Conventional Antipodal Vivaldi Antenna Research Articles

Ultra‐wide Band Antipodal Vivaldi Antenna Using Metasurface Lens for Gain and Front‐To‐Back Ratio (FBR) Improvement

AbstractThis paper addresses the limited gain of conventional Antipodal Vivaldi Antenna (AVA) at higher frequencies. We propose a novel Metamaterial Lens Vivaldi Antenna (MLVA) design that overcomes this limitation by integrating an exponentially tapered antenna lens and a strategically placed Near Zero Refractive Index (NRZI) metamaterial lattice. The MLVA achieves exceptional wideband performance with a −3 dB gain bandwidth exceeding 148.6% from 3.7 to 25 GHz. The result demonstrates a peak realized gain of 11.8 dBi at 11.2 GHz, compared to 9.1 dBi conventional AVA, especially beyond 5 GHz. The compact MLVA design measures only 120 × 78 × 1.524 mm3 (1.48 × 0.96 × 0.0188λ03) λ0 where free‐space wavelength is the lowest frequency and is fabricated on RO4350 B substrate with a 50‐Ω SMA connector. Key features of the design include exponential flaring, and trapezoidal lens geometries chosen for their inherent ability to effectively collimate and direct the spherical wavefront. The incorporation of a dielectric lens and metasurface further enhances gain and Front‐to‐Back Ratio (FBR) by directing the majority of energy in the end‐fire direction. Experimental results validate the effectiveness of the proposed design, confirming simulation predictions. These outstanding characteristics make the MLVA a promising candidate for diverse wireless communication and radar applications demanding high data rates across a broad frequency range.

A low profile antipodal Vivaldi antenna with improved front‐to‐back ratio and sidelobe levels for 5G applications

In this article, a novel miniaturized antipodal Vivaldi antenna (AVA) is proposed with significant improvement in the back and sidelobe levels (SLLs) to mitigate their adverse effect on the communication system components. The proposed AVA enhances SLL up to −5.7 dB and front to back ratio (FBR) to 20.2 dB. These improvements are accomplished by antenna size reduction and gain enhancement. The proposed AVA is miniaturized by 22.27% and the gain is increased up to 4 dBi compared to the conventional AVA (CAVA). The AVA is designed by incorporating substrate integrated waveguide (SIW) and corrugations. The use of corrugations improves the FBR and gain. Next, the improvements in the bandwidth and SLL are achieved by SIW. The antenna dimensions are 15 × 6 × 0.5 mm3 and it provides the enhanced and almost constant gain of 9.5 ± 1.5 dBi. The antenna is designed for the 38 GHz band of 5G applications and it has an impedance bandwidth of 36–48.43 GHz. The efficiency of an antenna is above 94% over the desired frequency range. The antenna is fabricated and verified with experimental results. The proposed antenna makes it as one of the best choices as a 5G antenna.

A Constant Gain and Miniaturized Antipodal Vivaldi Antenna for 5G Communication Applications

This paper proposes a stable gain and a compact Antipodal Vivaldi Antenna (AVA) for a 38 GHz band of 5G communication. A novel compact AVA is designed to provide constant gain, high front to back ratio (FBR), and very high efficiency. The performance of the proposed AVA is enhanced with the help of a dielectric lens (DL) and corrugations. A rectangular-shaped DL is incorporated in conventional AVA (CAVA) to enhance its gain up to 1 dBi and the bandwidth by 1.8 GHz. Next, the rectangular corrugations are implemented in CAVA with lens (CAVA-L) to further improve the gain and bandwidth. The proposed AVA with lens and corrugations (AVA-LC) gives a constant and high gain of 8.2 to 9 dBi. The designed AVA-LC operates from 34 to 45 GHz frequency which covers 38 GHz (37.5 to 43.5 GHz) band of 5G applications. Further, the presented AVA-LC mitigates the back lobe and sidelobe levels, resulting in FBR and efficiency improvement. The FBR is in the range of 12.2 to 22 dB, and efficiency is 99%, almost constant. The AVA-LC is fabricated on Roger’s RT/duroid 5880 substrate, and it is tested to verify the simulated results. The proposed compact AVA-LC with high gain, an improved FBR, excellent efficiency, and stable radiation patterns is suitable for the 38 GHz band of 5G devices.

A Fern Antipodal Vivaldi Antenna for Near-Field Microwave Imaging Medical Applications

This investigation presents an oval slot edge (OSE) antipodal Vivaldi antenna (AVA), hereinafter referred to as Fern AVA (FAVA), with an optimized radiation pattern. The use of OSE provided improvements in the antenna characteristics, especially regarding a lower frequency limit reduction, an increase in the main lobe (ML) gain, and the sidelobe level (SLL) reduction. Those contrasting characteristics are simultaneously obtained through the class of the Palm Tree antennas. The proposed FAVA at 1.5 GHz shows an improved gain of 6.66 dB, −12.9 dB of SLL, and 0° of ML squint (MLS), in contrast with 4.41 dB of gain, −4.5 dB of SLL, and 4° of MLS in the conventional AVA. For the FAVA, the notches in an elliptical shape, in addition to mitigating the SLL, direct the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}$ </tex-math></inline-formula> -fields distributions toward the ML, which categorizes it into the same class as the Palm Tree Vivaldi Antenna. To study the performance of the proposed antenna for medical applications of near-field microwave imaging, a conceptual proof was performed, thus obtaining the microwave image of a Child Head Phantom, homogeneous, and semirealistic, being possible to detect a brain tumor.

A compact wide-bandwidth Antipodal Vivaldi Antenna array with suppressed mutual coupling for 5G mm-wave applications

A modified miniaturized Antipodal Vivaldi Antenna (AVA) array with suppressed mutual coupling is proposed for broadband 5G millimeter wave (mm-wave) application. The configuration is constructed by using eight radiating elements with single 1-to-8 power divider networks. By adding several notch structures, printed on the ground plane, the mutual coupling between the array elements are suppressed. Therefore, the radiating system has maximal additional isolation of 35.6 dB, enhanced gain of 13.36 dB, and extended impedance bandwidth of 26.5–29.5 GHz. In order to validate the design of the radiating system, the AVA array configuration is fabricated and measured with an overall dimension of 21.45 × 52.35 × 0.787 mm3. The experimentally validated gain value of the conventional AVA array antenna and modified array antenna is 4.7–8.35 dB and 8.62–12.67, respectively.

Band-Notched Antipodal Vivaldi Antenna using Edge-Located Vias Mushroom EBG Structure for Ultra Wideband Applications

An Ultra wideband (UWB) Antipodal Vivaldi Antenna operating at 2.78 GHz to more than 12 GHz with dual notch band attributes is designed for application in ultra-wideband. The proposed double-layered antenna is designed on a low cost FR-4 dielectric material with combined thickness of 2.1mm. Two edge-located vias mushroom type EBG metamaterial structures were incorporated within a conventional antipodal Vivaldi antenna (AVA) in between the two substrate layers and below the feeding line, to realize the proposed antenna. Using the band gap property of the EBG structure, two notch bands were created within the ultra wideband frequency range of the antenna for WiMAX IEEE 802.16 application at 3.18 – 3.80 GHz and WLAN IEEE 802.11a application at 5.13 – 5.80 GHz. Simulation results showed a almost stable directional radiation pattern in the entire frequency range except in the two notch bands, having a peak realize gain of 7.69 dBi at 6.5 GHz. Additionally, surface current distribution and far-field radiation patterns are also studied to characterize the achievement of the presented antenna.

Design of an antipodal Vivaldi antenna with fractal‐shaped dielectric slab for enhanced radiation characteristics

AbstractA conventional antipodal Vivaldi antenna (CAVA) with fractal‐based parallel dielectric slabs is proposed for different wideband applications. At first, a CAVA is designed as a reference antenna, and then Koch fractal‐shaped dielectric slabs are placed parallel to CAVA. The presence of fractal‐shaped dielectric slabs increases the operating bandwidth, and also the field coupling between the antenna arms enhances the gain and directivity of the antenna. The optimized structure of the antenna produces |S11| &lt; −10 dB frequency band from 4.2 GHz to 50 GHz. The total dimension of the fabricated prototype of the proposed antenna is 122 × 66 × 7.692 mm3.

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 of a Wideband Antipodal Vivaldi Antenna with Dielectric Fractal Lens for Biomedical Imaging Applications

In this communication a novel fractal inspired antipodal Vivaldi antenna is designed which is appropriate for wideband applications. A step wise techniques has been applied to design and modify the performance of the designed Vivaldi antenna. First, a reference antenna which is a conventional antipodal Vivaldi antenna (CAVA) is designed and then a Koch fractal shaped dielectric lens has been added an extension of the antenna substrate. The fractal dielectric lens produces stronger radiation in the end fire direction and also enhances the gain and directivity of the antenna. The optimized antenna is fabricated and tested which shows S11 characteristics below -10 dB from 4.2 GHz to 42 GHz band. The dimension of the proposed antenna is 186×66×1.524 mm3.

Metasurface Lens for Ultra-Wideband Planar Antenna

In this article, an ultra-wideband metasurface lens is designed and integrated into an antipodal Vivaldi antenna (AVA) to improve its radiation directivity without affecting its efficiency and return loss characteristics. The metasurface lens consists of high permittivity metamaterial unit cells which resonate at frequencies far away from the operation bandwidth of 1–6 GHz. Electric field distributions of the antennas show that the near-field behaves more planar for the metasurface lens loaded AVA, as compared to conventional AVA. Both the original antenna and the newly proposed antenna are simulated, fabricated, and tested. The measurements are found in very good agreement with the simulation results. In the operation bandwidth of 1–6 GHz, the return loss is less than −10 dB for both antennas. As verified by far-field measurements, the metasurface loaded AVA has achieved higher gain in the operation bandwidth. Additionally, the half power beamwidth of the AVA is significantly reduced by the inclusion of the metasurface lens.

ROTATED RECTANGULAR SLOTS AND MIRRORED INVERSED CANTOR-SETS ON ULTRAWIDEBAND ANTIPODAL VIVALDI ANTENNA

Variants of antipodal Vivaldi antenna (AVA) design suitable for access point working on 0.5 – 6.0 GHz are proposed in this paper. The novel designs were produced by employing three novel techniques to conventional AVA: (i) rotated-slot pattern to shift down the frequency cutoff and enhancing bandwidth, (ii) curve design to miniaturize rotated-slot-inserted antipodal Vivaldi, and (iii) fractal-director (Cantor set) to increase the gain of antipodal Vivaldi. Using FR4 (relative permittivity of 4.4) with an overall dimension of 300 mm x 143 mm x 1.6 mm the antenna designs are able to work at a frequency of 0.472 GHz to higher than 6 GHz with a maximum gain of 11.9 dBi.

Design of a fractal inspired antipodal vivaldi antenna with enhanced radiation characteristics for wideband applications

A novel fractal inspired antipodal Vivaldi antenna is proposed for wideband applications. A step-by-step procedure has been employed to design and optimise the performance of the proposed antenna. First, a conventional antipodal Vivaldi antenna (CAVA) is designed as a reference antenna and then a Koch fractal-shaped parasitic lens is introduced in the CAVA. Finally, a fractal-shaped dielectric lens has been added as an extension of the antenna substrate. The presence of parasitic fractal lens in the flare aperture and fractal dielectric lens enhances the antenna bandwidth and also improves field coupling between the antenna arms and produces stronger radiation in the end fire direction which in turn increases the gain and directivity of the antenna. The optimised antenna is fabricated and tested showing| S 11 | below -10 dB from 4.2-42 GHz band. The dimension of the proposed antenna is 186 × 66 × 1.524 mm 3 . Results show that |S 11 | characteristics and other parameters are in good agreement with the simulation counterpart.

UWB radar cross section reduction in a compact antipodal Vivaldi antenna

This paper presents the design of a compact antipodal Vivaldi antenna (AVA) with reduced radar cross section (RCS) for directional UWB communications. The impedance characteristics of a conventional AVA are improved by introducing a BALUN taper in the ground plane and circular slots of different diameters in the wings of the AVA. The slots on the wings improve the RCS performance of the antenna by rejecting the orthogonal radiations from the AVA. Furthermore, drills of suitable diameter are introduced to further enhance the monostatic RCS performance. The proposed AVA offers 74% size reduction compared to the existing AVAs reported in literature with its bandwidth extending from 3 GHz to over 12 GHz. The prototype AVA is fabricated and the simulation results are verified using experimental measurements. The prototype antenna offers at least 11 dB reduction in RCS throughout the operating bandwidth with a peak reduction of 16 dB at 7 GHz and 11 GHz.

Antipodal Vivaldi antenna with improved radiation characteristics for civil engineering applications

An ultra-wideband elliptically tapered antipodal Vivaldi antenna designed for civil engineering applications is presented. It is based on design of a conventional antipodal Vivaldi antenna (CAVA) which impedance bandwidth is limited at low end of frequency band. To extend impedance bandwidth, inner edges of top and bottom radiators of the CAVA have been properly bent; however, its gain and front-to-back (F-to-B) ratio is low at the low frequencies. To enhance gain and F-to-B ratio, the comb-shaped slits on edges of the radiators of CAVA are applied. The obtained results exhibit the impedance bandwidth of 1.65-18 GHz, gain of 6.7 dB at 1.65 GHz, and F-to-B ratio of 42 dB at 13.5 GHz that are higher than those parameters of the CAVA. Applicability of the proposed antenna for detection of void inside concrete beam is demonstrated. First, models of the proposed antenna and concrete beam possessing void are created in computer simulation technology and numerical study is performed. Then, a prototype of the antenna is fabricated and employed as part of microwave imaging system to verify simulation results and to detect voids inside concrete beam.

Miniaturized UWB Antipodal Vivaldi Antenna and Its Application for Detection of Void Inside Concrete Specimens

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.

A high directive Koch fractal Vivaldi antenna design for medical near‐field microwave imaging applications

ABSTRACTWe present a new fractal slot edge antipodal Vivaldi antenna (AVA). When compared to a conventional AVA, it simultaneously extends the low‐end bandwidth limitation, mitigates the side lobe level, and increases the main lobe gain. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:337–346, 2017

Log periodic slot‐loaded circular vivaldi antenna for 5–40 GHz UWB applications

ABSTRACTA compact antipodal log periodic slot‐loaded circular Vivaldi antenna with dimension (L × W) 45 × 60mm is presented. Structural modification to the conventional antipodal Vivaldi antenna results in miniaturization, improved impedance and pattern bandwidth performance. Proposed designs are prototyped and measured to validate wide‐impedance bandwidths from 5 to 40 GHz. These are compared to measurements on similarly fabricated traditional antipodal and circular Vivaldi antennas which shows a bandwidth only up to 26 GHz. In addition, the measured antenna gain and radiation efficiency of the log periodic slot‐loaded circular Vivaldi antenna are also found higher than the conventional designs. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:159–163, 2017

Microwave and millimetre wave antipodal Vivaldi antenna with trapezoid‐shaped dielectric lens for imaging of construction materials

High-quality microwave and millimetre wave imaging of construction materials and structures requires ultra-wideband (UWB) techniques to provide high-range resolution as well as a reasonable penetration depth. A modified compact microwave and millimetre wave UWB antipodal Vivaldi antenna is designed and presented in this study. First, the conventional antipodal Vivaldi antenna is designed as a reference antenna. Then, to provide the desired frequency range (3.4-40 GHz) with increased gain at its lower frequencies, the slit edge technique is applied, thus creating a periodic slit edge antipodal Vivaldi antenna (PSEAVA). Finally, a trapezoid-shaped dielectric lens (TDL) as an extension of the substrate is added and optimised to increase gain and directivity at higher frequencies of the frequency range, creating PSEAVA with a TDL (PSEAVA-TDL). The results show that the PSEAVA-TDL has the highest gain (up to 16 dB) and front-to-back ratio (up to 37.5 dB), and the narrowest half power beamwidth (down to 11.7°). A prototype of the proposed PSEAVA-TDL with compact size of 40 × 90 × 0.508 mm 3 is fabricated and applied for the imaging of samples made of construction materials. High-range resolution images of the samples are obtained with this antenna by using synthetic aperture radar algorithm.

High-Gain Dielectric-Loaded Vivaldi Antenna for $K_{a}$ -Band Applications

In this letter, a novel concept of a high-gain Vivaldi antenna operating in the $K_{a}$ frequency band is proposed. The antenna is fed by the substrate integrated waveguide. The concept overcomes shortcomings of conventional antipodal Vivaldi antenna using dielectric load with printed metal transition and transverse ripples. The added parts are optimized to obtain a wideband high-gain antenna with low cross polarization. The fabricated antenna shows very good performance over the entire $K_{a}$ band where the measured gain is more than 10.5 dBi.

A Compact High-Gain and Front-to-Back Ratio Elliptically Tapered Antipodal Vivaldi Antenna With Trapezoid-Shaped Dielectric Lens

A modified compact antipodal Vivaldi antenna is proposed with good performance for different applications including microwave and millimeter wave imaging. A step-by-step procedure is applied in this design including conventional antipodal Vivaldi antenna (AVA), AVA with a periodic slit edge, and AVA with a trapezoid-shaped dielectric lens to feature performances including wide bandwidth, small size, high gain, front-to-back ratio and directivity, modification on E-plane beam tilt, and small sidelobe levels. By adding periodic slit edge at the outer brim of the antenna radiators, lower-end limitation of the conventional AVA extended twice without changing the overall dimensions of the antenna. The optimized antenna is fabricated and tested, and the results show that S 11 <; -10 dB frequency band is from 3.4 to 40 GHz, and it is in good agreement with simulation one. Gain of the antenna has been elevated by the periodic slit edge and the trapezoid dielectric lens at lower frequencies up to 8 dB and at higher frequencies up to 15 dB, respectively. The E-plane beam tilts and sidelobe levels are reduced by the lens.