Jithila V. George

Bio: Jithila V. George is an academic researcher from Anna University. The author has contributed to research in topics: Antenna measurement & Antenna factor. The author has an hindex of 4, co-authored 6 publications receiving 120 citations.

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.

Modified antipodal Vivaldi antenna for ultra-wideband communications

Abstract: In this study, a modified antipodal Vivaldi antenna (AVA) with low cross-polarisation is proposed for ultra-wideband communications. The bandwidth offered by conventional single petal AVA is enhanced by adding another petal. This dual petal antenna occupies a small volume of 60 × 60 × 0.8 mm 3 and provides operating bandwidth from 2.4 GHz to frequencies >14 GHz. The proposed antenna configuration provides low cross-polarisation level which is 5 dB and an average group delay variation of 0.5 ns. The prototype antenna is fabricated and tested to validate the simulation results.

Design of an X-band Vivaldi antenna with low radar cross section

Abstract: In this study, a passive Vivaldi antenna design is proposed for radar cross section (RCS) reduction using object shaping method. The implementation of annular slot along with exponential curves in the radiator reduced the scattering along the surface of the radiator. This contributes reduction in structural mode RCS throughout the operational bandwidth without affecting the impedance performance of the antenna. Monostatic RCS of the antenna is discussed for two incident angles. A minimum RCS reduction of 13 dB is achieved when the incident angle is Θ = 60° and a maximum of 19 dB reduction is achieved at Θ = 75°. The proposed antenna offers symmetric radiation pattern in both azimuth and elevation planes and also maintains co-polarisation to cross-polarisation ratio of 19 dB throughout the X-band (8–12 GHz). Prototype antenna is fabricated and tested to validate the simulated results.

Quad-Band Diversity Antenna for Automotive Environment

Abstract: A compact, unilateral grounded Coplanar Strip (CS) antenna for automotive communications is presented in this letter. The antenna is designed for quad band operation covering DCS1800, IEEE 802.11b/g/n standards, Wi-MAX, Vehicle-to-Vehicle (V2V), and Vehicle-to-Infrastructure (V2I) Communications. A simple folded microstrip line radiator along with unilateral ground plane of CS is attempted to generate the required frequency bands. To achieve polarization and pattern diversity functionality, a 4 port diversity antenna array is developed. The antenna unit cells are spaced $0.125{\lambda _{{\rm g}1}}$ calculated at the lowest resonant frequency and are oriented orthogonal to adjacent unit cells to achieve high isolation greater than 20 dB, correlation coefficient less than 0.25 and diversity gain greater than 9.5 dB. The proposed antenna is suitable for automotive communications as it can be conveniently placed anywhere inside the vehicle more specifically in the wind screen, side mirrors and fenders.

Dual-frequency phase shifter deploying complementary split-ring resonator

Abstract: Phase shifters are indispensable microwave components. In this paper, a dual-frequency, passive, analog, and reciprocal phase shifter is proposed, deploying the phase-delay characteristics of complementary split-ring resonator (CSRR). A transmission line is loaded with a pair of CSRR in the ground plane and the phase variations are compared with an ideal transmission line. The proposed phase shifter operates in the industrial, scientific and medical (ISM) and wireless local area network (WLAN) bands, providing a phase of 180° at 2.4 GHz and 90° at 5.4 GHz for beam steering 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.

A Survey of Performance Enhancement Techniques of Antipodal Vivaldi Antenna

Abstract: The increasing proliferation of advanced devices for UWB, 5G communication, micrometer-wave, and millimeter-wave communication demands an antenna which can handle huge data rates, provides high gain and stable radiation pattern as a panacea of most of the current wireless communication problems. Many different antenna designs have been proposed by the researchers but, Antipodal Vivaldi Antenna (AVA) has drawn the attention of most of the researchers because of its high gain, wide bandwidth, less radiation loss, and stable radiation pattern. Different methods are presented to make AVA more compact while maintaining the performance of an antenna to an acceptable level. These different methods are substrate choice, flare shape, slots, and feeding connectors. Also, AVA performance can be enhanced by incorporating corrugation, dielectric lens, patch in between two flares of AVA, balanced AVA (BAVA), metamaterial, computational intelligence (CI), and AVA array. The AVA performance enhancement techniques modify the electrical and physical properties of an antenna which in turn improves its performance. A large number of performance enhancement methods of AVA design have been proposed, however, no comprehensive study exists to categorize these performance enhancement techniques and outline their concepts, advantages, disadvantages, and applications. So, in this paper, we have attempted to outline all methods available for enhancing and optimizing the parameters of AVA. Additionally, to validate some of the important performance enhancement methods, they are incorporated in the basic conventional AVA design and further simulation results are obtained for the same which are in line with the surveyed literature. Each method is explained in detail by incorporating its key points, merits, and demerits. Moreover, illustrations from the literature are given to demonstrate improvement in the parameters as a result of applying a particular performance enhancement technique.

Miniaturized UWB Antipodal Vivaldi Antenna and its Application for Detection of Void inside Concrete Specimens

Abstract: A miniaturized antipodal Vivaldi antenna to operate from 1 to 30 GHz is designed for nondestructive testing and evaluation of construction materials, such as concrete, polymers, and dielectric composites. A step-by-step procedure has been employed to design and optimize performance of the proposed antenna. First, a conventional antipodal Vivaldi antenna (CAVA) is designed as a reference. Second, the CAVA is shortened to have a small size of the CAVA. Third, to extend the low end of frequency band, the inner edges of the top and bottom radiators of the shortened CAVA have been bent. To enhance gain at lower frequencies, regular slit edge technique is employed. Finally, a half elliptical-shaped dielectric lens as an extension of the antenna substrate is added to the antenna to feature high gain and front-to-back ratio. A prototype of the antenna is employed as a part of the microwave imaging system to detect voids inside concrete specimen. High-range resolution images of voids are achieved by applying synthetic aperture radar algorithm.

3-D Eight-Port Ultrawideband Antenna Array for Diversity Applications

Abstract: This letter presents an eight-port, multiple-polarization, ultrawideband (UWB) diversity antenna array. The unit-cell antenna is constructed from a basic square monopole antenna. With suitable modifications in the radiating plane and the ground plane, the unit-cell antenna is designed to operate between 2.9–12 GHz to cover the entire UWB range. The designed UWB radiator is then replicated within a small space to generate triple polarization. The proposed diversity antenna array consists of eight uncorrelated antennas, of which four are horizontally oriented and the remaining four are vertically oriented to achieve polarization diversity. Diversity performance metrics such as envelope correlation coefficient, apparent diversity gain, and effective diversity gain are evaluated and presented. The prototype diversity antenna is fabricated, and experimental results are presented.

Ultra-wideband (UWB) antenna sensor based microwave breast imaging: A review

Abstract: Globally, breast cancer is reported as a primary cause of death in women. More than 1.8 million new breast cancer cases are diagnosed every year. Because of the current limitations on clinical imaging, researchers are motivated to investigate complementary tools and alternatives to available techniques for detecting breast cancer in earlier stages. This article presents a review of concepts and electromagnetic techniques for microwave breast imaging. More specifically, this work reviews ultra-wideband (UWB) antenna sensors and their current applications in medical imaging, leading to breast imaging. We review the use of UWB sensor based microwave energy in various imaging applications for breast tumor related diseases, tumor detection, and breast tumor detection. In microwave imaging, the back-scattered signals radiating by sensors from a human body are analyzed for changes in the electrical properties of tissues. Tumorous cells exhibit higher dielectric constants because of their high water content. The goal of this article is to provide microwave researchers with in-depth information on electromagnetic techniques for microwave imaging sensors and describe recent developments in these techniques.