Novel wideband active microstrip antennas using distributed frequency multiplexers or de‐multiplexers

In this article, a novel approach is introduced for the design of wideband antennas in a specified frequency bandwidth (BW). In the proposed approach, the frequency BW is divided into some sub‐bands. Then, the narrowband antennas are designed for the consecutive frequency sub‐bands, and the antennas are connected together by a proposed active circuit, so that their frequency BWs combined. The proposed active circuit may be used to connect as many as antenna needed for the design. An active microstrip antenna is designed for the frequency BW of 4–10 GHz with a gain better than 5 dB by the proposed method. Fabrication and measurement results show the effectiveness of the proposed methodology. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

A CPW‐fed band notched wideband circularly polarized ZOR antenna based on CRLH‐TL approach

This article presents design and analysis of three wide band zeroth‐order resonance antennas (antennas I, II, and III) using composite right and left‐handed transmission line (CRLH‐TL) approach. Coplanar waveguide technology, single layer via‐less structures are used to have the design flexibility. The bandwidth characteristics are analyzed by using lumped parameters of CRLH‐TL. By introducing a simple slot in the ground plane of antenna I both bandwidth enhancement and circularly polarization characteristics are achieved in antenna II. Another quarter wave L‐shaped slot has been introduced in the ground plane of antenna II to introduce a notch band in the frequency response of antenna III. Achieved measured 10 dB return loss bandwidth of antenna I and antenna II are 960 (3.3‐4.26 GHz) and 2890 MHz (2.77‐5.66 GHz), respectively. Antenna III offers measured 10 dB return loss bandwidth of 3220 MHz (2.32‐5.54 GHz) with a band notch from 2.39 to 2.99 GHz that isolates the 2.4 GHz WLAN and 3.5 GHz WiMAX band. Antenna II and antenna III have circular polarization property with measured axial ratio bandwidth of 440 MHz. The measured peak realized gain of antennas II and III is around 1.53‐2.9 dBi.     

具有匹配反馈环的微波段RFID标签天线设计

针对标签天线在RFID系统中的重要性,基于微带天线设计和电磁散射理论,设计和分析了一种具有匹配反馈环的微波段RFID标签天线。谐振频率为2.45 GHz和2.41 GHz天线的尺寸为54 mm×33 mm左右,天线显示近线性相位特性,在电压驻波比小于2的条件下天线的阻抗带宽为300 MHz。可以通过调整匹配反馈环的长度来调整天线的谐振频率,天线的增益为2.4~2.7 dBi。谐振频率为5.8 GHz的天线阻抗带宽为7%,增益为2.8~3.2 dBi,尺寸大小为20 mm×12 mm。通过仿真和测量可知,这种天线能较好地满足RFID微波段标签的要求。     

Performance enhancement of nested hexagonal ring‐shaped compact multiband integrated wideband fractal antennas for wireless applications

In this paper, nested hexagonal ring‐shaped fractal antennas are designed and investigated which are different from each other in patch orientation. Initially, the multiband integrated wideband hexagonal nested ring antenna is designed (antenna‐I). To improve the multiband/wideband behavior, the patch orientation of antenna‐I is changed to ?60°/60° (antenna‐II), ?120°/120° (antenna‐III), and ?180°/180° (antenna‐IV). Antennas are designed on low cost FR‐4 glass epoxy substrate with relative permittivity of 4.4 and overall dimension 30 × 30 × 1.6 mm³. Comparison among antennas have been made and found that the antennas with negative orientation exhibit better results in terms of bandwidth, impedance matching, number of frequency bands, and gain. Designed antennas have been compared with each other and found that antennas‐II and III are better in performance as compared to antennas‐I and IV. Antenna‐II exhibits wider bandwidth of 1.26 (2.52‐3.78 GHz), 2.75 (4.03‐6.78 GHz), and 6.1 GHz (7.82‐13.92 GHz) with maximum gain of 7.14 dB. Similarly; antenna‐III exhibits the bandwidth of 340 MHz (1.92‐2.26 GHz), 820 MHz (3.04‐3.86 GHz), 4230 MHz (5.38‐9.61 GHz), and 3040 MHz (10.41‐13.45 GHz) with a maximum gain of 6.19 dB. Prototype of the designed antennas with satisfactory orientations are fabricated and tested for the validation of results. Simulated and measured results are also juxtaposed and observed in good agreement with each other. Antennas exhibit bidirectional and omnidirectional pattern in E‐plane and H‐plane, respectively, also the radiation efficiency of antennas are in acceptable range from 75% to 95%. Due to the wider bandwidth of designed antennas, they can be used for different wireless standards such as Advance Wireless Services AWS‐1, AWS‐2, AWS‐3, Wi‐MAX, WLAN, X‐band satellite communication, point‐to‐point wireless applications, ITU band, military satellite communication, television broadcasting, and military land and airborne systems.     

Compact broadband circularly polarized slot‐patch antenna array

A simple design of circularly polarized slot‐patch antenna array with broadband operation and compact size is presented in this article. The antenna element consists of a circular slot and a semicircular patch, which are etched on both sides of a substrate. For the gain and axial ratio (AR) bandwidth enhancement, its array antennas are implemented in a 2 × 2 arrangement and fed by a sequential‐phase feeding network. The final 2 × 2 antenna array prototype with compact lateral dimension of 0.8λ_L × 0.8λ_L (λ_L is the lowest frequency within AR bandwidth) yielded a measured impedance bandwidth of 103.83% (2.76‐8.72 GHz) and a measured AR bandwidth of 94.62% (2.45‐6.85 GHz). The peak gain values within the AR bandwidth are from 2.85 to 8.71 dBi. A good agreement between the simulated and measured results is achieved. This antenna array is suitable for multiservice wireless systems covering WiMAX, WLAN and C‐band applications such as satellite communications.     

Double‐ridged conical horn antenna for wideband applications

In this article, the design and analysis of a double‐ridged conical horn antenna with high gain and low cross polarization for wideband applications is presented. Double‐ridged pyramidal horn antennas have been investigated in many references. There are no papers in the literature which are devoted to design and analysis of double‐ridged conical horn antenna. The designed antenna has a voltage standing wave ratio (VSWR) less than 2.1 for the frequency range of 8–18 GHz. Moreover, the proposed antenna exhibits extremely low cross polarization, low side lobe level, high gain, and stable far‐field radiation characteristics in the entire operating bandwidth. A new technique for synthesizing of the horn flare section is introduced. A coaxial line to circular double‐ridged waveguide transition is introduced for coaxial feeding of the designed antenna. The proposed antenna is simulated with commercially available packages such as CST microwave studio and Ansoft HFSS in the operating frequency range. Simulation results for the VSWR, radiation patterns, and gain of the designed antenna over the frequency band 8–18 GHz are presented and discussed. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

A state‐of‐art review on performance improvement of dielectric resonator antennas

This article outlines a compressive review on investigation carried out targeting to gain, circular polarization (CP), and mutual coupling reduction in dielectric resonator antenna (DRA). The DRA has already been created a separate position in antenna engineering domain because of its adept characteristics, such as wide bandwidth, high efficiency, low‐loss, and mainly 3D‐design flexibility which is rarely available in conventional antennas. In this context, the research on gain, circular polarization, and mutual coupling are quite interesting and being carried out from the last two decades. The ultimate aim of this article is to (i) give an overview of different techniques adopted in context to gain, CP, and mutual coupling reduction; (ii) give a compressive review of notable research carried out targeting to these three characteristics; and (iii) find out the research gap concentration for furtherance of the same.     

Application of metamaterials for performance enhancement of planar antennas: A review

Metamaterials are assemblies of metallic and/or dielectric materials with properties that are not readily found in naturally existing materials. Hence, metamaterial structures are commonly loaded on/near the patch, embedded in the substrate, loaded/etched from the ground plane or placed as a superstrate layer for enhancing bandwidth and gain, and size miniaturization of conventional patch antennas. The demand for wide bandwidth, high gain, and compact antennas is highly contemplated in recent wireless communication research studies. Despite their lightweight, ease of fabrication, low profile, and simplicity for integration, patch antennas have performance limitations as result of their narrow bandwidth, lower gain, larger size, and lower power handling capacity. To address these problems, metamaterial‐based antennas have gained massive interest. There exist inadequate literatures about review of current state of extensive study reports on metamaterial application for patch antenna performance enhancement. Thus, this paper has reviewed and discussed latest research works on metamaterial applications for performance enhancement of planar patch antennas.     

一种高增益宽频带圆极化微带阵列天线的研制

针对微带天线阻抗匹配带宽一般较窄的自身缺陷,基于相控阵雷达天线的应用背景,设计了一种工作在X波段的双层圆极化微带天线结构,且优化发现,其各电磁参数良好。为提高其增益,还在此基础上设计并最终制作了双层2×2结构的微带天线阵列,其实测性能与设计值相符,增益达到10.7dB,带宽1.2GHz,相应轴比为4dB,符合圆极化要求。     

Wideband microstrip‐fed tapered slot antennas and phased array

Two wideband tapered slot antennas are designed, fabricated, and tested. The first antenna, which is fabricated on a high dielectric constant substrate (?_r = 10.2), shows a measured return loss of better than 10 dB from 1.6 to 12.4 GHz (7.7:1 bandwidth), and an antenna gain varying from 3.6 to 7.8 dBi. The second antenna is built on a low dielectric constant substrate (?_r = 2.2), and demonstrates return loss of better than 10 dB from 1.8 to 15.2 GHz (8.4:1 bandwidth). The second antenna also has improved antenna gain, from 5 to 15.6 dBi, and is used to build a wideband 1 × 4 H‐plane phased array with a total gain of 9–17 dBi and a beam steering angle of ±15° from 3 to 12 GHz. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Metamaterial inspired fabric antenna for wearable applications

A compact and robust fabric antenna incorporated with metamaterials (MTM) at 2.4 GHz is introduced for wearable devices application where the MTM behaves as EBG/AMC. The benefit of introducing MTM in a wearable antenna is to diminish the influence of frequency detuning and reduces the backward radiation specifically when loaded on the human body. The overall size of the presented antenna incorporated with MTM is 60 × 60 × 2.4 mm3. Furthermore, the integrated design has the capability of controlling Specific absorption rate (SAR) and improved the bandwidth, front‐to‐back ratio (FBR), and gain up to 14.5%, 13.7dB, and 7.5dBi, respectively. The operations under different bending diameters on real and modelled human body are studied. Compared with conventional antennas, MTM‐inspired antennas reduce the SAR to safe levels of more than 90%. The presented integrated design can be a good candidate for incorporation into a variety of flexible systems for medical application.     

Wideband linear microstrip array antenna with high efficiency and low side lobe level

In this letter, the design and fabrication of the linear microstrip array antenna by series fed are presented. The array antenna consists of 16 reflector slot‐strip‐foam‐inverted patch (RSSFIP) antennas. The gain and efficiency of the linear array antenna is 16.6 dBi and 61% at 10 GHz, respectively. The antenna has a bandwidth (BW) of 45% from 8.1 to 12.8 GHz (S₁₁ < ?10 dB) and side lobe level (SLL) of ?25.6 dB across the BW of 19.2% from 9.4 to 10.4 GHz. These are achieved by using a microstrip series fed with defected ground structure (DGS) to feed the patch array antenna. Good agreement is achieved between measurement and simulation results.     

Design and characterization of millimeter wave planar reflectarray antenna for 5G communication systems

This work provides design and characterization of millimeter wave reflectarray antenna based on unit cells as well as periodic reflectarray design at 26 GHz. Diverse unit cell design configurations have been investigated based on simulations and scattering parameter measurements for feasibility of designing an optimum performance 5G reflectarray antenna. It has been demonstrated that the rectangular patch element provided minimum reflection loss of 1.02 dB and maximum bandwidth of 560 MHz. However, the phase error for rectangular patch element was observed to be 80°, which is much higher as compared to 10° and 13° in the case of rectangular ring and circular ring elements respectively. Periodic reflectarray antennas were also designed with main beam focused at 40° in the azimuth plane achieved with tilted array instead of using an offset feed. Radiation pattern measurements were carried out for further characterization where a maximum gain of 26.7 dB was provided by reflectarray designed with circular ring elements with variable radius. On the other hand, rectangular patch element array provided higher 1 dB gain drop bandwidth of 13.6% as compared to circular ring element reflectarray, which demonstrated a bandwidth of 13.1%. However, side lobe levels were observed to be higher at ?18.4° for rectangular patch element reflectarray as compared to ?19.4° in the case of circular ring elements based reflectarray antenna.     

Design and Analysis of Novel Antenna for Millimeter-Wave Communication

At present, the microwave frequency band bandwidth used for mobile communication is only 600 MHz. In 2020, the 5G mobile Communication required about 1 GHz of bandwidth, so people need to tap new spectrum resources to meet the development needs of mobile Internet traffic that will increase by 1,000 times in the next 10 years. Utilize the potentially large bandwidth (30∼300 GHz) of the millimeter wave frequency band to provide higher data rates is regarded as the potential development trend of the future wireless communication technology. A microstrip patch implementation approach based on electromagnetic coupling feeding is presented to increase the bandwidth of a dual-polarized millimeter-wave antenna. To extend the antenna unit's impedance bandwidth, coplanar parasitic patches and spatial parallel parasitic patches are used, and a 22 sub-array antenna is developed using paired inverse feed technology. The standing wave at the centre frequency of 37.5 GHz is less than 2 GHz. The antenna array's relative bandwidth is 6.13 percent, the isolation is >30 dB, the cross-polarization is −23.6 dB, and the gain is 11.5 dBi, according to the norm. The proposed dual-polarized microstrip antenna has the characteristics of wide frequency bandwidth, large port isolation, low cross-polarization, and high gain. The antenna performance meets the general engineering requirements of millimeter-wave dual-polarized antennas.     

Circularly polarized 1 × 4 square slot array antenna by utilizing compacted modified butler matrix and branch line coupler

Circularly polarized (CP), beam steering antennas are preferred to reduce the disruptive effects such as multi‐path fading and co‐channel interference in wireless communications systems. Nowadays, intensive studies have been carried out not only on the specific antenna array design but also their feeding networks to achieve circular polarization and beam steering characteristics. A compact broadband CP antenna array with a low loss feed network design is aimed in this work. To improve impedance and CP bandwidth, a feed network with modified Butler matrix and a compact ultra‐wideband square slot antenna element are designed. With this novel design, more than 3 GHz axial ratio BW is achieved. In this study, a broadband meander line compact double box coupler with impedance bandwidth over 4.8‐7 GHz frequency and the phase error less than 3° is used. Also the measured impedance bandwidth of the proposed beam steering array antenna is 60% (from 4.2 to 7.8 GHz). The minimum 3 dB axial ratio bandwidth between ports, support 4.6–6.8 GHz frequency range. The measured peak gain of the proposed array antenna is 8.9 dBic that could scan solid angle about ～91 degree. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:146–153, 2016.     

Dual‐polarized textile‐based two/four element MIMO antenna with improved isolation for dual wideband application

This article presents the designs of dual‐polarized dual wideband textile‐based two and four elements multiple‐input multiple‐output (MIMO) antennas for WLAN (IEEE 802.11a/b/g/c/n) and WiMAX (IEEE 802.16d) applications. These MIMO antennas cover the frequency spectra from 1.5 to 3.8 GHz (87% bandwidth) and 4.1 to 6.1 GHz (40% bandwidth). The characterization of the textile jeans substrate is determined experimentally using a vector network analyzer and dielectric assessment kit. These antennas provide near about 70% radiation efficiency with around 4 dBi peak gain in desired frequency ranges. The diversity performance is improved noticeably by printing meandered line structures on both planes. The proposed MIMO structure has a very low envelop correlation coefficient (ECC) <0.1 and high diversity gain (DG) >9.9. The Medium effective gain (MEG) also lies within a satisfactory value of ±3 dB. The two elements MIMO Antennas provide linear polarization at all desired frequency band while the four‐element antenna provides circular polarization at 2.4 GHz and linear polarization at 5.2 and 5.8 GHz application bands. The antenna also depicts good performance in wearable condition with safe specific absorption rate < 1.6 W/kg in all desired frequencies.     

Nonuniform reflect‐array antennas

A center‐fed reflect‐array antenna with nonuniform substrate as a reflecting surface is proposed. To design and analyze this kind of antennas, a simple method based on an equivalent circuit model is introduced. Using this method a low cross‐polarization of about ?21 dB below the main beam peak and wide 3‐dB gain bandwidth of 19.5% are obtained at X‐band frequency. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Comparative Design and Study of A 60 GHz Antenna for Body-Centric Wireless Communications

In this paper performance of three different designs of a 60 GHz high gain antenna for body-centric communication has been evaluated. The basic structure of the antenna is a slotted patch consisting of a rectangular ring radiator with passive radiators inside. The variation of the design was done by changing the shape of these passive radiators. For free space performance, two types of excitations were used—waveguide port and a coaxial probe. The coaxial probe significantly improved both the bandwidth and radiation efficiency. The center frequency of all the designs was close to 60 GHz with a bandwidth of more than 5 GHz. These designs achieved a maximum gain of 8.47 dB, 10 dB, and 9.73 dB while the radiation efficiency was around 94%. For body-centric applications, these antennas were simulated at two different distances from a human torso phantom using a coaxial probe. The torso phantom was modeled by taking three layers of the human body—skin, fat, and muscle. Millimeter waves have low penetration depth in the human body as a result antenna performance is less affected. A negligible shift of return loss curves was observed. Radiation efficiencies dropped at the closest distance to the phantom and at the furthest distance, the efficiencies increased to free space values. On the three layers human body phantom, all three different antenna designs show directive radiation patterns towards off the body. All three designs exhibited similar results in terms of center frequency and efficiency but varied slightly by either having better bandwidth or maximum gain.     

Additively manufactured trapezoidal grooves for wideband and high gain Ku‐band antenna

Grooves around aperture antennas are known to be instrumental in obtaining directive antenna patterns. The shapes of the grooves are often restricted to rectangular or triangular due to manufacturing difficulties in traditional metal machining, and because of this reason, the effect of groove shape on antenna performance is often overlooked. The aim of this study is to analyze different groove shapes with the help of additive manufacturing. Waveguide slot fed, dual cavity aperture antenna with grooves is designed and the effect of groove shapes on antenna performance is studied at Ku band. Two antennas with and without grooves are built using 3D printing technology. Measured antenna performance reveals 5 GHz bandwidth covering 10 to 15 GHz for Ku‐band satellite communications and part of the X‐band applications. Proposed antenna achieves 13.25 dBi peak gain at 14 GHz and the gain is better than 11.25 dBi over the entire Ku‐band uplink and downlink frequency bands.     

Design of a tunable omnidirectional circularly polarized antenna based on VO2

In this article, a VO₂‐based tunable omnidirectional circularly polarized (CP) antenna is designed. The proposed antenna combines copper and metamaterial VO₂. By utilizing the characteristics of insulator‐metal phase transition of VO₂, we can change the length of the resonant branches to achieve tunable working bandwidth. The proposed antenna is composed of a modified floor loaded with VO₂ and copper resonant branches, a top patch with slits, and 14 shorting vias connecting the top path and bottom floor. Different from the traditional electric controlled antennas, antennas based on metamaterial VO₂ do not need to design complicated circuit structures and can be easily tailored by the external temperature (T). The simulated results illustrate that when T ≥ 68°C (state I), the proposed antenna has a 10‐dB impedance bandwidth of 15.9% (2.09‐2.45 GHz), and a 3‐dB axial ratio (AR) bandwidth of 23.4% (2.04‐2.58 GHz). When T < 68°C (state II), it has a bandwidth of 6.5% (2.38‐2.54 GHz) with S₁₁ below ?10 dB, and a bandwidth of 19.9% (2.39‐2.92 GHz) with AR below 3 dB.