基于石墨烯材料的太赫兹波段频率可重构八木天线

传统天线中使用电子开关或PIN二极管开关等方式实现天线可重构功能,但是在太赫兹波段上会面临切换速度慢,偏置电路复杂等问题。石墨烯具有优异的电磁性能,可运用于太赫兹可重构天线中。根据石墨烯表面电导率模型,研究其电导率随频率、化学势的变化关系,证明了石墨烯在可重构天线设计中的可行性。设计了一款太赫兹波段石墨烯频率可重构八木天线,通过改变石墨烯贴片偏置电压改变石墨烯化学势,从而改变天线的工作模式。在HFSS软件中进行仿真优化,天线具有300GHz和500GHz两种频率的工作模式,最大增益分别达到9.29dB和10.28dB,表现出良好的辐射特性。     

A π/4 bi‐orthogonal monopole antenna for operation on and beyond of the UWB band

An ultra‐wideband (UWB) π/4 bi‐orthogonal monopole antenna with a highly omnidirectional radiation pattern in the azimuthal plane with a quasi‐independent on the frequency behavior is presented in this article. Here, it is shown that by combining two orthogonal UWB planar monopole elements rotated 45° with respect to each other in a single structure, it is possible to enhance the performance of the radiation pattern at high frequencies of the operational bandwidth without affecting the radiation pattern at lower frequencies. The measured antenna bandwidth goes from 2.82 to 16.7 GHz for a reflection coefficient lower than ?10 dB. The radiation pattern remains almost omnidirectional, and it is enhanced with respect to a conventional single planar monopole antenna of similar characteristics. The basic element used for both the single and the proposed π/4 bi‐orthogonal UWB planar monopole antenna has a rectangular shape, whose impedance bandwidth ratio is achieved based on the bevelling and height‐width ratio techniques. Although the antenna prototype presented in this article has an operational bandwidth of 13.88 GHz, it is possible to design a UWB monopole antenna with the shape and structure proposed here, but for different bandwidths following a design methodology suggested also in this article. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Planar UWB antenna with modified slotted ground plane

A compact coplanar waveguide‐fed (CPW) monopole antenna for ultra‐wideband wireless communication is presented. The proposed antenna comprises of a CPW‐fed beveled rectangular patch with a modified slotted ground. The overall size of the antenna is 30 mm × 27 mm × 1.6 mm. The lower edge of the band is attained by properly decoupling the resonant frequencies due to the extended ground plane and the beveled rectangular patch of the antenna. The upper edge of the radiating band is enhanced by beveling the ground plane corners near the feed point. Experimental results show that the designed antenna operates in the 2.7–12 GHz band, for S₁₁ ≤ ?10 dB with a gain of 2.7–5 dBi. Both the frequency domain and time domain characteristics of the antenna are investigated using antenna transfer function. It is observed that the antenna exhibits identical radiation patterns and reasonable transient characteristics over the entire operating band. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

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.     

A novel compact planar ultra‐wideband antenna with dual band‐notched characteristics

A novel planar ultrawideband monopole antenna with dual notched bands is presented. The antenna mainly consists of a radiation patch and a modified ground plane. To realize dual band‐notched characteristics, a U‐shaped stub embedded in the rectangular slot of the radiation patch and a novel coupled open‐/shorted‐circuit stub resonator are used on the backside of the substrate. The bandwidth of the dual notched bands can be controllable by adjusting some key parameters. The simulated and measured results indicate that the proposed antenna offers a very wide bandwidth from 2.6 to 18 GHz with Voltage Standing Wave Ratio (VSWR) < 2, except the dual notched bands of 3.3–3.7 GHz (World Interoperability for Microwave Access [WiMAX]) and 5.15–5.825 GHz (Wireless Local Area Network [WLAN]). Furthermore, good group delay and stable gains can be achieved over the operating frequencies. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:48–55, 2015.     

Planar antenna beam deflection using low‐loss metamaterial for future 5G applications

A method to tilt the beam of a planar antenna in the E‐plane is demonstrated by implementing a metamaterial (MM) structure onto the antenna substrate at the fifth‐generation (5G) band of 3.5 GHz. The beam tilting is achieved due to the phase change that occurs when the electromagnetic (EM) wave traverses through two media with different refractive indices. A new adjacent square‐shaped resonator (ASSR) structure is proposed to achieve the beam tilting in a dipole antenna. This structure provides a very low loss of ?0.2 dB at 3.17 GHz. The simulation and measurement results illustrate that the radiation beam of the dipole antenna is tilted by +25° and ?24° depending on the position of the ASSR array onto the dipole antenna substrate. In addition, no degradation in the gain is observed as in the conventional beam‐tilting methods; in fact, gain enhancement values of 3 dB (positive deflection) and 2.7 dB (negative deflection) are obtained compared with that of a dipole antenna with no ASSR array. The reflection coefficient of the dipole antenna with ASSR array has a good agreement with that of the dipole antenna with no ASSR array. The measured results agree well with the simulated ones.     

Switched beam dielectric resonator antenna array with six reconfigurable radiation patterns

A single feed, four element rectangular Dielectric Resonator Antenna (DRA) array, with beam switching capability is proposed. A wide impedance bandwidth of more than 25% at the center frequency of 1.95 GHz is achieved. Each DRA has two excitation strips and four parasitic patches. The six cases are discussed; each case corresponds to a diverse radiation pattern. The antenna beam is switched in azimuth (θ = 45°) at Φ = 0°, 60°, 120°, 180°, 240°, and 300°. The antenna gain is found to be more than 7 dB in most of the frequency band of interest. A passive prototype is developed and tested to validate simulation results. The comparison between the simulated and measured reflection coefficients and the radiation patterns for the six cases is presented. A good agreement between the measured and simulated results is observed. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:519–530, 2016.     

Design guidelines for single and dual wide band leaky periodic microstrip line antennas

Leaky wave antennas using periodic microstrip lines are natural choices for versatile beam scanning applications. In this work, a shorted stub and an open stub are simultaneously used in the same unit cell to generate resonant frequencies dependent on the stub dimensions. Placing one such resonant frequency at the second Bragg stop band, a single wideband response is obtained. Next, the stub lengths are tuned to obtain two resonant frequencies which are placed at the second and fourth Bragg stop bands, respectively to obtain a dual wideband response. Design guidelines are outlined for obtaining these wide bands and corresponding radiation regions. Two such geometries with single and dual‐band nature are fabricated. The single wide‐band antenna has a pass‐band from 5.89 to 11.57 GHz with a beam scanning range of ?56° to 33°. The dual‐band antenna has two pass‐bands radiating in the frequency range 5‐6.5 GHz and 10.7‐14.7 GHz. Beam scanning range in the first pass‐band is ?72° to ?5°. The second pass‐band, in part, demonstrates a dual‐beam nature with the forward beam scanning from 28.9° to 54.5° and backward beam scanning from ?54.5° to 14.76° as the frequency varies from 12 to 14.5 GHz.     

Design and analysis of multiband notched pitcher‐shaped UWB antenna

To mitigate the interference with coexisting wireless systems operating over 3.3–3.6 GHz, 5.15–5.825 GHz, and 7.725–8.5 GHz bands, a novel triple band notched coplanar waveguide fed pitcher‐shaped planar monopole antenna is presented for ultrawideband applications. Bands notched characteristics are achieved using a novel mushroom type electromagnetic band gap structure like resonator and a split ring slot. A conceptual equivalent RLC (Resistor‐Inductor‐Capacitor)‐resonant circuit is presented for the band notched characteristics . Furthermore, the input impedance and VSWR (voltage standing wave ratio) obtained from the equivalent circuit are validated with simulated and measured results. Performances of the antennas in both, the frequency domain and the time domain are investigated. The simulated and measured results demonstrate that the proposed antennas have wide impedance bandwidth, nearly stable radiation patterns, and suppression of gain and total radiation efficiency at notched bands. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:795–806, 2015.     

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.     

Dual‐band beam scanning filtering antenna using dual‐eighth mode substrate integrated waveguide‐based metamaterial structure

In this article, a dual‐band beam scanning antenna with filtering capability is proposed by using novel dual‐eighth mode substrate integrated waveguide‐based dual‐band metamaterial (DB‐MTM) structure. The novel DB‐MTM structure consists of two interconnected modified eighth mode substrate integrated waveguide (EMSIW) structures, which is designed by etching four interdigital fingers on the upper ground, and has two balanced composite right/left‐handed (CRLH) passbands. Taking advantage of the continuous phase constant changing from negative to positive values within the two CRLH passbands of the DB‐MTM structure, a beam scanning antenna, which is composed of 11 dB‐MTM unit cells, is designed to achieve continuous beam scanning from backward to forward directions within dual operating frequency bands. For verification, the proposed dual‐band antenna is fabricated and measured. According to the measurements, the fabricated antenna can scan its main beam from ?72° to +57° and ?70° to +38° over the two operating frequency bands of 3.40‐4.95 GHz and 5.85‐6.80 GHz, respectively; and exhibits very sharp transitions at the band edges over the two operating frequency bands. Besides, the measured peak gains in the two operating bands are 14.0 dB at 4.5 GHz and 14.5 dB at 6.4 GHz. Moreover, the measurements show good agreement with the simulations, proving the validity of the design method, and further expanding the applications of EMSIW.     

Uniplanar ACS fed multiband high‐gain antenna with extended rectangular strips for portable system applications

In this article, a compact uniplanar asymmetric coplanar strip (ACS)‐fed multiband antenna with extended rectangular strips is proposed for portable system applications. It is composed of a modified mouse and rectangular‐shaped radiating strip for generating three resonance frequency bands simultaneously. The proposed antenna has a compact size of 16 × 26 × 1.6 mm³. Antenna has |S₁₁| ≤ ?10 dB at three independent controlled bandwidths from 2.2 to 2.4 GHz, 3.5 to 3.7 GHz, and 4.85 to 6.85 GHz. The proposed ACS‐fed antenna is suitable for LTE 2300, WiBro 2300 GHz, 5.2/5.8‐GHz WLAN, 3.5/5.5‐GHz WiMAX, 4.9‐GHz US public safety band, and 5.9‐GHz WAVE applications. The antenna has omnidirectional radiation characteristics in the desired frequency bands in both E‐plane and H‐plane. It has better gain value performance compared with other antenna designs discussed in the literature.     

A modified split ring resonator based printed compact monopole UWB antenna with spiked elliptical radiator having five band rejection features

A coplanar waveguide (CPW) fed printed compact monopole antenna with five band rejection features is presented. Wide bandwidth was achieved by beveling the lower part and adding a modified ellipse on the upper portion of the patch. An inverted circular arc, single circular split ring resonator (SRR) with wide opening and two symmetrical circular single SRRs were embedded for obtaining three stop‐band characteristics. Two symmetrical slits were inculcated in the ground forming defected ground structure (DGS) to get another stop‐band characteristic. Two concentric rectangular modified SRRs were etched to obtain a higher frequency stop‐band feature. The proposed antenna was designed, fabricated, and experimentally tested for the validation of results. The overall dimensions of the proposed antenna were 29 mm × 24 mm × 1.6 mm. The measured impedance bandwidth of the antenna was 2.87 to 13.3 GHz at | S₁₁ |< ? 10 dB. The measured results show that the proposed antenna has five band notches centred at 3.96, 4.35, 5.7, 8.54, and 9.95 GHz to reject WiMAX band (3.65‐4.04 GHz), ARN band (4.29‐5.18 GHz), WLAN band (5.5‐6.9GHz), ITU‐8 band (7.37‐8.87), and amateur radio band (9.2‐10.3 GHz) respectively. The proposed antenna maintains omnidirectional radiation pattern in H‐Plane and dumbbell‐shape radiation pattern in E‐plane. Further, stable gain over the whole UWB except at notched frequency bands was reported.     

Broadband printed quadrifilar helix antenna using parasitic strip technique

A circularly polarized (CP) printed quadrifilar helix antenna (QHA) with enhanced bandwidth is proposed in this communication. This QHA is fed by a feeding structure with superior performance, which uses wide‐band 90° and 180° planar bulun. The feeding network can simply realize the 90° phase shift and four equal power divisions within a wide band range. Enhanced impedance matching and CP radiation characteristics can be achieved with the parasitic strips between helix arms. The study of proposed antenna performance with different geometric parameters has been conducted. The final antenna exhibits a good impedance bandwidth (IBW) of approximately 37.4% (1.65‐2.41 GHz), and the 3‐dB axial‐ratio bandwidth (ARBW) is over 43.9% (1.6‐2.5 GHz). Broad pattern coverage, pure CP radiation at all designed bands and a wide 3 dB axial‐ratio beam width of 150° makes this antenna an excellent candidate for satellite communications and navigation systems.     

Design of a microstrip fed printed monopole antenna for bluetooth and UWB applications with WLAN notch band characteristics

In this article, a microstrip fed printed dual band antenna for Bluetooth (2.4–2.484 GHz) and ultra‐wide band (UWB; 3.1–10.6 GHz) applications with wireless local area network (WLAN; 5.15–5.825 GHZ) band‐notch characteristics is proposed. The desired dual band characteristic is obtained by using a spanner shape monopole with rectangular strip radiating patch, whereas the band‐notch characteristics is created by a mushroom‐like structure. The Bluetooth and notch bands can easily be controlled by the geometric parameters of the rectangular strip and mushroom structure, respectively. The proposed antenna has been designed, fabricated, and tested. It is found that the proposed antenna yields both the Bluetooth and UWB performance in the frequency regions of 2.438 to 2.495 GHz and 3.10 to 10.66 GHz, respectively for |S₁₁| ≤ ?10 dB with an excellent rejection band of 5.14 to 5.823 GHz to prevent WLAN signals. The experimental results provide good agreement with simulated ones. Surface current distributions are used to analyze the effects of the rectangular strip and mushroom. The designed antenna exhibits nearly omnidirectional radiation patterns, stable gain along with almost constant group delay over the desired bands. Hence, the proposed antenna is expected to be suitable for both Bluetooth and UWB applications removing the WLAN band. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:66–74, 2015.     

Compact 2 × 2/4 × 4 tapered microstrip feed MIMO antenna configuration for high‐speed wireless applications with band stop filters

In this research, compact tapered feed 2 × 2/4 × 4 MIMO antenna are presented and investigated. The proposed MIMO antenna consists of a square patch and modified rectangular ground, which is chamfered at edges and etched with two semicircular slots. Likewise, obstruction caused by WiMAX and WLAN interfering bands is also taken care of by introducing notched filters. WiMAX is removed by embedding an rotated T‐type stub and a C‐type slot eliminates the WLAN band. The proposed antenna configuration covers the usable bandwidth of 3.07 to 11.25 GHz for 2 × 2 MIMO and 2.97 to 11.28 GHz for 4 × 4 MIMO. Also, both the MIMO antennas provide isolation <–20 dB. Proposed MIMO antennas are fabricated and characterized in near, far‐field, and diversity performance where envelope correlation coefficient, directive gain (DG), total active reflection coefficient (TARC), and channel capacity loss are simulated and measured. 4 × 4 MIMO antenna configuration provides stable gain with a maximum radiation efficiency of 91% and monopole radiation patterns.     

Design of a compact triple band antenna with independent frequency tuning for MIMO applications

In this article, a planar, low profile microstrip line‐fed triple band multiple input multiple output (MIMO) antenna is presented for WiMax (2.5/3.5/5.5 GHz)/WLAN (2.4/3.6/5.8 GHz) applications simultaneously. The single element of the MIMO antenna consists of (i) a rectangular split ring resonator (SRR), (ii) a stepped impedance resonator (SIR) inside the SRR and (iii) a slot on the SIR. Each of the resonators generates its own individual band and each band is independently tunable. The antenna exhibits three operating bands at 2.35‐2.85 GHz, 3.25‐3.90 GHz and 5.45‐5.65 GHz. Four antenna elements are used to design the proposed MIMO antenna. The simulated results are observed and reported in terms of S‐parameters, gain, radiation patterns, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL) and total active reflection coefficient. ECC and CCL are within the acceptable range defined for 4G and 5G application standards. To validate the simulation results a prototype structure is fabricated and the measured results are compared with those obtained from the simulation.     

A compact slot antenna configuration for ultrawideband (UWB) terminals and mobile phones

A novel technique to design a mobile phone antenna by using an ultrawideband (UWB) antenna configuration is proposed. The technique is validated with a novel printed slot antenna configuration. The slot is composed of a circle connected to a trapezoid and fed by means of a 50 Ω microstrip line connected to a patch with similar shape to the slot. An UWB antenna with size of 19 mm × 24 mm and measured ?10 dB bandwidth of 2.97‐11.32 GHz is developed based on the configuration. When the configuration is applied in a system circuit board of 60 mm × 115 mm to design a mobile phone antenna, the simulated ?6 dB bandwidths are 1.0‐1.2 GHz and 2.25‐15 GHz. To enhance antenna bandwidth, another slot with rectangular shape is etched in the ground plane, and the microstrip line is moved to the center of the circuit board and folded to distribute along the rectangular slot. The measured ?6 dB bandwidths of the mobile phone antenna are 0.69‐1.09, 1.68‐2.75, 3.45‐3.52, and 3.62‐15 GHz.     

A metamaterial hepta‐band antenna for wireless applications with specific absorption rate reduction

Present article embodies the design and analysis of slotted circular shape metamaterial loaded multiband antenna for wireless applications with declination of SAR. The electrical dimension is 0.260 λ × 0.253 λ × 0.0059 λ (35 × 34 × 0.8 mm³) of proposed design, at lower frequency of 2.23 GHz. The antenna consists of circular shape rectangular slot as the radiation element loaded with metamaterial split ring resonator (SRR) and two parallel rectangular stubs, etched rectangular single complementary split‐ring resonator (CSRR) and reclined T‐shaped slot as ground plane. Antenna achieves hepta bands for wireless standards WLAN (2.4/5.0/5.8 GHz), WiMAX (3.5 GHz), radio frequency identification (RFID) services (3.0 GHz), Upper X band (11.8 GHz—for space communication) and Lower K_U band (13.1 GHz—for satellite communication systems operating band). Stable radiation patterns are observed for the operating bands with low cross polarization. The SRR is responsible for creating an additional resonating mode for wireless application as well as provide the declination in SAR about 13.3%. Experimental characteristic of antenna shows close agreement with those obtained by simulation of the proposed antenna.     

A coaxial probe fed wideband circularly polarized antenna using unequal and adjacent‐slided rectangular dielectric resonators for WLAN applications

In this article, a coaxial probe fed wideband circularly polarized antenna has been designed and investigated using unequal and adjacent‐slided rectangular dielectric resonators radiating in broadside direction (Φ = 0°, θ = 0°). Wi‐Fi wireless network use radio signal either in 2.4 or 5 GHz band. Owing to high rush in 2.4 GHz band, the proposed antenna is designed for 5 GHz (5.15‐5.825 GHz) WLAN band. The proposed design uses fundamental orthogonal modes and excited in two individual rectangular dielectric resonators to achieve wide axial‐ratio bandwidth (below 3 dB). Measured input reflection coefficient (below ?10 dB) and axial ratio bandwidth (below 3 dB) of 26.07% (5.27‐6.85 GHz) and 26.85% (5.32‐6.97 GHz) has been attained, respectively, in this proposed antenna. The measured far‐field patterns such as gain and radiation patterns are showing consistent performance throughout the working band.