Frequency Tunable Filter Patch Antenna Based on Spoof Surface Plasmon Polaritons

In this paper, a novel filter patch antenna based on spoof surface plasmon polaritons (SSPPs) utilizing metal patch and fish-bone corrugated slot structure (FCS) as its transmission line is proposed in the microwave region. Traditionally, limited by causality, strong dispersion is always accompanied by high loss for natural materials. For SSPPs, as the frequency gets closer to the cut-off frequency, the loss also becomes larger. Nevertheless, thanks to the design flexibilities of the dispersion curve of SSPPs, strong dispersion can be accumulated by a longitudinal combination of SSPPs structures with different dispersion curves, resulting in size miniaturization of the proposed filter antenna. This paper utilizes the FCS as transmission line instead of microstrip, providing a cut-off frequency for the patch antenna. With the increase of the height of metal corrugated slot, the cut-off frequency decreases gradually, and at the same time, the wave vector is gradually away from the free space. Thus the cut-off frequency of the patch antenna is tunable by changing the maximum length of the FCS according specific application requirement. The designed patch antenna works well in the working frequency band, while it can no longer radiate electromagnetic (EM) waves above the cut-off frequency. The 2-D E-field distribution and surface current flow are all calculated and illustrated to demonstrate the EM characteristics of the proposed FCS. To validate the predicted performance, the proposed filter patch antenna is finally designed and simulated. Simulation results illustrate high performance of the filter antenna, showing good agreement with numerical simulations.