Wide‐bandwidth multifrequency circularly polarized monopole antenna for wireless communication applications

In this article, wideband circularly polarized monopole antennas with multiresonating frequencies are presented for Bluetooth, WLAN, WiMAX, and X‐band applications. The designed antennas have dimensions of 50 × 35 × 1.6 mm³. Two different substrates (FR4‐epoxy and PTFE) are used for fabricating the antennas. The antennas consist of corner truncated I‐shaped and C‐shaped strips excited by a 50 Ω microstrip feed line. The parametric analyses are performed with the help of Ansoft HFSS V.11 EM simulator. Both antennas have been fabricated and measured. The measured percentage bandwidth of the antenna made by FR4 substrate is 31.32% (centered at 1.66 GHz), and 64.85% (centered at 5.69 GHz). The percentage bandwidth of antenna made by PTFE substrate is 20.57% (centered 2.43 GHz) and 68.74% (centered at 7.39 GHz). In addition to that, there exists 3 dB AR bandwidth for LHCP of about 1050 MHz for 5.2 GHz WLAN‐band. The reflection coefficient, radiation patterns, and the gains of both the antennas are studied in detail. It is found that the measured and simulated results are in good agreement.     

Dual‐band reconfigurable circularly polarized monopole antenna

A microstrip antenna with dual‐band reconfigurable circular polarization (CP) characteristics in Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) bands is presented in this article. The proposed antenna has a symmetrical U‐shaped slot with PIN diodes on the ground plane. The slotted ground generates a resonant mode for broad impedance‐band width, and excites contrary CP state at 2.45 GHz for WLAN and 3.4 GHz for WiMAX, respectively. Because switching the states of PIN diodes on the slot can redirect the current path, the CP state of the proposed antenna can be simply switched between the right‐handed CP and left‐handed CP. The proposed antenna has a low profile and a simple structure. Measured results of the fabricated antenna prototype are carried out to verify the simulation analysis. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:109–114, 2015.     

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.     

Circularly polarized planar monopole antenna for ultrawideband applications

A broadband circularly polarized (CP) planar monopole antenna is proposed here for ultrawideband (UWB) communication. The antenna is composed of a modified annular ring patch fed by a tapered microstrip line and a rectangular semiground plane on the opposite side of the substrate. Capability of generating wide axial ratio bandwidth (ARBW) is another feature of the proposed antenna. Wide ARBW is achieved by introducing a rectangular slot and a stub in the ground plane. The CP antenna has an impressive ARBW of 5.52 GHz (81.42%, 4.02‐9.54 GHz) within the UWB frequency range (3.1‐10.6 GHz). Measured 10‐dB return loss bandwidth of the proposed antenna is 120.86% centered at 7.48 GHz (2.96‐12 GHz). The proposed antenna is well used for wireless local area network (5.2 and 5.8 GHz), Worldwide Interoperability for Microwave Access (5.5 GHz), and other wireless systems in C band as well as CP‐UWB antenna communication.     

A compact widebeam circularly polarized antenna with wide impedance and axial ratio bandwidths

A compact widebeam circularly polarized antenna with wide impedance and axial ratio (AR) bandwidths is proposed in this study. The antenna is composed of a pair of crossed dipoles, four sequentially rotated parasitic elements, a slotted ground plane with four vertical plates, and four inverted L‐shaped structures. A prototype is fabricated and measured. An impedance bandwidth (S11 < ?10 dB) of 102.4% and a 3‐dB AR bandwidth of 83.5% are measured. And half‐power beamwidth is more than 120° over the whole operating band. Radiation patterns are symmetrical and identical in both principal planes. The compact size of antenna is 0.42λ₀ × 0.42λ₀ × 0.16λ₀.     

Compact meander T‐shaped monopole antenna for dual‐band WLAN applications

A compact coplanar waveguide‐feed monopole antenna with dual‐band characteristics is proposed in this article. The proposed antenna mainly consists of meander T‐shaped monopole and small ground plane embedded with a pair of L‐shaped couple slots and two pairs of I‐shaped notched slots symmetrically. By elongating the meander T‐shaped arms and carefully selecting the positions and lengths of L‐shaped slot and I‐shaped slot, the antenna excites four resonant frequencies at 2.42, 2.52, 4.75, and 5.54 GHz which are formed into two wide bands to cover all the 2.4/5.2/5.8 GHz wireless local area network (WLAN) operating bands, and is with miniaturization structure. Moreover, the antenna can provide nearly dipole‐like radiation patterns and good gains across the dual operating bands. These results prove that the proposed dual‐band antenna is very suitable for WLAN applications. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Dual‐band dual‐sense circularly polarized antenna based on crossed dipole structure for WLAN/WiMAX applications

This paper presents a new approach to design dual‐band antenna with dual‐sense circularly polarized (CP) operation. A principle for CP radiation is the use of two orthogonal dipoles and properly choosing their lengths can produce either right‐hand CP (RHCP) or left‐hand CP (LHCP) operation. In the proposed structure, the lower frequency band at 2.4 GHz is designed with RHCP radiation and LHCP is the operating mode of the higher band at 3.5 GHz. For verification, an antenna prototype is fabricated and measured. Measured data indicate that good performances over the RHCP and LHCP bands can be obtained with usable bandwidths of 2.9% (2.36‐2.43 GHz) and 1.7% (3.48‐3.54 GHz). Along with this, it also observes good unidirectional radiation patterns and the measured broadside gains are around 7.7 and 7.4 dBic across these frequency ranges.     

Dual‐band dual‐polarized hybrid aperture‐cylindrical dielectric resonator antenna for wireless applications

A dual‐band dual‐polarized hybrid aperture‐cylindrical dielectric resonator antenna (CDRA) is examined in this article. Inverted regular pentagon shaped aperture is not only used to launch two radiating hybrid modes (HEM_11δ and HEM_12δ mode) in CDRA but also act as a radiator. Out of two frequency bands, the lower frequency band is linearly polarized while upper frequency band is the combination of both circular and linear polarization. A circular polarization (CP) characteristic in upper frequency band is created by loading quarter annular stub with microstrip line. LHCP/RHCP can easily be controlled by alternating the position of quarter annular stub. It is operating over two frequency ranges i.e. 2.48‐2.98 GHz and 4.66‐5.88 GHz with the fractional bandwidth 18.31% and 23.14% respectively. Axial ratio bandwidth (3‐dB) is approximately 8.78% (4.9‐5.35 GHz) in upper frequency band. The proposed antenna design is suitable WiMAX (2.5/5.5 GHz) and WLAN (2.5/5.5 GHz) applications.     

A Dual‐band and dual‐polarized antenna array for 2G/3G/LTE base stations

A dual‐band antenna array is proposed for the application of base station (BS) in 2G/3G/long term evaluation (LTE) mobile communications. This antenna consists of two independent ±45° dual‐polarized arrays, one of which operates from 1.71 to 2.17 GHz, and the other of which is designed from 2.5 to 2.69 GHz. The proposed BS antenna array has a high isolation of greater than 29 dB and high front‐to‐back ratio of more than 26 dB at the operating frequencies. The measured peak gain is 17.9 and 18.1 dBi for the lower and upper bands, respectively, and the cross polarizations isolation (CPI)(within ±60º of the mainlobe) is 16 dB lower than the broadside co‐polarization. It was confirmed that the proposed antenna array meets the communication standards in China. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:154–163, 2016.     

Novel dual‐band asymmetric U‐shaped slot antenna for dual‐circular polarization

A novel dual‐band, dual‐circularly polarized antenna is proposed and fabricated. The proposed antenna consists of an asymmetric U‐shaped slot and an inverted L‐shaped slot which are designed to excite two orthogonal E vectors with equal amplitude and 90° phase difference (PD), in addition, fed by a coplanar waveguide (CPW) Furthermore, a left‐hand circular polarization in the direction of z > 0 and a right‐hand circular polarization instead of the opposite direction both at the lower and upper bands are exhibited by the radiations of the antenna. Good agreement is achieved between the measurement and simulation, which indicates that a 10‐dB bandwidth of 38.75% from 2.56 to 3.8 GHz and 21.8% from 10.01 to 12.53 GHz, while a 3‐dB axial‐ratio bandwidth (ARBW) of 13.4% from 2.77 to 3.2 GHz and 9.23% from 10.25 to 11.25 GHz at two operation bands, respectively, are covered in the designed antenna. To explain the mechanism of dual‐band dual‐circular polarization, the analysis of magnetic fields distributions and a parametric study of the design are given. Meanwhile, compared to other recent works, a single layer structure, wider axial ratio and impedance bandwidths and a more compact size are the key features of the proposed antenna.     

Circular polarized dual‐band antenna for WLAN/Wi‐MAX application

A novel square ring printed antenna has been suggested for dual‐band circular polarization (CP). The geometry contains a square patch and a square ring structure for dual‐band operation. Circular polarization is achieved using triangular cut at the boundary and right angle bend with inner perturbation. The suggested antenna is excited from the lower layer through electromagnetic (EM) coupling technique. The antenna shows good impedance bandwidths of 90 MHz (2.43‐2.52 GHz) and 800 MHz (5.7‐6.5 GHz, respectively. The antenna shows 3 dB axial ratio bandwidth of 20 MHz at lower band and 120 MHz at upper band with improved gain > 6 dBi. The simulated and measured results are well agreed with each other. The antenna is promising wideband operation at the upper band. This antenna was implemented on fiberglass reinforcement laminated Arlon substrate with dielectric constant (?_r = 2.55), and the overall physical dimension of 30 × 30 × 3.048 mm³. The designed antenna can be extensibly applicable in WLAN/Wi‐MAX communication. The presented antenna is designed using hyperlynx IE3D and the simulated results are presented.     

A broadband circularly polarized monopole antenna

A compact modified C‐shaped monopole antenna with broadband circular polarization is proposed, fabricated and measured. The antenna structure is simple and only consists of combined modified C‐shaped radiation patch and an improved ground plane with the overall size of 25 × 25 × 1 mm³. By cutting the corner on the modified C‐shaped patch and adding triangular stubs on the ground plane, the wide impedance bandwidth and axial ratio bandwidth are achieved. The design process of the antenna is given, and the circular polarization mechanism of the circularly polarized antenna is analyzed from the surface current distributions. The measured impedance bandwidth is 95.2% (4.4‐12.4 GHz) with return loss better than 10 dB, and the measured 3 dB axial ratio bandwidth is 96.8% (4.42‐12.72 GHz). The peak gain is above 3.0 dBi within the working band, which indicates that it is suitable for application of ultra‐wideband (UWB) wireless communication systems and satellite communication systems.     

Design of a dual‐polarized omnidirectional antenna for broadband applications

A broadband dual‐polarized omnidirectional antenna is presented. The proposed antenna consists of two parts, an asymmetric biconical antenna and a cylindrical multilayer polarizer. To have an almost perfect omnidirectional radiation pattern in the horizontal plane and the main radiating beam position at around , in the elevation plane, the asymmetric biconical antenna is used. Moreover, to provide dual polarization performance over the 2–18 GHz operational bandwidth, a multilayer polarizer is designed and optimized. Numerous simulations via Ansoft HFSS and CST microwave Studio CAD tools have been made to optimize the radiation pattern, gain, polarization, and the reflection coefficient of the antenna. Simulation results show that the radiation characteristics of the proposed antenna are extremely sensitive to the configuration and dimensional parameters of the multilayer polarizer. The designed antenna was fabricated with high mechanical accuracy and measured. Satisfactory agreement of computer simulations and experimental results was obtained. The main feature that distinguishes this antenna from the previous designs is the ability to provide the omnidirectional radiation pattern with small ripples, dual polarizations performance, and the wide bandwidth simultaneously. Based on these characteristics, the proposed antenna can be useful for broadband communication applications. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:591–600, 2015.     

A compact broadband coplanar waveguide fed circularly polarized printed monopole antenna with asymmetric modified ground plane

In this communication, a broadband circularly polarized (CP) monopole antenna with coplanar waveguide (CPW) feeding is proposed. It consists of a modified rectangular monopole, an asymmetric ground plane, a two‐linked inverted L‐shaped strips on the left CPW ground, and two rectangular horizontal slots in asymmetric CPW ground plane. The overall dimension is only 0.47λ _o × 0.47λ _o. The antenna prototype has been fabricated. The measured results indicate that a broad ?10 dB impedance bandwidth (IBW) of 107.5% (4.3 GHz, 1.85‐6.15 GHz) and a broad 3 dB axial ratio ARBW of 104.3% (4 GHz, 1.855‐5.9 GHz) can be achieved; the average realized gain is 2.3 dBi for the entire CP band. The proposed antenna is an attractive candidate for several wireless communication systems.     

An efficient dual‐band rectenna using symmetrical rectifying circuit and slotted monopole antenna array

In this article, an efficient dual‐band rectenna making use of the newly proposed symmetrical rectifying circuit working at the frequency of 1.8 and 2.45 GHz, is proposed. The proposed dual‐band rectifying circuit is combined with an array of compact wideband planar monopole modified circular slot antenna in order to facilitate the efficient rectenna design. The rectifying circuit employs symmetrical matching network in addition to the symmetrical rectifier thereby facilitating the suppression of the odd order harmonics. This eventually results into the higher output voltage as compared to the conventional rectifier circuits. Moreover, the dual‐band topology of the proposed rectenna increases the overall voltage by harvesting energy from two independent RF sources. The measured results of the fabricated structure show that the maximum RF to dc conversion efficiency of the proposed rectifier circuit reaches up to 70% at 9 dBm input RF power. From application point of view, the proposed rectenna circuit is tested to extract the RF energy from 1.8 GHz cellular and 2.45 GHz Wi‐Fi bands to energize a low‐power LED. The overall rectenna structure is reasonably compact providing good performance, which can potentially be employed for efficient wireless power transmission system.     

A dual‐polarized cross‐dipole antenna with wide beam and high isolation for base station

In this paper, a dual‐polarized cross‐dipole antenna with wide beam and high isolation is designed and analyzed for base station. The proposed antenna consists of two planar cross dipoles with four square patches, two L‐shaped microstrip lines, two ground plates, four parasitic patches, and a reflector. The square patches are placed between the center of cross dipoles to couple with L‐shaped microstrip lines. By introducing the parasitic patches, the wide beam can be realized. The measured results show that the proposed antenna achieves an impedance bandwidth (|S₁₁| < ?10 dB) of about 18.7% (1.9‐2.35 GHz) and an isolation better than 30 dB. A measured gain of 5.7 dBi and a half‐power beamwidth over 120° at the center frequency are obtained. Furthermore, the size of the proposed antenna is only 0.5λ₀ × 0.5λ₀ × 0.22λ₀ (λ₀ is wavelength at the center frequency).     

A compact dual‐band filtering antenna for wireless local area network applications

A printed dual‐band filtering antenna with decent frequency selectivity at 2.45 and 5.2 GHz for wireless local area network (WLAN) applications is developed. The filtering antenna is compact, which comprises a tapped feed line, two dual‐band stub‐loaded open‐loop resonators, and a dual‐band bended monopole. It can be easily printed on a single layer PCB substrate with low profile and low cost. The entire structure is very simple compared with the previously reported dual‐band filtering antennas that requiring multi‐layer structures. The monopole functions as not only a radiator, but also the last resonator of a dual‐band filter. The developed antenna exhibits good frequency selectivity and out‐of‐band suppression. In addition, the two operation bands can be adjusted relatively individually. The proposed antenna is optimized and fabricated. The experimental results show it has good frequency selectivity at both 2.45 and 5.2 GHz, wide bandwidth 11.8% and 7.8%, and excellent out‐of‐band suppression.     

A new compact planar UWB monopole antenna

A new compact planar monopole antenna which covers an ultra wide bandwidth of ～147% from 2.96 to 19.43 GHz for S₁₁ ≤ ?10 dB is presented. The proposed antenna has simple configuration and easily fed by using a 50 Ω microstrip line. The total size of the antenna is 30 × 26 × 1.6 mm³. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Circularly polarized quad‐band monopole antenna of wireless communication system

In this article, multiband monopole antenna has been designed for the applications of wireless communication systems. The antenna is composed of I‐shaped strips which are placed in such a way that the each of the resonating strips produced distinct frequency bands. The optimum dimension of the proposed antenna is printed on dielectric substrates of FR4 epoxy having dimensions of 0.3λ₀ × 0.21λ₀ × 0.009λ₀. The antenna has been fabricated and measured for evidence. The measured results are verified with simulated results. The comparison of simulated and measured S₁₁ parameter, radiation pattern, peak gains, and circular polarization are described in the section of experimental results. The measured result shows that the antenna may cover the frequency band of Digital Cellular System, Personal Communications Service, Long Term Evolution‐4G, Bluetooth, Worldwide Interoperability Microwave Access, Wireless Local Area Network, 802.11j (WLAN‐Public Safety), and X‐band (Satellite Communication‐downlink).     

Dual‐band circularly polarized aperture‐coupled stack antenna with fractal patch for WLAN and WiMAX applications

This article presents a novel circular polarized (CP) aperture coupled stack antenna for wireless local area network and worldwide interoperability for microwave access dual‐band systems. The compact stack antenna consisted of square fractal patch, aperture couple, feed line and the perturbation. The square patch is constructed with the complementary Minkowski‐island‐based fractal geometry. By way of adjusting the relevant parameters, we can obtain the dual‐band responses at 3.5 and 5.25 GHz respectively. The CP of each band are presented. The measured 10 dB return loss impedance bandwidth are 270 MHz (7.5%) for 3.5 GHz band and 450 MHz (8.6%) for 5.25 GHz band. The 3 dB axial ratio bandwidths for each bands are 1.4 and 0.76%, the polarization of radiation patterns are both left‐hand CP, and the antenna power gain are 2.84–3.1 and 0.16–2.2, dBic respectively. The proposed antenna is successfully simulated and measured with frequency responses, radiation patterns and current distributions. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:130–138, 2014.