A high Q factor sensor to measure the complex permittivity and effective permittivity based on a band stop frequency-selective surface

In this paper, a metamaterial sensor is proposed based on a band stop frequency-selective surface (FSS) with high Q factor of 421.9 at 8.032 GHz. The sensor consists of a square loop FSS and a F4B dielectric substrate. This is the first sensor based on a band stop FSS sensing the effective permittivity of 3D printed hollow structures. The equivalent circuit method is used to analyze the characteristics of the sensor, and the results agree well. Two materials under test and four different hole radii of 3D printed hollow structures are used to verify the sensing function. At the same time, the effective permittivity of the 3D printed hollow structure is analyzed, and the correctness of the effectiveness is verified by simulation inversion and Maxwell-Garnett formula. The sensor has the advantages of high Q factor, wide incidence angle and polarization angle insensitivity, which can provide some guidance in metamaterials sensing.