Circular Patch Filtenna with Adjustable Radiation Null

This paper presents a circular-shaped filtering antenna design. By incorporating a rectangular slot into a conventional circular patch antenna, the design introduces a filtering feature with an adjustable radiation null, which can be easily controlled by varying the length of the slot. The antenna operates at a frequency of 5.8 GHz, making it suitable for WLAN/WiFi applications. It achieves an impedance bandwidth of 5.70-5.93 centered at 5.8 GHz, with a radiation null at the upper edge of the band at 6.05 GHz. The antenna also exhibits flat in-band realized gain characteristics, around 7.74 dBi. Additionally, simulated results show unidirectional radiation in the boresight direction with extremely low cross-polarization. The proposed design is straightforward, yet it effectively combines filtering performance with a simple configuration.