Characteristic Mode Analysis of Metasurface Antenna and Its Application on Compact Filtering Antenna Design

In this paper, a compact filtering antenna, operating at 6.35 GHz, based on metasurface is designed by using characteristic mode analysis (CMA). First, we study the modal features of the introduced metasurface antenna using the CMA. It can be seen that the designed antenna can realize the filtering function according to the far-field patterns of different modes. Then symmetrical shorting pins are added to achieve good filtering performance. Finally, the feeding point is optimized. A compact (0.4λ0 ×0.2λ0) filtering metasurface antenna is fabricated and measured. The measured peak gain is 6.64 dBi and measured 10 dB bandwidth is 3.5%. Two radiation nulls are observed at 7.05 GHz and 8.15 GHz and the measured out-of-band suppression levels are greater than 12.1 dB. Furthermore, the cross-polarization suppression levels are larger than 30 dB.