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 work presents a modified Antipodal Vivaldi Antenna (AVA) designed for microwave and millimeter wave imaging applications. First the AVA is designed as reference. Then to obtain high gain at lower frequency, corrugations are added, followed by dielectric lens, metamaterial slabs and a dielectric cavity to improve the gain at higher frequencies to make the antenna desirable for microwave and millimeter wave imaging applications. The proposed structure demonstrates simulated return loss of > 10 dB over 2.2 - 50 GHz with a peak gain of 19 dBi at 32 GHz. © 2021 IEEE.

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Department of Electrical Engineering

2021 IEEE Asia-Pacific Microwave Conference (APMC), 49-51,

UWB Antipodal Vivaldi Antenna with Metamaterial Slabs and Dielectric Enclosure for Microwave to Millimeter Wave Imaging Applications

This work presents a high gain Ultra-Wideband (UWB) Antipodal Antenna (AA) with four paddle shaped stubs, an elliptical parasitic patch and a elliptical cylindrical dielectric enclosure utilizing a systematic approach, for microwave imaging of concealed metal objects. Initially the paddle shaped stubs are designed and their performance are optimized. Then, the elliptical patch is added to improve the high frequency performance. Lastly an elliptical cylindrical dielectric was introduced to further enhance the antenna performance. The proposed antenna provides simulated return loss of < 10 dB over 1.3 - 14 GHz with a simulated peak gain of 13.2 dBi at 10 GHz. © 2021 IEEE.

2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI {\ldots}

UWB Antipodal Antenna With Parasitic Patch and Elliptical Cylindrical Dielectric For Concealed Object Detection with Microwave Imaging

A simple broadband polarization-insensitive Circuit Analog Absorber (CAA) is proposed in this work. The unitcell comprises two Frequency Selective Surfaces (FSSs). The top FSS is an eight-lumped resistor-loaded corner modified square loop resonator, and the bottom is a circular ring with middle cuts. Both the FSS were printed on the thin FR-4 dielectric substrates, which were separated by an air-spacer. The proposed design exhibits 90% absorptivity from 6.72 GHz to 19.82 GHz (98.7% fractional bandwidth) with almost 95% absorption from 7.54 GHz to 17.85 GHz covering the whole X and Ku-bands. Because of four-fold symmetry exist in the design, it is polarization insensitive for different polarization angles (o) in the azimuthal plane, and it is obliquely stable up to 45° for both Transverse Magnetic (TM) and Transverse Electric (TE) modes in the elevation plane. The design is compact with a total thickness of0.081λL and a cell periodicity of 0.164λL, where λL is the free-space wavelength corresponding to the absorption bandwidth's lowest frequency. The proposed design's Radar Cross Section (RCS) ability is observed, and it shows a peak RCS reduction of 7.4 dBsm under normal incidence. According to the author's expertise, the design can be utilized in a variety of real-time applications. © 2021 IEEE.

2021 IEEE Indian Conference on Antennas and Propagation (InCAP)

A Novel Broadband Polarization Insensitive Circuit Analog Absorber (CAA) for Radar Cross Section (RCS) Reduction Applications at X. and Ku-Bands

This work describes a compact Double Ridge Horn (DRH) antenna utilized for ultra-wideband (UWB) Microwave Imaging (MI). The proposed DRH is appended with a dielectric lens in the flared region to improve its radiation performance. The suggested antenna achieves a wide impedance band from 1.2 GHz to 14 GHz with good impedance matching. The described antenna also attains a peak gain of 16 dBi at 8 GHz. The applicability of the put forward antenna for microwave imaging applications is tested by checking its Specific Absorption Rate (SAR) value and the antenna has been utilized to image a tumor in a realistic planar breast phantom. © 2021 IEEE.

Double Ridge Horn Antenna with Curved Dielectric Loading for Microwave Imaging Applications

This work presents a compact broadband wide angular stable polarization-insensitive circuit analog absorber at sub 6 GHz. It shows almost 95% absorption from 2.26 to 5.76 GHz over the entire operating range. A transmission line equivalent circuit is modeled, and the response is validated. The design is obliquely stable up to 45° for both transverse electric and transverse magnetic incidences. The analysis of surface current distributions at two resonant frequencies confirming magnetic resonances' role in near-unity absorption. It is compact with a periodicity of 0.1 λL and thickness of 0.08 λL. Finally, bistatic radar cross section reduction of the proposed absorber attached with an antenna is measured. © 2021 Wiley Periodicals LLC.

Microwave and Optical Technology Letters

Compact, broadband, wide angular stable circuit analog absorber at sub-6 GHz for radar cross section reduction

This paper presents two new compact unit cells for single and dual broadband linear co to cross-polarization conversion. Two metasurfaces are printed on perfect conductor-backed dielectric substrate. The first unit cell consists of slotted rectangular patch with meander line at the center. The structure exhibits a broadband linear cross conversion from 10.63-22.27 GHz (11.64 GHz or 70.8 %) with a polarization conversion ratio (PCR) is > 90 %. The converter response is found incidence angle stable up to 38°. Periodicity of the unit cell is 0.43 λ0, where λ0 is free-space wavelength. A linear dipole is incorporated in the first structure to realize the second converter with dual broadband characteristics. The design shows PCR > 80% from 7.28-10.52 GHz (36.4 %) and from 17.44-24.13 GHz (32.2 %). © 2021 IEEE.

Single/Dual Broad Band Reflective Type Linear Cross Polarization Converters With Slotted Meander Lines for X/Ku/K Band Applications

A novel reflective type linear-cross polarizer is proposed in this article for X-and Ku-bands. This design consists of top FSS, including a dipole covered with Interdigital Capacitances (IDCs) on its periphery on a 2.6 mm thin FR-4 dielectric substrate. The structure exhibits Polarization Conversion Ratio (PCR) greater than 90% from 7.94 to 17.77 GHz (76.46% Fractional Bandwidth), with three resonant peaks approaching the PCR nearly 100%. For oblique incidence TE and TM, the response is stable up to 45° up to 80% PCR and slightly reduced bandwidth. Multiple plasmonic resonances are the reason behind the broadband polarization conversion, and it is investigated from the surface current profiles of top FSS and ground planes. The novelty of this design exists in the introduction of IDCs, enabling the highest resonant peak tuning without degrading the performance on the lowest side. It possesses the unitcell periodicity and thickness of 0.185 λL and 0.069λL, respectively, where λL is the lowest broadband frequency's free-space wavelength. The authors are confident in the design's compactness, low profile, and angular stability, making it well-suited for real-time applications that need broadband linear-cross polarization conversion. © 2021 IEEE.

A Novel Interdigital Capacitances (IDCs) Based Linear-Cross Reflective Type Polarization Converter for X-and Ku-Band Applications

Analysis of Optimized Subarray Configuration for Cross Polarization Reduction for Phased Array Antennas used in Weather Radar

mmWave radars play a vital role in autonomous systems, such as unmanned aerial vehicles (UAVs), unmanned surface vehicles (USVs), ground station control and monitoring systems. The challenging task when using mmWave radars is to estimate the accurate angle of arrival (AoA) of the targets, due to the limited number of receivers. In this paper, we present a novel AoA estimation technique, using mmWave FMCW radars operating in the frequency range 77–81 GHz by utilizing the mechanical rotation. Rotating the radar also increases the field of view in both azimuth and elevation. The proposed method estimates the AoA of the targets, using only a single transmitter and receiver. The measurements are carried out in a variety of practical scenarios including pedestrians, a car, and an UAV, also known as a drone. With measured data, range-angle maps are created, and morphological operators are used to estimate the AoA of the targets. We also process radar range-angle images for improved visual representation. The proposed method will be extremely beneficial for practical ground stations, traffic control and monitoring frameworks for both on-ground and airborne vehicles. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

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Electronics (Switzerland)

Localization of multi-class on-road and aerial targets using mmwave FMCW radar

The optical pickup unit (OPU) is an optical assembly, which is used for reading and writing digital optical disks. It consists of a laser diode, quadrant photodetector, and other optical components to maintain focus. This arrangement of the laser and photodetector is very similar to those in expensive equipment, such as atomic force microscopes, used for nanoscale metrology. Many researchers have hence investigated the use of an OPU to design low-cost alternatives. However, these nonstandard uses of an OPU are challenging since the OPU has originally been optimized to sense reflections from the highly reflecting surface of an optical disk. In this work, we present a new synchronous detection-based method that improves the performance of the OPU in measuring the reflection from poorly reflecting substrates. This method utilizes the high bandwidth of both the laser and photodetector of the OPU. We excite the laser with a pulsed input and look for a signal at the pulsing frequency in the output from the OPU. This signal is further processed through a phase-sensitive detector. We show that this method reduces the offsets in the measurement and allows us to make effective use of a higher gain to measure the reflection from substrates with poor reflectivity. © 1963-2012 IEEE.