Institute of Radio Physics and Electronics

Kolkata, India

Institute of Radio Physics and Electronics

Kolkata, India
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Basu R.,National Institute of Technology Delhi | Chakraborty V.,Institute of Radio Physics and Electronics | Mukhopadhyay B.,Institute of Radio Physics and Electronics | Basu P.K.,Institute of Radio Physics and Electronics
2015 6th International Conference on Computers and Devices for Communication, CODEC 2015 | Year: 2017

Heterojunction Photo Transistors (HPTs) provide optical gain but no excess noise. Recently good quality alloys of GeSn are regularly grown on Si substrate, opening up the possibility of having lasers, photodetectors etc. using standard VLSI technology. In this paper signal-to-noise ratio (SNR) for an HPT having GeSn as base has been estimated at telecommunication wavelength of 1.55 μm. The calculated gain-bandwidth product indicates high values and satisfactory SNR. © 2015 IEEE.

Sarkar C.,Institute of Radio Physics and Electronics | Guha D.,University of Calcutta | Kumar C.,Communication Systems Group
IEEE Antennas and Wireless Propagation Letters | Year: 2017

A newly conceived compound ground technique has been explored for dielectric resonator antenna (DRA) and arrays. The aim is to discard the traditional bonding by chemical glue which suffers from several limitations, especially in arrays. Proposed configuration uses a secondary ground plane with strategic perforations and clipping arrangement to achieve required mechanical stability along with accurate DRA positioning. It does not affect any radiation mode(s) or characteristics. The design has been tested for a single as well as a 4-element array in S-band indicating close corroboration with its traditional counterpart. Scalability study ensures its operation up to K-band. This technique should find potential applications, especially in large arrays and in any platform subjected to mechanical vibrations. IEEE

Acharya R.,Space Applications Center | Roy B.,Space Applications Center | Sivaraman M.R.,Space Applications Center | Dasgupta A.,Institute of Radio Physics and Electronics
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2011

The total electron content (TEC) of the equatorial ionosphere is controlled by photochemical processes as well as the transport of the ionospheric plasma near the magnetic equator. The transport phenomenon is initiated by the vertical drift driven by the eastward electric field, which also drives the Equatorial Electrojet. The empirical relation between the Equatorial Electrojet and the anomaly component of the equatorial TEC has already been established. Taking this relation as a reference, a simplified physical model of the anomaly component of equatorial TEC is obtained as a function of Equatorial Electrojet. Influence of other factors like the solar incidence angle and the solar flux are also considered here and the extent of their influence are also investigated. This has been done using TEC data obtained from dual frequency GPS receivers during the low solar activity period of 2005. The derived model is based on the physics of the underlying fountain effect and matches with the observed empirical relation to a fair extent. Obtained results are found to corroborate with previous findings and these physical model values are found to have improved correlation with the observed data than the reference empirical relation. This establishes the conformity between the EEJ based ionospheric model and the physical phenomenon of the fountain effect. © 2011 Elsevier Ltd.

Acharya R.,Space Applications Center | Roy B.,Space Applications Center | Sivaraman M.R.,Space Applications Center | Dasgupta A.,Institute of Radio Physics and Electronics
Advances in Space Research | Year: 2011

The Ionospheric Total Electron Content is responsible for the group delay of the signals from the Navigation satellites. This delay causes ranging error, which in turn degrades the accuracy of position estimated by the receivers. For critical applications, single frequency receivers resort to Satellite Based Augmentation Systems in order to have improved accuracy and integrity. The performance of these systems in terms of accuracy can be improved if predictions of the delays are available simultaneously with real measurements. This paper attempts to predict the Total Electron Content using adaptive recurrent Neural Network at three different locations of India. These locations are selected at the magnetic equator, at the equatorial anomaly crest and outside the anomaly range, respectively. In-situ Learning Algorithm has been used for tracking the non-stationary nature of the variation. Prediction is done for different prediction intervals. It is observed that, for each case, the mean and root mean square values of prediction errors remain small enough for all practical applications. Analysis of Variance is also done on the results. © 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.

Acharya R.,Space Applications Center | Roy B.,Space Applications Center | Sivaraman M.R.,Space Applications Center | Dasgupta A.,Institute of Radio Physics and Electronics
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2010

The variability of Total Electron Content (TEC) at Trivandrum, located within equatorial anomaly region at the dip equator, with respect to a reference level derived from the TEC measurements at Shimla, located outside the region has been studied during low solar activity period. Chapman function is assumed to hold good for regions outside the anomaly extent. It shows that the difference of total measured TEC at the equator from the derived reference is highly correlated with equatorial electrojet. The observations conform to the previous investigations and are interpreted in light of established relations. A stochastic relationship with electrojet is derived and validated. © 2010 Elsevier Ltd.

Mazumdar K.,Indian School of Mines | Singh V.P.,Indian School of Mines | Sharan A.,Indian School of Mines | Ghosal A.,Institute of Radio Physics and Electronics
Superlattices and Microstructures | Year: 2015

The fetching of a single-flux scattering theory of the InAs nanowire based MOSFET has been presented here. The backscattering coefficient has been studied for 1nm, 5nm and 10nm nanowire radius. The calculations are made for <100>, <110> and <111> nanowire orientations. It has been found that the value of the backscattering coefficient increased as the radius of the nanowire is increased from 1nm to 10nm but the spacing between <100>, <110> and <111> nanowire orientations decreased. The drain current IDsat-(VGS-VT) characteristics of InAs ballistic nanowire (5nm radius) has been discussed in detail. Also, the significant drain current IDsat versus electric field (V/m) characteristics of nonballistic InAs nanowire (5nmradius) MOSFET transistor for different orientations are obtained. © 2015 Elsevier Ltd.

Bhattacharya D.P.,Jadavpur University | Midday S.,Jadavpur University | Nag S.,Jadavpur University | Biswas A.,Institute of Radio Physics and Electronics
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2013

Theory of acoustic scattering rate of the carriers in a quantum wire has been developed under the condition of low temperature when the approximations of the traditional theory are hardly valid. The scattering rates thus obtained are then used to estimate the zero-field mobility characteristics in a narrow channel GaAs-GaAlAs quantum wire. On comparison with other available results it is revealed that the finite energy of the acoustic phonons and the complete phonon distribution without any truncation lead to significantly different transport characteristics at low temperatures. © 2012 Elsevier B.V.

Kumar C.,Communication Systems Group | Guha D.,Institute of Radio Physics and Electronics
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2012

Functioning of Defected Ground Structure (DGS) employed to suppressing cross-polarized (XP) radiations from a microstrip patch has been investigated. It is observed that the distributions of the substrate fields beneath the patch have strong relation with the XP radiation fields. And this can be manipulated favorably to reduce the XP fields. Both simulated and measured results will be provided. This would help a designer to choose universal configuration of DGS irrespective of patch geometry. © 2012 IEEE.

Rakshit P.,Institute of Radio Physics and Electronics | Das N.R.,Institute of Radio Physics and Electronics
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

In this paper, the frequency response of a VLSI compatible Si-CMOS p-i-n photodetector suitable for high-speed, lowvoltage operation is studied. The model is developed considering the effects of diffusion of carriers from the substrate region and the parasitic elements due to the presence of multiple diodes in lateral configuration. The current density is calculated considering square-area photodetector. Results indicate the possibility of optimum designs to maximize 3dB bandwidth. © 2012 SPIE.

Bhattacherjee S.,Institute of Radio Physics and Electronics | Biswas A.,Institute of Radio Physics and Electronics
Microelectronics Reliability | Year: 2011

In this paper, electrical behavior of symmetric double gate Ge channel MOSFETs with high-k dielectrics is reported on the basis of carrier concentration formalism. The model relies on the solution of Poisson-Boltzmann equations subject to suitable boundary conditions taking into account the effect of interface trap charge density (D it) and the Pao-Sah's current formulation considering field dependent hole mobility. It is continuous as it holds good for sub-threshold, weak and strong inversion regions of device operation. The proposed model has been employed to calculate the drain current of DG MOSFETs for different values of gate voltage and drain voltage along with various important device parameters such as transconductance, output conductance, and transconductance per unit drain current for a wide range of interface trap charge density, equivalent oxide thickness (EOT) and bias conditions. Moreover, most of the important device parameters are compared with their corresponding Si counter parts. Accuracy of the model has been verified by comparing analytical results with the numerical simulation data. A notable improvement of the drive current and transconductance for Ge devices is observed with reference to Si devices, particularly when D it is small. © 2011 Elsevier Ltd. All rights reserved.

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