Broadband Tunable Frequency Selective Surface for Steerable Antenna Applications

Resonant frequency tunable range is an important character for active frequency selective surfaces (AFSSs), especially when building electronically steerable antennas based on AFSS. In this communication, a broadband tunable bandpass AFSS is presented. The tunable ability is achieved by the varactors mounted on the surface. The proposed design has zigzag resonant current flows through multiple unit cells. Thus, the magnetic field coupling between unit cells is enhanced and the resonant frequency tunable range is extended. The measured resonant frequency tunable range is from 935 MHz to 2.405 GHz. Another advantage of this design is that no additional bias grid is required. Furthermore, this design has stable response under different angles of incidence because it has subwavelength dimensions.