Dual-Band and Polarization-Flexible CRLH Substrate-Integrated Waveguide Resonant Antenna

A dual-band and polarization-flexible substrate-integrated waveguide (SIW) resonant antenna based on composite right-/left-handed (CRLH) structure is presented in this letter. The proposed antenna consists of a CRLH SIW resonator and dual feeding lines. A slot and surface-mount technology capacitors on the top metallic layer of SIW resonator provide necessary reactance to realize multiresonance CRLH structure. Due to the intrinsic multiband characteristic of a CRLH structure, the proposed antenna can provide dual-band broadside radiations. Polarization flexibility is realized by two orthogonal feedlines. Utilizing the CRLH resonator instead of the conventional square resonator, such as patch antenna, allows antenna miniaturization. The electrical lengths of the sidewalls for the proposed square SIW resonant antenna are 75% (for first resonant mode) and 44% (for second resonant mode) shorter than that of the previously proposed dual-band polarization-flexible SIW antenna. To highlight the unique advantages, the dual-band circularly polarized antenna array based on the proposed antenna element is presented. Dual-band circularly polarized radiation is supported by the dual-band CRLH transmission-line-based feeding network.