Browsing by Subject "Millimeter waves"

Now showing 1 - 4 of 4

Open Access
How to design and characterize metal-dielectric based metamaterials: experimental demonstrations of metamaterial applications at the millimeter-wave regime
(OSA, 2008-10) Alıcı, Kamil Boratay; Özbay, Ekmel
In the present work, after detailed explanation of the metamaterials design methods, we demonstrate two different double negative metamaterial media and their properties in terms of radiation and negative refaraction at the millimeter-wave regime. © 2008 Optical Society of America.
Open Access
Laser-micromachined millimeter-wave photonic band-gap cavity structures
(American Institute of Physics, 1995) Özbay, Ekmel; Tuttle, G.; McCalmont, J. S.; Sigalas, M.; Biswas, R.; Soukoulis, C. M.; Ho, K. M.
We have used laser-micromachined alumina substrates to build a three-dimensional photonic band-gap crystal. The rod-based structure has a three-dimensional full photonic band gap between 90 and 100 GHz. The high resistivity of alumina results in a typical attenuation rate of 15 dB per unit cell within the band gap. By removing material, we have built defects which can be used as millimeter-wave cavity structures. The resulting quality ~Q! factors of the millimeter-wave cavity structures were as high as 1000 with a peak transmission of 10 dB below the incident signal. © 1995 American Institute of Physics.
Open Access
Millimeter-wave scale metamaterials
(IEEE, 2009-11) Alıcı, Kamil Boratay; Özbay, Ekmel
We review two metamaterial configurations, which are operating at the millimeter-wave scale, in terms of design, fabrication, and characterization. We observed both numerically and experimentally at around 100 GHz a narrow frequency band for which the metamaterial was low loss and had a negative index of refraction. We investigated flat and wedge shaped samples to support our characterization results. We analyzed the transmission band with respect to number of layers at the propagation direction and commented on the bulk nature of these metamaterials. Oblique response of the planar sample was also included in this study. Finally, we demonstrate a device, which yields a rather small angular width at the far field radiation pattern, and composed of a horn antenna and flat metamaterial slabs at the propagation direction. ©2009 IEEE.
Open Access
Simulation of millimeter-wave gunn oscillations in gallium nitride
(2004) Sevik, C.; Bulutay, C.
High field transport in wide bandgap semiconductors like GaN is of great technological importance. The negative differential mobility regime at high fields, under suitable conditions, can lead to millimeterwave Gunn oscillations. Using extensive simulation based an ensemble Monte Carlo technique, the prospects of GaN Gunn diodes are theoretically investigated. The possibility of operating these Gunn diodes at their higher harmonic modes are explored. The main finding of this research is that the carrier dynamics in GaN can be tailored by an optimum choice of doping profile, temperature and bias conditions so that the efficiency of higher harmonic Gunn oscillations can be boosted. Finally, the physical origin of these Gunn oscillations is sought exploring whether it is the intervalley scattering mechanism, the Γ valley nonparabolicity, or the effective mass discrepancy between the Γ and the lowest satellite valleys as the responsible mechanism.