Broadband Tunable Metamaterial Absorber with Active Lumped Diodes

This paper presents a novel and practical way to realize broadband tunable microwave metamaterial absorber by utilizing the resistance properties of active PIN diodes. The proposed metamaterial absorber consists of metallic square-ring unit cell loaded with four identical PIN diodes, of which the resistance value can be adjusted from nearly conductor to several hundred Ohm, thus leading to a continuous tunability of the reflection rate by tuning the bias voltage on the PIN diodes. Simulation results show that the fractional bandwidth of 85.6% with at least 10 dB reflectivity reduction can be realized from 2.11 GHz to 5.26 GHz when the resistance of diodes is tuned to 315 Ω.