Rajesh Natarajan

Bio: Rajesh Natarajan is an academic researcher from VIT University. The author has contributed to research in topics: Radiation pattern & Vivaldi antenna. The author has an hindex of 10, co-authored 18 publications receiving 383 citations. Previous affiliations of Rajesh Natarajan include Valliammai Engineering College & Anna University.

A Compact Frequency Selective Surface With Stable Response for WLAN Applications

Abstract: In this letter, a compact frequency selective surface (FSS) composed of a modified swastika unit cell having the smallest dimension of 7 × 7 mm2 is proposed. The design is aimed at the rejection of 5-GHz WLAN band. The unit-cell geometry resembles the shape of crossed dipoles to achieve compactness. The proposed FSS provides 400 MHz bandwidth with 20 dB insertion loss. The proposed design holds a stable response for TE and TM modes of polarization as well as oblique incidence angles, thus ensuring polarization and angular independent operation. The simulated results are validated with measured results obtained from the fabricated FSS.

A Compact Antipodal Vivaldi Antenna for UWB Applications

Abstract: A compact antipodal Vivaldi antenna (AVA) with the dimension of $42 \times 36 \times 1.6~\hbox{mm}{^3}$ is proposed in this letter. Structural modifications in the radiating fins have increased the electrical length thereby reducing the lower operating frequency from 5.2 GHz to 3.7 GHz. Proposed antenna maintains $-20~\hbox{dB}$ copolarization to cross-polarization ratio throughout the operating bandwidth. The prototype is fabricated and the measurement results are presented to validate the performance of the proposed AVA.

Triband Antenna Structures for RFID Systems Deploying Fractal Geometry

Abstract: In this letter, two triband RFID antennas are proposed, one for the radio frequency identification (RFID) reader and the other for the RFID tag. The antenna is the crucial part in designing any RFID system. The reader antenna operates at 3.6, 5.8, and 8.2 GHz. The tag antenna operating frequencies are 3.9, 5.9, and 8.2 GHz. The applications of these frequencies are RFID for logistics management, traffic toll collection, and tagometry (telemetry using RFID), respectively. Fractal structures are employed as radiating elements for this multiband antenna.

Compact Monopole Antenna Backed With Fork-Slotted EBG for Wearable Applications

Abstract: A compact, low-profile ultrawideband directional antenna for a wireless body area network (WBAN) is reported in this letter. The directional antenna is designed using a monopole backed with an electromagnetic bandgap (EBG) structure, which acts as a reflector. The beveled Y-shaped monopole antenna covers the ultrawide bandwidth from 3.1 to 10.6 GHz. The monopole antenna backed with a fork-slotted EBG is designed with a size of 8 × 8 mm2. The 2 × 1 EBG array is printed on the same plane above the partial ground. This integrated structure provides band-stop characteristics from 3.1 to 10.6 GHz with a directional radiation pattern intended for wearable applications. It also acts as a protective shield against the electromagnetic radiation emerging from the monopole antenna toward the body tissue. The proposed directional antenna provides a peak gain of 6.25 dBi with high radiation and total efficiency. The calculated specific absorption rate value is 0.695 W/Kg, which is well below the desired 1.6 W/kg.

An Integrated Tri-Band/UWB Polarization Diversity Antenna for Vehicular Networks

Abstract: The design, fabrication, and testing of an integrated polarization diversity antenna array for maximizing the wireless channel link in vehicular networks are presented in this paper. The diversity antenna is constructed using unit cell radiators that provide two operating modes. The mode transition is achieved using a pair of PIN diodes. In one state, the antenna provides multiband operation centered at 2.4, 3.5, and 5.8 GHz. In the other state, the antenna covers the entire ultra-wideband (UWB) spectrum. The unit cell radiators are distributed in the horizontal and vertical plane to achieve polarization diversity. Apart from offering a polarization diversity antenna, the orientation of antennas offers a reliable link with the communication devices. The prototype antenna array is fabricated and tested for diversity performance. The performance metrics such as envelope correlation coefficient, diversity gain, and mean effective gain under isotropic, indoor, and outdoor conditions are evaluated and presented.

A Single-Layer Frequency-Selective Surface for Ultrawideband Electromagnetic Shielding

Abstract: An efficient approach to achieve the shielding effectiveness (SE) by using a frequency-selective surface (FSS) is presented. This FSS, which consists of cross dipoles and rings printed on the opposite sides of a single-layer FR-4 substrate, exhibits a wide, 7.5-GHz stopband to provide simultaneous shielding in both X- and Ka-bands. Experimental results confirm SE of the prototype over an ultra-wide band with more than 20-dB measured attenuation. The design is compact and suitable to provide shielding against the radiation interference caused by license-free and other radio systems.

Research Advances and Challenges of Autonomous and Connected Ground Vehicles

Abstract: Autonomous vehicle (AV) technology can provide a safe and convenient transportation solution for the public, but the complex and various environments in the real world make it difficult to operate safely and reliably. A connected autonomous vehicle (CAV) is an AV with vehicle connectivity capability, which enhances the situational awareness of the AV and enables the cooperation between AVs. Hence, CAV technology can enhance the capabilities and robustness of AV to be a promising transportation solution in the future. This paper introduces a representative architecture of CAVs and surveys the latest research advances, methods, and algorithms for sensing, perception, planning, and control of CAVs. It reviews the state-of-the-art and state-of-the-practice (when applicable) of a multi-layer Perception-Planning-Control architecture including on-board sensors and vehicular communications, the methods of sensor fusion and localization and mapping in the perception layer, the algorithms of decision making and trajectory planning in the planning layer, and the control strategies of trajectory tracking in the control layer. Furthermore, the implementations and impact of vehicle connectivity and the corresponding consequential challenges of cooperative perception, complex connected decision making, and multi-vehicle controls are summarized and their significant research issues enumerated. Most importantly, the critical review in this paper provides a list and discussion of the remaining challenges and unsolved problems of CAVs in each Section which would be helpful to researchers in the field. The comprehensive coverage of this paper makes it particularly useful to academic researchers, practitioners, and students alike.

Dual-Band EBG Integrated Monopole Antenna Deploying Fractal Geometry for Wearable Applications

Abstract: This letter presents the design of a dual-band wearable fractal-based monopole patch antenna integrated with an electromagnetic band-gap (EBG) structure. The prototype covers the GSM-1800 MHz and ISM-2.45 GHz bands. The EBG structure reduces the radiation into the human body over 15 dB. It also reduces the effect of frequency detuning due to the human body. The performance of the antenna under bending, crumpling, and on-body conditions has been studied and presented. Specific absorption rate (SAR) assessment has also been performed to validate the antenna for its usefulness in wearable applications.

A Low Cost and Portable Microwave Imaging System for Breast Tumor Detection Using UWB Directional Antenna array

Abstract: Globally, breast cancer is a major reason for female mortality. Due to the limitations of current clinical imaging, the researchers are encouraged to explore alternative and complementary tools to available techniques to detect the breast tumor in an earlier stage. This article outlines a new, portable, and low-cost microwave imaging (MWI) system using an iterative enhancing technique for breast imaging. A compact side slotted tapered slot antenna is designed for microwave imaging. The radiating fins of tapered slot antenna are modified by etching nine rectangular side slots. The irregular slots on the radiating fins enhance the electrical length as well as produce strong directive radiation due to the suppression of induced surface currents that radiate vertically at the outer edges of the radiating arms with end-fire direction. It has remarkable effects on efficiency and gain. With the addition of slots, the side-lobe levels are reduced, the gain of the main-lobe is increased and corrects the squint effects simultaneously, thus improving the characteristics of the radiation. For experimental validation, a heterogeneous breast phantom was developed that contains dielectric properties identical to real breast tissues with the inclusion of tumors. An alternative PC controlled and microcontroller-based mechanical MWI system is designed and developed to collect the antenna scattering signal. The radiated backscattered signals from the targeted area of the human body are analyzed to reveal the changes in dielectric properties in tissues. The dielectric constants of tumorous cells are higher than that of normal tissues due to their higher water content. The remarkable deviation of the scattered field is processed by using newly proposed Iteratively Corrected Delay and Sum (IC-DAS) algorithm and the reconstruction of the image of the phantom interior is done. The developed UWB (Ultra-Wideband) antenna based MWI has been able to perform the detection of tumorous cells in breast phantom that can pave the way to saving lives.