27-02-2013, 04:57 PM
ELECTROMAGNETIC METAMATERIALS
[attachment=52115]
INTRODUCTION
Metamaterials are artificial materials engineered to have properties that may not be found in nature.
Metamaterial antennas are a class of antennas which use metamaterials to increase performance of miniaturized (electrically small)antenna systems. Their purpose, as with any electromagnetic antenna, is to launch energy into free space.
Antenna designs incorporating metamaterials can step-up the radiated power of an antenna. Novel components such as compact resonators and metamaterial loaded waveguides offer the possibility of previously unavailable applications.
With conventional antennas that are very small compared to the wavelength, most of the signal is reflected back to the source. The metamaterial, on the other hand, makes the antenna behave as if it were much larger than it really is, because the novel antenna structure stores energy, and re-radiates it.
DEFINITION:
Fig. 1 A normal slab of flat glass (gray) is shown on the left illuminated by a point source (red lines). The rays diverge and refract at the interface according to Snell's Law. On the right, a flat slab of NI material is shown with rays from a point source (blue lines) incident upon it. In this case the rays refract at the interface, again governed by Snell’s law, but this time with an index of n = -1. Also shown on the bottom right is the evanescent component (black line) of this point source, which is also focused by this unique lens
Experimental setup
“The sample and the microwave absorber were placed between top and bottom parallel, circular aluminum plates spaced 1.2 cm apart. The radius of the circular plates was 15 cm. The black arrows represent the microwave beam as would be refracted by a positive index sample. The detector was rotated around the circumference of the circle in 1.5◦ steps, and the transmitted power spectrum was measured as a function of angle, θ, from the interface normal. The detector was a waveguide to coaxial adapter attached to a standard X-band waveguide, whose opening was 2.3 cm in the plane of the circular plates.
[attachment=52115]
INTRODUCTION
Metamaterials are artificial materials engineered to have properties that may not be found in nature.
Metamaterial antennas are a class of antennas which use metamaterials to increase performance of miniaturized (electrically small)antenna systems. Their purpose, as with any electromagnetic antenna, is to launch energy into free space.
Antenna designs incorporating metamaterials can step-up the radiated power of an antenna. Novel components such as compact resonators and metamaterial loaded waveguides offer the possibility of previously unavailable applications.
With conventional antennas that are very small compared to the wavelength, most of the signal is reflected back to the source. The metamaterial, on the other hand, makes the antenna behave as if it were much larger than it really is, because the novel antenna structure stores energy, and re-radiates it.
DEFINITION:
Fig. 1 A normal slab of flat glass (gray) is shown on the left illuminated by a point source (red lines). The rays diverge and refract at the interface according to Snell's Law. On the right, a flat slab of NI material is shown with rays from a point source (blue lines) incident upon it. In this case the rays refract at the interface, again governed by Snell’s law, but this time with an index of n = -1. Also shown on the bottom right is the evanescent component (black line) of this point source, which is also focused by this unique lens
Experimental setup
“The sample and the microwave absorber were placed between top and bottom parallel, circular aluminum plates spaced 1.2 cm apart. The radius of the circular plates was 15 cm. The black arrows represent the microwave beam as would be refracted by a positive index sample. The detector was rotated around the circumference of the circle in 1.5◦ steps, and the transmitted power spectrum was measured as a function of angle, θ, from the interface normal. The detector was a waveguide to coaxial adapter attached to a standard X-band waveguide, whose opening was 2.3 cm in the plane of the circular plates.