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.

&nbsp;

IIT Palakkad

Modern wearable or portable health monitoring devices are capable of photoplethysmogram (PPG) sensing, processing, analyzing, storing and transferring signal and parameters wirelessly but are generally energy constrained and have more false alarms under noisy PPG recordings. In this paper, we present computationally-efficient reliable pulse rate (PR) estimation in compressed sensing (CS) domain. The proposed CS-PPG based PR estimation method consists of measurement generation, high-pass filtering, average magnitude difference function (AMDF) features based signal quality assessment (SQA), and AMDF based quality-aware PR estimation. The proposed unified framework is evaluated using a wide variety of normal and pathological PPG signals taken from five standard databases. The proposed framework had an average sensitivity (SE) of 98.75% and specificity (SP) of 63.35%. Results show that the CS-PPG based quality-aware PR estimation method had a mean absolute error (MAE) of 3.1 ± 4.6%, Bland-Altman ratio (BAR) of 9.2% and root-mean-square error (RMSE) of 5.6 which are not only comparable with the results of the PR estimation method with the original PPG signals but also the proposed framework reduces 80% of the overall computational load. The proposed unified framework has great benefits in reducing processing time and energy consumption and thus can maximize battery lifetime of battery-operated health monitors. © 2023 IEEE.

World University root node

15th International Conference on Electronics, Computers and Artificial Intelligence, ECAI 2023 - Proceedings

Fast Quality-Aware AMDF Based Pulse Rate Estimation from Compressed PPG Measurements for Wearable Vital Signs Monitor

In recent years, memristive neuromorphic systems have gained significant attention. In our previous work, we developed a physics-based framework to model transport in electrochemical metallization (ECM)-based memristors with layered materials as switching layers, which was implemented in VerilogA. In this work, we demonstrate the efficacy of this model in a crossbar array/neural network for pattern classification. The performance of the system is analyzed based on classification accuracy in ideal and non-ideal conditions. Through the use of these simulations, the system-level performance can be predicted, along with its potential degradation, owing to variability. © 2023 IEEE.

PRIME 2023 - 18th International Conference on Ph.D Research in Microelectronics and Electronics, Proceedings

Variability-aware electrochemical metallization based memristive neural network for pattern classification

A novel multifunctional frequency selective surface (FSS) based switchable absorber&#x002F;reflector is demonstrated. The design consists of a resistor-loaded resonating patch, p-i-n diodes loaded inductive grid (IG) printed on different substrates and a ground plane separated by air spacers. In the diode&#x0027;s <sc>on</sc> state, it works as a wideband absorber from 2.30 to 5.95&#x00A0;GHz &#x005B;88.48&#x0025; fractional bandwidth (FBW)&#x005D; and 3-dB reflector at different air-spacers thicknesses between FSS and IG. It also behaves as a band-notch absorber at 3.5&#x00A0;GHz (sub-6&#x00A0;GHz) and a perfect reflector for a similar configuration in the diode&#x0027;s <sc>off</sc> state. In the absence of the ground and air spacers, it works as a spatial bandpass filter with a 3-dB insertion loss from 5.50 to 7.58&#x00A0;GHz and a bandstop filter with a transmission zero at 4.5&#x00A0;GHz (3-dB return loss with 124.65&#x0025; FBW) for the <sc>on</sc> and <sc>off</sc> conditions, respectively. The design periodicity is compact (0.068&#x00A0;&#x00D7;&#x00A0;0.068<inline-formula><tex-math notation="LaTeX">${\bm{\lambda }}_{\bm{L}}^2$</tex-math></inline-formula>) and performance is obliquely stable. The authors strongly believe that the proposed design performs multiple operations, such as absorbing, reflecting and filtering with stable angular performance. The miniaturized architecture makes this design a potential candidate and can be easily integrated for radar cross section, electromagnetic interference shielding and real-time wireless applications in the Sub-6&#x00A0;GHz range. IEEE

IEEE Transactions on Electromagnetic Compatibility

Wideband Reconfigurable Multifunctional Absorber/Reflector With Bandpass/Bandstop Filtering and Band-Notch Absorption for RCS and EMI Shielding

This paper demonstrates the initial stage of developing a 1-18GHz five port frequency multiplexer. The design details of 1-6GHz and 6-10GHz bandpass filters are discussed along with their results. Modified optimum short-circuited stub technique is used for designing a 1-6GHz bandpass filter and cascading high pass filter with low pass filter is used for the design of a 6-10GHz bandpass filter. Both filters achieve a passband return loss <-15dB, passband insertion loss <2dB and stopband attenuation > 50 dB. © 2023 IEEE.

2nd International Conference on Wireless, Antenna and Microwave Symposium, WAMS 2023

Ultra broadband 1-6GHz and 6-10GHz Bandpass Filters for Frequency Multiplexer

This study demonstrates a reconfigurable wideband reflective polarizer from X to Ka-band applications. The design unitcell consists of a single PIN diode integrated metallic patch printed on a grounded dielectric substrate. When the PIN diode is reversely biased, the designed polarizer effectively converts a linearly polarized incident wave into a circular one with an effective 3 dB Axial Ratio (AR) from 8.88-9.82 GHz, 12.61-20.17 GHz and 23.67-25.08 GHz. In addition, it also performs linear-cross conversion with a minimum 90% Polarization Conversion Ratio (PCR) from 10.43-11.68 GHz and 21.27-22.78 GHz. While in the forward bias, this polarizer behaves as a perfect reflector in the lower frequency region, linear-cross conversion (21.90-23.38 GHz) and linear-circular from 19.85-21.08 GHz and 24.44-26.77 GHz. No performance degradation for oblique incidences is observed in the elevation plane up to 45°. The dual functionality is due to several surface plasmonic resonances supported by the patterns seen in the local electric field. The polarizer/reflector unitcell is very compacted (0.053λL×0.077 λL) and has a low-profile thickness of 0.047λL. Dual operation is of paramount importance in real-time applications and angular stable linear-cross, linear-circular polarizers and perfect reflectors at distinct frequency bands in a single design would be ideal in these cases. © 2023 IEEE.

Wideband Reconfigurable Linear-Linear and Linear-Circular Polarizer/Reflector Integrated With RF PIN Diodes for X/Ku/Ka-Band Applications

The dual active bridge (DAB) converter is one of the widely explored topologies in recent years due to its remarkable features, such as inherent soft-switching characteristics, galvanic isolation, and high power density. However, the conducted electromagnetic interference (EMI) analysis of the DAB converter is seldom reported. In this article, the common-mode (CM) and the differential-mode (DM) equivalent circuits of the isolated DAB converter are presented to understand the propagation mechanisms of the conducted EMI noise in the converter. In particular, the mixed-mode DM (MMDM) noise component of the DM noise is quantified for the DAB converter. Furthermore, an experimental measurement method based on an external impedance-matched circuit is proposed to quantify the DM current due to capacitive coupling between the primary and secondary windings of the transformer. The quantified MMDM noise and the DM noise through the transformer are estimated using the proposed equivalent circuits in MATLAB-Simulink and validated experimentally on a prototype DAB converter. © 2022 IEEE.

IEEE Journal of Emerging and Selected Topics in Power Electronics

Analysis of Common-Mode Noise and Mixed-Mode Differential-Mode Noise in Dual Active Bridge Converter

Dual active bridge (DAB) dc-dc converter with integrated transformer is explored in recent years due to its advantages of the low component count, high power density and high efficiency. Although the operational performance of the DAB converter is well reported, the common-mode (CM) noise with the integrated transformer is yet to be thoroughly analyzed. Hence, this paper presents a detailed analysis of the CM noise performance of the DAB converter employing integrated transformer. Moreover, the conventional CM chokes incorporated to mitigate the CM noise cause a deleterious impact on volume and power density of the converter. This paper proposes a concentric CM choke that occupies less volume compared to its equivalent conventional CM choke of the same CM impedance. The analysis and design guidelines for the proposed concentric CM choke are presented. The above-mentioned analyses of the integrated transformer and the concentric CM choke are experimentally validated on a DAB converter prototype. IEEE

Analysis of Common-Mode Noise and Design of a Reduced-Volume Concentric Choke for Dual Active Bridge dc-dc Converter with Integrated Magnetics

Smart wearable and portable healthcare devices are used for continuous patient health monitoring but have limited battery power and on-board memory. Therefore, there is a huge demand for an automated photoplethysmogram (PPG) signal quality assessment (SQA) for energy-constrained smart medical devices. In this article, we propose a novel convolutional neural network (CNN)-based compressive sensing PPG-SQA method for low-power wireless healthcare devices. The main focus of this paper is to find the best compressive sensing matrix to directly classify the compressed PPG segments into noise-free and noisy segments using the optimal one-dimensional CNN architecture. The proposed CS-PPG SQA method was evaluated using 4-layer and 32 filters with a rectified linear unit (ReLU) activation function. Evaluation results showed that the deterministic binary block diagonal (DBBD) sensing matrix with a compression factor of 2 outperforms the existing methods with original PPG signal. The proposed method had an accuracy (ACC) of 99.55% for noise-free PPG (NF-PPG) versus wrist-cup noisy PPG database (MA-DB01), 99.99% for NF versus random noise-added PPG (RN-PPG) segments and 72.71% for NF-PPG versus acceleration corrupted PPG database (MA-DB02). The proposed method can reduce false alarms by discarding noisy PPG segments and reduce model size, and computational time by 50% as compared to other existing SQA methods. © 2023 IEEE.

Compressive Sensing-Based Automatic PPG Signal Quality Assessment Using CNN for Energy-Constrained Medical Devices

In this work, an accurate estimation of the amplitudes and frequencies of the flicker components has been proposed using dynamic mode decomposition (DMD). The proposed method consists of Hilbert transform for envelope extraction, DMD for spectral analysis, and finally, the assessment of flicker severity index ( V10) based on the eye-brain model. The DMD method constructs a shifted-stack matrix of the voltage signal, and thereby it is processed through singular value decomposition (SVD) for extracting the dominant signal parameters. To verify the effectiveness of the proposed technique, voltage flickers are considered with single flicker and multiple flicker components. It is also investigated in presence of sensitive conditions such as harmonic disturbance, power frequency deviation, noisy environment, phase jumps, and transients. The simulation results are compared with the existing techniques in terms of the relative errors of flicker parameters. Finally, a hardware prototype is developed for practical flicker measurement and the proposed algorithm has been implemented on the Raspberry pi board. The experimental results are presented and compared with simulation findings of the proposed technique to prove its applicability. © 1963-2012 IEEE.

IEEE Transactions on Instrumentation and Measurement

Dynamic Mode Decomposition Based Approach for Accurate Measurement of Voltage Flicker Components

Although many pulse oximeters are available in market with different blood oxygen saturation (SpO2) equations presented in the past studies, we investigate the performance of ten existing SpO2 equations by validating the robustness of calibrated coefficients and ratio of ratios (R) parameter. For this performance study, we used the pulse transit time (PTT-PPG) database having different dual-wavelength PPG signals with their ground truth SpO2 values. From the evaluation results in terms of mean absolute error (MAE), standard deviation (SD), root mean square error (RMSE) and Bland-Altman ratio (BAR), identifying the best SpO2 equation(s) is challenging because the above-mentioned error metrics are biased with averaging of error values with large number. Therefore, this study presents a new estimation error range (EER) metric to highlight the large error values of the SpO2 estimation algorithms. On the EER metric, the best SpO2 equation is presented based on the estimation results obtained for two different durations of signal. © 2023 IEEE.