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Register a new userGreat Wall-like Water-based Switchable Frequency Selective Rasorber with Polarization Selectivity
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A water-based switchable frequency selective rasorber with polarization selectivity using the Great Wall structures is presented in this paper. The proposed structure comprises a container containing horizontal and vertical channels enabling dividable injection of water, and a cross-gap FSS. The novelty of the design lies in its switchability among four different operating states by injecting water or not into the water channels. When the container is empty, the structure acts as a polarization-intensive FSS with a -0.42 dB insertion loss passband at 3.75 GHz. When the horizontal channel is filled with water and there is no water in the vertical channel, this structure can be used as an FSR with single polarization selectivity. The FSR with -10 dB absorption band from 6.8 GHz to 18.8 GHz only allows certain polarized electromagnetic (EM) waves to pass at 3.1 GHz with an insertion loss of -0.78 dB, while another polarized EM wave cannot pass. When the container is full of water, the structure operates as an absorber with a reflection band below the absorption band, where neither of polarization EM waves can transmit. Besides, a reconfigurable water-based FSR automatic control system is built to achieve state switching and temperature constancy of the water within the container. Ultimately, a prototype of the presented design is fabricated, simulated and measured to verify the feasibility. This work has potential application in radome design to realize the out-of-band RCS reduction.
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In this paper, a novel water-based reconfigurable frequency selective rasorber (FSR) at microwave band is proposed, which has a thermally tunable absorption band above the transmission band. The water-based FSR consists of a bandpass type frequency selective surface (FSS) and a 3D printing container. The water substrate is filled into the sealed space constructed by the above two structures. The numerical simulation results show that the FSR can achieve absorption with high absorptivity from 8.3 to 15.2 GHz, and obtain a transmission band of 5.2 to 7.0 GHz. The minimum insertion loss of the transmission band reaches 0.72 dB at 6.14 GHz. In addition, the FSR has the reconfigurable characteristics of absorbing or reflecting electromagnetic waves by filling with water or not. The proposed water-based FSR shows its good transmission/absorption performance under different polarizations and oblique incident angles. Due to the Debye model of water, the absorption band can be adjusted by water temperature, while the passband remains stable. At last, prototype of the FSR based on water has been fabricated, and the experimental results are presented to demonstrate the validity of the proposed structure.
A polarization-independent reconfigurable frequency selective rasorber (FSR)/absorber with low insertion loss based on diodes is proposed in this paper. The presented structure consists of a lossy layer based on square loops and a bandpass frequency-selective surface. These two layers are separated by an air layer. Each layer has an embedded bias network that provides the bias voltage to the diodes through metallic via. This configuration can avoid undesirable effects associated with the additional biasing wire. When the diodes are in off-state, the structure is in FSR mode and exhibits a transmission window at 4.28GHz with only 0.69dB insertion loss (IL) within the absorption bands. While diodes are in on-state and the structure switches to absorber mode, it achieves perfect absorption with absorptivity of over 90% ranging from 2.8 to 5.2 GHz. An equivalent circuit model (ECM) is developed to analyse the physical mechanism of the structure. A prototype of the proposed architecture is fabricated and measured, where reasonable agreements between simulations and measurements are observed, verifying the effectiveness of this design.
Single molecular electrets exhibiting single molecule electric polarization switching have been long desired as a platform for extremely small non-volatile storage devices, although it is controversial because of the poor stability of single molecular electric dipoles. Here we study the single molecular device of GdC82, where the encapsulated Gd atom forms a charge center, and we have observed a gate controlled switching behavior between two sets of single electron transport stability diagrams. The switching is operated in a hysteresis loop with a coercive gate field of around 0.5Vnm. Theoretical calculations have assigned the two conductance diagrams to corresponding energy levels of two states that the Gd atom is trapped at two different sites of the C82 cage, which possess two different permanent electrical dipole orientations. The two dipole states are stabilized by the anisotropic energy and separated by a transition energy barrier of 70 meV. Such switching is then accessed to the electric field driven reorientation of individual dipole while overcoming the barriers by the coercive gate field, and demonstrates the creation of a single molecular electret.
In this paper, we combine the design of band-pass frequency selective surfaces (FSSs) with polarization converters to realize a broadband frequency-selective polarization converter (FSPC) with lowbackward scattering, which consists of the top polarization conversion layer backed by a multi-layer bandpass FSS. It is numerically demonstrated that the 1 dB transmission window can be obtained from 8.5 GHz to 11 GHz with a 25.6% fractional bandwidth (FBW), and the bandwidth of reflection below -10 dB is up to 92% from 5.6 GHz to 15.13 GHz. Moreover, the proposed device can achieve two polarization conversion bands (5.66-6.9 GHz and 12.8-15.2GHz) with the polarization conversion ratio over 90%. Besides, by arranging the proposed structure in a checkerboard-like distribution, the backward scattering energy can be reduced in a wide frequency band ranging from 4 to 16 GHz. Both simulation and experimental results are in good agreements, which demonstrates our design strategy. Compared with the conventional polarization conversion designs, the proposed design presents an extra frequency-selective performance and hence can be applied to various practical situations, for instance, working as radomes to transmit the in-band signals with high-efficiency while keeping low-backward scattering for the out-of-band waves.
Polarization, denoting the precession direction with respect to the background magnetization, is an intrinsic degree of freedom of spin wave. Using magnetic textures to control the spin wave polarization is fundamental and indispensable toward reprogrammable polarization-based magnonics. Here, we show that due to the intrinsic cubic anisotropy, a $90^circ$ antiferromagnetic domain wall naturally acts as a spin wave retarder (wave-plate). Moreover, for a $90^circ$ domain wall pair developed by introducing a second domain in a homogenous antiferromagnetic wire, the sign of retarding effect can be flipped by simply switching the direction of the intermediate domain. The intimate connection between rich states of magnetic domains and the spin wave polarization in cubic anisotropic systems, offers new possibilities in constructing purely magnetic logic devices.
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