A Broadband Patch Filtering Antenna with Flat-Gain Based on ISGW

This paper presents a broadband filtering antenna with an ISGW feeding mechanism. The antenna consists of one radiation patch and four parasitic patches, totaling five patches. A rectangular slot is introduced on the radiation patch to disturb the current phase distribution, generating a low-frequency radiation null at 22 GHz. Parasitic patches are added to induce high-frequency radiation null at 30.9 GHz. Additionally, within the pass-band of the ISGW, only the quasi-TEM (Q-TEM) mode is transmitted, preventing multi-mode issues. Simulation results show that the filtering antenna has a bandwidth of 20.2%, with a frequency range from 24.4 GHz to 30 GHz. The average gain within this frequency range is 8.0 dBi, and the gain curve remains flat across the operating bandwidth.