Balanced Antipodal Vivaldi Antenna Research Articles

Design and Development of a High-Gain Broadband Balanced Antipodal Vivaldi Antenna Using a 3D-Printed Shaped Dielectric Lens

Design and Development of a High-Gain Broadband Balanced Antipodal Vivaldi Antenna Using a 3D-Printed Shaped Dielectric Lens

A compact Balanced Antipodal Vivaldi Antenna with improved phase center stability for imaging and ultrawideband localization applications

This paper introduces a phase center stability improved Balanced Antipodal Vivaldi Antenna (BAVA) loaded with ‘I’ shaped non-resonant director array. The proposed antenna operates from 6 GHz to 18 GHz with S11 less than −10 dB and addresses the issue of phase reversal. The rectification of phase reversal produces enhanced phase center stability. Standard deviation is used to find least dispersed set of the phase center span calculated by varying design parameters of the director through a parametric study. By effective circumventing of phase reversal through improved coupling between the signal and ground planes, the proposed antenna achieves a maximum of 65.31% of improvement of phase center stability when compared to the reported Vivaldi antennas. In addition, further fine tuning of H-plane phase center stability for phi-components of about 6.5% at higher frequencies of operation is also attained using a meander-line section in the feed. With a size of 3.2λ0×1.6λ0×0.02032λ0 mm3, the proposed antenna exhibits sustained radiation patterns. Where λ0 is free space wavelength at 12 GHz. Full wave simulation of the design using CST microwave studio and experimental validation with a fabricated prototype are carried out.

Beam‐squint rectified balanced antipodal Vivaldi antenna with sliced fins and quarter‐wavelength labyrinth director

AbstractThis paper introduces a gain‐enhanced, beam‐squint rectified balanced antipodal Vivaldi antenna (BAVA) with symmetrically sliced fins and a novel square‐shaped metallic labyrinth director. The proposed antenna operates from 2 to 18 GHz with S11 less than −10 dB maintaining a fractional bandwidth of 160%, realizes 12.564 dBi as maximum gain at 18 GHz, and achieves greater than 3.415 dBi gain throughout the functioning band of frequency. Improvement of broadside gain by reconfiguration of current loops through symmetric slicing of radiating flares and beam‐squint correction using quarter‐wavelength labyrinth director are addressed by the proposed antenna. The maximum realized size of the antenna is 80 × 40 × 0.508 mm3. Consistent radiation patterns are observed at selected frequencies. Numerical evaluation with a full wave simulation tool and consequent experimental validation with a compact antenna test range is performed.

A UWB Low-Profile Hemispherical Array for Wide Angle Scanning

We report the first low-profile array on a doubly curved surface that supports wide angle electronic scanning and ultrawide bandwidth (7:1 ratio). The array elements are based on the balanced antipodal Vivaldi antenna (BAVA). The antennas are optimized for a good impedance match in an infinite planar array environment and are then deformed to fit along the surface of a hemisphere. The array is comprised of 104 linearly polarized BAVA elements arranged along a quadrilateral mesh on the surface of a 100 mm diameter hemisphere. The antennas and SMP connectors are 3-D printed out of titanium. The array has grating lobe-free operation at frequencies < 8 GHz. The array can also maintain relatively low sidelobe levels above 8 GHz compared with planar arrays because the aperiodicity of the hemispherical element locations reduces the magnitude of grating lobes. The simulated and measured realized gain is within 1 dB of the theoretical limit from 2.5–18 GHz and scan angles with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta \le {\mathrm {90}}^{\circ }$ </tex-math></inline-formula> except near 14 GHz where a resonance reduces the gain by 3 dB for some scan angles.

Asymmetric meshed ground Balanced Antipodal Vivaldi Antenna with quarter-wavelength labyrinth director for ultrawideband microwave applications

This paper introduces a new compact Balanced Antipodal Vivaldi Antenna (BAVA) with asymmetrically meshed ground, square shaped metallic labyrinth and dual scale edge treatment. The proposed antenna operates from 4 GHz to 18 GHz with S11 less than −10 dB, 127.27% fractional bandwidth and realizes greater than 4.01 dBi gain throughout the functioning band of frequency and achieves a maximum of 13.46 dBi at 17 GHz. Group delay of less than 5 ns signatures are realized. Improvement of operating bandwidth through enhanced impedance matching by finely meshed pattern on the ground planes and containment of rate of change of deflection angle using quarter-wavelength labyrinth director are addressed by the proposed antenna. The maximum realized size of the antenna is 80 × 40 × 0.508mm3. In addition, consistent radiation patterns are observed at selected frequencies. Numerical analysis with a full wave simulation tool is performed to calculate the radiation characteristics of the antenna and are experimentally validated.

An ultrawideband balanced antipodal vivaldi antenna for medical imaging applications with performance analysis for different surface finish materials

An ultrawideband balanced antipodal vivaldi antenna for medical imaging applications with performance analysis for different surface finish materials

An Optimum Design of Paired Balanced Antipodal Vivaldi Antennas With Mirror-Imaged Symmetric Architectures for Ultra-Broadband Characteristics From Microwave to Millimeter-Wave Frequency Ranges

This paper presents a balanced antipodal Vivaldi antenna design to produce ultra-broadband radiations from microwave to millimeter-wave frequencies. In particular, this work relaxes the design constraints in [1] to optimize the geometrical parameters to broaden the operational frequency bandwidth, where 147% relative bandwidth has been achieved. Moreover, in this optimized design, the beam squint and cross-polarization (X-pol) discrepancy at high frequencies are improved by pairing two mirror-imaged antenna structures to form an integrated one. The resulted X-pol level can retain good performance in the entire band. The beam squint can be minimized by taking advantage of the 3dB gain increase provided by the array factor. HFSS full-wave simulations first examine the proposed work, further validated by measurement from a basic antenna prototype. The beam squint is less than 3 degrees in the major middle part of the achieved band, and the X-pol level is less than -30dB for the paired antennas.

A Survey of Performance Enhancement Techniques of Antipodal Vivaldi Antenna

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.

Design an Ultra- Wideband Modified Wilkinson Power Divider Fed-by Balanced Antipodal Vivaldi Antenna Array for Imaging Applications

this paper, design of compactand modified geometrical structure of 1-to-4 way ultra-wideband Wilkinson power divider used as a feeding network for 4-element of balanced antipodal Vivaldi antenna (BAVA) array has introduced. The proposed Wilkinson power divider has been designed and printed on low-cost Epoxy laminate substrate FR4 along with the thickness of 1.6mm and relative permittivity of ɛr =4.3 respectively. The transformation of power divider network which are based on bent corners as a replacement of sharp corners or edges used for the decrement in unintended radiation and employing a single radial stub on each branch to encounter the antenna-specifications. Further some adjustments in the dimension of stubs matching in order to increase the reflection of the power divider network. The design presents the model of a power divider and maintains an equal power splitting at different ports with practical insertion loss and conventional return loss below -10dB. The reasonable impedance matching has achieved at every single port with acceptable isolation performance values over the (3-to-10 GHz) frequency range. The divider as well as antenna elements design and its optimization are practicable via computer simulation technology (CST) simulation software. The experimental results are revealed to encounter the array-specifications under ultra-wideband frequency range.

Design of 2-18 GHz balanced antipodal Vivaldi antennas using substrate-integrated lenses

ABSTRACTConventional balanced antipodal Vivaldi antennas (BAVAs) normally have deep ripple levels in E-plane mainlobe region and significant H-plane beamwidth variation over upper frequency band, which are drawbacks for ultra-wideband (UWB) applications. To overcome these issues, this paper introduces two types of lens configurations in front of BAVA. A gradient-index semi-cylindrical lens and a cylindrical lens are employed to improve ripples depth of E-plane mainlobe and broaden H-plane beamwidth, respectively. Both these lenses and BAVA are integrated on the same substrate and the desired refractive indexes of lenses are realized by a combination of a set of air-filled holes in the substrate. Prototypes of the modified BAVA with lenses (BAVA-Ls) are designed, fabricated and experimentally investigated as well. Measured results show close agreement with simulation. The proposed BAVA-Ls exhibit promising performances such as smaller ripple levels in E-plane mainlobe, wider H-plane beamwidth, higher aperture efficiency, and excellent group delay, while maintaining good bandwidth characteristics over 2–18 GHz.

Design of 2 to 18 GHz balanced antipodal Vivaldi antennas using substrate-integrated lenses

ABSTRACTConventional balanced antipodal Vivaldi antennas (BAVAs) normally have deep ripple levels in E-plane mainlobe region and significant H-plane beamwidth variation over upper frequency band, which are drawbacks for ultra-wideband (UWB) applications. To overcome these issues, this paper introduces two types of lens configurations in front of BAVA. A gradient-index semi-cylindrical lens and a cylindrical lens are employed to improve ripples depth of E-plane mainlobe and broaden H-plane beamwidth, respectively. Both these lenses and BAVA are integrated on the same substrate and the desired refractive indexes of lenses are realized by a combination of a set of air-filled holes in the substrate. Prototypes of the modified BAVA with lenses (BAVA-Ls) are designed, fabricated, and experimentally investigated as well. Measured results show close agreement with simulation. The proposed BAVA-Ls exhibit promising performances such as smaller ripple levels in E-plane mainlobe, wider H-plane beamwidth, higher aperture efficiency, and excellent group delay, while maintaining good bandwidth characteristics over 2 to 18 GHz.

Balanced Antipodal Vivaldi Antenna With Asymmetric Substrate Cutout and Dual-Scale Slotted Edges for Ultrawideband Operation at Millimeter-Wave Frequencies

This communication examines how to improve the squinted radiation patterns produced by the balanced antipodal Vivaldi antenna (BAVA) while retaining its cross-polarization levels. In particular, we propose discarding the redundant substrate between the metal flares of the BAVA and implementing dual-scale slotted edges to improve the radiation characteristics. The gain at both the lower and the higher end of the band is significantly enhanced without increasing the antenna size. Moreover, significant reduction in the beam squint relative to the conventional BAVA designs is achieved. A microstrip-to-stripline transition is also introduced to improve low-end matching. The final design operates over 10–40 GHz with return loss <−10 dB, providing sufficient bandwidth and match for a variety of applications at millimeter-wave frequencies. Numerical and experimental assessments to validate the proposed antenna design are conducted.

From narrow-band to ultra-wide-band microwave sensors in direct skin contact for breast cancer detection

In this paper, the design and test of different microwave antennas and sensors for breast cancer detection are presented. The sensors are designed and optimized to be used in direct skin contact, and for this purpose a specific breast phantom model is proposed. First, a miniaturized microstrip back-cavity Hilbert fractal antenna, operating in the ISM band (2.4–2.5 GHz), was designed. Then, this antenna was used to investigate the possibility of detecting the presence of breast tumors based on a narrowband frequency method that monitors the shift of the antenna frequency response. The antenna prototype was fabricated and tested in real in vivo measurement conditions on two different patients diagnosed with breast cancer. Measurement results have led after a comparison with the retro-simulation results of the structure to a more realistic breast model and to draw the limitations of this narrowband frequency method. As a time domain study seems to be more relevant, an UWB monopole antenna of dimensions 3 cm × 3 cm, to be used in direct contact with the breast model was designed. This antenna was optimized to both enhance the antenna/human body matching and to maximize the transfer of energy into the breast phantom by using a cavity, increasing by this way the detection potential. In order to improve the sensor’s directivity and enhance the electromagnetic field level inside the breast, a balanced antipodal Vivaldi antenna was also designed and optimized for a direct breast contact to operate in the 3.1–10.6 GHz band. A mono static and a bi static study in the time domain are finally proposed to investigate the presence of the tumor.

Antipodal Vivaldi antenna with novel differentially fed structure for lowering cross‐polarisation level

A novel differentially fed double-slot structure with two metal layers is proposed for an antipodal Vivaldi antenna. When fed differentially, the slots can have their E-field vectors summed to an E-field vector parallel to the layers, which endows the antenna with a significantly lowered cross-polarisation level by comparison with a typical antipodal Vivaldi antenna whose E-field vectors in the slot are skewed to the layers. A wideband balun based on a double-sided parallel stripline is used to realise the demanded differential feeding. The simulation and measurement are carried out to validate the remarkable characteristic of a two-layer structure, which is simpler than a three-layer structure of a balanced antipodal Vivaldi antenna.

WIDEBAND BALANCED ANTIPODAL VIVALDI ANTENNA WITH ENHANCED RADIATION PARAMETERS

WIDEBAND BALANCED ANTIPODAL VIVALDI ANTENNA WITH ENHANCED RADIATION PARAMETERS

Dielectric lens balanced antipodal Vivaldi antenna with low cross‐polarisation for ultra‐wideband applications

The major deficiency of conventional ‘balanced antipodal Vivaldi antenna’ (BAVA) is its tilted beam over upper working frequencies. This study reports on a new BAVA to overcome this defect. By applying a dielectric lens in front of the antenna's aperture, beam-tilting in E-plane was improved within the ultra-wideband frequency range, as well as higher frequencies. In the new BAVA, the authors have also achieved an acceptable cross-polarisation. Measurements show that the antenna has better than 10 dB return loss within the aforesaid frequency range. The measurements successfully verify the simulation results. Group delay and fidelity factor as time domain characteristics of the proposed antenna have been studied. They have compared performance of the conventional BAVA, with achievements of the new BAVA as hereunder.

A modified balanced antipodal vivaldi antenna with improved radiation characteristics

AbstractA modified corrugated balanced antipodal Vivaldi antenna with director (CBAVA‐D) is presented for ultrawideband (UWB) applications in this article. The main features of the antenna, besides an UWB width are high gain, low cross‐polarization, and excellent group delay. The new antenna concept, including the hybrid structure of exponential tapered corrugation edge and curving dielectric director with high‐dielectric constant is demonstrated, based on simulation and measurement results in both frequency and time domain. The antenna prototype input match is better than −10 dB, the maximal gain of 12.6 dB and the cross‐polarization level less than −30 dB in the main beam direction at 1.5–15 GHz band are achieved. In the time domain measured group delay with variation less than ±0.25 ns in the whole operating band is also obtained and exhibited. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1321–1325, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27558

DESIGN OF MODIFIED 6-18 GHz BALANCED ANTIPODAL VIVALDI ANTENNA

In this paper, a modifled planar balanced Vivaldi antenna with endflre characteristics near the metal surface is proposed for 6{18GHz applications. The proposed antenna structure consists of three copper layers, among which two external layers locate on the two outsides of two dielectric substrates, and the central layer is sandwiched by these two dielectric substrates. To further enhance the end-flre radiation characteristic, a number of novel techniques are proposed, including elongation and shaping of the supporting substrate of a conventional balanced antipodal Vivaldi antenna beyond its aperture, using an I-shaped slot loaded radiation patch and cutting a triangle on the edge of three copper layers. Measured and simulated results show that the proposed antenna not only exhibits good impedance bandwidth, but also improves the end-flre performance in the operational frequency of 6{10GHz and achieves high gain in the end-flre direction, low cross-polarization and high front-to-back (F-to- B) ratio.

The Banyan Tree Antenna Array

A new wideband, wide-scan array is introduced, called the Banyan Tree Antenna (BTA) array, that employs modular, low-profile, low-cost elements fed directly from standard unbalanced RF interfaces. The elements consist of vertically-integrated, flared metallic fins over a ground plane that are excited by a vertical two conductor unbalanced transmission line. The antenna resembles the bunny-ear or balanced antipodal Vivaldi antenna (BAVA) designs, but most importantly uses metallic shorting posts between the fins and the ground plane that suppress a mid-band catastrophic common-mode resonance that occurs in 2D arrays of balanced radiators fed with unbalanced feeds. This work introduces simple circuit models that describe key performance attributes of the BTA array, leading to unique physical insights and design guidelines. Simulations of infinite single- and dual-polarized BTA arrays have achieved approximately two octaves of bandwidth for VSWR <; 2.2 at broadside and VSWR <; 2.8 at scans out to θ = 45°, while maintaining better than 14 dB polarization purity at θ = 45° in the D-plane.

Gain and radiation pattern enhancement of balanced antipodal Vivaldi antenna

Balanced antipodal Vivaldi antennas normally suffer from tilted beams and low axial gains. A simple technique, based on the substrate end shaping, is used to correct both problems. Consequently, the resulting antennas provide high axial gains, within a wide frequency band. Their performance is compared with the conventional Vivaldi antenna, and the improvements are discussed.