Department of Electrical Engineering

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IIT Jodhpur

This paper presents a noise-aided image enhancement algorithm focussed on addressing images that have a large dynamic range, i.e., images with both dark and bright regions. The application of a new mathematical model, in a shifted double-well system exhibiting stochastic resonance, is investigated for such images. The new mathematical model addresses the shortcomings of earlier SR-based enhancement model by deriving parameters purely from input values (instead of input statistics). This model is specific to spatial domain pixel representation and operates on a revised iterative equation. This iterative processing is here applied selectively to the under-illuminated regions of the image, characterized as the De Vries-Rose (DVR) region of a human psychovisual model. The idea of suitably modifying the existing universal image quality index is also proposed for its participation in iteration termination, and to gauge the property of dynamic range compression. While the iterative algorithm is terminated using the revised image quality index, entropy maximization, and contrast quality of DVR region with constraints on perceptual quality, the performance of the proposed algorithm is also characterized by observing color enhancement and subjective scores on visual quality. © 2014 IEEE.

World University root node

Image enhancement and dynamic range compression using novel intensity-specific stochastic resonance-based parametric image enhancement model

In this paper, the influence of gate-source and drain-source bias on the bias-stress stability and lifetime of pentacene-based low-voltage (-3 V) organic thin-film transistors (TFTs) built on plastic substrate has been investigated. The 10%-current-decay lifetime is used for analyzing the influence of applied bias on the bias-stress stability of TFTs, and to compare various biasing conditions. Our results show a 3 to 4 times higher 10%-current-decay lifetime when magnitude of gate-source and drain-source voltage are equal and less than 2.5 V during bias stress, compared to that when drain-source voltage is kept at -3.0 V. © 2014 IEEE.

2014 IEEE 2nd International Conference on Emerging Electronics: Materials to Devices, ICEE 2014 - Conference Proceedings

Influence of gate and drain bias on the bias-stress stability of flexible organic thin-film transistors

Organic thin-film transistors (TFTs) have potential as pixel drivers in flexible active-matrix organic light-emitting diode displays [1]. Hence it is essential to analyze the charge-carrier injection and extraction dynamics of organic TFTs to gain a better understanding of the trapping and detrapping at the TFT interfaces. From the current-voltage characteristics of the TFTs, many important parameters can be extracted, such as carrier mobility, threshold voltage, on/off ratio, subthreshold slope and transconductance. But to quantitatively evaluate the trapping and detrapping dynamics, displacement current measurements on two-terminal long-channel capacitors (LCCs) are far more useful [2, 3]. The cross-section and the layout of an LCC are schematically shown in Fig. 1. Unlike a TFT, an LCC has only one contact, so that carriers are injected into and extracted from the semiconductor through the same contact. To increase the signal-to-noise ratio, a very large channel length (up to 6 cm) is employed. While Liang et al. have performed displacement current measurements on pentacene-based LCCs [2,3], we report here on displacement current measurements on LCCs based on four different organic semiconductors: pentacene, dinaptho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT), 2,9-didecyl-DNTT (C 10-DNTT) and diphenyl-DNTT (DPh-DNTT). In TFTs, these semiconductors show hole mobilities ranging from 1 to 7 cm2/Vs. The goal of the displacement current measurements reported here is to study how the choice of the semiconductor affects the trapping and detrapping dynamics in organic TFTs. © 2014 IEEE.

Device Research Conference - Conference Digest, DRC

Charge-carrier injection, extraction and trapping dynamics in organic thin-film transistors based on different organic semiconductors evaluated by displacement current measurements

In this paper, a dual-frequency substrate integrated waveguide (SIW) cavity backed slot antenna has been presented. The unique slot structure includes a pair of slot stubs connected at the center of the radiating slot which helps to create an additional hybrid mode resonance at the higher frequency end. As a result, the antenna resonates at two different frequencies 8.96 GHz and 15.84 GHz with a bandwidth of 240 MHz (2.67 %) and 300 MHz (1.89 %) and gain of 4.47 dBi and 5.4 dBi respectively. The proposed design has been fabricated and measured results are also presented. The measured front-to-back ratio (FTBR) of the radiation pattern is 12 dB and 10 dB respectively and cross polarization level is 20 dB below at both frequencies in the broadside direction. © 2014 European Microwave Association.

European Microwave Week 2014: Connecting the Future, EuMW 2014 - Conference Proceedings; EuMC 2014: 44th European Microwave Conference

Substrate integrated waveguide cavity backed slot antenna for dual-frequency application

In this paper, design principles for implementation of broadband T-type and Y-type power divider based on Substrate-Integrated Waveguide (SIW) technology has been presented. Different design curves have been developed based on simulation results and are used to implement 1×2 power dividers of Y-type and T-type. Finally, by cascading T-type and Y-type stages a 1×4 Power divider of equal division is designed and simulated. The proposed design shows a broad bandwidth (-20 dB) of 18.3% and insertion-loss Bandwidth (1%) of 17.86%. © 2013 IEEE.

2013 IEEE Applied Electromagnetics Conference, AEMC 2013

Design of broadband power divider based on Substrate-Integrated Waveguide technology

In this paper, a dynamic stochastic resonance (DSR) technique is used for blind watermark extraction in discrete cosine transform (DCT) domain. The watermark embedding has been done on mid-band DCT coefficients. DSR has been used to improve the robustness of the extraction algorithm by utilizing the degradation introduced during attacks. DSR is an iterative process that tunes the coefficients of the possibly attacked watermarked image so that the effect of noise is suppressed and hidden information is enhanced. Resilience of this technique has been tested in the presence of various attacks. An adaptive optimization procedure has been adopted for the selection of bistable parameters to achieve maximum correlation coefficient under minimum computational complexity. Using the proposed technique, robust extraction of watermark is obtained without trading-off with visual quality of the watermarked image. When compared with the plain DCT-based technique, DSR-based technique has been found to give remarkable performance. © 2013 Published by Elsevier Ltd. All rights reserved.

Computers and Electrical Engineering

Dynamic stochastic resonance-based improved logo extraction in discrete cosine transform domain

We present a single-mode-multimode-multimode (SMm) fiber structure with a few interesting device applications. Unlike the single-mode-multimode-single-mode (SMS) structure, SMm has the unique feature of more than one mode in the output fiber. A detailed physical understanding of the transmission properties, and the differences from the SMS structure, is presented. The device can be used to excite selected modes in the output multimode fiber (MMF). This can be used to reduce the number of modes in high-speed MMF applications using an all-fiber structure instead of bulk optics. In yet another possible application, we show a way of designing sensitive refractive index sensors for measurement in different RI ranges. © 2014 Optical Society of America.

Applied Optics

Multimode interference devices with single-mode-multimode-multimode fiber structure

We achieve single, wavelength tunable LP0,n modes in a multimode fiber using an all-fiber structure. The device can be used to generate fiber based Bessel beams and to achieve a seed for fiber amplifiers. © OSA 2014.

International Conference on Fibre Optics and Photonics, 2014

Design of an all-fiber device for exciting a single LP0,n mode in a multimode fiber

Recently loosely coupled inductive power transfer (IPT) has gained worldwide attention for battery charging applications for electric vehicles (EVs). Since a high frequency operation is a must for transferring power inductively over a large air gap with reasonable efficiency, a careful design is needed. This paper reviews the basic design considerations for designing such a system. Critical design parameters, such as skin effect, proximity effect (at high frequency), and field-shaping techniques, to reduce leakage flux, has been demonstrated using Finite Element Analysis (FEA). In addition, different compensation technique and control strategies for IPT system has been discussed.. © 2014 IEEE.

2014 IEEE Transportation Electrification Conference and Expo: Components, Systems, and Power Electronics - From Technology to Business and Public Policy, ITEC 2014

Design considerations for loosely coupled inductive power transfer (IPT) system for electric vehicle battery charging - A comprehensive review

Loosely coupled inductive power transfer (IPT) systems have recently gained enormous attention for electric vehicle (EV) battery charging. For EV battery charging, a constant-current source is required. Numerous published papers suggest that the secondary of loosely coupled IPT systems, if series compensated, can act as constant-voltage source; and, if parallel compensated, it can act as constant-current source. In this paper, the authors prove that both series as well as parallel compensated secondary can act as constant-current source as well as a constant-voltage source, depending on the nature of power supply. Hence, either of the topological options can be utilized efficiently for EV charging. The authors intend to present the work for the case where primary is in the form of a long track, such as in a mono-rail or electric traction metro system. Hence, the primary is always considered to be series compensated. © 2014 IEEE.