Patch antennas partially filled with CRLH cells for self-diplexed antennas for RFID application

In this paper two dual-frequency (2.45 GHz and 1.72 GHz) self-diplexed two-port antennas based on patches partially filled with CRLH cells are proposed. The polarization at both ports can be either equal or orthogonal linear polarizations. The proposed radiator allows a multi-frequency performance keeping an easy manufacturing structure. The high isolation level is achieved thanks to a joint effect of the proposed feeding structure plus the addition of bandpass filters based on SSR coupled to the feeding lines. The isolation levels between each port are quite large for either polarization. This avoids the use of external filters or diplexers getting reduced-size self-diplexed antennas.