Electromagnetic (EM) waves have been widely applied in wireless communications, radar detection, navigation, and target recognition. Radiation and scattering are two common behaviors in the EM community, but it remains a long‐standing challenge to control them in a dynamical way, especially using a single, low‐cost, and compact hardware. Here, a promising solution is proposed by combining a programmable metasurface with a radiation array, which can manipulate the scattering properties, digitally and in real‐time, and exhibit different radiation modes simultaneously. More advantageous over previous investigations with the fixed radiation‐scattering performance, a field‐programmable gate array is introduced to extend, realize, and verify the multiple functions of the meta‐microstructure (MMS). As a proof‐of‐concept, multiple functions, including polarization conversion, scattering beam manipulation, diffusion scattering, radar cross‐section reduction, EM waves radiation, and vortex beam generation, have been adequately demonstrated by the MMS prototype.

We propose a chiral metasurface (CMS) that exhibits asymmetric transmission (AT) of double circularly and linearly polarized waves at the same frequency band. In order to realize the manipulation of electromagnetic (EM) waves in the whole space, the unit cell of CMS consists of three layers of dielectric substrate and four layers of metal patches. The Z-shaped chiral micro-structure and a grating-like micro-structure are proposed and designed to achieve AT. The simulated results show that the x-polarized wave that is incident along one direction can be transmitted into the right-hand circularly polarized (RHCP) wave and the left-hand circularly polarized (LHCP) wave that is incident along the opposite direction can be reflected as the LHCP wave in the frequency band of 4.69GHz-5.84 GHz. The maximum chirality response can be reflected by AT and circular dichroism (CD) and they can reach up to 0.38 and 0.75, respectively. In addition, we also produced the sample of CMS, and the experimental results are in good agreement with the simulated results.

Metasurface is a momentous periodic or aperiodic microstructure which has capabilities in controlling polarization of electromagnetic waves. To realize polarization controlling, many microstructures have been designed to achieve the function. However, multi-band linear to dual-circular polarization converter is rarely proposed and designed in the last few years. Here, a quad-band dual-circular transmissive metasurface (QCT-MS) is proposed to manipulate polarization of transmissive wave. QCT-MS is designed as a three-layer microstructure, with substrate in the middle and two metal patches in the shape of bi-symmetrical arrow on both sides. The proposed microstructure manipulates linear polarization waves to dual-circular polarization waves in different frequency bands with x-polarized or y-polarized incident waves. The experimental and simulated results reveal that left-hand circularly polarized waves can be realized in 3.14-3.32, 4.41-4.46, and 14.82-16.05 GHz while the right-hand circularly polarized waves can be achieved from 9.45 to 10.12 GHz for QCT-MS with x-polarized incidences. Moreover, the simulated results also demonstrate its characteristics of wide-angle transmission and periodic changes. The proposed transmissive metasurface can be utilized in multiband communication and multifunctional dual-circularly polarized antenna systems.

The Pancharatnam-Berry (PB) phase can be used to control the phase of circularly polarized electromagnetic waves. However, there are few studies on the modulation of dual-circularly polarized multi-beam using the transmissive coding metasurface. A scheme of spin-controlling multi-beam by transmissive coding metasurface is proposed for dual-circular polarization simultaneously. The transmissive coding metasurface (TCMS) can transmit linearly polarized incidence into multi-beam with orthogonally circular polarization. The phase distribution is designed based the convolution theorem, and the elements of metasurface conforming to the PB phase are arranged according to the phase distribution. In order to compensate the emitting spherical waves into plane waves and realize the transmissive waves with dual-circular polarization, an interesting scheme of elements in different regions with different rotating phase are presented based on the principle of phase compensation. TCMS can transmit linearly polarized waves into two left-hand circularly polarized (LHCP) beams and two right-hand circularly polarized (RHCP) beams. The prototype of TCMS is fabricated and measured, and the experimental results agree well with the simulated data. The transmissive metasurface has potential application in holograms and satellite communication.

Abstract:In this paper, an injecting method of physical damping to haptic interfaces is proposed. For injecting adjustable physical damping, time-domain passivity controller is implemented in hardware level with FPGA. Noise free velocity signal can be estimated with T-method. Instead of force command from the virtual environment, directly measured current signal with Hall sensor is used for calculating more accurate energy flow. The entire time-domain passivity control scheme is implemented with several different control routines inside FPGA, and through this hardware implementation, noisy behavior of the conventional software based time-domain passivity controller can be significantly removed.