Slot Loop Research Articles

Broadband Circularly Polarized Rectenna With Wide Dynamic-Power-Range for Efficient Wireless Power Transfer

This paper presents a circularly polarized (CP) rectenna with the advantage of achieving high efficiency in both wide operating power and frequency ranges. The proposed rectenna is composed of a high-efficiency rectifier and broadband CP antenna. In the proposed rectifier, a novel wideband resistance compression technique is presented, highly improving the matching performance of the circuit in a wide range of input power and frequency. The technique is achieved by an impedance manipulation network and a coupled-lines-based resistance compression network (RCN). Theoretical analysis is carried out and closed-form equations are derived for the design of the rectifier. Simulated and measured results show that over 60% (up to 76%) conversion efficiency is achieved for the input power range of 5-17 dBm and frequency band of 1.7-2.9 GHz (mobile, Wi-Fi and ISM bands). Subsequently, unlike the conventional half-wavelength slot antenna, a compact CP antenna with a side length of quarter wavelength is designed by using a 1-wavelength loop slot and a coupled-line-based phase shifter. It has wide axial-ratio bandwidth and good radiation pattern. At last, by integrating the proposed rectifier together with the CP slot antenna, a broadband CP rectenna is completed with higher efficiency by about 18.6% than that without wideband RCN.

An efficient hybrid solar and electromagnetic harvesting system for autonomous operation of small sensors

In this study, we propose a combination of solar cells and a rectenna to realize a solar and electromagnetic energy harvesting system. The proposed harvester consists of a circular slot antenna, a rectifier circuit which is designed with a reverse-biased Schottky diode, and SHJ solar cells with a combination of AZO/TiO2 as antireflection coating and a diffraction grating morphology. Each designed component has been characterized through simulations and measurements. First, the solar cells are designed and investigated separately. Then, they are carefully placed near the slot loop antenna, which is attached to the rectifier circuit, to realize the combined harvesting system. The heterojunction solar cells with an intrinsic thin layer (SHJ) have been designed based on light trapping mechanism, which reduces the reflection of solar radiation and interfacial traps effects significantly. Solar cells’ simulations are obtained using an analytical model. The parameters of light trapping, as well as the effects of the position of the solar cells on board of the patch, are studied carefully. Simulation and experimental results validate that the combined harvesting system is a promising candidate for autonomous operation of some sensors and small devices. Indeed, the efficiency of the rectenna is enhanced greatly from 21to 74 % when combined with the solar cells.

Review Design of Slot Antenna Based on Ansoft HFSS Software

Abstract In this paper, a micro-strip fed slot antenna array for application in the 2.4GHz industrial, scientific and medical(ISM) band is implemented using the Ansoft HFSS software. Standard formulas are used to calculate different antenna parameters. The proposed antenna is designed to work at 2.4GHz frequency band. A half power beam width(HPBW) of 57°. A bandwidth of around 7.7% is attained. This may have been brought about by poor impedance matching and a high level of surface waves. A way of improving the bandwidth would have been to use proximity coupling feeding method which offers the highest bandwidth and is somewhat easy to model and has low spurious radiation. However, its fabrication would have been more difficult. A directivity of 2.01 dB is achieved. This is a fairly high though directivity increase could have been studied through use of different substrate material and thickness. Adjusting length and width of narrow slot loop antenna will influence on the resonance frequency and bandwidth. By using HFSS software, the characteristics of antenna are investigated and analyzed, including voltage standing wave ratio (VSWR), return loss and far field radiation patterns.

Dual Polarized Cylindrical Loop Slot Antenna for Omni Cell Application

Dual Polarized Cylindrical Loop Slot Antenna for Omni Cell Application

Planar quasi‐isotropic antenna for drone communication

AbstractIn this article, a planar antenna with quasi‐isotropic radiation pattern is proposed for applications in drone communication. The proposed antenna consists of top‐loaded monopole and slotted loop antennas. The top‐loaded monopole provides a monopole‐like radiation pattern with a planar profile. To compensate for nulls in the monopole radiation pattern, a slotted loop antenna is added. Therefore, when two radiation patterns are combined, a quasi‐isotropic pattern is achieved with a low profile thickness of 7.2 mm. The performance of the proposed antenna is verified by simulation and experimental results. The antenna's 10‐dB impedance bandwidth is in the range of 2–2.4 GHz. The quasi‐isotropic radiation pattern is verified from both simulation and measured results.

DC ground compact wideband omnidirectional vertically polarised slot loop antenna for 4G long‐term evolution applications

A compact, wideband, omnidirectional, vertically polarised antenna without electrostatic discharge problems is proposed in this study for 4G long-term evolution applications. The proposed antenna is composed of three identical basic radiators separated by an angle of 120°. The basic radiator is based on a slot loop which is a wideband and DC ground structure. By bending the basic radiators, the antenna achieves better impedance matching and lower gain variation in the horizontal plane in a compact size. The proposed antenna reaches a fractional bandwidth of 45.5% for the voltage standing wave ratio (VSWR) <;1.5, a peak gain from 2.4 to 3.8 dBi with a gain ripple around 2 dB in the omnidirectional plane. It operates from 1700 to 2700 MHz, covering most 4G long-term evolution frequency bands. Both simulation and measurement of a prototype is done in this study to verify the antenna performance.

A Multiband Dual-Polarized Omnidirectional Antenna for 2G/3G/LTE Applications

A multiband dual-polarized omnidirectional antenna for 2G/3G/Long Term Evolution (LTE) mobile communications is proposed in this letter, which consists of horizontal polarization (HP) and vertical polarization (VP) element with separate feeds. The VP element consists of three polygonal radiation patches with three equally spaced legs shorted to the ground plane. The HP element consists of three wideband slot loop structures, which is nested on the top of the VP element. Three slot loop structures provide a 360° coverage for HP and enhance its bandwidth. Both the simulated and measured results indicate that the frequency bands of 1650–2900 MHz for HP and 780–2700 MHz for VP can be achieved. The reflection of VP improves the gain of the HP element at least 1 dBi after nesting. The gain of HP element is more than 3 dBi for LTE, and the gain of VP element is more than 5 dBi in the LTE band and 1.5 dBi in the 2G band. Port isolation larger than 30 dB and low-gain variation levels are also obtained. The proposed antenna can be applied in mobile communications.

BP Network Control for Resource Allocation and QoS Ensurance in UAV Cloud

Unmanned aerial vehicle (UAV) cloud can greatly enhance the intelligence of unmanned systems by dynamically unloading the compute-intensive applications to cloud. For the uncertain nature of UAV missions and fast-changing environment, different UAV applications may have different quality of service (QoS) requirements. This paper proposes a mixed QoS ensurance and energy-balanced (MQEB) architecture for UAV cloud from a view of control theory, which can support both hard and soft QoS ensurance with the consideration of energy saving. The hard and soft QoS requirements are decoupled by being normalized into a two-level cascaded feedback loop. The former is time slot loop (TS-Loop) to enforce the absolute QoS ensurance for real-time applications, and the latter is contention window loop (CW-Loop) to enforce the plastic QoS ensurance for non-real-time applications. Finally, the back propagating (BP) neuron network is used for parameters’ self-tuning and controller design. The hardware experiments demonstrate the feasibility of MQEB. In heavy load, MQEB has greater throughput and better energy efficiency, and in light load, MQBE has lower total power consumption.

Nano-Fluidic Millimeter-Wave Lab-on-a-Waveguide Sensor for Liquid-Mixture Characterization

This paper reports on a miniaturized lab-on-a-waveguide liquid-mixture sensor, achieving highly accurate nanoliter liquid sample characterization, for biomedical applications. The nanofluidic-integrated millimeter-wave sensor design is based on a near-field transmission-line technique implemented by a single loop slot antenna operating at 91 GHz, fabricated into the lid of a photolaser-based subtractive manufactured WR-10 rectangular waveguide. The nanofluidic subsystem, which is mounted on the top of the antenna aperture, is fabricated by using multiple polytetrafluoroethylene layers to encapsulate and isolate the liquid sample during the experiment, hence, offering various preferable features, e.g., noninvasive and contactless measurements. Moreover, the sensor is reusable by replacing only the nanofluidic subsystem, resulting in a cost-effective sensor. The novel sensor can measure a liquid volume of as low as 210 nanoliters, while still achieving a discrimination accuracy of better than 2% of ethanol in the ethanol/deionized-water liquid mixture with a standard deviation of lower than 0.008 from at least three repeated measurements, resulting in the highest accurate ethanol and DI-water discriminator reported to date. The nanofluidic-integrated millimeter-wave sensor also offers other advantages, such as the ease of design, low fabrication and material cost, and no life-cycle limitation of the millimeter-wave subsystem.

A Two Concentric Slot Loop Based Connected Array MIMO Antenna System for 4G/5G Terminals

In this paper, an integrated design with a multiple-input multiple-output (MIMO) antenna system for fourth generation (4G) and fifth generation (5G) applications is presented. The proposed design contains a two-element slot-based MIMO antenna system for 4G and a connected antenna array (CAA)-based two-element MIMO antenna system for a potential 5G band. Two rectangular loops are etched on the periphery of the ground plane. The top and bottom portions of the thin loops act as the two 4G MIMO antennas, while parts of their sides are acting as 5G arrays. The antenna system is fabricated on a commercially available Roger 4350 substrate with $\epsilon _{r}$ equal to 3.5, while the dimensions of the board are $100\times 60 \times 0.76$ mm3 representing a typical smart phone back plane size. The integrated antenna system covers multibands at 4G with a combined bandwidth of 1.565 GHz (−6 dB BW) in addition to the band between 16.50 and 17.80 GHz for 5G. The design is planar, low profile, simple, and compact in structure making suitable for wireless handheld devices and mobile terminals. The measured gain at 3.46 GHz was at least 2.22 dBi and at 17 GHz was 8 dBi for the 4G and 5G MIMO antenna systems, respectively. The envelope correlation coefficient was also calculated from the measured 3-D patterns and showed good MIMO performance. This is the first integrated 4G/5G MIMO antenna system with below 6 GHz and above 10-GHz covered bands using CAA.

Design of a bandwidth enhanced hybrid slot loop antenna for GSM/UWB standards

PurposeThis paper aims to presents the bandwidth enhancement of a hybrid slot–loop antenna using a modified feed structure.Design/methodology/approachThe conventional monopole feed of the hybrid slot–loop radiator is loaded with a flat microstrip patch to excite higher-order modes. The proposed antenna combines the resonant modes of the slot antenna, the loop antenna and the patch loading.FindingsThe antenna exhibits a dual-band response suitable for GSM 1800/1900 and ultrawideband (UWB) standards. The impedance bandwidth extends from 1.65 to 1.95 GHz (11.42 per cent) and 3 to 11.1 GHz (114.9 per cent). The proposed antenna has the smallest footprint with a peak gain of 5.07 dBi at 1.8 GHz and 4.97 dBi at 6 GHz. The prototype antenna is fabricated and the simulation results are validated using experimental measurements. The performance of the bandwidth-enhanced hybrid slot–loop antenna is compared with that of other slot antennas.Originality/valueThus, a hybrid slot–loop antenna with an enhanced bandwidth has been reported in this study. The conventional monopole feed of the antenna is replaced with a monopole ending with a microstrip patch load. The antenna covers the operating bands of GSM 1800/1900 and UWB. The proposed antenna has a smaller footprint compared with other wide-slot antennas reported in the literature.

Co-simulation of a complete rectenna with a circular slot loop antenna in CPW technology

This study starts with the design of a planar and compact CPW antenna fabricated on Arlon AD1000 substrate, εr=10.35. The antenna is a coplanar waveguide (CPW) fed circular slot loop antenna matched to the standard impedance 50 Ω by two stubs. The goal is to implement this antenna with a CPW RF/DC rectifier to build an optimized low power level rectenna. The rectenna design is restricted to allow easy and fast fabrication of an array with a high reproducibility. The full rectenna is simulated and achieves 10% effciency at −20 dBm.

Meander line‐based low profile RIS with defected ground and its use in patch antenna miniaturization for wireless applications

ABSTRACTA reactive impedance surface (RIS) comprising of 4 × 4 array of grounded unit cells having meander line structure is designed. A detailed impedance analysis of the RIS is presented and validated with simulation results. A triangular patch antenna with metallic ground plane is designed to resonate at 3.78 GHz. The metallic ground is substituted by the RIS which results in shifting of resonant frequency from 3.78 GHz to 2.90 GHz thus exhibiting 23.28% miniaturization. The metallic ground of RIS is made defected by etching a rectangular slotted loop which leads to 50.8% miniaturization as the resonant frequency of the structure shifts to 1.86 GHz which resembles to GSM communication frequency. A tuning parameter has been identified in the slotted loop to control the resonant frequency of the structure. Satisfactory gain, efficiency and stable radiation pattern with low cross polarization level in both E and H planes qualify the proposed structure as a promising candidate for practical wireless applications. A comparison of the proposed structure with previous works in literature is provided to demonstrate the superiority of the proposed technique in terms of the profile of RIS and its miniaturization capability. Experimental verification of the proposed structure is provided. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:732–738, 2017

Vertically polarized omni-directional loop slot array antenna for mobile base station

A slim vertically polarized omni-directional feed circuit integrated loop slot antenna for mobile base station is proposed in this paper. Picocell antenna requires a compact and slim structure, because its construction space is limited in urban areas. The proposed antenna consists of loop slots and patches to improve omni-directional pattern and bandwidth. In order to enhance the directivity gain, we arrange two loop slot antennas in vertical plane with microstrip line connecting the slots. The size of antenna is only 0.17λ× 1.45λ. This antenna realizes more than 15% relative bandwidth, and an omni-directional pattern in both simulation and measurement results.

AN ISM BAND CONVENTIONAL CPW RECTENNA FOR LOW POWER LEVELS

This paper presents the design and fabrication of a coplanar waveguide (CPW) rectenna using a sequential modular approach. The rectenna is printed on high permittivity, low-loss board ARLON AD1000 (r = 10.35 and tan δ = 0.0023 @ 10 GHz). The rectifier section is realized with a single reverse-biased schottky diode SMS-7630 in reverse topology for which a diode model is obtained at −20 dBm for frequencies F 0 = 2.45 GHz and 2F 0 = 4.9 GHz. The low-pass filter and the impedance matching are synthesized from passive CPW structures. Co-simulation technique is used to overcome CPW simulation limitations and to integrate the diode characteristics. The antenna consists of a circular slot loop antenna with stub matching such that its input impedance is close to 50 Ω. The goal of this work is to design a rectifier to simplify and speed up the fabrication process of a rectenna array. We reduced the number of processes to etch the rectifier on the board and minimized the number of lumped elements. At −20 dBm, simulation of the rectifier with an ideal impedance matching network shows rectification at 2.45 GHz with efficiency of 12.8%. The rectifier and rectenna show efficiency of approximately 10% at an operating frequency of 2.48 GHz.

金属溶液雾化器中气体流场的计算模拟与分析

本文基于一种旋涡环缝式雾化器，采用Catia建立实体模型，ICEM对模型进行网格划分，Fluent进行对气流流场的数值模拟计算，研究了气体流过雾化器内部的流动过程以及气流从雾化器环缝喷嘴喷出后的射流流场特性。研究发现气流在雾化器内部的流动存在漩涡，从雾化器环缝喷嘴喷出后，射流呈空心的对顶气锥形态，且存在一个旋度。沿喷射方向，射流流速逐渐减小，射流宽度增加。通过对雾化器流场的计算模拟分析，可以为改进该雾化器雾化性能提供依据。 Based on a vertical loop slot atomizer, Catia was used to establish the solid model. The grid was di-vided by ICEM. Fluent was used to simulate the flow field. The flow field characteristics of the gas flowing through the atomizer and the characteristics of the jet spraying out from the atomization nozzle of the atomizer were studied. It was found that there were vortices in the flow inside the at-omizer. After ejecting from the atomizer nozzle, the jet appeared in the shape of a hollow double cone and there was a rotation. Along the ejecting direction, the flow rate of the jet decreased and the width of the jet increased. Through the calculation and analysis of the flow field of the atomi- zer, it provides the basis for improving the atomization performance of the atomizer.

A Novel Planar Printed Dual-Band Magneto-Electric Dipole Antenna

In this paper, a novel planar printed dual-band magneto-electric dipole antenna is proposed. The proposed antenna is composed of a conventional bow-tie patch as an electric dipole, a semi-circular loop that operates as a magnetic dipole, a coplanar ground plane, and a wideband microstrip-to-coplanar-stripline transition balun. By etching a pair of complementary capacitively loaded loop slots on the bow-tie radiation patch, a notched band is introduced to form the dual-band antenna. And a coplanar ground is adopted to make the entire antenna become a planar printed structure. Additionally, the proposed antenna loads the periodical interdigital capacitance structure on the semi-circular loop for the purpose of making the current flowing along the loop maintain the same phase and improving the performances of the magnetic dipole. The proposed antenna was fabricated and measured. The measured results keep in good accordance with the simulated ones. Consequently, the proposed antenna achieves a dual-band operation at 2.37~2.82 GHz (17.3%) and 3.14~4.10 GHz (26.5%) with the Voltage Standing Wave Ratio (VSWR) less than 2, so it can be applied for WLAN (2.4–2.484 GHz) and WiMAX (2.5–2.69 GHz/3.4–3.69 GHz). Meanwhile, the stable gain, symmetrical, and stable unidirectional radiation patterns, low cross polarization, and low back lobe are also obtained at the dual bands.

Square loop slots loaded substrate integrated waveguide based horn antenna

This article represented the effective approach to improve the bandwidth and gain response of substrate integrated waveguide antenna (SIW) using novel defected microstrip structure (DMS) technique for Ku band applications. First of all, Horn antenna was designed using SIW technique and it provided gain around 6 dB. Single square loop slots and multiple square loop slots were introduced in SIW based horn antenna and performance analysis have been carried out. Their responses proved that they were not only responding the fundamental mode but also at different high order modes. Creation of multiple square loop slots not only increased bandwidth but also it increased gains more than 8.5 dB. Moreover, the proposed antennas also responding dual frequencies with more than 500 MHz bandwidth, −2 dB side-lobe levels and VSWR was around 1.35. All the structures were simulated using Ansoft high frequency structure simulator. Comparison between results verified the effectiveness of the proposed idea. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1577–1582, 2016

CPW-Fed Printed Antenna Array With Conical Beam

A printed antenna array with conical beam is presented. Coplanar waveguide (CPW) is used to feed the antenna. Loop slots with finite width of ground plane, which play the role of radiating elements are arranged collinearly to form a traveling wave antenna array. The widths of the loop slots are adjusted to achieve low sidelobe performance. The design procedures are proposed and a 16-element array with beam-pointing angle of 77° is fabricated and measured to verify the design. The measured 15-dB return loss bandwidth is 11.4% at central frequency of 10.5 GHz. The measured gain and the sidelobe level are 10.3 dBi and $-20\;\text{dB}$ , respectively. The agreement between the measured and the simulated results is acceptable.

Pattern diversity antenna with high‐temperature tolerance for body area networks

A high-temperature tolerant pattern diversity antenna is presented for body wearable applications in hostile conditions. The proposed system consists of a dielectric resonator antenna (DRA) placed at the centre of a slot loop antenna. The combination yields pattern diversity with broadside and endfire radiation patterns from slot loop and DRAs, respectively. The antenna system offers common bandwidth of 4.95% with port isolation of better than 13 dB at 2.4 GHz. The thermal characteristics of antenna have been studied for high-temperature operation and no discernible change in the radiation behaviour is noted. The antenna undergoes 2% resonant frequency shift when operated at elevated temperature. The antenna diversity has been measured for three on-body communication channels. The antenna offers 9.5 dB diversity gain in a pure non-line-of-sight channel surrounded by a rich fading environment subjected to the selection combining scheme. The antenna has dimensions of 0.4λo × 0.4λo × 0.1λo .