Broadband and High Transmission Metasurface Bandpass Filter Based on Electromagnetic Wave Tunneling and Strong Magnetic Field Coupling for the X-Band Application

Spatial spectral filters, also known as frequency-selective surfaces, have consistently been in high demand in the past decades due to their diverse and extensive applications across numerous fields. Here, a design and comprehensive analysis of a broadband, high-transmission metasurface (MS) bandpass filter (BPF) is presented that incorporates an ABA tri-layer structure. Tailored for X-band applications, this BPF utilizes electromagnetic (EM) wave tunneling and strong magnetic field coupling to deliver exceptional performance. The unit cell of the BPF is composed of a square-aperture (SA) situated between two identical layers of four-square-patches (FSPs), sandwiched between dielectric substrates. The experimental results reveal that the designed BPF demonstrates a transmission coefficient exceeding −3 dB within the frequency range of 9.06–11.14 GHz, achieving a relative bandwidth of 20.6%. This performance closely aligns with the predictions obtained from both the equivalent circuit model (ECM) and the finite element method (FEM) simulation, thereby validating the accuracy and effectiveness of the design approach. Additional numerical simulations have verified that the designed BPF exhibits robust performance across a broad range of incident angles, encompassing both transverse electric (TE) and transverse magnetic (TM) polarizations. Given its exceptional transmission characteristics, the proposed MS BPF demonstrates promising potential for X-band radome applications.