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In this paper, a novel compact broadband antenna at UHF frequencies is presented with canonical shapes. Hemispherical, conical and cylindrical shapes have all been considered for antenna configuration. The designed antenna provides an instantaneous frequency range from 370 to 5,000 MHz with omnidirectional characteristics. The antenna was simulated in CST Microwave Studio, fabricated and evaluated; the results are presented. The simulated and measurement results are in good agreement. The antenna has voltage standing wave ratio (VSWR) ≤ 1.9:1 in 400–570 MHz, 2,530–3,740 MHz and 4,180–4,620 MHz; it has VSWR ≤ 3:1 over the operating frequency range 370–5,000 MHz and the measured gain varies from -0.6 to 4.5 dBi over the frequency band. The concept of canonical-shaped antenna elements and the incorporation of triple sleeves resulted in a reduction of the length of the antenna by 62% compared to the length of a half-wave dipole antenna designed at the lowest frequency. The antenna can be used for trans-receiving applications in wireless communication.

A novel miniaturized dipole antenna design incorporating triple sleeves and shorting load leading to enhanced bandwidth is proposed in the present work. The Triple Sleeve Dipole Antenna with Shorti...

In this study, a novel metamaterial inspired compact cylindrical conformal dual-band antenna with a shunt fractal inductor and bottom patch is proposed. The conformal antenna consists of three meander lines type unit cells of composite right/left-handed metamaterials for modification and compactness. To improve the operating bandwidth in the first band i.e at 2.45 GHz, a shunt fractal inductor with large inductance is proposed. A similar patch with a slot along the bottom side is additionally used for better impedance matching. The second band at 3.5 GHz is obtained due to the loading of two meander line unit cells on the patch as parasitic elements. The proposed conformal antenna is placed on a 15 mm radius cylinder whose equivalent planar dimension is 0.48 λ g × 0.36 λ g (where λ g is the guided wavelength). Asymmetrical coplanar waveguide feed is implemented. Measurement results showed that the proposed cylindrical conformal antenna achieves a wideband −10 dB fractional bandwidth of 44.5% and a gain of 1.26 dBi at the operating frequency of 2.45 GHz and 4.5% of bandwidth and a gain of 2.2 dBi at the 3.5 GHz. The radiation efficiency is 70 and 86% at the said frequencies respectively. There is good agreement between measured and simulation data.

In this paper, novel techniques are presented for gain enhancement of a wideband directional conformal antenna. Initially a wideband conformal antenna is proposed as a basic antenna which consists of an array of three fork shaped elements. To achieve the gain enhancement of the basic conformal antenna, three triangular shaped parasitic elements and an array of 3 × 6 number of low index metamaterial unit cells are integrated on both side of the substrate. The phase velocity in the metamaterial region is higher than the other region due to low refractive index as compared with other region. So, the proposed metamaterial can be considered as a beam focusing lens. As a result, the proposed antenna is more directive with narrow beamwidth and the half power beamwidth is reduced by 24° in the H-plane. The gain of the proposed conformal antenna which is integrated with parasitic elements and metamaterial unit cells is enhanced by 1.8 dBi compared to basic conformal antenna. The impedance bandwidth of the proposed conformal antenna achieves a bandwidth of 22.3% from 3.1 to 3.88 GHz which is suitable for WiMAX application.

In this article, a novel wideband cylindrical conformal antenna using a wide slot in the ground plane is proposed. A bow-tie-shaped patch antenna is designed for Global Positioning System applications. The bandwidth of the antenna is improved by using a similar bow-tie-shaped slot in the ground plane with a larger dimension. The bandwidth is further enhanced by introducing a dumbbell-shaped slit in the patch. The antenna is fed by a 50- Ω " role="presentation"> Ω Ω \Omega microstrip line. The proposed planar antenna is printed on a ground plane of size 0.5 λ " role="presentation"> λ λ \lambda mm × " role="presentation"> × × \times 0.5 λ " role="presentation"> λ λ \lambda mm, where λ " role="presentation"> λ λ \lambda is the operating wavelength, and then it is transformed into a cylindrical conformal antenna with the desired radius of curvature. The proposed planar antenna is simulated, fabricated, and measured for conformal geometry with good agreement between measurements and simulation results. It is observed that the conformal antenna exhibits a fractional bandwidth of 81.4 % " role="presentation"> % % \% operating from 0.75 to 1.78 GHz, which is useful for all GPS and Galileo frequencies. The radiation pattern exhibits an omnidirectional pattern and gain of the proposed antenna is 3.5 to 4.78 dBi within the operating frequency range.

In this paper, a novel technique using frequency selective surface (FSS) superstrate is proposed to increase the antenna gain. In addition to that, a combination of reactive impedance surfaces (RIS) is included to enhance the bandwidth. So, a conventional pentagon shape patch antenna is designed at 5.3 GHz. The frequency selective surface is designed as a 6×6 array of unit cell structures to operate around 5.3 GHz. Each unit cell consists of three metal conductive layers with substrates in between them. Reactive Impedance Surface is considered as an array size of 6×6 square patches embedded between two substrates. FSS is designed on Rogers 4003C and FR4 is used for RIS. The pentagon shape patch antenna is designed on RIS. A cavity created by the contribution of these layers acts like a fabry perot resonator which improves the gain and bandwidth simultaneously. The proposed antenna has an impedance bandwidth of 17.72% (4.93-5.89 GHz); this is about a 10 percent improvement over the impedance bandwidth of a conventional pentagon shape antenna and the axial ratio bandwidth is 2.4% (5.01-5.14 GHz). The designed antenna gain is around 12dBi; this is about a 9 dBi improvement over the gain of a conventional pentagon shape antenna.

A novel compact broadband Canonical Sleeve Antenna (CSA) covering 500-3600 MHz with omni directional characteristics is presented in this paper. A new method is employed in which the radiating antenna structure is designed as combination of three different canonical structures: hemispherical, conical and cylindrical elements. To accomplish the broad bandwidth with compact size, dipole antenna is designed by using cylindrical sleeve over the hemispherical dipole with conical extensions and cylindrical attachments. Performance characteristics of CSA is simulated and compared with BiConical Antenna (BCA) and other antenna configurations and found to be best antenna configuration with compact form factor. The antenna has height of 111.43 mm and diameter of 116.66 mm. Simulation studies are carried out using CST Microwave Studio. The simulated results are validated by fabricating CSA and evaluating its performance metrics. CSA has 7.2:1 bandwidth with measured VSWR

This paper introduces a novel technique to enhance the gain of the basic monopole antenna by using broadband gradient refractive index (GRIN) metamaterial. The proposed GRIN is designed by using a parallel-line unit cell metamaterial with different refractive index. A seven GRIN lens is placed on the omnidirectional printed basic monopole antenna, perpendicularly. Due to the non-resonant and subwavelength properties of the parallel-line elements, the proposed GRIN metamaterial lens has a broad bandwidth property with low loss. The simulation and measurement results confirmed that the beam is more directive with narrow beam width. The measured reflection coefficient of the GRIN antenna is below -10 dB over the frequency bandwidth of 3.4-11 GHz. Due to GRIN lens, the peak gain of the basic monopole antenna is increased by 5.3 dB at 8.8 GHz.

A novel wideband log spiral antenna with superstrate design is proposed for C-band applications. Initially spiral antenna is designed on a 20.4 mm diameter then Minkowski fractals are placed on outer boundary of spiral antenna. The bandwidth of an antenna is improved using Minkowski fractals. Further one more single layer is added as a superstrate design which making the radiation pattern unidirectional. The single layer spiral antenna with fractals has return loss bandwidth of 0.59 GHz and fractional bandwidth of 11.98% where as double layered spiral antenna has return loss bandwidth of 1.34 GHz and a fractional bandwidth of 27.50%. The proposed antennas have a gain varying in the range of 2.5 to 4.64 dBi over the operating frequency band for both the single layer spiral antenna and double layer (superstrate) spiral antenna.

In this paper, a compact log spiral antenna with slots on the spiral arm is designed to achieve wideband bandwidth and compact structure. These circular slots are also providing better impedance matching in terms of lower return loss. The introduction of slots increased the gain of the antenna. The proposed antenna has achieved a fractional bandwidth of 43.83 % over the S-band frequency range from 2.68 to 4 GHz. The radiation pattern is bidirectional along broadside direction. The gain of proposed antenna varies from 2.2 to 3.4 dBi over the S-band frequency range.

In the present paper a novel technique is applied to ground plane of patch antenna to reduce the size of the radiating patch and simultaneously increase the gain of the antenna. A rectangular microstrip antenna is designed for Wi-Fi application at 2.45 GHz. Fractal structures are self symmetry structures which can be used for size miniaturization. Sierpinski carpet fractal slots are applied to the ground plane of the rectangular patch antenna working at 2.4 GHz frequency. The results are simulated for first iteration and second iterations of fractal DGS antenna. There is size reduction of the radiating patch is 30.78%, 32.9% for 1st and 2nd iterations fractal slots respectively. The performance of the antenna has also showed improvement.

In this paper, a compact, dual-band patch antenna is proposed over Minkowski fractal defected ground structure (DGS) for bandwidth enhancement of global positioning system (GPS) applications. The proposed design combines the truncated dual L-shaped slits cut on diagonal corners of radiating patch and fractal defect on the metallic ground plane. This concept shifts the frequencies to lower bands with improvement in antenna radiation properties. By deploying symmetrical and asymmetrical boundaries to the structure for the fractal DGS on metallic ground plane, improvement in bandwidth and gain are obtained. Compact antenna size is achieved for dual-band GPS frequencies of L1 (1.575 GHz) and L2 (1.227 GHz). The measured results for antenna prototype are (1.2–1.245 GHz): L2 band and (1.51–1.59 GHz): L1 band for 10 dB return loss bandwidth with better pattern radiation. Gain value with and without DGS is observed for compact antenna overall volume of 0.32λ0 × 0.32λ0 × 0.024λ0.

A novel tri-band asymmetric slot with defective ground structure (DGS) microstrip antenna for dual circular polarization (CP) is proposed. By placing a slot with 45° across diagonally at the center of the patch, excites resonant bands with narrow bandwidth and dual CP operation. The main design challenge is to introduce optimized defected element of circular dumbbell shape to enhance the impedance bandwidth with frequency shift operation at all bands. DGS enabled antenna is practically fabricated and simulated. Antenna is compact in size and shows a good quality of CP at two resonant bands and linearly polarized at one band. Structure displays the impedance bandwidth of 8% (2.26–2.45 GHz), 5.45% (3.41–3.6 GHz) and 3.07% (5.12–5.28 GHz). The design also shows 40 and 11 MHz, 3-dB axial ratio bandwidth at lower and middle bands, respectively. Simulated gain for each band is 4.72, 6.2 and 4 dB. Performance of antenna with and without DGS is also studied and compared. This single probe feed proposed antenna remains consistent with good radiation patterns and sufficient antenna gain over the operating bands. Excellent agreement was obtained between measurements and simulations.

In this letter, a compact zigzag-shaped-slit rectangular microstrip patch antenna with circular defected ground structure (DGS) is designed for wireless applications. The probe-fed antenna consisting of a zigzag-shaped slit, dual T-shaped slits on either sides of a rectangular patch, and circular dumbbell-shaped defected ground plane is optimized. The antenna was able to generate three separate resonances to cover both the 2.45/5.28-GHz WLAN bands and the 3.5-GHz WiMAX bands while maintaining a small overall size of $40 \times 28 \times 3.175~\hbox{mm}^3$ . The return-loss impedance bandwidth values are enhanced significantly for three resonant frequencies. The designed antenna is characterized with better radiation patterns and potentially stable gain around 4–6 dBi over the working bands. Good agreement was obtained between measurements and simulations.

The novel approach of this paper describes the suppression of grating lobe level with the element count optimization in planar antenna array. Rectangular lattice (RL) and triangular lattice (TL) structures are chosen for determining the achievable array element patterns (EP) and further suppressing the grating lobe level. The element spacing and number of elements (10 × 20 array) are taken into account for particular lattice. Grating lobe peaks are observed for the 200-element planar array at maximum scan angle (θ) with the set frequency of 3 GHz. Further, it is found that 14°; bore sight elevation of rectangular lattice produces a transformed field of view, which permits a reduction in element count of 20.39% compared with 10° bore sight elevation. Finally, the typical values of elevation, element count and array size (25 cm2) are trained using artificial neural network (ANN) algorithm and element count is predicted after testing the network. The network shows a high success rate.

A novel wideband conformal slot antenna is proposed for GPS application. Initially a planar antenna with dumbbell shape slot on three sides of patch is designed at a slightly higher frequency and then the planar antenna is transformed to the corresponding cylindrical conformal antenna with the desired radius of curvature. The antenna used in this study employs a dumbbell shape slot on the three sides of patch. To design the wideband antenna, combination of partial ground concept and dumbbell shape slots on patch is employed. The flexible and higher thermal stable substrate like Rogers RT/duroid 5880 with permittivity of 2.2 and thickness of 0.787 is used. Microstrip line feeding is used in the proposed antenna. The proposed conformal antenna exhibits a fractional bandwidth (for the definition of −10 dB) of 75.94% operating from 1056 to 2349 MHz, which is suitable for all GPS band, GLONASS and GALILEO application. The radiation pattern exhibits an omnidirectional pattern and gain of proposed conformal antenna is 2.09 to 4.9 dBi within operating frequency range.

In this study, a dual band-notched ultra-wideband tapered slot antenna is introduced. Here, split ring resonator and balun are used to suppress spurious unwanted bands. The split ring resonator is etched to the certain distance from the excitation point. Hence, one resonance is excited with extended band width. According to the feeding configuration, the stepped microstrip line and slotline connected with circular slot. So, strong EM wave coupling is generated with balun. The electric-field-coupled (ELC) resonator structure is placed inside the circular balun. The size of the tapered slot antenna is 55×40 mm2. The simulation results show that the impedance bandwidth of the antenna is covered an ultra-wideband frequency range (3.1 to 11 GHz) with VSWR< 2 and the band rejection is created at WLAN and ITU band.

A novel planar and conformal antenna with dual U slot are proposed at 2.41GHz and 2.45GHz respectively. The antenna is designed on RT Duroid 5880 substrate of permittivity 2.2 and thickness of 0.787mm with microstrip inset feed. The proposed planar antenna also has bandwidth of 24.9MHz and has maximum gain of 4.2dB. The planar antenna is transformed to conformal cylindrical of 25mm, 45mm and 60mm radii. The gain values are decreased from 5.9dB to 2.81dB but the bandwidth values varies from 23MHz to 22.1MHz by changing the radius of curvature from 60mm to 25mm. The planar and conformal antenna on different radii has a single band at 2.41GHz and 2.45GHz respectively which is suitable for Wi-Fi application.

This paper describes a corrugated antipodal Vivaldi antenna with improved performance by using negative index metamaterial (NIM) of the Archimedean spiral design. A single layer NIM piece is placed perpendicular middle of the two arm of the proposed antenna. The antenna size is 30×60×0.787 mm3 operating at 8GHz. The simulated results of NEVI corrugated antipodal Vivaldi antenna show that the gain and directivity has increased up to 1.2dB and 1dB respectively. The HPBW is increased by 90 with the reflection coefficient less than DIO dB from 4.7 GHz to 11 GHz for UWB application.

Single probe feed triangular patch antenna with asymmetric dual V-shaped slots is designed, fabricated and tested for tri-band applications. The unequal length arms of inner and outer V-slots gives provision to achieve two degenerate orthogonal modes, which lead to circular polarization (CP) at lower and middle bands respectively. The antenna resonates at frequencies of 2.4GHz, 3.5GHz with CP and 5.28GHz with linear polarization (LP). Good agreement obtained between simulated and measured results.

Compact microstrip patch antenna with L-shaped spur lines using Hilbert shaped fractal defective ground structure (DGS) is proposed and investigated for multiband applications. The objective of the paper is to obtain average size reduction of about 72% using resonant frequency shift method with the help of DGS. The impedance bandwidth, gain and efficiency are observed and compared for the proposed antenna with and without DGS. Excellent agreement is found between simulated and measured results.

In this paper, a novel wideband conformal fractal antenna is proposed for GPS application. The concepts of fractal and partial ground are used in conformal antenna design for miniaturization and bandwidth enhancement. It comprises of Minkowski fractal patch on a substrate of Rogers RT/duroid 5880 with permittivity 2.2 and thickness of 0.787mm with microstrip inset feed. The proposed conformal antenna has a patch dimension about 0.39λmm×0.39λmm, and partial ground plane size is 29mm×90mm.The proposed antenna is simulated, fabricated and measured for both planar and conformal geometry, with good agreement between measurements and simulations. The size of the fractal patch is reduced approximately by 32% as compared with conventional patch. It is observed that the conformal antenna exhibits a fractional bandwidth(for the definition of -10dB) of 43.72% operating from 1.09 to 1.7GHz, which is useful for L1(1.56-1.58GHz), L2(1.21-1.23GHz), L3(1.37-1.39GHz), L4(1.36-1.38GHz), and L5(1.16-1.18 GHz) in GPS and Galileo frequencies: E=1589.742MHz(4MHzbandwidth), E2=1561. 098MHz(4MHzbandwidth), E5a=1176.45MHz(=L5),E5b= 1207.14MHz, and E6=1278.75MHz(40MHz bandwidth). The radiation pattern exhibits an omnidirectional pattern, and gain of proposed antenna is 2.3dBi to 3.5dBi within operating frequency range.