Eye Antenna Research Articles

Terahertz Corrugated and Bull's-Eye Antennas

The radiation and temporal properties of one-dimensional and two-dimensional (Bull's-eye) corrugated antennas are investigated numerically and experimentally at terahertz. The thickness of the antenna is miniaturized, within the fabrication limits, by using the transverse slot resonance rather than the longitudinal resonance. Square and triangular corrugations are discussed. The comparison between these two profiles shows that, in terms of return loss and gain, the antenna is robust to the corrugation shape, which alleviates the fabrication complexity. The temporal analysis of the Bull's eye antenna is also shown to demonstrate the contributions coming from the leakage of the surface wave at each groove. This insight allows us to engineer the temporal shape of the output pulse by varying independently the depth of each groove. The antennas presented here hold promise for manipulating with very low profiles pulse- and beam-shapes of THz radiation.

Split Bull’s Eye Shaped Aluminum Antenna for Plasmon-Enhanced Nanometer Scale Germanium Photodetector

Bull's eye antennas are capable of efficiently collecting and concentrating optical signals into an ultrasmall area, offering an excellent solution to break the bottleneck between speed and photoresponse in subwavelength photodetectors. Here, we exploit the idea of split bull's eye antenna for a nanometer germanium photodetector operating at a standard communication wavelength of 1310 nm. The nontraditional plasmonic metal aluminum has been implemented in the resonant antenna structure fabricated by standard complementary metal-oxide-semiconductor (CMOS) processing. A significant enhancement in photoresponse could be achieved over the conventional bull's eye scheme due to an increased optical near-field in the active region. Moreover, with this novel antenna design the effective grating area could be significantly reduced without sacrificing device performance. This work paves the way for the future development of low-cost, high-density, and high-speed CMOS-compatible germanium-based optoelectronic devices.

A Novel Omni-Directional UWB Monopole Antenna

A novel omni-directional ultrawideband (UWB) monopole antenna is described. In the first part, the monopole antenna which is in the shape of an eye placed above a flat ground plane is designed and fabricated. This antenna operates from 3-20 GHz with low voltage standing wave ratio (VSWR) (<1.5). To keep the main radiating beam fixed over the frequency range of interest without degrading the VSWR, ground plane shaping will be introduced leading to an antenna that operates from 3-20 GHz with low VSWR ( <1.8). This eye antenna is fed by a coaxial probe through a SMA connector. The length of the proposed monopole element above the ground is slightly less than lambda/4 of the lowest frequency in the band. Simulation and test results for VSWR, gain and radiation pattern of both antennas are presented and discussed.

The hernandez and fernandez genes of Drosophila specify eye and antenna

The formation of different structures in Drosophila depends on the combined activities of selector genes and signaling pathways. For instance, the antenna requires the selector gene homothorax, which distinguishes between the leg and the antenna and can specify distal antenna if expressed ectopically. Similarly, the eye is formed by a group of “eye-specifying” genes, among them eyeless, which can direct eye development ectopically. We report here the characterization of the hernandez and fernandez genes, expressed in the antennal and eye primordia of the eye–antenna imaginal disc. The predicted proteins encoded by these two genes have 27% common amino acids and include a Pipsqueak domain. Reduced expression of either hernandez or fernandez mildly affects antenna and eye development, while the inactivation of both genes partially transforms distal antenna into leg. Ectopic expression of either of the two genes results in two different phenotypes: it can form distal antenna, activating genes like homothorax, spineless, and spalt, and it can promote eye development and activates eyeless. Reciprocally, eyeless can induce hernandez and fernandez expression, and homothorax and spineless can activate both hernandez and fernandez when ectopically expressed. The formation of eye by these genes seems to require Notch signaling, since the induction of ectopic eyes and the activation of eyeless by the hernandez gene are suppressed when the Notch function is compromised. Our results show that the hernandez and fernandez genes are required for antennal and eye development and are also able to specify eye or antenna ectopically.

Patterns of protein synthesis in the imaginal discs of Drosophila melanogaster: a comparison between different discs and stages.

High-resolution two dimensional gel electrophoresis has been used to study the patterns of protein synthesis in imaginal discs of Drosophila melanogaster. In this paper we first compare the patterns of protein synthesis in wing, haltere, leg 1, leg 2, leg 3 and eye antenna imaginal discs of late third instar larvae. We have detected only quantitative changes: differences in 17 proteins among the different imaginal discs. In addition, we have analysed the variations in pattern of proteins in the wing disc of the last larval stage and early pupae as well as in wing discs cultured in vivo for 6 days. Variations in these patterns affect more than 20% of the proteins and involve both qualitative and quantitative changes. Some of the changes may correspond to protein phosphorylation. Correlations of these changes between discs and through development are also discussed.

Morphology of the compound eyes as an indicator of life-style in carabid beetles

Twelve diurnal, 9 nocturnal, and 6 intermediate species of carabid beetles common in central Europe were investigated with respect to hunting behaviour and the morphology of the head and eyes. Diurnal visual hunters are characterized by typical visually guided predatory behaviour, which consists of a turn toward the prey, followed by a jerky approach and a lunge. Nocturnal species do not react to visual stimuli but use exclusively chemical or tactile cues for orientation. Visual hunters have broader heads than the other two groups (≈ 26% of the body length as opposed to ≈ 20%), shorter antennae (≈ 45% of the body length compared with ≈ 52% in the other two groups), ≈ 50% larger eye surfaces, and, correspondingly, 50% more ommatidia per eye. The binocular overlap of the frontal visual fields of both eyes is more than 50° in visual hunters; in nocturnal and intermediate species it is usually less than 40°. Nearly all species have acute zones with small interommatidial angles in the frontolateral parts of the eye, but in visual hunters these are much more distinct. As a readily measurable indicator of the hunting behaviour and life-style of a species we describe an eye–antenna angle that is more than 60° in typical visual hunters and, in most cases, much less than 55° in nocturnal species.

Retrotransposon-induced overexpression of a homeobox gene causes defects in eye morphogenesis in Drosophila.

Insertion of the tom transposable element into various Drosophila ananassae genes results in dominant phenotypes that affect eye morphology. One of these genes encoded by the Om(1D) locus was isolated by transposon tagging. The Om(1D) gene encodes a 2.7 kb transcript that is expressed in every stage of development. The deduced Om(1D) protein is 606 amino acids long and contains two glutamine/histidine, two alanine-rich and one histidine/proline repeats, as well as a homeodomain located near the carboxy terminus. Tom-induced alleles of Om(1D) show a 1.7-fold increased accumulation of Om(1D) RNA in whole individuals during late larval--early pupal stages of development, whereas expression of this transcript is 7-fold higher in the eye--antenna imaginal disc of mutant versus wild-type flies. D. melanogaster flies transformed with the Om(1D) coding region under the control of the hsp70 promoter display an eye phenotype similar to that of Om(1D) when expression of the homeobox protein encoded by the chimeric gene is induced by temperature elevation at the end of the third instar period. These results suggest that the eye-specific mutant phenotype caused by the insertion of the tom retrotransposon in the Om(1D) locus may be a consequence of the tissue-specific induction of the expression of this gene by sequences present in the transposable element.

Morphological Evolution of the Amphipod Gammarus minus in Caves: Quantitative Genetic Analysis

-Cave-dwelling populations of the amphipod Gammarus minus have reduced eyes and elongated antennae relative to surface spring-dwelling populations. The hypothesis that the reduction in eye size in cave populations results as a negatively pleiotropic conse- quence of selection for increased antenna size in the aphotic environment is examined. The genetic patterns of variation and covariation underlying eye size traits and antenna size traits were obtained from two spring and two cave populations and an intermediate pop- ulation located in two subterranean drainage basins. Heritability estimates indicated sub- stantial heritable variation in eye size and antenna size in all populations. The median of genetic correlations between eye and antenna traits is near zero for each of the two spring populations, is negative for the intermediate population, and is positive for the two cave populations. The relative difference between the spring and cave populations was consistent between drainage basins. It is argued that the observed patterns agree with the hypothesis of indirect selection with negative pleiotropy. It is also argued that these patterns are not in accord with the hypothesis that the reduction in eye size in cave populations results from accumulation of neutral mutations alone.