Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

This communication presents the design of a compact loop antenna with independent frequency tuning. The proposed antenna consists of a feed line fed by a 50Ω coaxial probe and four resonating arms on the adjacent sides of the feed line. The two outer resonating arms are directly coupled to the feed line and the other two inner resonating arms are coupled to the outer arms. The proposed antenna has a footprint of 25 mm × 10 mm ×0.2 mm. The designed antenna operates at 0.9, 2.4, 3.5, and 5.5 GHz. Each of these bands is individually tuned using varactor diodes. Thus, the aggregation of these tunable bands provides wide bandwidth. The impedance bandwidth and percentage bandwidth of the antenna are 270/1000/400/700 MHz and 33%/47.6%/11%/12.7%, respectively. Furthermore, the gain and efficiency of the antenna are 1.7/1.3/2.1/2 dBi and 60%/63%/65%/69%, respectively. The prototype antenna is fabricated and tested. The measured impedance and radiation characteristics of the antenna are in good correlation with the simulation results. © 1963-2012 IEEE.

World University root node

Department of Communication Engineering

School of Electronics Engineering

Vellore Campus

IEEE Transactions on Antennas and Propagation

A Compact Frequency-Reconfigurable Antenna with Independent Tuning for Hand-Held Wireless Devices

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. © 2002-2011 IEEE.

IEEE Antennas and Wireless Propagation Letters

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

A compact, low-profile button antenna for off-body communication is reported. The proposed antenna is composed of coupled circular strips, Y-shaped and L-shaped slots. This configuration covers the application bands such as 0.867 GHz (industrial, scientific, and medical bands), 2.38 GHz (medical body area network), and 5.8 GHz (wireless local area network/industrial, scientific, and medical bands). The percentage bandwidth obtained at the said operating bands is 4.37, 2.10, and 2.56, respectively. The directional radiation pattern obtained from the developed antenna ensures the low backward radiation to the body tissue, thereby, making it more suitable for WBAN applications. The simulated gain and efficiency obtained at the operating bands are 2.5/3.52/4.8 dBi and 78%/85%/89%, respectively. To validate the simulation results, the antenna is fabricated and some experimental results on the body tissue are performed. The SAR value obtained follows the Federal Communication Commission (FCC) limit. © 1963-2012 IEEE.

Miniaturized Button-Like WBAN Antenna for Off-Body Communication

This article presents the design of a three-port diversity antenna capable of producing three-directional radiation pattern for vehicular communications. The proposed antenna consists of three uncorrelated Vivaldi antennas that are interconnected and developed on a single printed circuit board. Unlike many other antennas reported for the vehicular environment, the proposed antenna offers ultra-wideband characteristics with end-fire radiation pattern leading to high realized antenna gain. The integrated antenna has a footprint of 65 × 40 × 1.6 mm3 and offers 6 GHz impedance bandwidth extending from 5 to 11 GHz. The port-to-port isolation is greater than 20 dB within the operating bandwidth. Furthermore, the diversity performance of the proposed three-port antenna system is evaluated and presented. The calculated envelope correlation coefficient, diversity gain, and mean effective gain are well above the minimum requirement. The prototype antenna is fabricated and the experimental results are presented. © 2019 Wiley Periodicals, Inc.

International Journal of RF and Microwave Computer-Aided Engineering

Integrated Vivaldi antenna for UWB/diversity applications in vehicular environment

A novel ellipsoid slot array integrated with the compact MIMO antenna accomplishes the increasing demand of customers with 4G and 5G application bands. The proposed antenna incorporates a front FR4 layer holding a planar radiator, ground plane etched with ellipsoid slot array and back FR4 layer with the corporate feed network. The corporate feed network delivers power to the framework of 2 × 4 matrix ellipsoid slot array in the ground plane. The front and the back FR4 layer are detached by the ground plane, which acts as both radiator as well as isolator. The ground plane containing ellipsoid slot array antenna resonates at 17 GHz. It also provides 25 dB isolation in the LTE application bands. This antenna arrangement achieves the impedance bandwidth of 600 MHz (2–2.6) GHz for LTE 2300 MHz, LTE 2500 MHz and 2 GHz (15–17) GHz for 17 GHz 5G application band. Apart from this, the simulated gain of 3.33/4.67/7.5 dBi and measured gain of 3.01/4.58/7.3 dBi is achieved for resonating frequencies such as 2.3/2.5/17 GHz. High efficiency of 84/91/90% is obtained for microwave and millimeter wave frequencies. Envelope correlation coefficient evaluated from the radiation pattern is found to be &lt; 0.5. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Wireless Personal Communications

Integration of Slot Array with MIMO Antenna for 4G and 5G Applications

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. © 1967-2012 IEEE.

Chennai Campus

IEEE Transactions on Vehicular Technology

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

This article presents the design and testing of a novel frequency reconfigurable microwave filter. The filter structure is composed of an all stop resonator coupled with C- and E-shaped parasitic resonators. PIN diodes are located at suitable positions to achieve multi-band reconfiguration from 1.2 to 3.2 GHz making the filter suitable for multiple wireless communication systems. The frequency and bandwidth of the filter are governed by the length of the resonators and coupling between the resonators and the transmission line, respectively. A sharp rejection of −30 dB is observed between the passbands. The proposed filter offers 56% size reduction with flat group delay performance. The prototype filter is fabricated and the simulation results are validated using experimental measurements. The measurement results show good agreement with the simulation results. © 2018 Wiley Periodicals, Inc.

Multi-band reconfigurable microwave filter using dual concentric resonators

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 mm3 and provides operating bandwidth from 2.4 GHz to frequencies &gt; 14 GHz. The proposed antenna configuration provides low cross-polarisation level which is &lt;-15 dB over the entire operational band. The designed antenna offers realised gain &gt; 5 dB and an average group delay variation of 0.5 ns. The prototype antenna is fabricated and tested to validate the simulation results. © The Institution of Engineering and Technology.

IET Microwaves, Antennas and Propagation

Modified antipodal Vivaldi antenna for ultra-wideband communications

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. © The Institution of Engineering and Technology 2016.

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

In this study, a dual mode antipodal Vivaldi antenna is developed to operate in ultra-wideband and two narrowbands [global system for mobile communication (GSM) 1800, wireless local area network (WLAN)]. The antenna provides an impedance bandwidth of 9.7 GHz in wideband mode and 800 MHz, 280 MHz (WLAN, GSM 1800) in narrowband mode at -10 dB reference level. The antenna maintains symmetric radiation pattern in both the principal planes and provides minimum gain of 6 dB in both narrowband and wideband mode. Additionally, radar cross-section performance of the antenna is calculated through simulation and discussed. Prototype antenna is fabricated with ideal switch and simulated results are validated through the measured results. © The Institution of Engineering and Technology 2016.

Dual mode antipodal Vivaldi antenna

A compact antipodal Vivaldi antenna (AVA) with the dimension of 42 × 36 × 1.6 mm3 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 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. © 2002-2011 IEEE.

A Compact Antipodal Vivaldi Antenna for UWB Applications

This paper describes a novel FSS which functions as band stop filter to shield the GSM 1800 MHz downlink band. The FSS is designed to operate with the resonant frequency of 1820 MHz which is the centre frequency for the GSM 1800 MHz downlink band. The novelty is attributed to its unique geometry and the circular apertures endowed with it. The proposed geometry provides shielding effectiveness of 20 dB alongside with 133 MHz bandwidth. The structure holds identical response for both TE and TM Modes of polarization. In addition, the geometry with its circular apertures, a hitherto unexplored feasibility serves the purpose of ventilation and heat dissipation. The simulated results are validated using experimental measurements.

Progress in Electromagnetics Research Letters

A novel shield for GSM 1800 MHz band using frequency selective surface

In this letter, a compact frequency selective surface (FSS) composed of a modified swastika unit cell having the smallest dimension of 7$\,\times\,$7 mm$2$ 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. © 2013 IEEE.

A compact frequency selective surface with stable response for WLAN applications

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. © 2002-2011 IEEE.