A Low-Profile Third-Order Half-Mode SIW Filtering Antenna With Low <i>H</i>-Plane Cross Polarization and Good Sideband Suppression

Abstract

A new type of low-profile filter antenna with low H-plane cross polarization (cross-pol) and good suppression of sidebands is proposed using multifunction single slot and five shorting pins integrated into half-mode substrate integrated waveguide (SIW). Initially, the TM1,3/2 mode, the TM1,5/2 mode, and the TM3,1/2 mode have been excited successively in the low H-plane cross-pol SIW. Then, in order to realize third-order half-mode radiation of the antenna, the five shorting pins and the key slot have been used to reallocate those modes above. In addition, the slot also introduces two transmission zeros at 4.94 and 6.12 GHz to improve the filtering characteristic and to suppress the sidebands of the antenna. Finally, the filtering antenna is designed at 5.16 GHz with 2.5% impedance bandwidth for WLAN wireless communication application. The attenuation for lower sideband is always below 30 dBi, while the corresponding bandwidth for upper sideband achieves high out-of-band suppression levels of 20 dBi is about 1.52 GHz. The cross polarization can reach below -30 dB; meanwhile, its gain in frequency band is 6.79 dBi above. In addition, the low-profile property has been obtained with the height of 0.0087 free-space wavelength.