A Metamaterial Absorber With a New Compact Unit Cell

This letter focuses on the modification of a unit cell of a metamaterial absorber to decrease its operational frequency. By decreasing the operational frequency, we can increase capability of the absorber for practical applications and decrease sensitivity of the structure response to the curvature. The structure has been implemented by the array of the unit cell on the FR4 substrate in the front of a conductive plate. Both the simulated and experimental results indicate the structure provides 20% decrease in the minimum operation frequency with respect to the reference structure. Also, the operating frequency range of the structure with absorptivity more than 90% is 1.35-3.5 GHz, i.e., 88% fractional bandwidth. The structure has appropriate response under oblique incident angle from 0° to 40°.