Multifrequency self-diplexed single patch antennas loaded with split ring resonators

In this paper a novel approach to design multifrequency self-diplexed single patch antennas is proposed. This approach is based on a square microstrip patch antenna loaded with split ring resonators (SRRs). The working frequencies can be arbitrarily chosen and frequency ratios lower than 1.07 have been achieved. In addition self-diplexing characteristics are also achieved between transmitting and receiving ports by including SRRs in the feeding lines. Several prototypes have been manufactured and measured in the X-band showing good performance.