A wideband circularly polarized crossed magneto‐electric dipole

A novel wideband crossed magneto‐electric (ME) dipole for circularly polarized (CP) radiation is proposed in this paper. The proposed antenna consists of a crossed dipole, four parasitic elements, and two pairs of folding metal plates (magnetic dipole). The parasitic elements and magnetic dipole are employed to enhance the axial ratio bandwidth (ARBW). The antenna size is 0.51λ₀ × 0.51λ₀ × 0.33λ₀, where λ₀ is the corresponding free‐space wavelength at the center frequency. A prototype antenna is fabricated and tested. The experiment results depict that the impedance bandwidth (IBW) for voltage standing wave ratio < 2 is 79.2% (2.5‐5.78 GHz) and the 3‐dB axial ratio bandwidth (ARBW) is 72.5% (2.7‐5.77 GHz). At the same time, good CP characteristics and stable symmetrical radiation patterns can be obtained across the operation bandwidth.     

A wideband planar magneto‐electric tapered slot antenna with wide beamwidth

In this article, a wideband planar magneto‐electric (ME) tapered slot antenna (TSA) with wide beamwidth both in the E‐plane and H‐plane is investigated. By simply etching slots on the basic TSA, which can function as a combination of magnetic dipole and electric dipole, stable unidirectional patterns with wide beamwidth are obtained. The metal ground plane is further modified to realize wide beamwidth across a wide frequency bandwidth. Moreover, a double‐layer structure is employed to suppress the cross polarization. The measured results show that the proposed antenna can achieve an impedance bandwidth of 51.7% (7.22‐12.25 GHz) with a stable gain of 2.3 dBi, and a pattern bandwidth of 43% (7.8‐12.2GHz) for more than 135° half‐power beamwidth. The measured front‐to‐back (F/B) ratio is more than 15 dB in the pattern bandwidth.     

Substrate integrated low‐profile dual‐band magneto‐electric dipole antenna

In this article, a novel substrate integrated low‐profile dual‐band magneto‐electric (ME) dipole antenna is proposed. The entire antenna is constructed by four‐layer printed circuit boards (PCBs). Consequently, the height of the proposed antenna is decreased from 0.25λ₀ to 0.11λ₀ (λ₀ is the free‐space wavelength at 5.5 GHz). By introducing rectangular patches with different sizes as electric dipoles, dual operating bands are achieved. Meanwhile, for the purpose of improving the impedance matching at the lower frequency band, a pair of complementary split‐ring resonators (CSRRs) is etched on the larger rectangular patches. Moreover, the short walls composed of plated through holes operate as a magnetic dipole. The antenna is fed by an equivalent wideband microstrip‐to‐parallel stripline balun. The results show that the antenna obtains dual bandwidths of 4.31‐4.71 GHz (8.8%) and 5.07‐5.89 GHz (14.9%) with VSWR <2, which can be applied for C‐band and 5G WiFi. Over the dual operating bands, stable gain and unidirectional radiation patterns with low polarization and low back lobe are also obtained.     

A novel wideband high‐gain modified biquad dipole antenna

This article thoroughly investigates a novel modified biquad dipole antenna with a simple structure, wideband, high‐gain and linear polarization key features for wireless communication systems fabricated on FR4 substrate. The proposed antenna is investigated using circular wire loop antenna designing and is, then, extended to a strip structure antenna. Here, a circular reflector is employed to achieve maximum gain, while a coax line feeds the dipole element. Additionally, the presence of a balun, or lack thereof, is examined. The bazooka balun balances the coaxial cable and increases the bandwidth. Consequently, a wide bandwidth and a triple bandwidth are achieved. The resulting parameters demonstrate that the entire S, partial L and C IEEE radio bands comprise the bandwidth of the proposed antenna. The simulated current distribution, experimented and simulated efficiency, radiation pattern, reflection coefficient and gain of the designed antenna are also examined. The simulation and experimentation results exhibit an impedance bandwidth of 105.4% (1.3‐4.2 GHz) for (S₁₁ < ?10 dB). The broadside radiation pattern fills the entire band with maximum simulated and measured gains of 11.8 and 11.02 dBi, respectively. The simulated and measured results tie in closely with each other.     

Design and evaluation of a wideband reflectarray antenna using cross dipole with double‐ring elements

This article reports the design and analysis of a wideband, single layer, and dual‐polarized microstrip reflectarray for Ku‐band applications. The array element is constructed using a crossed dipole enclosed by two cross dipole loops. The element is optimized to exhibit a linear phase response and wide reflection phase range. The reflection characteristic of the unit cell is analyzed using an infinite array approach and the results are presented. A 324‐element Ku‐band microstrip reflectarray antenna of size 20 × 20 cm² is simulated, fabricated, and experimentally evaluated. The 2.9‐dB gain‐bandwidth and aperture efficiency of the reported reflectarray are 45.3% and 35%, respectively. The reflectarray operates in the frequency range of 10.6 to 16.8 GHz.     

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 of a printed log‐periodic dipole array antenna with high gain for millimeter‐wave applications

In this article, a V‐band printed log‐periodic dipole array (PLPDA) antenna with high gain is proposed. The antenna prototype is designed, simulated, fabricated, and tested. Simulation results show that this antenna can operate from 42 to 82 GHz with a fractional impedance bandwidth of 64.5% covering the whole V‐band (50–75 GHz). The antenna has a measured impedance matching bandwidth that starts from 42 to beyond 65 GHz with good agreement between the experimental and simulated results. At 50 and 65 GHz, the antenna has a measured gain of 10.45 and 10.28 dBi, respectively, with a gain variation of 2.6 dBi across the measured frequency range. The antenna prototype exhibits also stable radiation patterns over the operating band. It achieves side‐lobe suppression better than 17.26 dB in the H‐plane and better than 8.95 dB in the E‐plane, respectively. In addition, the cross‐polarization component is 18.5 dB lower than the copolarization with front‐to‐back ratio lower than 24.1 dB in both E‐ and H‐planes across the desired frequency range. Based on a comparison of performance among the reported work in the literature, we can say that the proposed PLPDA antenna is a proper candidate to be used in many applications at V‐band frequency. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:185–193, 2015.     

A compact wideband dual‐polarized linear array with hybrid structure and resistive loadings

A wideband, wide‐scan dual‐polarized linear tightly coupled dipole array is presented. The array is based on a prior work, but it employs a hybrid design of planar cross‐finger dipoles and vertical tapered dipoles to form a non‐oversampled aperture with reduced array width and robust structure. Moreover, wider bandwidth and lower profile height are also achieved in the array as compared to the prior work by introducing resistive loadings between dipoles and ground plane, at the expense of acceptable gain loss. Consequently, the array with width of 99.8 mm and profile height of 86.3 mm provides a performance of 5.7:1 bandwidth (0.35‐2 GHz) for active Voltage Standing Wave Ratio (VSWR) < 3.0 while scanning up to 50°, with orthogonal port isolation below ?15 dB. A 1 × 18 prototype array was fabricated and measured, showing good agreement with simulations.     

A new printed log‐periodic dipole array (PLPDA) antenna with bandwidth broadening and gain improving

A broader impedance bandwidth and higher gain printed log‐periodic dipole array antenna fed by half‐mode substrate integrated waveguide (HMSIW) is proposed in this letter for ultra‐wideband (UWB) wireless communication applications. The bandwidth of the reference antenna (5.1‐11.4 GHz) is expanded by 1.3 GHz by introducing a new resonance frequency with additional patches. Moreover; gain is enhanced over full band by attaching metal plate to narrow beam and adding directors to attract energy radiated by dipoles. A simulation analysis of the improved antenna with broader bandwidth of 4.1 to 11.7 GHz and higher gain is presented, along with a design procedure and experimental results. Measurement results are consistent with simulation results, which verifies the feasibility of this technique.     

A high gain wideband circularly polarized antenna with asymmetric metasurface

An asymmetric‐metasurface based wideband circularly polarized (CP) microstrip antenna using a coaxial probe is proposed for L‐band applications. The antenna involves a stacked asymmetric‐metasurface, a radiating rectangular‐patch and a coaxial feed. An asymmetric‐metasurface is designed using rectangular unit cells and smaller size unit cells along one of the diagonal lines. The asymmetric‐metasurface is placed above a radiating rectangular‐patch with support of foam layer to achieve a wideband CP radiation. The measured performance of the prototype antenna achieves an impedance bandwidth (?10 dB return loss bandwidth) of 15.7% (1.58‐1.85 GHz) with CP bandwidth (3‐dB axial ratio) of 13% (1.58‐1.80 GHz) and gain of ≥9 dBic.     

Dual‐wideband filtering power divider based on center‐fed three‐line coupled structure

In this article, a dual‐wideband filtering power divider is proposed by using a center‐fed three‐line coupled structure with three open stubs and two isolation resistors. The center‐fed three‐line coupled structure can generate two wide passbands separated by a transmission zero (TZ). The three open stubs can achieve four TZs around the two passbands, which is conducive to the frequency selectivity. Compared with the reported designs, the bandwidth is extended and the performance of isolation, insertion loss and circuit size can reach balance. The proposed design is implemented with size of 0.22 λ_g × 0.39 λ_g (λ_g is the guided wavelength at the center frequency of the lower passband) which exhibits the 3‐dB fractional bandwidths of 56.5%/24.27% and the insertion loss of 0.51/0.68 dB at the center frequency of two passband (f₁/ f₂) of 1.94/4.2 GHz, while the isolation at f₁/f₂ are higher than 22.5/20.1 dB.     

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.     

Design of high gain/directional ultra‐wideband antenna for radar imaging systems

A compact size of 40 × 40 mm² ( λ₀ × λ₀ ) semi‐elliptical slotted ground structure (SESGS) directional ultra‐wideband (UWB) antenna is proposed for radar imaging applications. A vertical semi‐elliptical slot is inserted into ground and subsequently, an axis of semi‐ellipse is rotated diagonally (with 45°) in direction of the substrate. Axes of semi‐ellipse are optimized symmetrically around the circular patch to work antenna as a reflector. Furthermore, semi‐elliptical slot is rotated horizontally (with 90°) again to improve the impedance bandwidth. Proposed antenna achieves fractional bandwidth around 83% covering the UWB frequency range from 4.40 to 10.60 GHz (S₁₁ < ?10 dB) having 4.5/6/7/8/9.3/10.2 GHz resonant frequencies. Also, antenna is capable to send low‐distortion Gaussian pulses with fidelity factor more than 95% in time‐domain. Measured gain and half power beam width (HPBW) are 6.1‐9.1 dBi and 44°‐29° in 4.40‐10.60 GHz band, respectively, which show an improvement of 1‐3 dBi in gain and half power beam‐width is reduced by 5°‐10° when compared with previously designed antennas. Experimental results show good agreement with CST simulation.     

High‐gain dual‐polarized antenna for ultrawideband applications

In this article, a high‐gain and dual‐polarized antenna with UWB operation is proposed. The antenna is composed of two tapered dipoles as radiating elements, which are arranged orthogonally and fed perpendicularly to achieve polarization diversity. A metallic cavity reflector is placed behind the radiator for high gain radiation entire the operating bandwidth. To validate the design method, an antenna prototype is designed, fabricated, and measured. The measured results demonstrate that the proposed design has good performance with |S₁₁| ≤ ?10 dB and isolation ≥20 dB over a frequency band 3.2‐8.8 GHz, equivalently to about 93.3%. In addition, unidirectional radiation pattern and broadside gain of from 8.1 to 11.8 dBi are obtained across the operating bandwidth.     

Design of a miniaturized planar half elliptical ultra‐wideband dipole using a concaved arm

This article presents the miniaturization of a planar half elliptical ultra‐wideband dipole. By simply placing a concaved arm in close proximity to the original structure, a 45% area reduction in terms of electrical wavelength can be achieved. The proposed antenna exhibits a wide measured return loss bandwidth of 2 to 9.9 GHz and omnidirectional radiation patterns across the band. The design features a footprint size of 41.5 × 41.5 mm² and an electrical size of 0.28λ × 0.28λ at 2 GHz. Compared with some previously reported planar designs, the proposed antenna presents a more compact electrical dimension and better or comparable bandwidth. Critical geometric parameters of the structure, particularly the concaved arm, are investigated to understand the miniaturization and operating mechanism of the design. Satisfactory correlation between the simulation and measurement data is obtained.     

Small gain problem in coupled differential‐difference equations,time‐varying delays,and direct Lyapunov method

This article presents a Lyapunov–Krasovskii formulation of scaled small gain problem for systems described by coupled differential‐difference equations. This problem includes H_∞ problem with block‐diagonal uncertainty as a special case. A discretization may be applied to reduce the conditions into linear matrix inequalities. As an application, the stability problem of systems with time‐varying delays is transformed into the scaled small gain problem through a process of either one‐term approximation or two‐term approximation. The cases of time‐varying delays with and without derivative upper‐bound are compared. Finally, it is shown that similar conditions can also be obtained by a direct Lyapunov–Krasovskii functional method for coupled differential‐functional equations. Numerical examples are presented to illustrate the effectiveness of the method in tackling systems with time‐varying delays. Copyright © 2010 John Wiley & Sons, Ltd.     

A metasurface‐based slit‐loaded wideband circularly polarized crossed dipole antenna

A metasurface‐based low‐profile crossed dipole antenna with wide circularly polarized bandwidth for 2.45 GHz ISM band wireless communications is proposed and fabricated in this article. Consisting of four slit‐loaded rectangular patches, the double‐sided printing crossed dipoles are fed by a pair of vacant‐quarter printed rings which circularly polarized (CP) radiation could be generated. With slits loaded, by properly combining the fundamental mode of the two inverted L‐shaped dipole, the slot mode and extra resonance generated by the AMC surface, a wideband circularly polarized operation can be obtained. After optimization, the final design with an overall size of 0.44λ₀ × 0.44λ₀ × 0.1448λ₀ at 2.4 GHz had measured a 31.6% (2–2.75 GHz) impedance bandwidth and 3 dB axial ratio bandwidths of measured were 23.2% (2.1–2.65 GHz), respectively. In addition, the antenna performed a small gain variation (7.0–7.5 dBic) and a front‐to‐back ratio (FBR) of over 25 dB across the whole CP region.     

Ultrawideband high‐gain dual‐polarized antenna with anti‐interference capability

In this article, a high‐gain dual‐polarized antenna with band‐rejection capability for ultrawideband (UWB) applications is proposed. Tapered dipoles are chosen as a primary radiator to achieve UWB operation and it is reflected by a metallic cavity reflector for high gain radiation. A notch at WLAN band is realized by etching a set of four bent slots in the radiating elements. The measured results demonstrate that the proposed design with overall dimensions of 0.69λ _L × 0.69λ _L × 0.16λ _L (λ _L is free‐space wavelength at the lowest operating frequency) has operating bandwidth of 95.1% (3.2‐9.0 GHz) and the rejected frequency band from 5.0 to 5.9 GHz. Additionally, good unidirectional radiation patterns with a broadside gain from 8.1 to 11.5 dBi and radiation efficiency of better than 90% are also achieved.     

采用噪声抵消技术的高增益CMOS宽带LNA设计

设计了一种面向多频段应用的CMOS宽带低噪声放大器。采用噪声抵消技术以及局部负反馈结构,引入栅极电感补偿高频的增益损失,电路具有高增益、低噪声的特点,并且具有平坦的通带增益。设计采用UMC 0.18μm工艺,后仿真显示:在1.8 V供电电压下,LNA的直流功耗约为9.45 mW,电路的最大增益约为23 dB,3 dB频带范围为0.1 GHz¹.35 GHz,3 dB带宽内的噪声约为1.7 dB1.35 GHz,3 dB带宽内的噪声约为1.7 dB⁵ dB;在1 V供电电压下,电路依然能够保持较高的性能。     

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.