Department of Electrical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

An Ultra-Wideband (UWB) Antipodal Vivaldi Antenna (AVA) is presented here for microwave imaging applications. To start with, a conventional AVA is designed for reference, and then periodic slit edges or corrugations in the form of sinusoids are furnished at the edges to obtain the desired performance for microwave imaging applications. The proposed antenna achieves high bandwidth from 1.2 - 14 GHz with a peak gain of 13 dBi at 10 GHz with a matching better than 15 dB from 3 - 14 GHz. The proposed antenna will be used for the detection of a concealed gun with different clutter removal algorithms applied to obtain its precise image. © 2021 IEEE.

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2020 IEEE MTT-S Latin America Microwave Conference (LAMC 2020)

Microwave Imaging over UWB with Antipodal Vivaldi Antenna for Concealed Weapon Detection

Nowadays, wearable sensors or portable devices have great potentials for real-time monitoring of health and fitness of an individual but they are constrained with limited battery power. Therefore, exploring lightweight signal processing technique is highly demanded for accurately measuring the pulse rate (PR) and respiration rate (RR) from the photoplethysmo-gram (PPG) signal in addition to the data compression in order to reduce or even eliminate the need for frequent charging of devices and replacement of batteries. In this paper, we present a lightweight unified predictive coding framework for achieving simultaneous data compression, PR and RR extraction from the PPG signal. Evaluation results demonstrate that the proposed unified framework can achieve compression ratio of 4:1 with energy saving of 52.38 %. For PR estimation, the method had mean absolute error (MAE) of 1.20 (bpm), Pearson coefficient of 0.9829 and Bland Altman ratio of 5.37. The RR estimation had promising MAE results of 3.1 (1.5-5.6 for 25th-75th percentiles) and outperforms the existing methods. © 2021 IEEE.

BioSMART 2021 - Proceedings: 4th International Conference on Bio-Engineering for Smart Technologies

Predictive Coding with Simultaneous Extraction of Pulse and Respiration Rates from PPG Signal for Energy Constrained Wearable Devices

In the case of vector flow imaging systems, the most employed flow estimation techniques are the directional beamforming based cross correlation and the triangulation-based autocorrelation. However, the directional beamforming-based techniques require an additional angle estimator and are not reliable if the flow angle is not constant throughout the region of interest. On the other hand, estimates with triangulation-based techniques are prone to large bias and variance at low imaging depths due to limited angle for left and right apertures. In view of this, a novel angle independent depth aware fusion beamforming approach is proposed and evaluated in this paper. The hypothesis behind the proposed approach is that the peripheral flows are transverse in nature, where directional beamforming can be employed without the need of an angle estimator and the deeper flows being non-transverse and directional, triangulation-based vector flow imaging can be employed. In the simulation study, an overall 67.62% and 74.71% reduction in magnitude bias along with a slight reduction in the standard deviation are observed with the proposed fusion beamforming approach when compared to triangulation-based beamforming and directional beamforming, respectively, when implemented individually. The efficacy of the proposed approach is demonstrated with in-vivo experiments.

2021 43rd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)

An angle independent depth aware fusion beamforming approach for ultrafast ultrasound flow imaging

In this article, a closed ring resonator-based absorber with eleven consecutive absorption peaks is proposed over X and K bands with an average absorption rate of 96.29%. The proposed design consists of circular ring resonators embedded in the circularly slotted square patch printed on the top of the grounded FR-4 substrate. The surface current distributions well illustrates the reason behind the electromagnetic (EM) wave absorption. The design is polarization insensitive for normal incidence and wide angular stable up to 45° for TE (60° for TM) polarization. The structure is fabricated on a single-layered FR-4 dielectric substrate with a periodicity of {{\boldsymbol{\lambda }}_{\boldsymbol{o}}}/2.32 and thickness of {{\boldsymbol{\lambda }}_{\boldsymbol{o}}}/16.74, where {{\boldsymbol{\lambda }}_{\boldsymbol{o}}} is the free-space wavelength at the lowest resonant frequency. A transmission line-based equivalent circuit model has been illustrated and good agreement is observed with full-wave simulations. This article's novelty lies in the absorption mechanism of eleven consecutive absorption peaks, demonstrating the controllability of the absorptivity peaks and resonant frequency. To the best of the authors' knowledge, the proposed absorber demonstrates the highest number of near-unity successive absorption bands with better angular stability. The proposed structure was checked for radar cross section reduction application with an X-band antenna and results show 19.7-dBsm reduction at normal incidence. © 1964-2012 IEEE.

IEEE Transactions on Electromagnetic Compatibility

A Simple Polarization-Insensitive and Wide Angular Stable Circular Ring Based Undeca-Band Absorber for EMI/EMC Applications

—In this work, a radio frequency (RF) micro-electromechanical system (MEMS) based analog phase shifter is presented over 17–30 GHz. The proposed phase shifter is made using two back-to-back single-pole-seven-throw (SP7T) switches and connected through seven distributed MEMS transmission lines (DMTL). The SP7T switch is designed with lateral electrostatic actuation and demonstrates measured average return loss of &gt; 11.3 dB, insertion loss of &lt; 5.94 dB, and isolation of &gt; 22 dB up to 30 GHz. Total area of the SP7T switch is only 0.89 mm2 including bias lines and pads. The proposed wide-band phase shifter can be tuned at all the frequencies between 17 and 30 GHz. Phase shifter gives measured average insertion loss of &lt; 6.94 dB, return loss of &gt; 10 dB, and phase error of ∼ 1◦ at 17 GHz to 30 GHz over 500 MHz bandwidth. All phase shifts can be tracked with a resolution of 22.5◦ based on predefined actuation voltages. Total area of the fabricated device is ∼ 11.72 mm2. In addition, switches and phase shifter work satisfactorily &gt; 1 billion cycles with 0.1–1 W of RF power. The proposed phase shifter bank gives phase shifting performances at each frequency over 17–30 GHz with a constant resolution utilizing analog tuning, and it operates &gt; 1 billion cycles of reliability with 1 W of RF power. © 2021, Electromagnetics Academy. All rights reserved.

Progress In Electromagnetics Research C

17–30 GHz reliable and compact analog phase shifter using lateral micromachined SP7T switches, and DMTL arrays

This paper presents a broadband transmission type linear to circular polarization converter (LCPC) with the advantages of a single metal layer, high conversion efficiency, and low insertion loss (IL). The proposed unit cell consists of narrow and wide metal strips which are oriented along the two diagonals. The strips exhibit high pass filtering characteristics with low cutoff frequency and higher resonance outside the operational band. The two orthogonal transmitted components from the metasurface have approximately equal magnitudes with a phase difference of 90° and the resultant wave is right-hand circular polarized (RCP). The proposed converter shows a 3 dB axial ratio bandwidth (ARBW) of 48.2 % between 19.22-31.42 GHz. The unit cell has a periodicity of 2.4 mm or 0.2 λ0, where λ0 is the wavelength at the center frequency of the operational bandwidth (BW). The proposed structure shows incidence angle stability up to 35° in two principal planes. © 2021 IEEE.

2021 IEEE 19th International Symposium on Antenna Technology and Applied Electromagnetics, ANTEM 2021

Broadband Single Layer Transmission Type Linear to Circular Polarization Converter with Higher Conversion Efficiency

This work presents radio frequency (RF) microelectromechanical system (MEMS)-based compact, high power, and reliable tunable bandpass filter for millimeter-wave RF front end. The design is fabricated on 635- μ \text{m} alumina substrate using surface micromachining process. All functional building blocks of the filter are fabricated and tested independently to ensure the optimum filter performances. Total area of the filter is only 2.3 mm2 including bias lines and pads. The proposed filter can be tuned to any frequency between 27 and 29 GHz and it demonstrates insertion loss of 1.92 dB and matching of 23.4 dB at 28 GHz with fractional bandwidth (FBW) of 6.7%. Filter also gives bandwidth tuning of 4.4 GHz with acceptable loss. Filter works satisfactorily up to 1 billion cycles with 1 W of power. Device reliability tested within a low-cost package. To the best of our knowledge, this is the first reported tunable MEMS bandpass filter in the literature which has undergone and presented with extensive reliability results. © 1963-2012 IEEE.

IEEE Transactions on Microwave Theory and Techniques

Reliable, Compact, and Tunable MEMS Bandpass Filter Using Arrays of Series and Shunt Bridges for 28-GHz 5G Applications

Organometal halide perovskite-based solar cells have shown rapid improvement in their performance. One of the predominant issues that serves as a bottleneck for further improvement is the hysteresis observed in their current-voltage characteristics, as it leads to inaccurate estimation of power conversion efficiencies. While there have been many approaches to modeling hysteresis in single perovskite-based solar cells, modeling hysteresis in perovskite-silicon tandem solar cells has largely remained unexplored. We have setup simple models, using circuit-based and TCAD-based approaches, that capture hysteresis behaviour in perovskite-silicon tandem solar cells. Our simulated current-voltage characteristics using both modeling approaches, have been validated with measured characteristics from experimentally fabricated devices reported in literature.

2021 IEEE 16th Nanotechnology Materials and Devices Conference (NMDC)

Modeling of Hysteresis in Perovskite-Silicon Tandem Solar Cells

Electrochromic devices (ECDs) are extensively used in various applications. While multiple compositions of electrochromic, electrolyte, and ion storage layer materials have been investigated, design guidelines that account for the impact of thickness of these layers on the optical response of ECDs remains unexplored. The optical performance of ECDs have been analyzed using the transfer matrix method. Our calculations show the significance of optimizing thickness of different layers in ECDs, for obtaining high-performance devices. We have illustrated the same by applying these analysis techniques to experimentally fabricated devices reported in literature. We believe that this insight will aid in the design of ECDs.

Design of optimal layer thickness in electrochromic devices

Photovoltaic (PV) grid support functionality (frequency support) can be accomplished with the aid of flexible power point tracking (FPPT) technology. However, the convergence rate of FPPT algorithms needs to be fast, to provide grid support under transients. To fulfil this purpose, a Newton's method-based (NM-B) FPPT algorithm is proposed in this paper that offers quadratic convergence, which is a higher convergence rate compared to the existing methods. Moreover, the search algorithm requires only a single initialization point, thus eliminating the difficulty of setting up the search boundary as in the case of the binary search-based and secant method-based (SM-B) FPPT algorithms. Simulation validation is performed for the proposed NM-B FPPT algorithm and the results are compared with the SM-B FPPT algorithm. © 2021 IEEE.