Wideband Filter with Continuously Reconfigurable Rejection Band Based on Spoof Surface Plasmon Polaritons

In this paper, a wideband filter with controllable rejection band based on spoof surface plasmon polaritons (SSPP) is proposed. By employing a varactor to change the equivalent electrical length of SSPP unit cell to make the rejection frequency reconfigurable. To verify the design theory, one wideband lowpass filter with reconfigurable rejection band based on SSPP is simulated, fabricated and measured. The measurement results show that the rejection frequency can be tuned in the range of 6.68 $\mathrm{GHz} \sim 8.49 \mathrm{GHz}$ continuously, and the rejection bandwidth stays at about 2.73 GHz basically. The rejection in the notch band is maintained above 40 dB, and the maximum depression reaches 55.6dB.