Slow-Wave Substrate Integrated Filtering Antenna with Defected Ground Structure

This work reports a slow-wave substrate integrated waveguide (SIW) filtering antenna with defected ground structure (DGS). The open side of the half mode substrate integrated waveguide (HMSIW) cavity is extended with an epitaxial dielectric plate to be utilized as a radiation resonator, while the other side is cascaded with the SIW cavity to form the second-order filtering response. The proposed filtering antenna has two controllable transmission zeros (TZ), which is generated by the cross coupling between microstrip, SIW cavity, and HMSIW cavity. The DGS and slow-wave structure are loaded into the resonant cavities to change the distributed inductance and capacitance, which can contribute to bandwidth widening and size reduction. Then, with the epitaxial radiation dielectric plate, the radiation area is widened, and the realized gain can be further enhanced effectively. To verify the design concept, a prototype was simulated. The simulated results exhibit that the center frequency is 8.74 GHz, the relative bandwidth is 4.8%, and the return loss is better than 16.2 dB. Moreover, two radiations zero locates at 7.95 GHz and 9.6 GHz, respectively, and the realized gain can reach up to 6.5 dBi.