Three‐dimensional cylindrical design multiple‐input‐multiple‐output/diversity antenna with high isolation for wireless communication applications

In this article, a three‐port nonplanar multiple‐input‐multiple‐output/diversity antenna with very high isolation between the radiating elements is presented. To realize diversity from the proposed three‐dimensional (3‐D) antenna configuration, three monopole radiating elements are arranged at an angle of 120°. The isolation between the radiators is enhanced by using a multilayered cylindrical decoupling structure and defected ground structure (DGS). The DGS reduces the coupling due to surface waves while the cylindrical decoupling structure reduces the coupling due to space waves. The proposed antenna offers consistent pervasive connectivity in the wireless communication environment due to its 3‐D geometry with multiple radiating elements and good diversity performance. The prototype is fabricated and measured result shows that more than 42 dB isolation is obtained at the center frequency 1.45 GHz. An increment of 1.2 dBi in the antenna gain is also achieved by using DGS and decoupling structure arrangement. The proposed antenna can be easily placed inside the cylindrical housing or it can be integrated with the existing electronics chip, thus nullifying the requirement for dedicated location in the system.     

Single‐layer high‐gain flat lens antenna based on the focusing gradient metasurface

A single‐layer transmitting focusing gradient metasurface (F‐GMS) has been proposed that can realize high gain increment at 10 GHz. The unit of F‐GMS is composed of two identical structures placed on the top and bottom of one dielectric layer, which can have high transmitting efficiencies that over 0.8 and achieve [0, 2π] phase range in X‐band. The F‐GMS can convert the spherical waves into plane waves. A patch antenna working at 10 GHz is positioned as the focus of the proposed F‐GMS as the feed source to develop an ultrathin flat lens antenna system. It achieves a simulated gain of 19.6 dBi which is 12.9 dB greater than that of the single patch antenna at 10 GHz. Lastly, the F‐GMS and the patch antenna are manufactured and then measured in an anechoic chamber. A good agreement was demonstrated between experimental and simulated results.     

A wide‐scanning ellipsoid lens antenna fed by phased array antenna

Luneburg lens antennas have been widely applied to many communication systems for their multibeam scanning and high gain characteristics. However, the large profiles of conventional Luneburg lens antennas restrict their applications. To solve these issues, an ellipsoid lens antenna fed by phased array antenna (PAA) operating at Ka‐band is proposed in this article. The profile of the ellipsoid lens is reduced by half compared to the conventional Luneburg lens, based on the transformation optics theory. The wide‐angle scanning property is obtained by optimizing the amplitude and phase distributions of the PAA, combined with the element pattern superposition principle. The proposed five‐layer ellipsoid lens antenna is able to scan up to ±45° with less than 3 dB scanning loss at 28 GHz. Finally, the lens was easily fabricated through three dimensional printing technology and computer numerical control. Experimental results are in good agreement with the numerical results, thus validating the proposed design.     

A lightweight multi‐beam cylindrical Luneberg lens antenna loaded with multiple dielectric posts

A multi‐beam cylindrical Luneberg lens antenna loaded with multiple light dielectric posts for the purpose of light weight is presented. The antenna is based on a parallel‐plate waveguide and specifically composed of 10 E‐shaped patch antennas feeds, 2 parallel plates, and 491 epoxy posts. The equivalent gradient index of the Luneberg lens antenna is realized via the positions of the epoxy posts between the parallel plates. The features of low‐profile height (0.55λ) and large radiating area (4.4 × 0.55λ²) of the cylindrical Luneberg lens result in wide beamwidth in elevation plane and high gain while operating at 4 GHz. Consequently, the 3 dB beamwidth in the elevation plane is >65°. Furthermore, the multi‐beams cover a wide scan angle of 120° in the azimuth plane. The measured aperture efficiency of the fabricated lens antenna is above 50% from 3.9 to 4.3 GHz. In addition to the good radiation performance, features of light weight and ease of fabrication have also been demonstrated for the proposed lens antenna.     

Dual‐polarized low sidelobe Fabry‐Perot antenna using tapered partially reflective surface

A novel dual‐polarized Fabry‐Perot (FP) cavity antenna with low sidelobes is proposed. Low sidelobes are obtained by using a tapered partially reflective surface (PRS) in the form of circular lattice instead of the conventional rectangular lattice. As the PRS can be regarded as a 2D leaky wave surface on which cylindrical waves propagate outward radially in the form of concentric rings, so arranging the PRS elements in the form of circular lattice and then applying tapering on it yields low sidelobes in both the E‐ and H‐planes. The performance of the proposed PRS is validated by fabricating a dual‐polarized FP antenna and measuring its radiation patterns. Peak realized gains of 18.6 and 18.5 dBi are obtained for horizontal and vertical polarizations respectively, giving an aperture efficiency of around 42%. Measured sidelobe levels are reduced to lower than ?21.3 dB in both the E‐ and H‐planes for the two orthogonal polarizations.     

Low‐profile omnidirectional circularly polarized antenna based on substrate integrated waveguide technology

A substrate integrated waveguide (SIW) circularly polarized (CP) antenna with omnidirectional radiation in the azimuthal plane is proposed. The antenna consists of five identical end‐fire CP antenna elements in a pentagonal array configuration, which is loaded on a circular substrate. Each element contains an H‐plane horn antenna in SIW structure and a printed dipole antenna. Five parasitic curve elements are introduced to improve the omnidirectional property of the antenna. Combined with complementary dipoles theory and SIW technology, prototype antenna is designed, fabricated and measured. With a low profile of 0.024λ₀, the antenna has a 10‐dB return‐loss impedance bandwidth of 4.08% (2.4～2.5 GHz) and a 3‐dB axial‐ratio (AR) bandwidth of 5.76% (2.36～2.50 GHz). The antenna works well in the 2.45 GHz ISM band, with good cross‐polarization and excellent omnidirectional property.     

A coplanar waveguide‐fed flexible antenna for ultra‐wideband applications

This paper presents a novel ultra‐wideband (UWB) antenna printed on a 70 μm thick flexible substrate. The proposed antenna consists of a hybrid‐shaped patch fed by coplanar waveguide (CPW). The ground planes on opposite sides of the feeding line have different height to improve antenna bandwidth. Simulation shows that the proposed antenna maintain wide bandwidth when changing its substrate's thickness and dielectric constant, as well as bending the antenna on a cylindrical foam. The proposed antenna is fabricated in laboratory with a simple and low‐cost wet printed circuit board (PCB) etching technique. Measured bandwidths cover 3.06 to 13.58, 2.8 to 13.55, and 3.1 to 12.8 GHz in cases of flat state and bent with radii of 20 and 10 mm, respectively. Measured radiation patterns show the antenna is omnidirectional in flat and bent cases.     

Quasi‐corrugated substrate integrated waveguide H‐plane horn antenna with wideband and low‐profile characteristics

A wideband H‐plane horn antenna based on quasi‐corrugated substrate integrated waveguide (SIW) technology with a very low profile is presented in this article. Open‐circuited microstrip stubs are applied to create electric sidewalls of the quasi‐corrugated SIW structure. The quasi‐corrugated SIW H‐plane horn antenna shows high performance and simple structure. A specify‐shaped horn aperture is utilized, so that the poor impedance matching owing to the structure restriction can be smoothened. The structure is simulated by ANSYS HFSS and a prototype is fabricated. The measured results match well with the simulated ones. An enhanced impedance bandwidth ranging from 5.3 GHz to 19 GHz (VSWR < 2.5) is achieved. The presented antenna also brings out stable radiation beam over the same frequency band.     

Millimeter‐wave antenna with wide‐scan angle radiation characteristics for MIMO applications

A three‐element quasi Yagi‐Uda antenna array with printed metamaterial surface generated from the array of uniplanar capacitively loaded loop (CLL) unit‐cells printed on the substrate operating in the band 25‐30 GHz is proposed. The metamaterial surface is configured to provide a high‐refractive index to tilt the electromagnetic (EM) beam from the two dipole antennas placed opposite to each other. The metamaterial region focuses the rays from the dipole antenna and hence increases the gain of the individual antennas by about 5 dBi. The antenna elements are printed on a 10 mil substrate with a center to center separation of about 0.5 λ ₀ at 28 GHz. The three‐element antenna covers 25‐30 GHz band with measured return loss of 10 dB and isolation greater than 15 dB between all the three ports. The measured gain of about 11 dBi is achieved for all the antenna elements. The three antenna elements radiate in three different directions and cover a radiation scan angle of 64°.     

Electric‐field‐driven LC lens for 3‐D/2‐D autostereoscopic display

Abstract— The use of an electric‐field‐driven liquid‐crystal (ELC) lens cell for switching between a 3‐D and 2‐D display is proposed. Due to the phase retardation of the non‐uniform LC directors, an ELC lens functions the same as a geometric lens. The parameters of an ELC for 3‐D applications are optimized through the simulation of the electrode configuration and voltage levels. A prototype was made where the ELC lens is placed in front of a liquid‐crystal display (LCD) 15 in. on the diagonal with a 99‐μm subpixel pitch. Under zero voltage, the ELC lens is a transparent medium and the users can see a clear 2‐D image. In 3‐D mode, the ELC lens array performs the same as a cylindrical lens array to the incident vertical polarization under suitable driving voltages. Placing a half‐wave plate between the LCD and ELC lens is proposed to change the polarization of the LCD to be parallel with the polarization lens direction of the ELC lens. The measurement of the horizontal luminance profile, performance of the ELC lens, and feasibility for 3‐D/2‐D switching was verified. The fabrication process for the ELC lens is compatible with the current LCD production process and enables the accurate control of the lens pitch of the ELC lens.     

3D‐printed high‐gain circularly polarized antenna for broadband millimeter‐wave communications over the power line

It is well known that high transmission loss occurs when millimeter waves traveling through the atmosphere. As an alternative, power line is proposed as a transmission media to combat the high loss. In this article, a three‐dimensional (3D) printed high‐gain circularly polarized antenna was proposed for millimeter‐wave broadband power line communications. It has a simple structure, where tapered slots are designed between the upper and lower layers of the waveguide to generate the circularly polarized operation. A wide impedance bandwidth of 31.58% (24‐33 GHz) and an axial ratio bandwidth of 28.07% (24.5‐32.5 GHz) are achieved by the proposed design. A maximum gain of 11.2 dBi is measured from the 3D printed structure. The proposed antenna has a simple structure which is easy to adjust to any working frequency. The antenna can be excited by properly integrated to the waveguide that connected to the power line end. The use of 3D printing technology enables a low‐cost solution millimeter‐wave broadband communications over the power line.     

2‐D/3‐D switchable autostereoscopic display with multi‐electrically driven liquid‐crystal (MeD‐LC) lenses

Abstract— A cylindrical multi‐electrically driven liquid‐crystal lens (MeD‐LC lens) is proposed to extend the range of focusing. The MeD‐LC lens could be applied to switching 2‐D and 3‐D images by supplying a specific operating voltage on each electrode. Therefore, the MeD‐LC lens has less cross‐talk than that of a conventional LC lens. Furthermore, the simplified structure of a MeD‐LC lens with a homogeneous LC layer is much easier for fabrication without a LC‐alignment issue.     

A 60‐GHz on‐chip slot‐array antenna in integrated‐passive‐device technology for antenna‐in‐package applications

A new millimeter‐wave antenna structure on a low‐cost, production platform integrated passive device technology is presented. The antenna consists of a 2‐by‐1 array of slot antennas at 60 GHz. An in‐house developed on‐chip antenna measurement setup was used to characterize the fabricated antenna. The measurement results show an antenna gain of more than 5 dBi with a return loss of 18 dB at 60 GHz. The better‐than‐10‐dB impedance bandwidth of the antenna covers the 60‐GHz unlicensed band from 57 to 64 GHz. The 3‐dB beamwidths of the antenna are 105° and 76° at E‐plane and H‐plane at 60 GHz, respectively. The size of the die of the antenna is 2 mm × 4.5 mm. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:155–160, 2014.     

A novel design of high performance multilayered cylindrical dielectric lens antenna using 3D printing technology

In this work, design and realization of high performance, low‐cost X‐band multilayered cylindrical dielectric lens antenna (MLCDLA) is presented using 3D printing technology. Firstly, MLCDLA is designed and simulated in the complete 3D CST microwave studio (MWS) within the X‐ band as consisting of six layers and being fed through a conventional rectangular waveguide (WR90). These layers are in the form of cylindrical discs having different radii, thicknesses and made of a cheap polylactic acid material. These layers have also varying dielectric constant from 1.2 to 2.7 that are compatible for fused deposition modeling (FDM) based 3D‐printing process. Secondly, a prototype of MLCDLA is produced by using a FDM based 3D‐printer. 3D printed dielectric lens antenna is measured and a good return loss of almost more than 10 dB within the X‐band with a high gain of 16‐18 dBi are achieved as compared with the counterpart alternative designs. Thus, it can be concluded that the proposed novel design and prototyping method not only achieves the high radiation performance characteristics along X‐band but also is a fast, low‐cost, and effective method for prototyping dielectric lens structures for the microwave applications.     

A compact substrate integrated waveguide H‐plane horn antenna with dielectric arc lens

An H‐plane horn antenna constructed into SIW (substrate integrated waveguide) is proposed. It has a dielectric arc lens for better directivity and a simple microstrip transition as feed. The horn, the lens and the transition share the same substrate. The resulting formula from optical principles shows that the suitable dielectric lens can improve the directivity of the antenna significantly. A prototype was fabricated; the antenna size is 39.175 × 14 × 2 mm³. The frequency band is from 25.5 to 28.5 GHz. The measured gain of this antenna is about 9 dB; the bandwidth, at 10 dB return loss, is over 12%. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

A vertex‐fed hexa‐band frequency reconfigurable antenna for wireless applications

Present article embodies the design and analysis of an octagonal shaped split ring resonator based multiband antenna fed at vertex for wireless applications with frequency‐band reconfigurable characteristics. The proposed antenna is printed on FR4 substrate with electrical dimension of 0.4884 λ × 0.4329 λ × 0.0178 λ (44 × 39 × 1.6 mm³), at lower frequency of 3.33 GHz. The antenna consists of SRR based vertex fed octagonal ring as the radiation element and switchable reclined L‐shaped slotted ground plane. Antenna achieves six bands for wireless standards viz: upper WLAN (5.0/5.8 GHz), lower WiMAX (3.3 GHz), super extended C‐band (6.6 GHz), middle X band (9.9 GHz—for space communication), and lower K_U band (15.9 GHz—for satellite communication systems operating band). Stable radiation patterns are observed for the operating bands with low cross polarization. The proposed design achieves hexa band characteristics during switching ON state of PIN diode located at reclined L‐shaped slot in the ground plane. Experimental characteristic of antenna shows close agreement with those obtained by simulation of the proposed antenna.     

A new compact dual‐wideband printed monopole antenna for WLAN/WiMAX applications

A new compact printed monopole antenna with dual‐wideband characteristics is presented for simultaneously satisfying wireless local area network and worldwide interoperability for microwave access applications. The antenna structure consists of a circular monopole with a microstrip feed‐line for excitation and a hexagon conductor‐backed parasitic plane. The antenna has a small size of 13 mm × 26 mm × 1 mm. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Asymmetric circularly polarized open‐slot antenna

A circularly polarized printed antenna using an asymmetric open‐slot is designed in this paper. The presented antenna consists of conducting ground plane with open wide‐slot, fed electromagnetically by a microstrip feedline. The slot and feedline are positioned at the edge of the ground plane and substrate, hence making the antenna asymmetric. The measured results show that the |S₁₁| < ?10 dB impedance bandwidth is 125% (3.2‐14 GHz) and the broadband axial ratio bandwidth is 61% (3.2‐6 GHz). The antenna is very simple and has a small size of 25 mm × 25 mm, making it attractive for compact wireless WLAN, ISM, WiMAX, and C‐band applications.     

A dual‐broadband circularly polarized halved falcate‐shape printed monopole antenna

A halved falcate‐shape dual‐broadband circularly polarized printed monopole antenna is proposed. To generate the equal amplitude orthogonal modes, two halved falcate‐shaped antenna are used. Also, to provide the 90° phase difference between the two modes, three stubs are used in the ground plane of the antenna. The proposed antenna provides 22.6 (1.36–1.72 GHz) and 44.4% (5.25–8.25 GHz) 3 dB axial ratio bandwidth over the lower and upper bands, respectively. By adjusting the parameters of the antenna, the lower and upper band center frequencies can be tuned individually. The proposed antenna is fabricated, and results are compared with those of the simulation. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Tri‐band composite cylindrical dielectric resonator antenna with hybrid mode excitation and cross‐polarization suppression

This communication investigates composite cylindrical dielectric resonator antenna (CDRA) for various wireless applications. Three important features of proposed antenna design are (i) realization of two different hybrid modes, that is, HEM_11δ and HEM_12δ mode in CDRA with the help of modified annular ring printed line (work as both magnetic dipole and electric dipole), both the hybrid modes support broadside radiation characteristics (ii) suppression of HEM_21δ mode, in order to reduce the cross‐polarization level in H‐plane of other hybrid modes (HEM_11δ and HEM_12δ mode) by an amount of 8‐10 dB (iii) creation of triple‐band attribute using the concept of composite antenna. The proposed antenna design has been fabricated and practically tested. Simulated outcomes show good agreement with measured outcomes. It works in three frequency bands, that is, 2.25‐2.79 GHz, 3.1‐4.0 GHz, and 5.05‐5.6 GHz. The designed antenna structure is appropriate for WLAN and WiMAX applications.