Electrically Small Eighth-Mode Substrate-Integrated Waveguide (EMSIW) Antenna With Different Resonant Frequencies Depending on Rotation of Complementary Split Ring Resonator

Electrically small antennas are proposed, based on a substrate-integrated waveguide (SIW) and a complementary split-ring resonator (CSRR). The antenna's electrical size is reduced by introducing both CSRR and the eight-mode substrate-integrated wave guide (EMSIW). A forward electromagnetic wave can be achieved with frequency below the characteristic waveguide cuff-off frequency due to the CSRR. The EMSIW occupies only 12.5% of the conventional SIW with the same dominant resonant frequency. In addition, by rotating the CSRR on the EMSIW, the resonant frequency of the antenna is varied, while maintaining the same radiation pattern and performance. The S-parameters and radiation patterns are investigated by a full-wave simulation and measurement. The resonant frequency is changed from 4.74 GHz to 5.07 GHz by varying the orientation of the CSRR from 0 to 360 degrees. Omnidirectional radiation patterns are observed, and the measured peak gains are 4.5-5.9 dBi.