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

This communication presents the miniaturized low-profile second-order (SO) bandstop frequency selective surfaces (FSSs) for single- and dual-band resonances. The unit cell comprises two identical first-order (FO) elements in a back-to-back configuration with the metal grid in between. Two thin dielectric substrates separate the three metal layers. The proposed FO unit cell consists of intercell-connected spiral resonators (SRs) with capacitively coupled cross loop dipole. The SO filter response of the proposed FSS exhibits a wide stopband ( S21 < -10 dB) bandwidth (BW) of 27.6%. The unit cell has the periodicity of 0.162λ0, where λ0 is the free space wavelength at the lower passband. The novelty of the proposed work is a miniaturized simple unit cell geometry, at the millimeter-waveband but not limited to it, with polarization insensitive and high angular stable filter response up to 60° with small variations in the BW. An unconventional four-unit cell element FSS is designed for dual-band SO stopband resonances with the BWs of 8.3% and 13.8%. Prototypes of both FSSs were fabricated and their measured results were found consistent with the simulated filter responses. © 1963-2012 IEEE.

World University root node

IEEE Transactions on Antennas and Propagation

Second-Order, Single-Band and Dual-Band Bandstop Frequency Selective Surfaces at Millimeter Wave Regime

This Chapter presents radio frequency (RF) micro-electromechanical system (MEMS) based compact, high power and reliable tunable bandpass filter for millimetre wave RF front end. The design is fabricated on 635 µm 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 27–29 GHz, and it demonstrates insertion loss of 1.92 dB and matching of 23.4 dB at 28 GHz with fractional bandwidth of 6.7%. Filter also gives bandwidth tuning of 4.4 GHz with acceptable loss. A complete set of MEMS based tunable bandpass filter design guidelines are given for the readers. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Micromachined Circuits and Devices

Micromachined Tunable Filters Using MEMS Switches

A radio frequency micromachined based phase shifter is one of the key components in a modern electronically steerable phased array for satellite communication, radar systems and high precision instrumentation. The phase shifter controls the signal phase to steer the direction of the beam. MEMS technology provides a superior performance in terms of low loss, low power consumption and excellent linearity compared to other technologies. MEMS based digital phase shifters provide a large phase shift and low sensitivity to electrical noise with a high tuning ratio compared to analog versions. This Chapter describes different types of TTDTrue-time-delayPhotoresist phase shifters utilizing MEMS switches and MEMS varactors. A gold-based surface micromachining process is used to develop different kinds of MEMS phase shifters on alumina (εr = 9.8) substrates. All phase shifters are implemented using coplanar waveguide (CPW) transmission lines and actuated by electrostatic actuations. These include the analog type Distributed MEMS Transmission LineDistributed MEMS transmission line (DMTL) phase shifter using push–pull actuation, a 5-bit DMTL phase shifter using MEMS bridge and a fixed capacitor, 5-bit switched line phase shifter using DC-contact MEMS switches and a 2-bit &amp; 5-bit phase shifter using MEMS SP4T and SPDT switches. This Chapter includes details on the design, development, and characterization of MEMS phase shifters. Furthermore, all experimental results are validated with a circuit analysis and full-wave EM simulation. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Micromachined Phase Shifters

In this study, a compact modified circular ring-based circuit analog absorber (CAA) is proposed. It comprises a resistor-loaded frequency selective surface (FSS) underneath an FR-4 substrate, and the other end is terminated with a perfect electric conductor (PEC) separated by an air-spacer. The proposed design shows a minimum -10 dB reflectance from 10.55 to 36.03 GHz (25.48 GHz bandwidth and 109.4% fractional bandwidth) with two dips at 13.5 GHz and 35.23 GHz having reflectivity -17.18 dB and -24.9 dB, respectively. The existing four-fold circular symmetry architecture shows insensitivity for different polarization angles under normal incidences and up to 45° stability for Transverse Electric (TE) and Transverse Magnetic (TM) modes under oblique incidences. The proposed cell is compact with a periodicity of 0.193λL, and a thickness of 0.09λL, where λL is the free-space wavelength corresponding to the lowest frequency of the absorption band. The novelty of the design lies in the topology of using an underneath FSS to take advantage of effective permittivity control for both broader bandwidth and better angular stability. To demonstrate the ability of the proposed design, a 28 GHz microstrip patch antenna prototype is fabricated, and its radar cross section (RCS) is measured after loading with the absorber. A 15.15 dBsm RCS reduction is observed in comparison with the PEC. The authors strongly believe that the proposed design has potential applications such as RCS reduction and radio-frequency energy harvesting. © 2022 The Author(s). Published by Cambridge University Press in association with the European Microwave Association.

International Journal of Microwave and Wireless Technologies

A novel modified circular ring-based broadband polarization-insensitive angular stable circuit analog absorber (CAA) for RCS applications

Real-time photoplethysmogram (PPG) denoising and data compression has become most essential requirements for accurately measuring vital parameters and efficient data transmission but that may introduce different kinds of waveform distortions due to the lossy processing techniques. Subjective quality assessment tests are the most reliable way to assess the quality, but they are time expensive and also cannot be incorporated with quality-driven compression mechanism. Thus, finding a best objective distortion measure is highly demanded for automatically evaluating quality of reconstructed PPG signal that must be subjectively meaningful and simple. In this paper, we present four types of objective distortion measures and evaluate their performance in terms of quality prediction accuracy, Pearson correlation coefficient and computational time. The performance evaluation is performed on different kinds of PPG waveform distortions introduced by the predictive coding, compressed sampling, discrete cosine transform and discrete wavelet transform. On the normal and abnormal PPG signals taken from five standard databases, evaluation results showed that different subjective quality evaluation groups (5-point, 3-point and 2-point rating scale) had different best objective distortion measures in terms of prediction accuracy and Pearson correlation coefficient. Moreover, selection of a best objective distortion measure depends upon type of PPG features that need to be preserved in the reconstructed signal. © 2013 IEEE.

Fulltext

IEEE Access

Evaluation of Objective Distortion Measures for Automatic Quality Assessment of Processed PPG Signals for Real-Time Health Monitoring Devices

For the internet of medical things (IoMT) enabled long-term health monitoring and disease prediction applications, there is a demand for an automatic photoplethysmogram (PPG) signal quality assessment (SQA) for reducing false alarms and energy consumption. This paper presents a PPG-SQA method by using raw PPG signal and convolutional neural network (CNN) with optimal parameters. The main focus of this paper is to find an optimal number of filters (16, 32, 64) and number of layers (2 and 4 layers) with rectified linear unit (ReLU) activation function and to study robustness of trained CNN models by using unseen PPG datasets and different kinds of noise sources, which are not addressed in the past studies on the CNN-based PPG-SQA methods. Evaluation results showed that the 4 layer CNN-based method had the higher accuracy of 99.58% for noise-free PPG (NF-PPG) versus wrist-cup noisy PPG signal database (MA-DB01), 99.99% for NF versus random noises added PPG (RN-PPG) signals, and 75.80% for NF-PPG versus acceleration corrupted PPG signals (MA-DB02). For the unknown dataset, the 4-layer CNN model had the higher accuracy of 96.71% for NF-PPG versus MA-DB01 and 99.04% for NF versus RN-PPG, and the 2-layer CNN model had the higher accuracy of 76.16% for NF-PPG versus MA-DB02 PPG segments. Results demonstrate that the CNN-based PPG-SQA method with optimal parameters is not only improve the accuracy but can also reduce the computational load as compared with other existing methods. © 2022 IEEE.

Proceedings - 2022 International Conference on Artificial Intelligence of Things, ICAIoT 2022

CNN Based PPG Signal Quality Assessment Using Raw PPG Signal for Energy-Efficient PPG Analysis Devices in Internet of Medical Things

Automatic atrial fibrillation (AF) detection is essential for preventing stroke due to silent heart diseases. In this paper, we propose an automatic AF detection by using electrocardiogram (ECG) signals and convolutional neural network. The proposed method is tested by using the ECG signals from Physionet. On the benchmark performance metrics, the proposed method achieved an average accuracy of 98.26% for detecting AF events. The proposed method can achieve the AF event detection with a processing time of 0.77±0.037 ms with the selection of optimal hyperparameters. The method has great potential in detection of AF events in ECG signal. © 2022 IEEE.

2022 4th International Conference on Cognitive Computing and Information Processing, CCIP 2022

Convolutional Neural Network Based Atrial Fibrillation Detection from ECG Signal

The toroidal inductors are known for their higher flux densities, higher inductances, low losses in the windings, and less acoustic noise. This paper proposes novel concentric toroidal inductor configurations namely concentric toroidal inductors (CTI) used as power inductors and concentric toroidal differential-mode chokes (CTDMC) employed for DM noise filtration. The presented concentric toroidal structures provide improved inductances by utilizing the window area of the toroidal core. Analytical and experimental verifications prove the increment of inductance in CTI and CTDMI when compared to the corresponding traditional inductor confiaurations. © 2022 IEEE.

1st IEEE Industrial Electronics Society Annual On-Line Conference, ONCON 2022

New Toroidal Inductor Configurations for Improved Inductance

Global maximum power point tracking (GMPPT) algorithms are employed to extract the maximum available power from the photovoltaic (PV) arrays during partial shading conditions. However, the available GMPPT algorithms in the literature have disadvantages such as low convergence rate and requirement to scan for the local peaks. To overcome these drawbacks, this paper presents a fast and simple hybrid GMPPT algorithm, which combines the advantages of the binary search and the secant algorithms. The binary search algorithm is used for the global maximum power point (GMPP) reference generation and the secant algorithm is applied for tracking the generated power reference. The superlinear convergence rate of the secant algorithm and the logarithmic convergence rate of the binary search algorithm aid in fast convergence to the GMPP. The performance of the proposed hybrid GMPPT algorithm is validated through simulations in MATLAB-Simulink and also compared with a conventional GMPPT algorithm. © 2022 IEEE.

2022 IEEE Energy Conversion Congress and Exposition, ECCE 2022

Global Maximum Power Point Tracking for Photovoltaic Systems Using Hybrid Secant and Binary Search Algorithms

Power routing imbalance through the sub modules of a cascaded isolated medium-voltage AC - low-voltage DC (MVAC-LVDC) converter is inevitable due to the unavoidable drift/mismatch in values of passive components. In this paper, a comparative overview of the power imbalance issue and its mitigating control technique along with pertinent analysis is discussed for two-stage and single-stage isolated MVAC-LVDC cascaded converters. It is observed that for a two-stage conversion architecture, apart from the 2Nf-{sw} grid-current harmonics, characteristic of a cascaded multilevel converter, some lower order switching frequency based harmonics remain. On the other hand, for the single-stage conversion architecture counterpart, the dominant switching frequency based grid-current harmonics appear at 2 f-{sw} • The respective power balance control (PBC) schemes for the two conversion architectures are found to be effective, and the PBC reinforced single-stage converter displays lower grid-side current's THD compared to its two-stage counterpart. A suitable experimental verification of the implemented PBC strategy on two-stage and single-stage cascaded converter topologies is presented to demonstrate their comparative performance. © 2022 IEEJ-IAS.