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Abstract--A tunable wideband absorber is presented in this paper. It is based on periodic resistive patterned graphene operating in microwave regime. The proposed absorber not only has wide absorption band but also can be tuned by changing the conductivity of graphene. At chemical potential of 0.3 eV, 90% absorption can be achieved from 10.2GHz to 43.5GHz with 124% fractional bandwidth. Furthermore, the absorber shows relatively stable performance with respect to the incident angle of plane waves. IntroductionElectromagnetic absorbers have been of great interest over the last decades. The main aim of such absorbers is to reduce the unwanted reflections significantly in certain frequency range. Since the classical Salisbury screen[1] and Jaumann absorber[2] are introduced, there have been numerous absorbing structures put forward [3][4]. However, these absorbers have shortcomings of narrow bands and heavy thickness. In order to improve the performance of absorbers, periodic resistive patterns called frequency selective surfaces(FSSs)are applied to absorbers [5]. Without the limitation of one quarterwavelength thickness, it can achieve a wideband in terms of 90% absorption. However, the aforementioned absorbers remain fixed structures, which makes bandwidth invariant. The solution to achieve a tunable absorber is to combine pin diodes or new materials such as graphene into the FSS structure.Graphene has appealed a great attention in absorbing owing to its excellent and unique electrical, optical and mechanical properties, since it is first acquired by using micromechanical cleavage by Geim and Novoselov in 2004[6]. In recent years, a large number of graphene-based absorbers have been discussed in [7]-[12]. A transparent graphene absorber with 28% fractional bandwidth at 140GHz has been experimentally demonstrated in [7]. In[8], graphene-based high impedance surface is proposed as an absorbing structure at microwave frequencies. Graphene periodic resistive patterns called frequency selective surfaces are applied to absorber [9].In[10] and [11], by changing chemical potentials, the absorption energy of transparent graphene broadband absorber is controlled over a relatively large interval in the frequency band. A transparent absorber based on patterned graphene film is theoretically illustrated, practically fabricated and experimentally demonstrated [12].In this paper, a novel, thin and graphene-based absorber is designed by placing Jerusalem-shaped graphene patch between dielectric layers. Graphene's tunability and frequency-independent surface impedance in microwave band is utilized for broadband matching and high absorption. Consequently, the proposed absorber can obtain wideband characteristic and be tunable. Moreover, the absorption stays large when the incident angle is smaller than 60°. The design and performance of the absorber will be discussed in details in the following parts.

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