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

Respiratory rate (RR) is one of the most vital signs to predict symptoms of serious illnesses and also used as a vital indicator or significant physiological parameter for early disease warning (early detection of patient deterioration) and to monitor person's physical and emotional stress. In this paper, we propose an automated Hilbert envelope based respiration rate estimation method using the photoplethysmogram (PPG) signal. The proposed Hilbert transform RR (HT-RR) method is tested by using the signals taken from BIDMC and CapnoBase databases. On the benchmark performance metrics, the proposed method had an mean absolute error (MAE) in terms of median (25th-75th percentile) of 3.7(1.8-5.5) breaths per minute (brpm) and 2.6 (0.8-5.5) brpm for 30 and 60 second PPG signals respectively. Evaluation results further showed that the processing time of 4.81 ± 0.80 milliseconds are required to compute RR value from 30 seconds duration PPG signal. The method has great potential in improving the accuracy and reliability of wearable and portable diagnosis system. It is observed that the proposed method outperforms the recent RR estimation methods. © 2022 IEEE.

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

Automated Hilbert Envelope Based Respiration Rate Measurement from PPG Signal for Wearable Vital Signs Monitoring Devices

A novel broadband linear-circular and linear-cross polarization converter for K to Ka-band applications is demonstrated in this work. The proposed structure primarily consists of an inductive grid in orthogonal with an H-shaped dipole as top Frequency Selective Surface (FSS) and a modified horizontal dipole as bottom FSS; a 1 mm thin FR-4 substrate is separating both. During transmission, it can convert the linearly polarized EM wave to a circular one, with Axial Ratio (AR) ≤ 3 dB from 13.08 to 25.13 GHz with 63.07% Fractional Bandwidth (FBW). In addition, this polarizer can work in reflection mode also when the bottom FSS is replaced by a Perfect Electrical Conductor (PEC), demonstrating the linear-circular polarization with AR (≤3 dB) from 16.94 to 18.64 GHz (RHCP/LHCP) and 24.5–40.32 GHz (LHCP/RHCP) with FBW 9.56% (Ku-band), and 48.81% (K- and Ka-band), respectively. Besides, linear-circular conversion, it performs linear-cross conversion in reflection mode with polarization conversion ratio (PCR) above 90% from 19.71–22.22 GHz, 43.57–48.81 GHz, 53.50–55.32 GHz with 13.89%, 11.34%, 3.32%, FBW, respectively. The equivalent circuit model of the proposed converter is extracted. Surface current distribution profiles at multiple plasmonic resonances are investigated to understand the reason behind the multi-polarization conversion. The performance is angular stable up to 45° for both transverse electric (TE) and transverse magnetic (TM) incidences for reflection as well as transmission modes. The unitcell is compact with periodicity 0.114λL × 0.114λL and a thickness of 0.044λL, where λL is the free-space wavelength of the lowest frequency. This design's novelty lies in dual-mode stable angular performance in both reflection and transmission cases. Also, highly miniaturized architecture and circular rotation switching in the consecutive bands make this design suitable for real-time scenarios. © 2022 Wiley Periodicals LLC.

International Journal of RF and Microwave Computer-Aided Engineering

Novel broadband angular stable linear-circular and linear-cross polarizer based on inductive grid loaded H-dipole in both reflection and transmission modes

This work introduces a miniaturized monopole antenna based on metamaterials for breast cancer detection. The proposed antenna is designed on a low-cost FR4 substrate with a dielectric constant of 4.4, loss tangent 0.025 and thickness of 1.6 mm. For gain enhancement, the designed antenna is equipped with a frequency selective surface (FSS) on its back side. The suggested antenna obtains a broad bandwidth (S11> 10 dB) between 3.4 and 9 GHz, with a peak gain of 6.2 dBi at 5 GHz. The proposed work also achieves a maximum gain enhancement of 4.7 dBi with the addition of FSS at the back side of the antenna. The Specific absorption Rate (SAR) study of the antenna with a realistic hemispherical breast phantom modelled in the simulator is performed to assess the impact of radiation on the human breast. It is observed that the proposed antenna complies with the International limits when averaged over 10g of tissue. © 2022 IEEE.

2022 IEEE International Conference on Emerging Electronics, ICEE 2022

Breast Cancer Detection with Metamerial Enabled Monopole Antennas using Microwave Imaging

A novel transmission type polarizer for K-and Ka-band applications is demonstrated in this work. A thin dielectric substrate is sandwiched between the top and bottom Frequency Selective Surfaces (FSSs) that comprise the polarizer's unitcell. The transmitted wave is circularly polarized for the linearly polarized wave incidence, with a minimum 3dB Axial Ratio (AR) over the frequency from 16.52-39.93 GHz (82.94% relative bandwidth). The performance is stable up to 45° for Transverse Electric (TE) and Transverse Magnetic (TM) incidences. The equivalent circuit model of the polarizer is extracted, and the response agrees with the EM solver results. The possibility to perceive the circular polarization rotation sense is captured by studying electric field patterns at two frequencies. The design is compact with a structural periodicity of 0.088?Lx 0.116?L and thickness of 0.044?L, where ?L is the free-space wavelength corresponds to the lowest frequency of the operating range. The minimum Polarization Extinction Ratio (PER) of 21 dB is observed over the entire operating range. Realtime satellite applications could benefit from the miniaturized volumetric design 0.448(?3L/1000), and the stable angular response of the presented wideband polarizer. © 2022 The Institute of Electronics Information and Communication Engineers (IEICE) of Japan.

Asia-Pacific Microwave Conference Proceedings, APMC

Novel Wideband Single-Layered Substrate Linear-to-Circular Metasurface Enabled Transmission Type Polarizer for K-/Ka-Bands Satellite Applications

This paper presents two new reflection type linear cross converters at the terahertz (THz) waveband. The proposed converter possesses the advantages of compact and simple unit cell geometry, which can be optimized easily for single wideband and dual broadband polarization conversion. The unit cell of the converter comprises anisotropic geometry of double E-shaped resonators. The designed structure converts a linear polarized incident wave into cross-polarization over the frequency range of 0.67 to 1.65 THz (84.5 %) with above 90 % polarization conversion ratio (PCR). At three frequencies of 0.73, 1.11, and 1.55 THz near 100 % polarization conversion is achieved. The converter exhibits stable polarization conversion characteristics for incidence angle > 35°. A pair of parallel slits are placed along the length of the E-shaped resonators to obtain a notch in the converter's response. The modified metasurface exhibits dual-band cross-polarization conversion between the frequency ranges of 0.67-1.06 THz (45.1 %) and 1.37-1.74 THz (23.8 %). © 2022 IEEE.

2022 IEEE Wireless Antenna and Microwave Symposium, WAMS 2022

Compact Single and Dual Broadband Reflective Type Linear Cross Converters at Terahertz Regime

In this paper, a new high gain dual band antenna array is proposed using substrate integrated waveguide (SIW) for X and Ku band satellite communication applications. Two major parts of the SIW array are pair of cavity backed slot antenna and a 1 to 2 way SIW based Y-junction divider. The multimode high order resonances are excited within the cavity resonator to obtain dual broadband performance. Impedance bandwidth (BW) of the array exists between frequency ranges of 11.47-11.74 GHz (2.3 %) and 12.79-14.15 GHz (10.1 %) in the lower and higher bands. The simulated peak gain and efficiency of the array are 10.6 dBi and 94.4 % at the lower resonance and 11 dBi and 95.4 % at the higher resonance. © 2022 IEEE.

2022 IEEE Microwaves, Antennas, and Propagation Conference, MAPCON 2022

High Gain Dual Broadband Antenna Array Using Substrate Integrated Waveguide at X/Ku Bands

In this paper, the design and simulation of a new compact unit cell of reflection-type linear co to cross-polarization converter is proposed for C and X band applications. The unit cell consists of double semi-circular goblet shaped resonators printed on a perfect conductor-backed dielectric substrate. Periodicity of the unit cell is 0.243 λ0, where λ0 is the free space wavelength at the lowest resonant frequency. The polarization conversion efficiency and its mechanism are studied carefully on the basis of surface current wave characteristics at all the three resonant frequencies within the operating bands. The structure exhibits dual band linear cross conversion from 4.71-5.68 GHz and 10.0-11.99 GHz with a polarization conversion ratio (PCR) > 90 %. Moreover, the PCR at the first and third resonant frequencies (5.2 and 11.75 GHz) shows the ideal 100 % polarization conversion efficiency while the PCR for second resonant frequency at 10.4 GHz is > 99%. The simulation results demonstrate that the proposed converter response is found to be stable at a high incidence angle of >30°. Furthermore, this proposed converter finds its potential application in enhancing the stealth ability of the modern electronic and information warfare technologies by radar cross-section (RCS) reduction. At frequencies 5.2, 10.4 and 11.75 GHz, the 4 × 4 array of the converter reduces the RCS by more than 12, 10 and 9 dB for both monostatic and bistatic conditions. © 2022 IEEE.

2D Double Semi Circular Goblet Shaped Angular Stable Dual Band Reflection Type Polarization Converter And Its Application in Radar Cross Section Reduction

This work presents design of circulators using active elements like transistors. Metamaterial based structure consisting of ring resonators loaded with FET's is used to make the circulator design with nonreciprocity. The proposed work deals with two designs, the first circulator shows its operation at 6 GHz that can be used for Wi-Fi 6E communications. The second design which is an extension of the first one acts like a Tri-band circulator having resonances at 1.3 GHz, 3.2 GHz and 5.9 GHz. The circulator demonstrates simulated insertion loss of 3.8 dB, isolation of better than 10 dB and matching of > 22 dB at 5.9 GHz. The proposed circulator can be used for both Wi-Fi 6E and WiMAX applications. © 2022 IEEE.

Design of Tri-band RF Circulators using Non-Magnetic Metamaterial Based Structures for Wi-Fi 6E and WiMAX Applications

Rapid integration of distributed generations (DGs) in the traditional grid presents new protection system challenges. These DG units are usually connected to the power network through power electronic interfaces. According to the grid code, the DG units are expected to support the grid during fault conditions. Therefore, these DG units have provisions of ancillary services like voltage ride-through (VRT) and frequency regulations. To fulfill the grid code requirements, the inverter manufacturers follow different control strategies to capture the required dynamics. Consequently, the voltage and current signatures are highly unpredictable and very much are dependent on the type of control strategy adopted. In this paper, in the first few sections, different types of control strategies for DG units are discussed under both balanced and unbalanced fault scenarios. In the later sections, detailed performance analysis of negative sequence directional relay is done in presence of these controllers and their fault behavior is studied. © 2021 IEEE.

2021 IEEE 2nd International Conference on Smart Technologies for Power {\ldots}

Rethinking Grid Codes from Protection Perspective: A Case Study on Negative Sequence Directional Relay

When radio frequency microelectromechanical system (RF MEMS) based switches appeared more than 25 years ago, micromechanics has attracted huge attention for enabling near-ideal microwave devices. Since then, MEMS switches and circuits went through different development stages and are currently proving themselves commercially viable. Micromachining technology has the potential to become an enabling technology for microwave, millimetre wave to even sub-millimetre wave systems. The reliability of MEMS devices is one of the prime challenges to meet present state-of-the-art performances due to occurrence of multiple failure modes after few cycles of operations. The reliability becomes more critical when multiple MEMS switches operate simultaneously like in a higher order switching networks, multi-bit digital phase shifters or in a tunable filters. This Chapter presents detailed experimental studies on these devices considering life cycles up to 1 billion cycles of operation. A complete design guideline for reliable MEMS switches, phase shifter and filters are given for readers. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.