197,964 research outputs found
A reconfigurable wideband and multiband antenna using dual-patch elements for compact wireless devices
No full textThis is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 IEEEA reconfigurable wideband and multiband C-Slot patch antenna with dual-patch elements is proposed and studied. It occupies a compact volume of 50 × 50 × 1.57 (3925 mm3), including the ground plane. The antenna can operate in two dual-band modes and a wideband mode from 5 to 7 GHz. Two parallel C-Slots on the patch elements are employed to perturb the surface current paths for excitation of the dual-band and the wideband modes. Two switches, implemented using PIN diodes, are placed on the connecting lines of a simple feed network to the patch elements. Dual-band modes are achieved by switching “ON” either one of the two patch elements, while the wideband mode with an impedance bandwidth of 33.52% is obtained by switching “ON” both patch elements. The frequencies in the dual-band modes can be independently controlled using positions and dimensions of the C-Slots without affecting the wideband mode. The advantage of the proposed antenna is that two dual-band operations and one wideband operation can be achieved using the same dimensions. This overcomes the need for increasing the surface area normally incurred when designing wideband patch antennas. Simulation results are validated experimentally through prototypes. The measured radiation patterns and peak gains show stable responses and are in good agreements. Coupling between the two patch elements plays a major role for achieving the wide bandwidth and the effects of mutual coupling between the patch elements are also studied
A C-squared Polygonal Surface Patch
No full textA polygonal patch is defined to fill an n-sided hole within a C2 parametric continuous rectangular patch complex
Gridded circular patch antennas
No full textThe performance of circular microstrip patch antennas is presented where the conducting patch and ground plane are constructed from a grid. Improved cross polarization, mode suppression, and band-width are possible, but are accompanied by lower gain and reduced front-to-back ratios. A computer simulation reveals the current structure. The density and shape of the grid pattern are important parameters. Such antennas are can be manufactured within glass laminates. (C) 1999 John Wiley & Sons, Inc
Reconfigurable wideband patch antenna for cognitive radio
No full textCognitive radio communication is envisaged to be a new paradigm of methodologies for enhancing the performance of radio communication systems through the efficient utilization of radio spectrum. A key enabler for realization of a cognitive communication system is the capability of re-configurability in the underlying hardware and the associated protocol suite. Reconfigurable double C-Slot microstrip patch antenna fed by 50 ohm microstrip line is proposed in this paper. The frequency tuning is performed by switching on and off two patches. The antenna can operate in dual-band or in very wide band mode in 5, 6 and 7
GHz bands. The wide-band mode can be obtained when both switches are in the ON state with impedance bandwidth of 33.52
% from 4.99 to 7 GHz. The total size of the ground plane is 50 x 50 mm2. The proposed antenna verified through both numerical
simulation and measurement of an experimental prototype. The antenna achieves a gain of 5 to 8 dBi and radiation efficiency
about 80%
Double U-slots patch antenna for tri-band wireless systems
No full textFile shown is the pre-print version of the published paper, with the title "Connected u-slots pathch antenna for WiMAX applications"ABSTRACT: A compact microstrip patch antenna with two U-slots shape is presented.
Detailed simulation and experimental investigation are conducted to understand the behavior
of the two U-slots. The proposed antenna generates three resonant frequencies at 2.7, 3.3, and
5.3 GHz. It can, therefore, be used in Worldwide Interoperability for Microwave Access compliant
communication equipment. The proposed antenna has two U-slot shaped and two
bridge elements to connect both shapes together to adapt the structure to the desired interest
operating frequency. A comprehensive parametric study has been applied to understand the
effect of each U-slot on the antenna’s performance. Moreover, the current distribution for the
three bands is investigated to give further understanding of the antenna behavior. The proposed
antenna is verified experimentally and the simulated and measured results are in good
agreement
Rapid Establishment of a Regular Distribution of Adult Tropical Drosophila Parasitoids in a Multi-Patch Environment by Patch Defence Behaviour.
No full textFemales of the larval parasitoid of Drosophila, Asobara citri, from sub-Saharan Africa, defend patches with hosts by fighting and chasing conspecific females upon encounter. Females of the closely related, palearctic species Asobara tabida do not defend patches and often search simultaneously in the same patch. The effect of patch defence by A. citri females on their distribution in a multi-patch environment was investigated, and their distributions were compared with those of A. tabida. For both species 20 females were released from two release-points in replicate experiments. Females of A. citri quickly reached a regular distribution across 16 patches, with a small variance/mean ratio per patch. Conversely, A. tabida females initially showed a clumped distribution, and after gradual dispersion, a more Poisson-like distribution across patches resulted (variance/mean ratio was closer to 1 and higher than for A. citri). The dispersion of A. tabida was most probably an effect of exploitation: these parasitoids increasingly made shorter visits to already exploited patches. We briefly discuss hypotheses on the adaptive significance of patch defence behaviour or its absence in the light of differences in the natural history of both parasitoid species, notably the spatial distribution of their hosts
Bandwidth enhancement for microstrip patch antenna using stacked patch and slot
No full textSmall size wideband microstrip patch antenna with slot in ground plane and stacked patch fed through microstrip line is presented. By inserting slot on ground plane and stacked patch supported by wall, the bandwidth can improve up to 25% without significant change in the frequency. The bandwidth before adding the slot and the stacked patch was 3.72%, whereas after adding the slot and the stacked patch the bandwidth increased up to 25% ranging from 2.45 to 3.3 GHz. The radiation pattern has acceptable response at both E-plane and H-plane. The ground plane size is 30 mm by 90 mm, the antenna designed is based on Roger RT/duroid 5880 with dielectric constant 2.
Dual-band pin-patch antenna for wi-fi applications
No full textThe pin-patch antenna provides a low-profile monopolar element suitable for wireless access point requirements. This design concept is extended here to provide dual-band operation. Experimental results are compared to predictions from a FDTD package confirming monopolar radiation in two bands at 2.4 GHz and 5.7 GHz. This band spacing can be adjusted from 1.8:1 to more than 4:1
Geometric continuous patch complexes
No full textA theory of geometric continuity of arbitrary order is presented. Conditions of geometric continuity at a vertex where a number of patches meet are investigated. Geometric continuous patch complexes are introduced as the appropriate setting for the representation of surfaces in CAGD. The theory is applied to the modelling of closed surfaces and the fitting of triangular patches into a geometric continuous patch complex
Travelling-wave similarity solutions for an unsteady shear-stress-driven dry patch in a flowing film
No full textWe investigate unsteady flow of a thin film of Newtonian fluid around a symmetric slender dry patch moving with constant velocity on an inclined planar substrate, the flow being driven by a prescribed constant shear stress at the free surface of the film (which would be of uniform thickness in the absence of the dry patch). We obtain a novel unsteady travelling-wave similarity solution which predicts that the dry patch has a parabolic shape and that the film thickness increases monotonically away from the dry patch
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