921 research outputs found
Fading correlation of co-located transmitters
No full textFading or attenuation of a signal due to environment is a phenomenon often encountered in wireless communications. It is expected that co-located transmitters i.e. transmitters placed very close to each other show a high signal fading correlation due to the presence of similar fading environment. In this thesis, we present an experimental study of this phenomenon. Correlation of received signal strengths obtained from co-located transmitters in dynamically varying environments indicate that the large scale signal variations (shadow fading) are highly correlated while the small scale variations (multipath or fast fading) show a low correlation. Highly correlated large scale variations suggest a presence of same large shadowing elements in the transmit-receive path while a low correlation among the multipath variations is due to mutual coupling between the antennas at very close distances. This has two implications: it suggests that shadow fading variations can serve as an indicator of the co-location of closely spaced transmitters while the multipath variations cannot. However, low multipath signal correlations suggest that antenna diversity could be investigated for implementation in mobile handsets.M.S.Includes bibliographical referencesby Prashant Jadha
Quad-band circularly polarized super-wideband MIMO antenna for wireless applications
No full textIn this article, a Super-wideband (2.6–22 GHz) two-elements multiple-input-multiple-output antenna (MIMO) is presented with a dimension of 49 × 54.5 × 1.6 mm3 on an FR-4 substrate. The antenna is also exhibited dual circular polarization (RHCP and LHCP) simultaneously at two separate ports at four frequencies of 5.2, 11.5, 14.66, and 16.75 GHz, which are extensively utilized for WLAN, X, and Ku-band applications. Four EBG cells of various sizes have been installed across the feed line to maintain the antenna's efficiency and control the specific absorption rate (SAR). The antenna has a minimum isolation of 17 dB (20 dB for the important portion) in Super-wideband (SWB) and excellent diversity performance. Simulated results of antenna-like return loss, isolation, and diversity parameters have also been verified experimentally, which are in the acceptable range. Also, the calculated maximum SAR at 10 g is 1.095 W/kg with the head voxel model at 3.5 GHz
Seismic coefficients for pseudo-static analysis of wrap faced geosynthetic reinforced soil walls
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Bed Rock Profile Analysis and Interpretation of Archaeological Features Using GPR at Dholavira
No full textDholavira is one of the five largest Harappan cities located in Khadir Island, district Kachchh, in the state of Gujarat, India. An ancient Harappan city was found there with superbly planned, aesthetic architecture and advanced water management system. A major portion of the city area is unexcavated till today. Therefore, to explore the city more, to decide the excavation strategy of the unexplored areas, it was necessary to conduct non-destructive ground probing survey. Ground Penetrating Radar (GPR) is a non-destructive, geophysical technique, which provides three dimensional image of the subsurface features and depth of such features. Two sites were selected for GPR survey at Dholavira after conducting a through reconnaissance survey to the site. These sites are located at the east of East reservoir and south of Lower Town, respectively. GPR survey was conducted using 200 MHz antenna and GSSI SIR 3000 system. GPR data was processed in conventional software RADAN 7 prior to interpretation. An average velocity of electromagnetic wave in the survey area was estimated as 0.125 m/ns which is later used for time to depth conversion. Low frequency noise and abundance of multiple reflections masked bed rock reflection making the interpretation a challenging task. With appropriate filtering and analysis of data, bed rock profile has been produced of both the surveyed sites. Bed rock in both the sites was found almost flat except some shallow interruptions in the bed rock in Site-1. These interruptions might be produced by nature as no signature of man-made interruptions were noticed. Several linear features were observed in Site-1 and Site-2. Two distinct rubble deposits were observed in Site-1. Archaeological understanding of the observed features has been hypothesized to include existence of water reservoirs, channels, bunds etc in the surveyed areas. GPR survey provided possible features based on interpretation of GPR data but more detailed information about dimension of features was not included in this study due to lack of available techniques
Design methodology of ash dyke using geosynthetics considering hydraulic conditions
No full textAsh dyke is an earthen embankment which is constructed at every thermal power plant for disposal of fly ash slurry. Seepage of water takes place into the dyke from the fly ash slurry. In order to control the seepage inside the dyke, conventionally ash dyke is provided with chimney and blanket drains, which required sand as a drainage material. Today sand is not often available at various sites in sufficient quantity and required quality. Hence, for dyke construction sand is transported from other locations. Transportation cost of such a huge quantity of sand from long distance can substantially increase the cost of construction. The deficit in availability of sand in dyke construction motivates to find an alternative solution. The various geosynthetics material like geotextile, geonet, geomembrane, geocomposite and perforated pipes are available. These materials are being used in various geotechnical structures like retaining wall, filter for rock toe, drainage trench for highway, liners for landfill and many more applications. In all the above structures functions performed by geosynthetics are similar to the function of chimney and blanket drain in ash dyke. The objective is to design ash dyke system such that, it does not require substantial amount of sand in dyke construction. Instead, it will use geosynthetics materials for proper functioning. Two alternative designs of ash dyke system have been proposed, and both of these have application of geosynthetics material to control the seepage in dyke body. These alternative designs are ash dyke with vertical drainage composite and ash dyke with horizontal drainage composite. The design of Ash dyke with vertical drainage composite is similar to the ash dyke with chimney drain. It consists of vertical drainage composite, drainage trench, horizontal drainage system and horizontal drainage composite. In this design a vertical drainage composite is placed at centre of the dyke to collect seepage water, which is connected to the drainage trench. A horizontal drainage system consisting of lateral pipes having initial portion perforated is connected to drainage trench, which collects seepage water from drainage trench and drain out from the dyke body. A drainage composite is also provided in downstream side of the dyke to collect seepage from foundation soil. Ash dyke with horizontal drainage composite consists of horizontal layers of drainage composite and down slope drainage system. Drainage composite in the dyke is installed in layers at different levels and top drainage composite is extended vertically up to height of fill slurry to collect seepage water. Arrangement of horizontal composite is depends upon the quantity of seepage. These drainage composites are connected to the downslope drainage system to drain out the seepage water. In both the alternate design raising of ash dyke is done by upstream method of raising. The methods proposed in this study have been developed to design each component of both the alternative ash dyke system by using the theories developed in the literature for the design of geosynthetics in above mentioned other structures. Also detailed specifications and various factors to be considered in the design of each component of ash dyke have been proposed. A step by step construction procedure for both the alternative designs has been proposed and a design example problem is solved for future reference
Development of homogenized interlayer theory (HIT) geosynthetic reinforced flexible pavements
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