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Arunachalam S.,Applied Technology Internet | Ramamoorthi P.,Center for Electromagnetics | Gunasekaran S.,CSIR - Central Electrochemical Research Institute
Proceedings of the Indian National Science Academy | Year: 2014

A few commercial publishers dominate provision of access to scientific and technical information sought after by researchers around the world. Increasing subscription prices of journals at rates higher than general inflation caused librarians to think of forming consortia, but publishers started selling online journals as bundles, and libraries ended up with many journals their researchers have very little use for. Scientists and librarians adopted open access, but publishers came up with hybrid journals and article processing charges to beat any adverse effect on their profits caused by the fast-spreading open access movement. We compare the steps taken by scientists and librarians in the West to reclaim ease of access to research findings with what is happening in India. We end with a few suggestions.


Wahid A.,Center for Electromagnetics | Sreenivasan M.,Center for Electromagnetics | Rao P.H.,Center for Electromagnetics
IEEE Antennas and Wireless Propagation Letters | Year: 2015

A novel technique for obtaining low sidelobes pattern in a planar microstrip array antenna is proposed. This technique involves the addition of two external complementary split ring resonators (CSRRs) at both the ends of each row of the antenna in the ground plane. These two CSRRs together produce an interferometer pattern for the reduction of sidelobes. An 8 × 4 planar array at 9.9 GHz is designed and fabricated to demonstrate the concept and a sidelobe reduction of 4.3 dB achieved. © 2015 IEEE.


Vishwanathan G.,Center for Electromagnetics | Narayanan S.,Center for Electromagnetics | Mrudula G.,Center for Electromagnetics
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

Thunderstorm, resulting from vigorous convective activity, is one of the most spectacular weather phenomena in the atmosphere which is associated with thunder, squall lines and lightening. On 13 April 2010, a severe storm struck parts of Bangladesh and eastern India which lasted about 90 minutes, with the most intense portion spanning 30-40 minutes. The severe Thunderstorm on 13th April 2010 spawned a large tornado, which lasted about 20 minutes and was the first tornado recorded in Bihar history. In the year 2015, Bihar experienced a similar storm on 21 April during which multiple microbursts were observed. Various meteorological parameters have been analyzed to study the factors affecting the development of the thunderstorm. Satellite images from KALPANA and Meteosat has been analyzed to capture the temporal and spatial evolution of these storms. The satellite images show the development of a convective clouds system in the early afternoon hours which developed further into the severe storms by late evening. The analysis carried out further using K-index, lifted index, CAPE etc also shows the development of multiple cells of convection. Further analysis of these storms is presented in the paper. © 2016 SPIE.


Rao P.H.,Center for Electromagnetics
2010 International Conference on Wireless Communication and Sensor Computing, ICWCSC 2010 | Year: 2010

Cognitive radio is a new concept that utilizes the spectrum efficiently by shifting the frequency bands with time and availability. This puts a challenge on the antenna design to meet the demands of cognitive radio. This paper reviews the possible antenna configurations like wideband antennas, polarization and frequency reconfigurable antennas. Whilst there are many possible ways in which such systems could be configured, few possible antenna configurations are discussed and some design approaches are outlined. ©2010 IEEE.


Thomas K.G.,Center for Electromagnetics | Sreenivasan M.,Center for Electromagnetics
IEEE Transactions on Antennas and Propagation | Year: 2010

A compact planar ultrawideband (UWB) antenna with band notched characteristics is presented. Modification in the shape of radiation element and ground plane with two symmetrical bevel slots on the lower edge of the radiation element and on the upper edge of the ground plane makes the antenna different from the rectangular printed monopole. These slots improve the input impedance bandwidth and the high frequency radiation characteristics. With this design, the reflection coefficient is lower than 10 dB in the 3.1-10.6 GHz frequency range and radiation pattern is similar to dipole antenna. With the inclusion of an additional small radiation patch, a frequency-notched antenna is also designed and good out of band performance from 5.0-6.0 GHz can be achieved. Measured results confirm that the antenna is suitable for UWB applications due to its compact size and high performance. Also an approximate empirical expression to calculate the lowest resonant frequency is proposed. © 2009 IEEE.


George Thomas K.,Center for Electromagnetics | Praveen G.,Center for Electromagnetics
IEEE Transactions on Antennas and Propagation | Year: 2012

A circularly polarized printed antenna, capable of operating over an octave bandwidth is designed and fabricated. The design is evolved from classical printed monopole/dipole geometry. It employs a microstrip-line fed rectangular radiator, printed on the top of a substrate. The ground, extended as another rectangular radiator is printed on the bottom of the substrate. Both the top and bottom radiators are asymmetrically configured in such a way that the surface currents on them are orthogonal so as to produce left-hand circular polarization (LHCP). The antenna configuration is simulated using a commercially available EM solver. The simulated and measured results closely match within the operating bandwidth. The measured results show a-10-dB return loss bandwidth of 800 MHz to 4.15 GHz and a 3-dB axial ratio bandwidth of 1.5 GHz to 3.4 GHz. For the designed center frequency of 2.45 GHz, these correspond to 136% and 77% respectively. A parametric study of the design is carried out and the mechanism of circular polarization is described. © 2012 IEEE.


Thomas K.G.,Center for Electromagnetics | Sreenivasan M.,Center for Electromagnetics
IET Microwaves, Antennas and Propagation | Year: 2011

A compact printed planar antenna fed asymmetrically by a 50 Ω microstrip line is presented. This novel structural configuration is derived from conventional printed rectangular monopole, by introducing feed-line asymmetry to offer octave bend-fire radiation patterns. A rectangular ground plane of considerably small length modified in shape with two symmetrical bevel slots on the upper edge, illustrate significant improvement in the input impedance matching of the antenna over the operating bandwidth. The influence of the length of the radiation patch thickness of the dielectric substrate on the gain of the antenna is explored numerically. By linearly tapering the radiation patch, significant improvement in gain is observed. Both numerical experimental reflection coefficient results confirm that the proposed antenna presents an impedance bandwidth of 94% for reflection coefficients less than -10 dB. The measured results present an optimum gain of 11.8 dBi stable unidirectional radiation patterns. This novel antenna has wide impedance bandwidth, compact size reasonably high gain, suitable for various broadbapplications including point-to-point communication. The antenna is simple in structure with very few design parameters. © 2011 The Institution of Engineering and Technology.


Thomas K.G.,Center for Electromagnetics | Sreenivasan M.,Center for Electromagnetics
Electronics Letters | Year: 2010

A novel coplanar waveguide (CPW) antenna is proposed for dual-band WLAN applications. It comprises a rectangular patch, a rectangular notch cut at the lower edge of the patch and a CPW transmission line. The rectangular patch together with the ground plane of the coplanar waveguide radiates at the lower frequency band, 2.4GHz for IEEE802.11b/g, while the rectangular notch resonates in the upper band, 5.2/5.8GHz for IEEE 802.11a. The designed antenna is only 32×5mm, which can provide stable omnidirectional radiation patterns with an average gain of 2dBi in both the bands. The antenna is very compact and suitable for 2.4 and 5.2/5.8GHz WLAN operations. © 2010 The Institution of Engineering and Technology.


Rao P.H.,Center for Electromagnetics | Swaminathan M.,Georgia Institute of Technology
IEEE Transactions on Electromagnetic Compatibility | Year: 2011

A compact reduced unit cell size electromagnetic bandgap (EBG) power plane, realized with a combination of alternating impedance EBG and multiple narrow slits, is presented. By concatenating 2 2 high-frequency unit cells, a virtual low-frequency EBG unit cell is synthesized without changing the overall dimensions. In this configuration, the basic slit in the high-frequency unit cell remained same, and an additional slit with longer dimensions is added in parallel to the basic slit by synthesizing a larger low-frequency unit cell. EBG is characterized for its dispersion diagram, noise suppression, signal integrity, and electromagnetic radiation. Fabricated EBG exhibits a bandgap from 0.9 to 3.5GHz with isolation better than 40 dB over the band. Radiated emission of the new EBG is small with an average value of 35 dBuV/m. Compact EBG also exhibits low impedance, which is less than 1 over the stopband. Eye patterns are generated to analyze signal integrity issues when the data lines are referenced over the solid ground plane and EBG plane. The degradation of the maximum eye opening and the maximum eye width for the proposed EBG power plane at 2 Gb/s data rate is about 17.8 and 1, respectively, with reference to the equivalent board with solid power plane. © 2006 IEEE.


Sundaravel M.E.,Hindustan University | Rao P.H.,Center for Electromagnetics
2015 IEEE Applied Electromagnetics Conference, AEMC 2015 | Year: 2015

A compact printed trapezoidal fractal shaped wide slot antenna with a microstrip line feed is presented. The proposed fractal wide slot, creates a miniaturized configuration for the specified frequency of operation. The electrical length of the antenna is increased due to the fractal configuration, without increasing the foot print of the antenna. The impedance matching is achieved by adjusting the position and length of the microstrip line feed under the slot. The proposed 3rd order printed trapezoidal fractal shaped wide slot antenna is operating at 1.9GHz and the reference printed square wide slot antenna operates at 3GHz for the same dimensions thus a size reduction of 61 % is achieved. Design and simulation results are presented and the antenna exhibits well defined radiation performance throughout the bandwidth of operation. © 2015 IEEE.

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