Design and Fabrication of 77-GHz Radar Absorbing Materials Using Frequency-Selective Surfaces for Autonomous Vehicles Application

The design of the 77-GHz radar absorbing materials (RAMs) that are suitable for the automotive environment is conducted using a square-patch frequency-selective surface (SP-FSS) on the surface of a grounded dielectric substrate. The inductance ( $L$ ) and capacitance ( $C$ ) of the SP-FSS were determined using the strip wire conductor model and used for determining the resonance frequency and substrate thickness. Impedance matching is satisfied at 77 GHz with a controlled FSS resistance matched to the free-space impedance. The optimized surface resistance of the SP-FSS conductor is $R_{s} = 94\,\,\Omega $ /sq (corresponding to the circuit resistance $R = 377\,\,\Omega$ ) for the lowest reflection loss of −37 dB at 77 GHz. The experimental result with a test sample prepared by the screen printing method is in good agreement with the simulation result and verifies the validity of the proposed design method.