A novel polarization converter based on the band-stop frequency selective surface

A dual-passband single-polarized converter based on the band-stop frequency selective surface(FSS)with a low radar cross-section(RCS)is designed in this article.The unit cell of the proposed converter is formed by a polarization layer attached to the band-stop frequency selective surface.The simulation results reveal that the co-polarization reflection coefficients below-10 d B are achieved in 3.82–13.64 GHz with a 112.4%fractional bandwidth(the ratio of the signal bandwidth to the central frequency).Meanwhile,a polarization conversion band is realized from 8.14 GHz to 9.27 GHz with a polarization conversion ratio which is over 80%.Moreover,the 1 d B transmission window is obtained in two nonadjacent bands of 3.42–7.02 GHz and 10.04–13.91 GHz corresponding to the relative bandwidths of 68.9%and 32.3%,respectively.Furthermore,the radar cross-section of the designed structure can be reduced in the wideband from 2.28 GHz to 14 GHz,and the 10 d B RCS reduction in the range of 4.10–13.35 GHz is achieved.In addition,the equivalent circuit model of this converter is established,and the simulation results of the Advanced Design System(ADS)match well with those of CST Microwave Studio(CST).The archetype of the designed converter is manufactured and measured.The experiment results match the simulation results well,which proves the reliability of the simulation results.

Real-time monitoring the formation and decomposition processes of methane hydrate with THz spectroscopy

Gas hydrates are crystalline clathrate compounds comprised of hydrogen-bonded water cavities, consisting of guest molecules trapped in a lattice of polyhedral water cages under elevated pressures and low temperatures [1]. The structures of the gas hydrates are closely related to the types and sizes of the guest species, and three distinct structures, including cubic structure-I （sI）, hexagonal structure-H （sH）, are cubic structure-II （sII）, and known to form [2].