In this paper, a broadband frequency selective surface (FSS) based on a multilayer coupling cascade is presented. The overall structure consists of three metallic layers and two dielectric substrates. In addition, a crosspatch terminated with an E-shaped structure and a gradient cross structure with a slot is introduced in the middle metallic layer to control the transmission zero and extent of the current path, respectively. The unit cell periodicity is about 0.27 λ 0 , and the overall thickness of the dielectric layer is about 0.087 λ 0 . Prototypes of the proposed FSS are designed and simulated, and an equivalent circuit model is developed to explain the mechanism further. Finally, the FSS prototype works at the center frequency of 12.2 GHz with a relative −0.5 dB bandwidth of 70% and a relative −3dB bandwidth of 104%. The frequency responses are relatively stable with the variation of incidence angles from 0°t o 60°.

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Based on a substrate integrated lens (SIL), a compact line source generator (LSG) for feeding continuous transverse stub (CTS) arrays with linear-polarized (LP) beam scanning and dual-polarized (DP) operations is presented in this paper. The SIL consists of metamaterial cells with different sizes being arranged as concentric annulus and is printed on the center surface of two substrate layers. The SIL can convert the cylindrical wave generated by the feed probe of SIW-horn to the planar wave for feeding the CTS array. This rotationally symmetric SIL can be used conveniently to design LSG for feeding CTS arrays with the continuous beam scanning and DP operations, which has been verified by the fabrications and measurements. By simply rotating the SIW-horn along the edge of SIL, the 10-element LP-CTS array obtains a measured beam scanning range of ±35° with the highest gain of 20.6 dBi. By setting two orthogonal SIW-horns at the edge of the proposed SIL, the nine-element DP-CTS array with orthogonal radiation stubs is excited. The DP array obtains the gain of 20.3 dBi at the center frequency with the isolation of 28 dB and the cross-polarization level <−25 dB.

The tunability of graphene's surface conductivity attracts tremendous interests in electromagnetic applications. This proposing feature enables graphene one of the ideal materials for reconfigurable antenna designs. In this paper, a new dipole antenna with two integrated graphene sheets operating in terahertz frequency is proposed and its reconfiguration of radiation properties is investigated. The two graphene sheets are deposited at the feeding positions of the two dipole arms, which increases the tunable freedoms of the dipole antenna's impedance up to two degrees. The tunable two-degree freedom of the dipole antenna enables antenna's operating frequency reconfigurable in a wide frequency range from 0.65 to 1 THz, and total radiation efficiency change from 13% to 89% when graphene chemical potential is electrically tuned from 0 eV to 0.5 eV. At 1 THz frequency, the realistic gain can be tuned from 1.6 dB to -8.7 dB. The more than 10 dB difference of the realistic gain makes the dipole antenna switchable. The fancy reconfigurable properties of the dipole antenna can be applied for multi-functional wireless THz systems and beam-forming THz antenna arrays.

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