Experimental Characterization of AMC-based Thin Tunable Absorber Using Varactor Diode

This paper deals with the experimental characterization of thin tunable absorber developed based on artificial magnetic conductor (AMC). To produce the tunable frequency response, the varactor diodes with varied reverse DC bias voltage are incorporated into the AMC structure of proposed absorber. By using an equivalent circuit of varactor diode, the performance of AMC-based thin tunable absorber is characterized through a simulation software. To improve the absorptivity, a resistor with the value of 470Ω is also incorporated into the AMC structure in parallel to each varactor diode. A 1.6mm thick FR4 epoxy dielectric substrate with the dimension of 104mm × 104mm is used for deploying the design as well as for the realization. The experimental characterization which is performed using a horn antenna shows that the realized absorber has a tunable frequency response from the frequency of 2.26GHz with the reflection coefficient (S11) value of -21.5dB at the reverse DC bias voltage of 0V to the frequency of 3.01GHz with the S11 value of -19.75dB at the reverse DC bias voltage of 10V. This performance is comparable to the simulation result for the proposed absorber with the varactor diode and 470Ω resistor incorporation.