength property allows current along the loop to remain the same magnitude and phase to create omnidirectional radiation pattern in azimuth plane at the lower band for on-body communications. On the other hand, a unidirectional radiation pattern is generated by a circular patch in direction normal to a human body at the upper frequency band for off-body communications simultaneously. In order to feed the MNG-TL conveniently, a transition based on a CPW transmission line is proposed. Finally, the proposed antenna is fabricated and measured. It is demonstrated that the measurement has good agreement with simulation.