Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMetasurface Retroreflector for Controlling Parasitic Surface Waves on Bodies of 5G Mobile Phones
91
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The smartphone, as a media device, should offer a large-size screen and fast data rates in a well-packed device. Emergent 5G technologies based on millimeter waves need efficiently radiating antennas integrated into devices whose bodies (especially glass screens) behave as waveguides in the antenna frequency bands. Using the concept of retroreflective surfaces, this work proposes a compact metasurface located below the smartphone glass screen which reduces surface-wave excitation and propagation, and significantly improves the radiation pattern and efficiency of millimeter-wave antennas integrated into mobile terminals.
rate research
Read More
We propose the design and measurement of an acoustic metasurface retroreflector that works at three discrete incident angles. An impedance model is developed such that for acoustic waves impinging at -60 degrees, the reflected wave is defined by the surface impedance of the metasurface, which is realized by a periodic grating. At 0 and 60 degrees, the retroreflection condition can be fulfilled by the diffraction of the surface. The thickness of the metasurface is about half of the operating wavelength and the retroreflector functions without parasitic diffraction associated with conventional gradient-index metasurfaces. Such highly efficient and compact retroreflectors open up possibilities in metamaterial-based acoustic sensing and communications.
We present Steadiface, a new real-time face-centric video stabilization method that simultaneously removes hand shake and keeps subjects head stable. We use a CNN to estimate the face landmarks and use them to optimize a stabilized head center. We then formulate an optimization problem to find a virtual camera pose that locates the face to the stabilized head center while retains smooth rotation and translation transitions across frames. We test the proposed method on fieldtest videos and show it stabilizes both the head motion and background. It is robust to large head pose, occlusion, facial appearance variations, and different kinds of camera motions. We show our method advances the state of art in selfie video stabilization by comparing against alternative methods. The whole process runs very efficiently on a modern mobile phone (8.1 ms/frame).
Modern wireless communication is one of the most important information technologies, but its system architecture has been unchanged for many years. Here, we propose a much simpler architecture for wireless communication systems based on metasurface. We firstly propose a time-domain digital coding metasurface to reach a simple but efficient method to manipulate spectral distributions of harmonics. Under dynamic modulations of phases on surface reflectivity, we could achieve accurate controls to different harmonics in a programmable way to reach many unusual functions like frequency cloaking and velocity illusion, owing to the temporal gradient introduced by digital signals encoded by 0 and 1 sequences. A theoretical model is presented and experimentally validated to reveal the nonlinear process. Based on the time-domain digital coding metasurface, we propose and realize a new wireless communication system in binary frequency-shift keying (BFSK) frame, which has much more simplified architecture than the traditional BFSK with excellent performance for real-time message transmission. The presented work, from new concept to new system, will find important applications in modern information technologies.
Although a rigorous theoretical ground on metasurfaces has been established in the recent years on the basis of the equivalence principle, the majority of metasurfaces for converting a propagating wave into a surface wave are developed in accordance with the so-called generalized Snells law being a simple heuristic rule for performing wave transformations. Recently, for the first time, Tcvetkova et al. [Phys. Rev. B 97, 115447 (2018)] have rigorously studied this problem by means of a reflecting anisotropic metasurface, which is, unfortunately, difficult to realize, and no experimental results are available. In this paper, we propose an alternative practical design of a metasurface-based converter by separating the incident plane wave and the surface wave in different half-spaces. It allows one to preserve the polarization of the incident wave and substitute the anisotropic metasurface by an omega-bianisotropic one. The problem is approached from two sides: By directly solving the corresponding boundary problem and by considering the ``time-reversed scenario when a surface wave is converted into a nonuniform plane wave. We develop a practical three-layer metasurface based on a conventional printed circuit board technology to mimic the omega-bianisotropic response. The metasurface incorporates metallic walls to avoid coupling between adjacent unit cells and accelerate the design procedure. The design is validated with full-wave three-dimensional numerical simulations and demonstrates high conversion efficiency.
Mobile Augmented Reality (MAR) mixes physical environments with user-interactive virtual annotations. Immersive MAR experiences are supported by computation-intensive tasks which rely on offloading mechanisms to ease device workloads. However, this introduces additional network traffic which in turn influences the motion-to-photon latency (a determinant of user-perceived quality of experience). Therefore, a proper transport protocol is crucial to minimise transmission latency and ensure sufficient throughput to support MAR performance. Relatedly, 5G, a potential MAR supporting technology, is widely believed to be smarter, faster, and more efficient than its predecessors. However, the suitability and performance of existing transport protocols in MAR in the 5G context has not been explored. Therefore, we present an evaluation of popular transport protocols, including UDP, TCP, MPEG-TS, RTP, and QUIC, with a MAR system on a real-world 5G testbed. We also compare with their 5G performance with LTE and WiFi. Our evaluation results indicate that TCP has the lowest round-trip-time on 5G, with a median of $15.09pm0.26$ ms, while QUIC appears to perform better on LTE. Through an additional test with varying signal quality (specifically, degrading secondary synchronisation signal reference signal received quality), we discover that protocol performance appears to be significantly impacted by signal quality.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
