No description available.

With the rapid adoption and development of new standards, Multiple-Input Multiple-Output (MIMO) technology is becoming a necessity in current wireless systems. One problem posed by using multiple antennas at a transmitter or receiver is the undesirable effect of signal correlation between closely-spaced radiating elements. This thesis presents the concept, design, and evaluation of a hemispherical lens antenna for use in MIMO systems. A high-permittivity dielectric material allows radiating elements to be placed in close proximity with reduced spatial correlation effects. An intermediate matching layer and a hemispherical lens design facilitate the preservation of the pattern characteristics in the transition between the dielectric and free-space. The antenna was simulated against benchmark antenna arrays in free-space and showed a 35%-70% improvement in channel capacity in multipath-rich environments, showing strength as a candidate for further development in MIMO applications.

Koreguoti kliniškai reikšmingą astigmatizmą būtina, nes visai nekoreguotas ar neteisingoje ašyje iškoreguotas astigmatizmas sukelia ne tik blogą matymą, bet ir astenopiją. Koreguoti kliniškai reikšmingą astigmatizmą būtina, nes visai nekoreguotas ar neteisingoje ašyje iškoreguotas astigmatizmas sukelia ne tik blogą matymą, bet astenopiją. Toriniai kontaktiniai lęšiai (TKL) suteikia galimybę labai tiksliai ištaisyti šią ydą, bet viena būtina sąlyga - jie turi būti stabilioje padėtyje. TKL stabilumas priklauso nuo vokų plyšio, ragenos formos, vokų prispaudimo jėgos, o taip pat nuo refrakcijos ydos dydžio ir astigmatizmo ašies. / N Scientific and Technical Progress century eyesight play an increasingly larger burden. To adjust clinically significant astigmatism is necessary, because completely uncorrected or wrong corrected axis of astigmatism cause not only poor vision, but asthenopia. Toric contact lenses (TKL) allows very precise remedy of this defect, but one necessary condition - they must be in a stable position. TKL stability depends on the eye crack opening, corneal shape, eyelid clamping force, as well as the refractive defect size and astigmatism axis.

No description available.

No description available.

No description available.

With the rapid adoption and development of new standards, Multiple-Input Multiple-Output (MIMO) technology is becoming a necessity in current wireless systems. One problem posed by using multiple antennas at a transmitter or receiver is the undesirable effect of signal correlation between closely-spaced radiating elements. This thesis presents the concept, design, and evaluation of a hemispherical lens antenna for use in MIMO systems. A high-permittivity dielectric material allows radiating elements to be placed in close proximity with reduced spatial correlation effects. An intermediate matching layer and a hemispherical lens design facilitate the preservation of the pattern characteristics in the transition between the dielectric and free-space. The antenna was simulated against benchmark antenna arrays in free-space and showed a 35%-70% improvement in channel capacity in multipath-rich environments, showing strength as a candidate for further development in MIMO applications.

Printed lens antennas offer the possibility of realizing shaped beam patterns using no more complexity than is required for pencil beam patterns. Shaped beam patterns can be obtained by appropriately determining the complex transmission coefficient required for each cell (or element) of the printed lens, taking into account the varying feed field over the input surface of the lens. Certain ranges of transmission coefficient amplitude and phase are undesirable (eg. too low an amplitude implies a large reflection at the lens input surface). It would be preferable to constrain the range of values that the transmission coefficient can take as an integral part of the lens synthesis procedure, and thus the transmission coefficient itself needs to be the synthesis variable. In this thesis a synthesis technique for doing this is developed based on the method of generalized projections, modified to “operate” in the space of transmission coefficients. This makes it possible to immediately perceive what influence constraints on the actual transmission coefficients have on the possible radiation pattern performance. In addition, an approach that allows one to constrain the transmission coefficient to values that must be selected from an available database of transmission coefficients is incorporated into the synthesis technique.

Pacific Rim International Conference on Advanced Materials and Processing <DA14524950> (5th : 2004 : Beijing, China)

Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2007. / Vita. Includes bibliographical references.