A Dual-Band Metamaterial Absorber Using Square Loops with Transmission Capability

Abstract

This paper presents the design, fabrication, and characterization of a dual-band metamaterial absorber that utilizes square-loop frequency-selective surfaces on FR-4 substrates. In contrast to traditional absorbers that rely on a solid ground plane, the innovative design features patterned loops in both the ground and front layers, allowing for targeted absorption while still permitting some transmission. Simulations conducted in CST Microwave Studio predicted absorption peaks of 76.9% at 3.47 GHz and 77.6% at 5.63 GHz, with adequate absorption levels of 70.9% at 3.5 GHz and 59.1% at 5.8 GHz. Measurements were performed using a Keysight N5232A vector network analyzer, along with horn antennas, inside an anechoic chamber. This setup confirmed absorption peaks at frequencies close to the desired frequencies, each with magnitudes exceeding 56%, which are sufficient to be used as a chipless identification tag and detect by a reader. The proposed approach highlights the viability of square-loop metasurfaces to achieve compact, tunable, and efficient absorbers with transmission capabilities that are suitable for microwave applications.