A Miniaturized Ultra-wideband Resistive Film Absorber for Radiation Suppression

Abstract

Package lid and heat sink incorporated in PCB or chip package are often used for solving the heat dissipation problem, which is easy to form a resonant cavity with the metal ground plane of the package substrate, and consequently result in the noise current coupling to the package cover and heat sink through the capacitive effect, causing serious EMI problems, therefore, we propose a new resistive film-based super material absorber structure. In this paper, a unit of the proposed structure has resistive film patterns on the FR-4 substrate in front of the conductive plate, and the top layer uses Jerusalem cross, square and L-shaped resistive film to achieve bandwidth expansion. The unit size of the entire absorber is 0.15$\lambda_{L}\times 0.15\lambda_{L}(\lambda_{L}$ is the wavelength corresponding to the lowest cut-off frequency), while the thickness is only $0.07\lambda_{L}$. The simulation results show that the absorption rates are more than 90% in the frequency range from 22-40GHz. When the electromagnetic waves are perpendicular to the proposed resistive film absorber, it is insensitive to the polarization of TE and TM modes, and the absorption rates remain stable when the incident wave is wide-angle. Based on the equivalent medium theory, it is demonstrated that the structure achieves good impedance matching with free space in a wide frequency band. Meanwhile, the absorption mechanism of this structure is analyzed by the distribution of electric field and surface current, and the equivalent circuit model of resistive film absorber is established. The proposed resistive film absorber is characterized by miniaturization, ultra-wideband, high absorption rates, and insensitivity to polarization, providing a new idea for radiation suppression of highly integrated electronic devices.