Department of Electrical Engineering

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IIT Jodhpur

A nonlinear analysis of a DC-DC buck converter is presented in context of its harmonics in a power delivery network (PDN). The closed-form relationships of the harmonic distortions associated with the DC-DC buck converter are derived by Volterra series to estimate the effects in a practical environment using S-parameters. For the validation of the proposed method, the buck converter is designed in a 180 nm LDMOS technology and three test cases are considered by using three different practical PDNs. A close matching is seen between the results obtained by proposed and conventional methods with a significant speedup reported. © 2018 IEEE.

World University root node

IEEE Electrical Design of Advanced Packaging and Systems Symposium, EDAPS 2018

A Quick Assessment of Nonlinearity in Power Delivery Networks

Power supply induced jitter (PSIJ) is becoming increasingly critical in modern high-speed and lower-power designs. In this paper, a semi-analytical method is presented to estimate the PSIJ in the presence of both the transmission media as well as the ground bounce. For this purpose, recently developed EMPSIJ method is extended to include the effects of both the ground bounce and the transmission line discontinuities. Results are presented by considering a voltage mode driver circuit and are compared against the conventional simulations (commercial tools) in a 55nm technology of STMicroelectronics. The new method while providing comparable accuracy yields significant speed-up. © 2018 IEEE.

2018 IEEE 22nd Workshop on Signal and Power Integrity, SPI 2018 - Proceedings

Analysis of PSIJ in the presence of both ground-bounce and transmission media

A low-power, high-speed on-chip compression and reconstruction technique is proposed in this paper. It takes the advantage of correlation between the consecutive pixels and reduces the total number of pixels to be read. The discarded pixels are interpolated on-chip using the proposed interpolation circuit. This reduces the total number of A/D conversions and hence results in power saving. The algorithm is verified for standard Lena image and about 5 dB better PSNR is observed for 20%- 90% compression, as compared to the existing techniques. Moreover, a promising performance is achieved on thermal image applications. The circuit is designed and simulated in AMS 350 nm OPTO process. For 57% compression, about 45% power saving in readout of the image sensor is observed. © 2018 IEEE.

Proceedings of IEEE Sensors

An On-Chip Interpolation Based Readout Scheme for Low-Power, High-Speed CMOS Image Sensors

A 12-bit, 1 MS/s, two-stage cyclic ADC, with novel 2.5-bit/cycle architecture is proposed in this paper. A 1.5-bit algorithm is used in a 2.5-bit framework, which reduces the required number of accurate comparators and power consumption by 42%. Further, the ADC shows 46% improvement in the conversion rate as compared to the state-of-the-art two-stage cyclic ADC. The proposed ADC is designed and fabricated in a standard 180 nm CMOS technology. The obtained values of DNL and INL are +0.5/-0.5 LSB and +0.8/-0.9 LSB respectively. The ADC consumes 0.8 mW of power and occupies an area of 0.045 mm2 with a FoM of 0.19 pJ/conversion-step. The proposed ADC when designed in a column pitch of 5.6 μm, will result in a frame-rate of 1000 frames/sec for a 1 Mpixel array. © 2018 IEEE.

Proceedings - IEEE International Symposium on Circuits and Systems

A 12-bit, 2.5-bit/cycle, 1 MS/s two-stage cyclic ADC, for high-speed CMOS Image sensors

This paper proposes a discrete-time robust control technique for an uncertain nonlinear system. The uncertainty mainly affects the system dynamics due to mismatched parameter variation which is bounded by a predefined known function. In order to compensate the effect of uncertainty, a robust control input is derived by formulating an equivalent optimal control problem for a virtual nominal system with a modified costfunctional. To derive the stabilizing control law for a mismatched system, this paper introduces another control input named as virtual input. This virtual input is not applied directly to stabilize the uncertain system, rather it is used to define a sufficient condition. To solve the nonlinear optimal control problem, a discretetime general Hamilton-Jacobi-Bellman (DT-GHJB) equation is considered and it is approximated numerically through a neural network (NN) implementation. The approximated solution of DTGHJB is used to compute the suboptimal control input for the virtual system. The suboptimal inputs for the virtual system ensure the asymptotic stability of the closed-loop uncertain system. A numerical example is illustrated with simulation results to prove the efficacy of the proposed control algorithm. © 2014 Chinese Association of Automation.

IEEE/CAA Journal of Automatica Sinica

Suboptimal robust stabilization of discrete-time mismatched nonlinear system

Recently proposed IEEE 802.15.4-2015 MAC introduced a new prioritized contention access (PCA) for transfer of time-critical packets with lower channel access latency compared to carrier sense multiple access - collision avoidance (CSMA/CA). In this paper, we first propose a novel Markov-chain-based analytical model for unslotted CSMA/CA and PCA for industrial applications. The unslotted model is further extended to derive the analytical model for slotted CSMA/CA and PCA. Primary emphasis is laid on understanding the performance of PCA compared to CSMA/CA for different traffic classes in industrial applications. The performance analysis shows that the slotted PCA achieves a reduction of 63.3% and 97% in delay and power consumption respectively compared to slotted CSMA/CA, whereas unslotted PCA achieves a delay reduction of 53.3% and reduction of power consumption by 96% compared to unslotted CSMA/CA without any significant loss of reliability. The proposed analytical models for both slotted and unslotted IEEE 802.15.4-2015 MAC offer satisfactory performance with less than 5% error when validated using Monte Carlo simulations. Also, the performance is verified using real-time testbed. © 2005-2012 IEEE.

IEEE Transactions on Industrial Informatics

Performance Analysis of CSMA/CA and PCA for Time Critical Industrial IoT Applications

Multi-hop wireless networks play a crucial role in extending the coverage of monitoring and automation applications in the Internet of Things arena. In this paper, we propose an analytical model for analyzing the performance of IEEE 802.15.4 based multi-hop networks. We accurately model the IEEE 802.15.4 MAC for three different kinds of nodes (leaf, relay and pre-gateway nodes) using 3D Markov chains. Performance of the proposed model is analyzed using reliability, channel congestion and duty cycle as the key performance metrics. The proposed model analyzes the network behavior accurately by achieving less than 5% error when compared with simulation outcomes. © 2017, Springer Science+Business Media, LLC, part of Springer Nature.

Wireless Personal Communications

Modeling and Analysis of IEEE 802.15.4 Multi-hop Networks for IoT Applications

The gas-sensing properties and topology of tungsten oxide thin films deposited by reactive-ion radiofrequency magnetron sputtering were investigated at room temperature. The abnormalities in sensing film behaviour were observed when acetone gas is flowed over surface. The reduction reaction of surface and oxidation reaction of acetone gas were studied. As the gas comes in contact with the surface, the molecules tend to reduce the surface, hence, decreasing the resistance. The sensing film was annealed at different temperatures, viz., 300, 400, 500, 600 and 700°C for 1 h each for the purpose of finding the optimum annealing temperature to detect acetone gas. Various characterizations, viz., XRD, AFM, FESEM, thickness measurement through surface profiler, gas-sensing characterization for recording resistance changes were performed. The optimum annealing temperature at which the sensing film gives maximum response when it comes in contact with acetone gas was computed to be 500°C. Also, operational optimum temperature for sensing film annealed at 500°C was computed to be 260°C. A grain size of 7.3 nm was computed through analysis of AFM image and a film thickness of 100 nm was calculated through surface profiler. The SEM image of the film demonstrates that the grains developed on the surface, which increase in size with increase in the annealing temperature. The XRD patterns reveal that the oxide showed up was WO2. It was observed that the response percentage is ~31% for acetone vapour concentration of 20 ppm, ~19% for the concentration of 15 ppm and ~15% for the concentration of 10 ppm. The response time of the sensor is ~5 min and the recovery time is 4 min. © Indian Academy of Sciences.

Fulltext

Bulletin of Materials Science

Effect of annealing on tungsten oxide thin films for acetone gas detection

In this paper a new approach based on silicon shadow mask has been reported to realize metal-carbon nanotubes (CNTs) contacts in end-contact configuration, which provides low-ohmic and stable contacts than that of side-contacted configuration. The source and drain contacts were fabricated by placing the fabricated silicon shadow mask over the single walled CNTs (SWNTs) coated wafer followed by deposition of Cr/Au∼100nm/500 nm using e-beam evaporation. The SEM image clearly shows the end-contacts of individual SWNTs with the gold electrodes. Further, Keithley SCS 4200 parameter analyzer was used to perform electrical characterization of the fabricated devices. The calculated ION/IOFF ratio and threshold voltage of the typically shown device are ∼120 and∼290 mV respectively. © 2018 Author(s).

AIP Conference Proceedings

Stable metal-CNT contacts using shadow mask technique for CNTFET fabrication

Design of cryptographic algorithms has ever been meant for making messages confidential strong enough for cryptanalysts. This has resulted into different categories of encryption/decryption algorithms while they have their own pros and cons. The cryptanalysts have played roles in observing confidential messages, identifying used algorithms to encrypt messages, and they have been successful in exploiting the weak points, if found any, in the algorithms’ designs. But Hybrid cryptographic algorithms, which bring mixture of randomness in the ciphered text, are ones of some obstacles for them. It is more difficult to break the hybrid ciphered text than that of block or stream cipher text. The current work presents design of a hybrid algorithm that makes uses of content replication removal in input data, block cipher and stream cipher cryptographic algorithms. © 2018, Springer Nature Singapore Pte Ltd.