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 article presents a new method of enhancing the capacitance of a single-layer conformal frequency selective surface (FSS) for multifunctional operation. The unit cell of the FSS consists of gridded square loop-loaded modified Jerusalem cross (JC) element. End capacitance of the conventional JC FSS is enhanced by placing parallel diagonal strips, resulting in a pair of reflection zeros near the sidebands. The modified geometry provides high selective stopband filtering that reflects the signal at 20.16 GHz with S21 < -10 dB stopband bandwidth of 20.52%. The FSS shows stable stopband reflection up to a high incidence angle of 85°. The stability in the filter response is also achieved at various conformal angles. The proposed FSS is optimized for dual-band near-perfect absorption. At two resonances 12.76 and 22.54 GHz, the absorption are 99.88% and 99.1%, respectively. Prototypes of the stopband FSS and the dual-band absorber are fabricated to verify the feasibility of the proposed concept. The measured filter and absorber responses are found consistent with the simulated results. As a conformal multifunctional structure, the proposed FSS has the merits of electromagnetic interference shielding and radar cross section reduction in stealth application. © 1964-2012 IEEE.

World University root node

IEEE Transactions on Electromagnetic Compatibility

Conformal Multifunction FSS With Enhanced Capacitance Loading for High Angle Stable Stopband Filtering and Microwave Absorption

In this Chapter an overview of the radio frequency microelectromechanical systems is given. Focus is oriented towards discussion on different micromachined passive circuits that includes transmission line, varactor, inductor, switch, and switch-based circuits followed by resonators. Fabrication of RF micromachined devices on different technology platforms are also discussed in this Chapter. Applications of RF micromachined devices and components are also discussed with respect to the super-heterodyne radio receiver and electronically steerable antenna for radar application. Finally, this Chapter discusses organisation of the book. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Micromachined Circuits and Devices

Introduction to Radio Frequency Micro Electromechanical Systems

This Chapter presents design, development, and characterization of broadband (1–30 GHz) microelectromechanical systems (MEMS) based electrostatically driven vertical and lateral switching networks. Initially, single switch performances are optimized, and the same switch is used to develop different switching networks starting from single-pole-double-thru (SPDTSingle-pole-double throw) to single-pole-fourteen-thru (SP14TSingle-pole-fourteen-throw) using vertically actuated beams. The vertically actuated switch is designed using three springs to gain the mechanical stability. Later, laterally driven single MEMS switches are designed, fabricated, and tested. Lateral switch is designed with a mechanical springs and stopper to improve the stability without compromising the electromagnetic performances. The lateral switch doesn’t use any dielectric layers. The operation principle of the lateral switch is described in detail. Both switch types (vertical and lateral) are electrostatically driven and implemented on coplanar waveguide transmission line. Switch performances is given importance over a broadband spectrum. The S-parameter performances of all switching networks are described in detail with design guidelines. 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 Single-Pole-Multi-throw Switching Networks

The Chapter presents future scope in radio frequency (RF) micromachined devices in the THz frequency range. The Chapter is broadly divided into two parts, first part focusses on different metamaterial based micromachined devices at THz frequency range. Major emphasis is given on the micromachined frequency selective surfaces and absorbers. The second part focusses on the micromachined waveguide-based switches, phase shifters and conductor backed coplanar waveguide to rectangular waveguide transition in the THz frequency range. Different state-of-the-art designs are discussed in this Chapter with recent references. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Future Scope of RF MEMS in THz Regime

A novel multiband dual-polarized reflective polarizer is demonstrated in this article, which performs dual-operation like linear-cross and linear-circular conversions in the THz regime. The unitcell consists of a thin gold film coated modified circular rings-based Frequency Selective Surface (FSS) on top of a polyamide substrate grounded with a gold film to make the reflective design. Under normal incidence, the design performs the linear-cross conversion from 0.62-0.65 THz, 0.98-1.10 THz, and 1.74-1.80 THz, with a 90% minimum Polarization Conversion Ratio (PCR), respectively. In addition, it also demonstrates linear to circular conversion with Axial Ratio (= 3dB) from 0.58-0.59 THz, 0.69-0.90 THz, 1.18-1.67 THz, and 1.87-1.90THz. Multiple plasmonic resonances are the reason behind these conversions, which are visualized with surface current distribution analysis. The device performance is stable for Transverse Electric (TE) and Transverse Magnetic (TM) incidences up to 45°. The proposed converter's dual-polarized linear-cross and linear-circular conversion influence real-time THz applications significantly. © 2022 IEEE.

2022 IEEE International Conference on Emerging Electronics, ICEE 2022

Wideband Linear-Circular and Linear-Cross Angular Stable THz Reflective Polarizer with Circular Ring Based Frequency Selective Surface

In this article, a 3-bit Reconfigurable Intelligent Surface (RIS) based metasurface is implemented for 3.5 GHz sub-6 GHz applications. The unitcell consists of a modified square loop Frequency Selective Surface (FSS) printed on top of a 1 mm thin low-loss grounded dielectric substrate. Two vias are introduced at the centre of the square patch for the reflection phase optimization and HF tunable varactor diodes whose junction capacitance strongly influences the applied voltage. A total of eight different phase states were shown from -180° to 135° insteps of 45°, and the process behind the information encoding for 5G wireless applications is detailed. The angular stability of the reflection phase is investigated for different oblique incidences, and a considerably stable response is observed. Simulated surface current patterns are visualized at resonant frequency for understanding reflection phenomena. The design is compact with a periodicity of 0.058λL×0.058λLand possesses a low-profile thickness of 0.012λL. Authors believe this design has many beneficial features like 3-bit information encoding, angular stability, and compact architecture that play key roles in the RIS design in real-time 5G wireless applications. © 2022 IEEE.

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

Implementation of 3-Bit Reconfigurable Intelligent Surface (RIS) for Sub-6 GHz Range Based on Modified Square loop FSS and Tunable Varactors

This article implements the high gain superstrate antenna and wideband bandpass microwave filter using a novel uniplanar compact Electromagnetic Bandgap (EBG) structure. The proposed EBG unitcell consists of an outer inductive grid connected to four square loops at corners separated by a center-spitted Jerusalem cross resembled dipole. The design is printed on top of a 0.8 thin Rogers RT Duroid 5880 grounded dielectric substrate. Wide bandgap behavior is observed in the intended EBG from 9.6 GHz to 12 GHz (22.22% FBW). Here, the two different applications of the proposed EBG are presented, which gain the main focus of this work, i.e., EBG loaded microstrip filter and an EBG superstrate for a microstrip patch antenna (MPA) gain enhancement. The unitcell performance is stable for different oblique incidences under Transverse Electric (TE) and Transverse Magnetic (TM) modes. Compared to the reference antenna, the EBG-loaded patch exhibits a gain improvement, and 10.95 dBi is achieved along with bandwidth improvement. The C-band is the intended operating range of a proposed EBG-based wideband filter having less than 1.05 dB Insertion Loss (IL) over the operational range 5.26-13.32 GHz or 86.86%, and its passband BW covers from 5.30 - 13.71 GHz (88.48%). © 2022 IEEE.

Implementation of Wideband Filter and High Gain Antenna Using Novel Uniplanar Electromagnetic Bandgap Structure for X-Band Applications

The paper demonstrates a novel setup for near-field inductive wireless power transfer (WPT) working at two ISM (industrial, scientific and medical) bands (868-868.6 MHz and 902-928 MHz). The designed WPT setup consists of modified loop antennas at the transmitting and receiving front-end, a voltage doubler circuit acting as a power detector, and a homogeneous phantom mimicking the human body. The setup is capable of supplying maximum DC power of about 350 μW at the output for an input radio frequency (RF) power of 30 dBm. The DC output power can be used in driving implanted sensors for pacemaker and glucose monitoring systems. © 2022 IEEE.

Near-Field Inductive Wireless Power Transfer at ISM Bands for Biomedical Applications

A novel interdigital capacitance (IDC) frequency selective surface (FSS) based linear-cross reflective polarizer for K- and Ka-band applications is demonstrated in this work. The suggested device includes an IDC-loaded dipole printed on a thin FR-4 grounded dielectric substrate. From 17.02 to 37.30 GHz, it shows linear-cross conversion with a minimum 90% polarization conversion ratio (PCR) of 20.28 GHz bandwidth (74.7% fractional bandwidth [FBW]) for a y/x polarized incident electromagnetic (EM) wave. Along with linear-cross conversion, this polarizer also performs linear-circular conversions with axial ratio ≤ 3 dB in two frequency bands (Ku band-right circular, 15.13–16.15 GHz; Ka-band-left circular, 38.52–39.78 GHz) with 6.52%, and 3.14% FBW, respectively. The design performance is stable up to 45° for both transverse electric (TE) and transverse magnetic (TM) modes. The polarizer unitcell has structural dimensions 0.177 × 0.177 × 0.061 (Formula presented.) where λL corresponds to the free-space wavelength of the lowest working frequency. The polariser's transmission line equivalent circuit model is extracted, and a good match is observed with the EM solver response. The broadband behavior of FSS and the ground plane is better understood by looking at surface current patterns at resonant frequencies. The proposed design's radar cross-section (RCS) analysis is compared to perfect electric conductor for the bistatic condition. The design novelty lies in its compact architectural volume of the unitcell 1.911 (Formula presented.)), low-profile, broadband PCR response with superior angle stability, dual-polarization conversion with circular rotation switching makes it a good option for real-time applications. © 2022 Wiley Periodicals LLC.

International Journal of RF and Microwave Computer-Aided Engineering

A novel broadband linear-cross and linear-circular reflective polarizer based on interdigital capacitance loaded dipole for radar cross-section applications

This paper describes a Planer Inverted F Antenna (PIFA) that can be used as a microwave imaging transducer. The planned antenna has a peak gain of 4.6 dBi at 1.7 GHz and operates between 1.68 and 1.71 GHz. The shape and performance of the proposed antenna are first investigated. This study investigates its applicability for imaging two cylindrical metallic objects followed by a metallic beam veiled by a cotton material. © 2022 IEEE.