Department of Electrical Engineering

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IIT Jodhpur

In this paper, a methodology for stabilization of fractional discrete-time system based on discrete sliding mode approach is attempted for the first time. The proposed controller is robust in the presence of matched uncertainties. Stability during sliding is analyzed in terms of gamma function based radius using the property introduced by Hilfer [8]. Numerical example along with simulation is presented to illustrate the efficacy of the proposed method. © 2012 IEEE.

World University root node

IEEE International Symposium on Industrial Electronics

Discrete sliding mode control of fractional linear systems

In 0.2Ga 0.8N layers were directly grown on Si(111) substrate by plasma-assisted molecular beam epitaxy (PAMBE). Structural characteristics of the as-grown InGaN epilayers were evaluated high resolution X-ray diffraction and composition of InGaN was estimated from photoluminescence spectra using the standard Vegard's law. High-resolution X-ray photoemission spectroscopy measurements were used to determine the band offset of wurtzite-In 0.2Ga 0.8N/Si(111) heterojunctions. The valence band of InGaN is found to be 2.08 ± 0.04 eV below that of Si. The conduction band offset (CBO) of InGaN/Si heterojunction is found ~0.74 eV and a type-II heterojunction. © 2012 The Japan Society of Applied Physics.

Japanese Journal of Applied Physics

Band-structure lineup at In 0.2Ga 0.8N/Si heterostructures by x-ray photoelectron spectroscopy

GaN/Si 3N 4/n-Si and InN/Si 3N 4/n-Si heterojunctions (HJs) were fabricated using plasma-assisted molecular beam epitaxy for a comparison study. Single-crystalline wurtzite structures of GaN and InN epilayers were confirmed by high-resolution X-ray diffraction and thickness of ultrathin Si 3N 4 layer was measured by transmission electron microscopy. n-GaN/Si 3N 4/n-Si HJs show diode-like rectifying current-voltage (I-V) characteristic, while n-InN/Si 3N 4/n-Si HJs show symmetric nonlinear I-V behavior. The I-V characteristics of both HJs were discussed in terms of the band diagram of HJs and the carrier transport mechanism. The activation energies of carrier conduction were estimated to be ∼29 meV for GaN/Si 3N 4/Si and ∼95 meV for InN/Si 3N 4/Si HJs. Copyright © 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Physica Status Solidi (A) Applications and Materials Science

Carrier-transport studies of III-nitride/Si 3N 4/Si isotype heterojunctions

Wavelet-based robust digital watermarking scheme for fingerprint authentication

Phase Noise optimization for RF oscillator using Design of Experiments (DOE) is presented. The constraint of keeping frequency deviation minimum is taken in to account by ANOVA and nominal-the-best approach of Taguchi methods. Phase Noise of the oscillator is improved by -3.6 dB with frequency deviation of 0.04 %. Power consumption is also reduced by 3.2 mW. © 2011 IEEE.

Midwest Symposium on Circuits and Systems

Optimizing phase noise of 2 GHz RF oscillator with minimum frequency deviation

This work establishes the diversity-multiplexing tradeoff (DMT) of the four-phase decode-and-forward (DF) protocol in the half-duplex, non-separated two-way relay channel. We consider a fading channel model where the source relay links are Rayleigh distributed but the direct link between sources is left more general as Nakagami-m distributed and investigate for any possible gains in the achievable DMT using four-phase hybrid broadcast (HBC) protocol, as compared to three-phase time-division broadcast (TDBC) protocol. For the statistically symmetric case of Rayleigh fading and asymmetric fading with more stable direct link (m > 1), the optimal DMT of the HBC protocol is computed and is shown to be achieved by a three-phase orthogonal variant, TDBC protocol. The operational meaning of this result is that the multiple access channel (MAC) phase of HBC protocol is not necessary to achieve optimal performance, this results in a simplification of the communication protocol. For less stable direct link (1/2 ≤ m < 1), the analysis establishes that the MAC phase of HBC protocol is necessary to achieve optimal DMT. {\textcopyright} 2011 IEEE.

IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC

Diversity-multiplexing tradeoff for the non-separated two-way relay DF channel

This work identifies the first lattice decoding solution that achieves, in the most general outage-limited MIMO setting and the high rate and high SNR limit, both a vanishing gap to the error-performance of the exact solution of regularized lattice decoding, as well as a computational complexity that is subexponential in the number of codeword bits as well as the rate. The proposed solution employs lattice reduction (LR)-aided regularized (lattice) sphere decoding and proper timeout policies. In light of the fact that, prior to this work, a vanishing gap was generally attributed only to full lattice searches that have exponential complexity, in conjunction with the fact that subexponential complexity was generally attributed to early-terminated (linear) solutions which have though a performance gap that can be up to exponential in dimension and/or rate, the work constitutes the first proof that subexponential complexity need not come at the cost of exponential reductions in lattice decoding error performance. Finally, these performance and complexity guarantees hold for the most general MIMO setting, for all reasonable fading statistics, all channel dimensions and all lattice codes. {\textcopyright} 2011 IEEE.

2011 49th Annual Allerton Conference on Communication, Control and Computing, Allerton 2011

Vanishing the gap to exact lattice search at a subexponential complexity: LR-aided regularized decoding

This paper presents the optimization in deflection caused by the inbuilt stress generated in mechanical or movable membrane of Symmetric Toggle RF MEMS Switch (STS). The movable membrane of STS was initially fabricated with two different materials, i.e. Chrome and Gold. The simulated deflection at 70°C was 11.9 μm, and experimental deflection was 11-12 μm. We present a study of inbuilt deflection reduction in multimetal movable layers without change in actuation voltage of the switch. The design study was initially carried out on cantilevers and then on structural membrane of STS. STS with proposed multilayer of Cr-Au-Au-Ti-Au has a simulated deflection of 0.56 μm at 70°C. © 2011 SumDU.

Journal of Nano- and Electronic Physics

Design optimization of deflection caused after release of multilayer structural membrane of symmetric toggle switch

A set of test structures for in situ stress measurement is presented. The test structures were realized by means of surface micromachining, adopting photoresist as a sacrificial layer and electroplated gold as a structural layer. Initially array of buckling type test structures cantilevers, fixedfixed beams, Guckel rings and diamond were used to find out critical buckling beam. Later on rotational type pointer, double indicator and long-short beam strain sensor were analyzed to find out stress. Stress measurement techniques using micromachined structures are compared with the wafer curvature technique. Analytical calculations of the fabricated structures were performed for plated gold for which the value of residual stress has been found between 100 and 150 MPa. © 2011 IFSA.

Sensors and Transducers

Fabrication and analysis of MEMS test structures for residual stress measurement

This paper presents the comparison of electrical performance of symmetric toggle switch (STS) by incorporating hafnium oxide (HfO2) as a dielectric layer instead of silicon dioxide (SiO2). Change in dielectic layer leads to the change in ratio of down to up state capacitance, which determines the performance of capacitive type RF MEMS switches. Simulated results show that for the same switch dimensions, response of the SiO 2 based switch is in X-Band (8-12 GHz), whereas the switch having HfO2 as a dielectric layer shows the resonance in C-Band (4-8 GHz). The advantage can be utilized for optimizing the size of STS to shift the operating frequency range in X-Band. Simulated isolation and insertion loss are also better in case of the optimized STS with HfO2 dielectric layer; -43 dB and -0.014 dB for 11 GHz respectively as compared to SiO2 dielectric layer with isolation of -29 dB and insertion loss of -0.016 dB at 11 GHz. The measured isolation for a SiO2 device over the frequency range of 9-13 GHz is better than -20dB. For the similar device dimensions, STS with HfO2 dielectric layer shows isolation better than -20 dB from 4-11.5GHz.