Compact ultra‐wideband slot antenna with three notched‐band characteristics

A very compact ultra‐wideband (UWB) slot antenna with three L‐shaped slots for notched‐band characteristics is presented in this article. The antenna is designed and fabricated using a new stepped slot with different size, integrated in the ground plane, and excited by a 50 Ω microstrip transmission line. The stepped slot is used to minimize the dimensions of the antenna and to achieve an impedance bandwidth between 2.65 and 11.05 GHz with voltage standing wave ratio (VSWR) less than 2. The length of the stepped slot is equal to a quarter wavelength to create a resonance in the desired frequency. Three L‐shaped slots with various sizes are etched in the ground plane to reject three frequency bands in C‐band (3.7‐4.2 GHz), WLAN (5.15‐5.825 GHz), and X‐band (7.25‐7.75 GHz), respectively. The notched‐band frequency can be controlled by changing the length of the L‐shaped slot. The proposed antenna has a very small size (20.25 × 8 × 1.27 mm³) compared with previous works. The measured and simulated results show a good agreement in terms of radiation pattern and impedance matching.     

Reconfigurable ultra‐wideband monopole antenna with single‐, dual‐, and triple‐band notched functions

A miniaturized ultra‐wideband (UWB) monopole antenna with reconfigurable multiple‐band notched performance is demonstrated. By modifying the shape of the patch and the ground plane, the UWB operation is achieved. The first and second band‐notches are respectively generated by etching a rectangular slot with open ends and a U‐shaped slot in the patch, and the third band‐notch is produced by loading a C‐shaped parasitic element beneath the patch. To realize the reconfigurable band‐notched functions, four PIN diodes are inserted in three band‐rejected structures. The antenna has a compact dimension of 30 mm × 26 mm. It can switch between a UWB state and several band‐notch states by alternating the states of the diodes. Also, good radiation patterns are obtained.     

A dual‐band and wideband omnidirectional circularly polarized antenna based on VO2

In this article, a dual‐band and wideband omnidirectional circularly polarized (CP) antenna based on the vanadium dioxide (VO₂) is investigated. The operating bandwidth of such an antenna can be regulated by altering the outside temperature (T), which is attained by the insulator‐metal transition of VO₂. The omnidirectional CP antenna is based on a loop antenna‐dipole model, which is composed of four tilted metal and VO₂ resonant units that are loaded around a cuboid and a feeding network for broadening bandwidth. The simulated results show that when T = 50°C (State I), the 10‐dB impedance bandwidth is 45.7% (1.67‐2.66 GHz), and the 3‐dB axial ratio (AR) bandwidth is 40% (1.9‐2.85 GHz). When T = 80°C (State II), the 10‐dB impedance bandwidth is 13.8% (1.62‐1.86 GHz), and the 3‐dB AR bandwidth is 21.8% (1.68‐2.09 GHz). In order to further characterize the concept of the proposed antenna, the related parameters of such an antenna are studied using simulation software HFSS.     

Low profile four‐port super‐wideband multiple‐input‐multiple‐output antenna with triple band rejection characteristics

A quad‐port planar multiple‐input‐multiple‐output (MIMO) antenna possessing super‐wideband (SWB) operational features and triple‐band rejection characteristics is designed. The proposed MIMO configuration consists of four modified‐elliptical‐self‐complementary‐antenna (MESCA) elements, which are excited by tapered co‐planar waveguide (TCPW) feed lines. A radiator‐matched complementary slot is present in the ground conductor patch of each MESCA element. The proposed MIMO antenna exhibits a bandwidth ratio of 36:1 (|S₁₁| < ?10 dB; 0.97‐35 GHz). Further, a step‐like slit‐resonator is etched in the radiator to eliminate interferences at 3.5 GHz. A hexagonal shaped complementary split ring resonator (CSRR) is also loaded on the MESCA radiator to remove interferences at 5.5 and 8.5 GHz. The MIMO antenna is fabricated on FR‐4 substrate of size 63 × 63 mm² and experimental results are found in good agreement with the simulated results. The MIMO antenna exhibits inter‐element isolation >17 dB and envelope correlation coefficient (ECC) <0.01 at all the four ports.     

Dielectric resonator array antenna for triple band WLAN applications with enhanced gain

An H‐shaped dielectric resonator array antenna is presented for wideband applications. The proposed antenna is excited by slot feed mechanism and investigated experimentally. The antenna covers the frequency ranges from 1.41 to 2.59 GHz, and 4.73 to 6.06 GHz with the corresponding impedance bandwidth of 59% and 24.65%, respectively. The simulation results fulfill the bandwidth requirements of IEEE 802.11a/b/g (2.4‐2.484 GHz/5.15‐5.35 GHz/5.725‐5.825 GHz) for Wireless local area network (WLAN) applications. The proposed antenna has simple structure, easy to fabricate and its measured radiation pattern shows a reliable performance in the desired operating bands.     

A wideband reflectarray antenna using single‐layer dipole element attached with T‐shaped stubs

A wideband reflectarray antenna consisting of single‐layer dipole element attached with T‐shaped stubs is proposed. By varying the lengths of the T‐shaped stubs, the unit cell can provide a linear phase curve covering about 420°. Critical design parameters are analyzed to understand its wideband operating mechanism. Using this novel type of unit cells, a 441 element 25° offset‐fed reflectarray with grid spacing of λ/3 at 10 GHz is designed, fabricated, and measured. The experimental results show that the proposed reflectarray can achieve 1‐dB gain bandwidth of 24% and 1.5‐dB gain bandwidth of 37%. In addition, aperture efficiency of 66.6% and cross polarization level of 29 dB are obtained at 10 GHz, respectively.     

Design and analysis of slot antenna with band notch function

In this article, the design, simulation, and construction of a novel wide rectangular slot antenna fed by a 50 Ω coplanar waveguide (CPW) are presented and investigated for multifunctional communication systems. The physical dimension of the antenna is 29 mm (length) × 32 mm (width) × 1.6 mm (thickness). Detailed simulations and experimental investigations are performed to understand its behavior and to optimize for 2.4 GHz wireless local area network (WLAN) and ultra wideband (UWB) operations. The proposed slot antenna is etched on an FR4 substrate with a thickness of 1.6 mm and relative permittivity of 4.4. To improve the impedance matching, a stepped stub structure with CPW feed technique is used. According to the measured results, the proposed antenna has a large bandwidth from 2.1 to 11.6 GHz for voltage standing wave ratio (VSWR) less than 2, totally satisfying the requirement of 2.4 GHz WLAN and UWB systems, while providing the required band notch function from 5.1 to 5.9 GHz. The study of time domain characteristics and surface current distributions also indicate the band‐notched function of the antenna. The radiation patterns display nearly omnidirectional performance and the antenna gain is stable except for the rejected frequency band (5.1–5.9 GHz). Moreover, group delays are within 1.5 ns except for the notch‐band. It is observed that the simulated and experimental results have good agreement with each other. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

A state‐of‐art review on band‐notch characteristics in UWB antennas

Ultra‐wideband technology has experienced a rapid growth over the last decade for its contribution in different sectors of human society. Printed antennas are considered as preferred platform for implementing this technology because of its alluring characteristics like light weight, low cost, ease of fabrication, integration capability with other systems, etc. Antennas developed for ultra‐wideband applications are desired to have notch characteristics for avoiding interference with other existing radio communication systems. The techniques related to design and developments of printed band‐notched antennas are continuously upgraded for improving the antenna performance. In this article, a comprehensive review has been carried out on ultra‐wideband antennas with band notch characteristics proposed in around last decade. The band notched UWB antennas available in the literature have broadly been classified into five different categories based on their notch characteristics like single band‐notch, dual band‐notch, triple band‐notch, quad/multiple band‐notch, and reconfigurable/tunable band‐notch, respectively. This review exercise may be helpful for beginners working on ultra‐wideband band‐notched antennas and also such a review process is not available in the open literature to the best of author's knowledge.     

Design approach for dual element hybrid MIMO antenna arrangement for wideband applications

This communication explains the designing of two‐port based hybrid radiator for multiple‐input‐multiple‐output (MIMO) applications. Hybrid radiator includes U‐shaped printed line and ring dielectric resonator antenna (ri‐DRA). Wideband characteristics have been achieved by exciting both the U‐shaped printed line along with ri‐DRA. The U‐shaped metallic line acts as a magnetic dipole and helps to excite fundamental hybrid mode (HE_11δ) in the ri‐DRA. Dual L‐shaped and a rectangular defect have been created in ground plane for achieving wideband isolation over the working frequency band. Optimized Scattering parameters and far‐field results are verified by fabricating and testing of antenna prototype. Experimental outcomes confirm that the proposed MIMO antenna gives wider impedance bandwidth (80%), improved port isolation (better than 18 dB), stable gain (~ 4 dB), and radiation pattern. Various MIMO performance factors are analyzed and instituted in the tolerable boundaries.     

Design of a compact protrudent‐shaped ultra‐wideband multiple‐input‐multiple‐output/diversity antenna with band‐rejection capability

In this endeavor, a new multiple‐input‐multiple‐output antenna with a sharp rejection at wireless local area network (WLAN) band is designed and practically examined for portable wireless ultra‐wideband applications. The intended diversity antenna possess a small size of 15 mm × 26 mm and two inverted L‐strip are loaded over the conventional rectangular patch antenna to form protrudent‐shaped radiator that acts as a radiating element. The sharp band‐rejection capability at WLAN is established by incising the L‐shaped slits at the decoupling structure. More than ?21 dB isolation is accomplished for the complete working band (ie, 2.87 ‐17 GHz). Degradation in the antenna efficiency at the center frequency of band rejection corroborates the good interference rejection capability. The working capabilities of the intended antenna are tested by using the isolation between the ports, total efficiency, gain, envelope correlation coefficient, radiation pattern, mean effective gain, and total active reflection coefficient.     

Investigation on novel wideband fractal antenna design based on cylindrical shape dielectric resonator

This article explains a novel approach for achieving wideband characteristics in case of dielectric resonator antenna (DRA). Wideband characteristic has been realized by uniting the concept of vastu purusha mandala (VPM)‐based fractal geometry with dielectric resonator antenna. VPM is Hindu religion‐based fractal geometry, which provides the advantage of decrease in volume to surface area of the radiator. This concept is useful to enhance impedance bandwidth of proposed antenna. For the purpose of validation, prototype of proposed antenna design has been fabricated as well as tested. After experimental testing, it is confirmed that the proposed radiator functions over the frequency range 2.6‐4.34 GHz with a percentage bandwidth of 46.52%. The proposed radiating arrangement provides peak gain of 6.3 dBi and stable far‐field characteristics. All these features make it applicable for WiMAX application (3.3 GHz).     

一种宽带天线的研究与设计*

为了满足宽带通信的需求,利用U形单极子天线和两个U形寄生辐射元的方法,设计了一种共面波导馈电的宽带天线,其阻抗带宽达到85%。所设计的天线印刷在尺寸为20 mm×30 mm×1.6 mm、介电常数为265的聚四氟乙烯介质基板上。为了满足无线局域网（WLAN）和全球互联微波接入（WiMAX）的工作需要,抑制不需要的信号,在U形单极子辐射元之间插入一条调谐微带线,产生一个陷波特性,使所设计的天线满足WLAN、WiMAX和低端UWB通信需求。利用高频结构仿真软件HFSS对影响天线性能的主要参数进行仿真、分析和优化,得到天线的优化尺寸,并对优化的天线进行制造和测试。实验结果表明,该天线比传统微带贴片天线性能有了较大的提高,证明了利用共面波导馈电和寄生技术设计宽带天线的可行性和有效性。     

A simple planar monopole UWB slot antenna with dual independently and reconfigurable band‐notched characteristics

An extremely simple and compact planar monopole ultrawideband (UWB) slot antenna with dual band‐notched characteristics is proposed. The antenna is composed of a circular radiation patch, a microstrip‐fed line, and a partial ground. By etching an arc‐shaped slot on the radiation patch and a C‐like slot on the feed line, dual notched frequency bands at 3.3–3.7 GHz for WiMAX and 5.15–5.825 GHz for WLAN are achieved. And, the two notched bands can be adjusted independently by varying the length of the slots. Moreover, the band‐notched characteristics can be reconfigurable by shorting the corresponding slots. So, the antenna is capable of operating in one of multiple modes which makes it an excellent candidate for UWB applications. Meanwhile, experimental results indicate that the antenna has an available impendence bandwidth from 2.9 to 11 GHz which covers the UWB frequency band, and nearly omnidirectional patterns, stable gains, small group delay in operating band except rejected bands. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:706–712, 2014.     

Compact triple‐band stacked monopole antenna for USB dongle applications

In this article, a novel compact triple‐band stacked monopole antenna for USB dongle applications is proposed. The antenna consists of an e‐shaped monopole connected directly to the feedline and a square patch‐shaped monopole at another layer connected to feedline by a metallic pin. The e‐shaped monopole is used to obtain WLAN band (2.4‐2.48 GHz) and WiMAX band (3.4‐3.69 GHz). On the other hand, square patch‐shaped monopole is introduced to get WLAN bands (5.15‐5.35 and 5.725‐5.825 GHz) and WiMAX band (5.25‐5.85 GHz). The antenna is compact with the dimension of 17 × 13 mm².     

Modified octahedron shaped antenna with parasitic loading plane having dual band notch characteristics for UWB applications

The design of a compact modified octahedron shaped dual band notched ultra wide‐band antenna is presented in this article. The impedance bandwidth of the designed antenna has been enhanced by modifying the shape of the radiator by introducing fractal geometry and a modified ground plane. The proposed antenna offered an impedance bandwidth of 2.4 GHz–19.5 GHz (156% Fractional bandwidth). Two rectangular split ring resonator structures are introduced in the radiator to achieve two notched bands which ranges from 3.3 GHz to 3.7 GHz (WiMAX) and 5.15 GHz–5.85 GHz (WLAN) band. The antenna gain varies from 1 to 4 dBi over the operating band except the notched bands. The overall dimension of the designed antenna has a compact size of 33 × 40 mm². The experimental and simulation results are in good agreement. The proposed antenna has wider bandwidth and smaller dimension over the already reported in the literature. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:426–434, 2016.     

Three‐dimensional printed wideband,dual‐cavity Ku‐band antenna

A novel three‐dimensional (3D) printed, wideband, and low cost bull's eye antenna is proposed and designed for Ku‐band applications. The proposed antenna covers entire Ku‐band satellite communication bands starting from 10.5 GHz to 14.5 GHz. The antenna structure consists of dual‐cavity radiating aperture surrounded by a circular groove. With the addition of cavity and corrugation, the antenna gain is increased more than 6 dB. The antenna is fabricated using 3D printing technology and conductive painting. Measurement results indicate that the antenna has 72% fractional bandwidth from 8 GHz to 17 GHz. Measured antenna peak gain is 13.5 dBi at 13 GHz and no less than 11.5 dBi throughout the entire Ku band.     

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.     

A triple‐band antenna for MIMO WLAN applications

A novel triple‐band antenna element by etching parasitic slot on ground plane is presented. A three‐element antenna system for WLAN MIMO communications is fabricated by using the proposed antenna element. The triple‐band antenna element is designed for the WLAN standard frequency ranges (2.4‐2.485, 5.15‐5.35, and 5.475‐5.725 GHz). The three identical antenna elements are rotationally symmetric on the substrate, isolated by using metal‐vias cavity. The measured average peak gain within the operational bandwidth is about 2.7 dBi. The isolation between the antenna elements can achieve better than 17 dB at the lower band (2.25‐2.65 GHz), while more than 32 dB at the higher bands (5.20‐5.35 and 5.47‐5.73 GHz) is obtained.