294 research outputs found
Experimental verification of the key properties of a three-dimensional isotropic transmission line based superlens
Design and experimental realization of a three-dimensional superlens based on
LC-loaded transmission lines are presented. Commercially available components
and materials are used in the design. Transmission properties of the designed
structure are studied experimentally and the observed lens properties are
compared with analytical predictions. Backward-wave propagation and
amplification of evanescent waves in the prototype structure are verified both
analytically and experimentally.Comment: 12 pages, 10 figure
Arbitrary beam control using passive lossless metasurfaces enabled by orthogonally-polarized custom surface waves
For passive, lossless impenetrable metasurfaces, a design technique for
arbitrary beam control of receiving, guiding, and launching is presented.
Arbitrary control is enabled by a custom surface wave in an orthogonal
polarization such that its addition to the incident (input) and the desired
scattered (output) fields is supported by a reactive surface impedance
everywhere on the reflecting surface. Such a custom surface wave (SW) takes the
form of an evanescent wave propagating along the surface with a spatially
varying envelope. A growing SW appears when an illuminating beam is received.
The SW amplitude stays constant when power is guided along the surface. The
amplitude diminishes as a propagating wave (PW) is launched from the surface as
a leaky wave. The resulting reactive tensor impedance profile may be realized
as an array of anisotropic metallic resonators printed on a grounded dielectric
substrate. Illustrative design examples of a Gaussian beam
translator-reflector, a probe-fed beam launcher, and a near-field focusing lens
are provided
One-way transparent sheets
In this paper we introduce the concept of metasurfaces which are fully
transparent when looking from one of the two sides of the sheet and have
controllable functionalities for waves hitting the opposite side (one-way
transparent sheets). We address the question on what functionalities are
allowed, considering limitations due to reciprocity and passivity. In
particular, we have found that it is possible to realize one-way transparent
sheets which have the properties of a twist-polarizer in reflection or
transmission when illuminated from the other side. Also one-way transparent
sheets with controllable co-polarized reflection and transmission from the
opposite side are feasible. We show that particular non-reciprocal
magneto-electric coupling inside the sheet is necessary to realize lossless
non-active transparent sheets. Furthermore, we derive the required
polarizabilities of constituent dipole particles such that the layers composed
of them form one-way transparent sheets. We conclude with design and
simulations of an example of a nonreciprocal one-way transparent sheet
functioning as an isolating twist-polarizer.Comment: 8 pages, 4 figure
Circularly Polarized Receiving Antenna Incorporating Two Helices to Achieve Low Backscattering
We propose to use an antenna composed of two orthogonal helices as a
low-scattering sensor. The vector effective length is derived for the antenna
using the small dipole approximation for the helices. The antenna can transmit
and receive circular polarization in all directions with the Huygens' pattern.
We observe that the antenna geometry does not backscatter, regardless of the
polarization, when the incidence direction is normal to the plane of the
helices. Scattered fields, scattered axial ratio, and the scattering cross
section are presented. We show that the zero-backscattering property holds also
for the antenna when it is capable to receive all the available power with
conjugate loading. The approximate analytical model is validated with full-wave
simulations.Comment: 14 pages, 7 figures. Submitted to IEEE Trans. Antennas Propa
Isotropic Chiral Objects With Zero Backscattering
In this paper we study electrically small chiral objects with isotropic
response and zero backscattering. A bi-isotropic sphere is used as a simple
example and its zero-backscattering conditions are studied. A theoretical model
of an object composed of three orthogonal chiral particles made of conducting
wire is presented as an analog of the zero-backscattering bi-isotropic sphere.
A potential application of the object as a receiving antenna or a sensor with
the ability to receive power from an arbitrary direction without backscattering
is discussed.Comment: 8 pages, 1 figure, submitted to IEEE Trans. Antennas Propa
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