New Compact antenna based on simplified CRLH‐TL for UWB wireless communication systems

This letter presents the experimental results of a novel planar antenna design which is synthesized using simplified composite left/right‐handed transmission‐line (SCRLH‐TL), which is a version of a conventional composite left/right handed‐transmission‐lines (CRLH‐TL), however, with the omission of shunt‐inductance in the unit‐cell. SCRLH‐TL exhibits a right‐handed response with nonlinear dispersion properties and a smooth Bloch‐impedance distribution. Arranged within the inner slot of the antenna are three smaller rectangular patch radiators. Each patch radiator is embedded with an E‐shaped notch, and located in the antenna conductor is a larger E‐shaped notch next to the 50‐Ω termination. The E‐shaped notches constitute SCRLH‐TL property. The gap in the slot between the smaller patches and the conductor next to the larger E‐shaped notch determines the impedance bandwidth of the antenna. The dimensions of the smaller patches determine the radiation characteristics of the antenna. The antenna is excited using a conductor‐backed coplanar waveguide transmission‐line. The antenna covers a bandwidth of 7.3 GHz between 0.7 GHz and 8GHz, which corresponds to 167.81%. In this band, the antenna resonates at 4.75 GHz and 7 GHz; the gain and radiation efficiency at these frequencies are 4 dBi—80% and 3.6 dBi—73%, respectively. The antenna's performance was validated through measurement. The antenna has dimensions of 0.0504λ₀ × 0.0462λ₀ × 0.0018λ₀, where λ₀ is free‐space wavelength at 700 MHz. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:217–225, 2016.     

A dual‐polarized low‐profile microstrip patch antenna with U‐ or M‐shaped feed network

In this article, a dual‐polarized low‐profile microstrip patch antenna with U‐ or M‐shaped feed network is presented. The U‐ or M‐shaped feed network is printed on the same layer, which can achieve dual bands (5.3 and 5.8 GHz) and low profile (0.06 λ_g). Dual polarizations and high isolation are realized by making use of a quasi‐cross‐shaped slot feeding. Moreover, the port isolation is better than 25 dB, and the antenna gain is above 8.4 dBi for the two ports. And the cross‐polarization levels in both E and H planes are better than ‐30 dB for the two polarization ports, respectively. The design is suitable for array application in MIMO system. Details of the proposed design and experimental results are presented and well agreed.     

A dipole‐type millimeter‐wave antenna with directional radiation characteristics

A dipole‐type millimeter‐wave (mm‐wave) antenna with directional radiation characteristics is presented. A radiating patch structure composed of a dipole‐type radiation patch and a rectangular‐shaped parasitic patch are initially investigated to achieve a wider bandwidth. To further improve the operating bandwidth and to realize a directional radiation characteristic, this radiating patch structure is top‐loaded above a conducting cavity‐backed ground structure, which has a low profile (thickness of 3 mm). The measured results show that the proposed mm‐wave antenna can achieve a wide 10‐dB bandwidth of 51.3% (29.6‐50.0 GHz) and stable gain across the desired frequency range. Furthermore, good directional characteristics over the entire mm‐wave frequency band with a compact antenna size of 0.64λ_40GHz × 0.91_λ40GHz × 0.43_λ40GHz are also realized. Hence, it is suitable for many small size wireless mm‐wave systems.     

Hybrid wideband dual‐cylindrical circularly polarized dielectric resonator antennas excited with S‐shaped microstrip feed for sub‐6 GHz frequency range

In this article, a hybrid microstrip fed dual‐cylindrical dielectric resonator antenna (dual‐CDRA) has been proposed for the sub‐6 GHz band application with a wide circular polarization band. The proposed hybrid microstrip feed cylindrical dielectric resonator antenna utilizes an S‐shaped microstrip feed line to excite fundamental HE_11δ like mode and hybrid mode in dual‐CDRAs. The presented antenna structures are acting as monopole antenna separately with 48.75% (3.88‐6.38 GHz) bandwidth whereas both radiators called dual‐CDRAs enhances the bandwidth up to 93.06% (2.16‐5.92 GHz) in addition with an axial ratio bandwidth of 15.2% (3.52‐4.1 GHz). The proposed antenna is applicable for WiMAX (3.4‐3.69 GHz), and WLAN application of 802.11d and 8.02.11e IEEE standard. For validation of simulated results, an antenna prototype has been fabricated and experimentally verified. A good agreement between simulation and measured results are obtained. The simulation results have been carried out by using Ansys HFSS 14.0 version software.     

A low‐profile wideband dual‐polarized antenna with gain enhancement,low gain variations,and low cross polarization for 5G indoor communications

A low‐profile wideband dual‐polarized antenna with high gain, low gain variations, and low cross‐polarization for the fifth generation (5G) indoor distribution system is proposed. By using circular‐thread vase‐shaped structure, a low profile of 0.23λ₀ (λ₀ is the free‐space wavelength at the starting frequency) as well as low gain variation feature can be achieved by the vertically polarized (VP) radiating element. An eight‐way power divider network is employed to feed the horizontally polarized (HP) dipoles so that wideband performance is obtained. Here, eight pairs of arc‐shaped parasitic strips are used to broaden the bandwidth, and eight pairs of director elements are introduced to enhance the gain and reduce the gain variations. In addition, the protruded stubs that are extended from the circular ground plane will help to reduce the cross polarization in the VP direction. Measured results show that a bandwidth of 46.5% (3.3‐5.3 GHz) (S₁₁ < ?10 dB) with a gain of 0.85 ± 0.35 dBi, and another bandwidth of 85.0% (2.5‐6.2 GHz) with a gain of 4.75 ± 1.75 dBi can be realized in the HP and VP directions, respectively. Furthermore, high isolation (>27 dB) and low cross polarization (<?24 dB) can also be attained. Therefore, the proposed antenna is a good candidate for 5G indoor distributed system.     

Low‐profile wideband patch antenna using double‐tuned impedance matching

A low‐profile wideband patch antenna utilizing double‐tuned impedance matching technology is investigated in this paper. To extend the operation bandwidth of the antenna, the step‐folded probe is used here to realize the double‐tuned impedance matching. Using equivalent circuit theory, the working principle of the antenna is analyzed and discussed. The full‐wave simulation is carried out to optimize the design while the prototype of the antenna is fabricated and measured. Good agreement between the simulation and measurement can be observed. The measured results show that the antenna has a height of 0.12λ_L (λ_L is the free space wavelength corresponding to lowest frequency) and the ?10 dB impedance bandwidth can cover 1.60‐2.83 GHz (55.5%). The low profile and wide operation bandwidth of the antenna make it a good candidate for wideband wireless communication systems.     

Bandwidth and gain improvements of low‐profile H‐shaped microstrip patch antenna under quadruple‐mode resonance

A wideband low profile H‐shaped microstrip patch antenna (MPA) with reallocated quadruple‐mode resonance is presented for indoor wireless communication application. In this paper, the TM₂₀ (mode 1), TM₀₂ (mode 2), TM₂₂ (mode 3), and additionally notch mode 4 of the proposed MPA are simultaneously employed. First, the rectangular radiating patch is reshaped as an H‐shaped radiator so as to separate a pair of degenerate modes (mode 1 and mode 2). Then, a pair of linear notches is cut on the diagonal of the patch to excite an additional notch resonance (mode 4). Finally, in order to improve the frequency of mode 1, four shorting pins are placed at the four corners of the H‐shaped patch. Therefore, the bandwidth of the antenna is dramatically increased up by utilizing four resonant modes (modes 1, 2, 3, and 4). A prototype of H‐shaped patch antenna with notches and shorting pins is manufactured and measured. The results show that the antenna achieves a broad bandwidth of about 31.7% (2.31‐3.18 GHz), and its profile is only 0.036 wavelength of center frequency. It is particularly noticed that a relative high gain of around 9.8 dBi is successfully acquired, while keeping relative stable dual‐beam radiation patterns.     

A dual‐patch polarization rotation reflective surface and its application to wideband wide‐beam low‐profile circularly polarized patch antennas

This study investigates the use of a polarization rotation reflective surface (PRRS) to construct a wideband, wide‐beam, low‐profile circularly polarized (CP) patch antenna. The device is composed of a feeding monopole antenna and a novel PRRS‐based dual‐patch artificial magnetic conductor (AMC) cell structure. The PRRS has two polarization rotation (PR) frequency points, generated by properly adjusting the width between square and L‐shaped metallic patches. A large PR band of 35.5% (5.1‐7.3 GHz) was achieved by combining two adjacent PR frequency points. The PRRS‐based patch antenna impedance bandwidth was measured to be 28.6% (5.1‐6.35 GHz), with a 3 dB axial ratio (AR) bandwidth of 21.8% (4.8‐6.4 GHz) and a profile of 0.045λ₀. Additionally, the proposed antenna exhibited the largest AR beamwidth (to our knowledge) of 175° and 128° in the xoz and yoz planes, respectively. It also produced a high broadside gain of 6.7 dBic within the operational bandwidth.     

Coplanar waveguide‐fed electrically small dual‐polarized short‐ended zeroth‐order resonating antenna using Ω‐shaped capacitor and single‐split ring resonator for GPS/WiMAX/WLAN/C‐band applications

This work explains the design and analysis of a triple‐band electrically small (ka = 0.56 < 1) zeroth‐order resonating (ZOR) antenna with wideband circular polarization (CP) characteristics. The antenna compactness is obtained due to ZOR frequency of composite right/left‐handed (CRLH) transmission line (TL) and wideband CP radiation are achieved due to the introduction of single‐split ring resonator and asymmetric coplanar waveguide fed ground plane. The proposed antenna obtains an overall electrical size including the ground plane of 0.124 λ₀ × 0.131 λ₀ × 0.005 λ₀ at 1.58 GHz and physical dimension of 23.7 × 25 × 1 mm³ are achieved. The antenna provides a size reduction of 44.95% compared to a conventional monopole antenna. The novelty behind the ohm‐shaped capacitor is the generation of extra miniaturization with better antenna compactness. The antenna provides dual‐polarized radiation pattern with linear polarization radiation at 1.58 and 3.54 GHz, wideband CP radiation at 5.8 GHz. The antenna measured results shows good impedance bandwidth of 5%, 6.21%, and 57.5% for the three bands centered at 1.58, 3.54, and 5.8 GHz with a wider axial ratio bandwidth (ARBW) of 25.47% is obtained in the third band. The antenna provides a higher level of compactness, wider ARBW, good radiation efficiency, and wider S₁₁ bandwidth. Hence, the proposed antenna is suitable for use in GPS L1 band (1.565‐1.585 GHz), WiMAX 3.5 GHz (3.4‐3.8 GHz) GHz, WLAN 5.2/5.8 GHz (5.15‐5.825 GHz), and C‐band (4‐8 GHz) wireless application systems.     

A low‐profile dual port UWB‐MIMO/diversity antenna with band rejection ability

A band notched ultra‐wideband (UWB) antenna is presented in this article as a good prospect for multiple‐input multiple‐output (MIMO)/diversity application. The proposed MIMO antenna is constituted of two modified rectangle‐shaped patch antenna elements. A stepped stub is extended from the modified ground plane as a decoupling element between the radiators to realize a good isolation level between them. A band rejection response is obtained by connecting an open resonant stub to each of the radiators. The simulated prototype is fabricated and tested for verification. Results reveal that the proposed prototype provides a 10 dB return loss bandwidth from 3.08 to 10.98 GHz with band notch characteristics from 4.98 to 5.96 GHz, and a good port isolation level (S₂₁ ≤ 20). Diversity performances are ensured in terms of total active reflection coefficient, envelope correlation coefficient (<0.013 except notch band), diversity gain (≈9.51 dB), mean effective gain ratio (≈1), and channel capacity loss (≤0.35 bps/HZ except notch band). It evidences that the presented band notched UWB antenna can be a good prospective for MIMO/diversity applications.     

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.     

A new dual C‐shaped rectangular dielectric resonator based antenna for wideband circularly polarized radiation

This article presents a new dual C‐shaped rectangular dielectric resonator (DR) based antenna for generation of wideband circularly polarized (CP) radiation. The proposed antenna comprises of a pair of C‐shaped rectangular dielectric DR and a metal strip with a coaxial probe. By utilization of a metal strip at the side surface of C‐shaped rectangular DR, the wideband CP radiation is achieved from the proposed dielectric resonator antenna (DRA). Fundamental orthogonal modes (TE^x_δ11 and TE^y_1δ1) are excited using the rectangular DRA with a metal strip for the generation of CP fields. The proposed antenna with dual C‐shaped rectangular CP DRA provides the measured ?10 dB reflection coefficient bandwidth of 30.07% (3.22 GHz‐4.36 GHz) with measured 3‐dB axial ratio bandwidth of 14.81% (3.25 GHz‐3.77 GHz) at the boresight. The proposed antenna covers the useful Wi‐MAX band.     

Design and its state‐of‐the‐art of different shaped dielectric resonator antennas at millimeter‐wave frequency band

This review article provides an extensive literature survey on the research progress of dielectric resonator antenna (DRA) at millimeter‐wave frequency band that includes concepts of DRAs, their empirical formulae and design methodologies for different shaped DRAs at 60 GHz frequency band. The different shaped DRAs such as cylindrical, rectangular, hexagonal, and octagonal at 60 GHz are designed, simulated and analyzed using CST microwave studio solver. The ?10 dB impedance bandwidth of cylindrical, rectangular, hexagonal, and octagonal DRAs are 52.7 to 62.8 GHz, 57 to 62.2 GHz, 55.8 to 64.2 GHz, and 54.2 to 63.5 GHz, respectively. The idea behind getting broad impedance bandwidth is due to use of double‐layer substrate with different permittivity (ε_r1 = 4 and ε_r2 = 11.9). Empirical formulae are deduced for hexagonal and octagonal DRA, by studying the analogy of dielectric resonator geometry. Consequently, the mode of different shaped DRAs, that is, HEM₁₁₁ and TE₁₁₁ are investigated by the electric field and magnetic field distribution. With these analysis, a comprehensive research review over the period of the last two decades is carried for investigating various techniques, targeted to realized gain, circular polarization, and impedance bandwidth. Along with these analysis the state‐of‐the‐art at different shaped DRAs at mm‐wave frequency band are also reported.     

A wideband circularly polarized slot antenna with antipodal strips for WLAN and C‐band applications

A single‐fed circularly polarized square shaped wide slot antenna with modified ground plane and microstrip feed has been presented. The field in the slot is perturbed by introducing an antipodal strips section attached with a microstrip line to produce circular polarization in a wide band of frequencies. The antipodal strip section consists of a group of four strips of unequal length and separation. The presence of asymmetric perturbations in the slot is mainly responsible for exciting two orthogonal modes in the slot having equal magnitude and 90° phase difference which results in circular polarization. A wide bandwidth of 3.3 GHz (4.4 GHz‐7.7 GHz) has been achieved for an axial ratio value AR < 3 dB with the minimum axial ratio value being 0.3 dB. The impedance bandwidth for |S₁₁| < ?10 dB ranges from 4.3 GHz to 8 GHz, and therefore covers most of the C‐band communication systems. The antenna exhibits stable radiation patterns throughout the circular polarization bandwidth with a gain around 6 dBi in entire operational bandwidth. A prototype of antenna was fabricated and measured. The antenna has a planar size 0.40λ₀ × 0.40λ₀ and thickness of 0.02λ₀ where λ₀ is the wavelength in free space at the lowest frequency. With its compact size and low profile, the antenna is a favorable choice for WLAN (5.15‐5.85 GHz) and a wide variety of C‐band wireless applications.     

Compact sub‐6 GHz 5G‐multiple‐input‐multiple‐output antenna system with enhanced isolation

A compact two‐element multiple‐input‐multiple‐output (MIMO) antenna system with improved impedance matching and isolation is presented for future sub‐6 GHz 5G applications. The two identical tapered microstrip line fed modified rhombus‐shaped radiating elements are placed in the same orientation at a compact substrate area of 0.24λ₀ × 0.42λ₀ (where, λ₀ at 3.6 GHz) on a shared rectangular ground. A remodeled T‐shaped ground stub is placed between a pair of radiating element to achieve improved impedance bandwidth and isolation. Further, a split U‐shaped stub connected to center of each radiating element to achieve the desired resonant frequency of 3.6 GHz. The proposed antenna covers a ?10 dB operating band of 3.34 to 3.87 GHz (530 MHz) with more than 20 dB isolation between a pair of elements. MIMO performances are also analyzed and experimentally validated. The measured performances of a prototype are found in good agreement with simulated performances. Further, the simulation study is carried out to see the effect of housing and extended ground plane on two‐element MIMO antenna for practical application. An idea of realization of 12‐element MIMO is also studied using the proposed two‐element MIMO antenna.     

Miniaturized low‐profile antenna based on uniplanar quasi‐composite right/left‐handed metamaterial

In this article, a metamaterial‐based broadband low‐profile antenna is presented. The proposed antenna employed an array of uniplanar quasi‐composite right/left‐hand (CRLH) metamaterial cells. This structure contributes to exciting the operating modes in lower frequencies. The antenna has an overall electrical size of 0.75 × 0.60 × 0.07 λ₀³ (λ₀ is the center operating wavelength in free space) and provides a 25% measured bandwidth with the center frequency of 5.1 GHz and maximum gain of 6.6 dB. The proposed antenna is an appropriate candidate for WLAN, WiMAX, and other wireless communication applications.     

Metasurface‐based low‐profile high‐gain substrate‐integrated Fabry‐Pérot cavity antenna

A metasurface‐based substrate integrated Fabry‐Pérot cavity (FPC) antenna is presented for improved radiation performance associated with the low profile. A novel partially reflective planar (PRS) artificial magnetic conductor (AMC) structure is proposed as the upper reflector of the substrate integrated FP resonant cavity. A microstrip patch antenna is embedded inside the cavity as a feed. The proposed antenna is designed to operate at 9.35 GHz with the maximum realized gain of 14.2 dBi and the overall profile of λ₀/10 (λ₀ is the operating wavelength in free space). The low‐profile performance of the proposed design outperforms any previous substrate‐integrated FPC antenna design with this gain performance. The influences of the FP cavity on the reduction of the antenna profile and the enhancement of the antenna gain are also investigated. Good agreement between the measured and simulated results validates the feasibility of the analysis and design approach.     

High inter‐port isolation dual circularly polarized slot antenna with interdigital capacitor

A planar dual circularly polarized slot antenna is presented. The designed antenna has two tilted “8” shaped slots fed by microstrip lines, one each for transmission (T_X) and reception (R_X) operations. The isolation between the two ports (T_X and R_X) is augmented by means of an interdigital capacitor based bandstop filter. The proposed antenna has an impedance bandwidth of 361 MHz centered at 2.293 GHz (2.113‐2.474 GHz) with the isolation between the ports being >17.6 dB which goes up to a value as high as 46 dB within the band of operation. The 3 dB axial ratio (AR) bandwidth is 11.52% centered at 2.1275 GHz (2.005‐2.25 GHz). Because of its high inter‐port isolation within the AR bandwidth, the design is suitable as a full‐duplex antenna for applications in S‐band.     

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.     

A‐shaped wideband dielectric resonator antenna for wireless communication systems and its MIMO implementation

In this article, a new A‐shaped dielectric resonator antenna (DRA) excited by a conformal strip is proposed for wideband applications. The wide bandwidth is achieved by combining two adjacent modes that is, TM₁₀₁ and TM₁₀₃. The experimental results demonstrate that the proposed DRA offers an impedance bandwidth (for S11?10 dB) of 59.7% (3.24‐6.0 GHz), covering IEEE 802.11 and U‐NII bands. The antenna provides a fairly stable radiation pattern with the gain ranging from 5.29 to 7 dBi across the operating bandwidth. A dual‐element multiple‐input multiple‐output (MIMO) system is also realized using the proposed wideband DRA. The impedance bandwidth of the dual‐element MIMO antenna is 59.2% and 60.9% for Port1 and Port2, respectively and the isolation between the ports is better than 20 dB across the bandwidth. For Port1, the gain of the MIMO antenna ranging from 6.03 to 7.45 dBi is obtained across the bandwidth. Furthermore, the diversity performance of the MIMO antenna is found to be good with envelope correlation coefficient below 0.003 over the operating band. The proposed antenna could be the potential candidate for worldwide interoperability for microwave access (WiMAX), wireless local area network (WLAN) and lower European UWB frequency band (3.4‐5.0 GHz) applications.