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

A systematic, analytical method to obtain the charge density and surface potential in an N-polar GaN/AlGaN heterostructure is presented. This method also provides the wave functions, sub-band energies, and band diagram. The model accounts for the greater leakage of the wave functions into the spacer and barrier layers in the N-polar structure as compared to the Ga-polar structure. The framework is based on the solution of Schrodinger-Poisson equations for an approximately triangular well potential with finite confinement, achieved using first-order perturbation theory. No fitting parameters are used. Results obtained using our model are in good agreement with numerical results (obtained using the finite difference method) for a wide range of bias conditions.

World University root node

TechRxiv

Airy function based model for 2-DEG charge and surface potential in N-polar Gallium Nitride heterostructures

A new frequency selective surface (FSS) and its complementary structure are proposed in this paper. The design structures have features of dual band stopband and dual band passband responses, being intended to work in the terahertz (THz) range. The unit cell of the FSS consists of an enhanced capacitance-loaded Jerusalem cross (JC) and an outer square loop resonator (SLR). Two resonances of the bandstop FSS are centered at 0.23 and 0.36 THz with 10 dB stopband bandwidths (BWs) of 16.5 % and 17.1 % respectively. The designed FSS provides excellent angular stability up to an incidence angle of 80°. The complementary geometry of the designed FSS exhibits dual passband characteristics. The 3 dB passband BW (S21 > -3 dB) covers the frequencies 0.18-0.25 THz and 0.31-0.45 THz. The unit cell has a periodicity of 245 μ m or 0.19 λL, where λL is the wavelength at the lower resonance frequency. © 2022 IEEE.

2022 IEEE Wireless Antenna and Microwave Symposium, WAMS 2022

Miniaturized All Angle Stable Dual Band Frequency Selective Surfaces at Terahertz Regime

A simple concentric circular ring resonator-based nonreciprocal deca-band absorber is demonstrated in this article. The design primarily consists of two frequency selective surfaces (FSSs) among one is a compliment to the other printed on either side of the 2.4 mm thin FR-4 dielectric substrate. It exhibits near-unity absorption effectively at ten different resonant frequencies over X-Ka bands with an average absorption efficiency of 94.6%. Surface plasmonic resonances are the reason behind the multiband absorption and are illustrated with current profiles at resonant frequencies. The performance is angular stable for both transverse electric and transverse magnetic oblique incidences up to 60o. The design is compact with a structural periodicity of 0.210 λ o and thickness 0.07 λ o, where λ o is the lowest resonant peak's free-space wavelength. The 20×20 array of the design prototype is fabricated, and the measured results agree with the full-wave analysis. Bistatic radar cross section (RCS) analysis of the proposed absorber is evaluated along with a conventional microstrip patch antenna at X-band. Since the absorber design is based on complementary FSSs, it can also be utilized as a reflector for the not absorbing frequencies. The novelty lies in the utilization of the dual-side of the substrate made this design compact with a greater number of absorption peaks and good angular stability, making it potential for real-time RCS, and electromagnetic interference and shielding applications. © 1964-2012 IEEE.

IEEE Transactions on Electromagnetic Compatibility

Novel Dual-Mode Polarization Insensitive Wide Angular Stable Circular Ring Based Deca-Band Absorber for RCS and EMI Shielding Applications

This article proposes a novel wideband reflective type metasurface that performs linear-cross polarization conversion and perfect reflector operation in different bands. The polarizer unitcell primarily consists of a top Frequency Selective Surface (FSS) printed on the low-loss grounded substrate. It shows the minimum 90% Polarization Conversion Ratio (PCR) from 9.66- 14.72 GHz and almost zero PCR from 15-22 GHz for the linearly polarized Electromagnetic (EM) wave incidence. In addition to the linear-cross, the design also demonstrates the linear-circular conversion with a 3 dB Axial Ratio (AR) from 8.27 to 9 GHz (X-band) and 14.90 to 15.07 GHz (Ku-band). The performance is stable up to 45° for oblique incidences in the elevation plane. Multiple surface plasmonic resonances are the reason for the dual operation, and the near electric field patterns agree with the presented response. The operational bands are tunable mechanically by adjusting open-ended stub dimensions connected to the unitcell's inner loop. The design has volumetric architecture of 1.709(λL3/1000), λL is the free-space wavelength of the lowest operational frequency. Due to the angular stable linear-cross polarizers and perfect reflectors at different frequency bands in a single design would be useful in real-time applications where dual-operation is the primary concern. © 2022 IEEE.

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

Novel Wideband Perfect Reflector with Linear-Cross Polarization Conversion Ability for X/Ku/Ka-Band Applications Including Bandwidth Adjustment

A mono-pulse comparator using rat-race couplers for tracking application at X-band is proposed in this paper. The comparator is designed for a frequency of 10 GHz. The overall dimension of the comparator is 28 mm × 75 mm × 0.508 mm, which yields good reflection coefficients and VSWR values over all the ports. © 2022 IEEE.

Monopulse Comparator For Tracking Application using Rat race Couplers at X-band

A simple linear-cross and linear-circular reflective polarizer is presented in this work. For a 45° linearly polarized EM wave incidence, this design exhibits linear-circular conversion with Axial Ratio (AR) ≤ 3dB from 20.01-21.83 GHz (RCP at K-band) and 28.66-50.14 GHz (LCP at Ka-band and V-band), with 8.70%, and 54.52% Fractional Bandwidth (FBW) respectively. It also results in linear-cross conversion with 90% Polarization Conversion Ratio (PCR) bandwidth from 23.09-26.33 GHz (K-band with 13.11% FBW). Multiple surface plasmonic resonances are responsible for this dual-polarization conversion. Surface current patterns of the top FSS and ground plane are investigated to get physical insight. The PCR and AR performance are stable up to 40° for Transverse Electric (TE) and Transverse Magnetic (TM) cases. The design is compact with a structural periodicity of 0.093 λL × 0.137 λL, and thickness of 0.053 λL. Here, λL corresponds to the lowest frequency's free-space wavelength of the operating range. The author firmly thinks that the miniaturized converter countervails Faraday's rotation experiences by Electromagnetic (EM) waves in satellite communication applications. © 2022 IEEE.

A Simple Wideband Angular Stable Linear-Circular and Linear-Cross Reflective Type Polarizer for Satellite Communication Applications

The monopulse comparator (MC) is considered one of the important modules of the automated target detection and direction finding system. The present work proposes two new aperture coupled monopulse antenna arrays for single and dual plane tracking. The proposed monopulse array consists of a 4-element linear aperture coupled antenna (ACA) array and a microstrip line comparator circuit as a feeding network. The designed monopulse arrays cover the entire n78 (3.3-3.8 GHz) sub-6 GHz band with a bandwidth (BW) of > 18 %. The gain in sum patterns of single and dual plane monopulse arrays are 5.9 and 8.5 dBi at 3.5 GHz. The two arrays achieve a null depth of < -24.1 and < -25.4 dB between the sum and difference patterns. © 2022 IEEE.

Aperture Coupled Linear Array for Single and Dual Plane Monopulse Comparators at 3.5 GHz

A time-domain novel beamforming algorithm for ultra-wideband (UWB) microwave imaging is furnished in this paper. A monostatic and bistatic antenna setup is utilized to transmit and receive custom UWB pulses. This setup is employed to image various metallic and non-metallic threats attached to a human body. The imaging results demonstrate that the proposed beamforming algorithm allows effective reconstruction of different targets for both monostatic and bistatic cases. An ultra-wideband high gain Antipodal Vivaldi Antenna (AVA) is used as the transducer for the proposed imaging setup. The designed transducer demonstrates measured impedance bandwidth from 660 MHz to 15 GHz (182%) with a peak gain of 15 dBi at 8 GHz. The quality and accuracy of the proposed beamforming algorithm is tested outside the anechoic chamber just to make it more convincing in a real-world dynamic scenario. The result shows that different concealed materials can be detected accurately with the beamforming algorithm. To the best of the authors' knowledge, the proposed algorithm can effectively add up the target responses to obtain a clear and distinct image of the metallic and non-metallic targets. © 2013 IEEE.

IEEE Access

Concealed Object Detection With Microwave Imaging Using Vivaldi Antennas Utilizing Novel Time-Domain Beamforming Algorithm

Lecture Notes in Electrical Engineering

Preface

This Chapter presents behavioral analysis of ohmic contact micromachined switches. In this Chapter, electrostatically actuated micromachined switch configurations that can be easily integrated in uniplanar circuits are presented. The design procedure and fabrication process of micromachined switch topologies that can control the propagating modes of multimodal uniplanar structures (based on a coplanar waveguide (CPW)) are be described in detail. Generalized electrical (multimodal) and mechanical models will be presented and applied to the switch design and simulation. The switch-simulated results are compared to measurements, confirming the expected performances. Mostly cantilever types of switches are chosen in this study and analysis procedure is described with lumped model representation. Different types of ohmic-contact switches are discussed in this Chapter with extensive set of measurement stages. It includes switch profile analysis where surface profile and initial deformation are measured using Optical Profilometer, mechanical resonance frequency measurement and characterization using Laser Doppler Vibrometer (LDV), characterization of switch actuation and release voltages using LCR meter under a DC probe station, switching and release time measurements utilizing a proposed set up, linearity and temperature stability analysis and characterizations within a laboratory environments, S-parameter measurements using RF probe station with a Vector Network Analyzer (VNA) followed by the power handling capability and its analysis within a laboratory environments. Switch performances are discussed against each measurement stages. Functionalities of ohmic contact broadband switches are discussed with behavioral analysis. Comparison between simulated versus all measured responses are discussed up to a reasonable extent. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.