2,485 research outputs found
On-Site Wireless Power Generation
Conventional wireless power transfer systems consist of a microwave power
generator and a microwave power receiver separated by some distance. To realize
efficient power transfer, the system is typically brought to resonance, and the
coupled-antenna mode is optimized to reduce radiation into the surrounding
space. In this scheme, any modification of the receiver position or of its
electromagnetic properties results in the necessity of dynamically tuning the
whole system to restore the resonant matching condition. It implies poor
robustness to the receiver location and load impedance, as well as additional
energy consumption in the control network. In this study, we introduce a new
paradigm for wireless power delivery based on which the whole system, including
transmitter and receiver and the space in between, forms a unified microwave
power generator. In our proposed scenario the load itself becomes part of the
generator. Microwave oscillations are created directly at the receiver
location, eliminating the need for dynamical tuning of the system within the
range of the self-oscillation regime. The proposed concept has relevant
connections with the recent interest in parity-time symmetric systems, in which
balanced loss and gain distributions enable unusual electromagnetic responses.Comment: 10 pages, 13 figure
Smart Table Based on Metasurface for Wireless Power Transfer
Metasurfaces have been investigated and its numerous exotic functionalities
and the potentials to arbitrarily control of the electromagnetic fields have
been extensively explored. However, only limited types of metasurface have
finally entered into real products. Here, we introduce a concept of a
metasurface-based smart table for wirelessly charging portable devices and
report its first prototype. The proposed metasurface can efficiently transform
evanescent fields into propagating waves which significantly improves the near
field coupling to charge a receiving device arbitrarily placed on its surface
wirelessly through magnetic resonance coupling. In this way, power transfer
efficiency of 80 is experimentally obtained when the receiver is placed at
any distances from the transmitter. The proposed concept enables a variety of
important applications in the fields of consumer electronics, electric
automobiles, implanted medical devices, etc. The further developed
metasurface-based smart table may serve as an ultimate 2-dimensional platform
and support charging multiple receivers.Comment: 8 pages, 7 figure
Magnetic superlens-enhanced inductive coupling for wireless power transfer
We investigate numerically the use of a negative-permeability "perfect lens"
for enhancing wireless power transfer between two current carrying coils. The
negative permeability slab serves to focus the flux generated in the source
coil to the receiver coil, thereby increasing the mutual inductive coupling
between the coils. The numerical model is compared with an analytical theory
that treats the coils as point dipoles separated by an infinite planar layer of
magnetic material [Urzhumov et al., Phys. Rev. B, 19, 8312 (2011)]. In the
limit of vanishingly small radius of the coils, and large width of the
metamaterial slab, the numerical simulations are in excellent agreement with
the analytical model. Both the idealized analytical and realistic numerical
models predict similar trends with respect to metamaterial loss and anisotropy.
Applying the numerical models, we further analyze the impact of finite coil
size and finite width of the slab. We find that, even for these less idealized
geometries, the presence of the magnetic slab greatly enhances the coupling
between the two coils, including cases where significant loss is present in the
slab. We therefore conclude that the integration of a metamaterial slab into a
wireless power transfer system holds promise for increasing the overall system
performance
Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications
Orbital angular momentum (OAM) has aroused a widespread interest in many
fields, especially in telecommunications due to its potential for unleashing
new capacity in the severely congested spectrum of commercial communication
systems. Beams carrying OAM have a helical phase front and a field strength
with a singularity along the axial center, which can be used for information
transmission, imaging and particle manipulation. The number of orthogonal OAM
modes in a single beam is theoretically infinite and each mode is an element of
a complete orthogonal basis that can be employed for multiplexing different
signals, thus greatly improving the spectrum efficiency. In this paper, we
comprehensively summarize and compare the methods for generation and detection
of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications
and technical challenges of OAM in communications, including free-space optical
communications, optical fiber communications, radio communications and acoustic
communications. To complete our survey, we also discuss the state of art of
particle manipulation and target imaging with OAM beams
- …