Effect of Weaving Direction of Conductive Yarns on Electromagnetic Performance of 3D Integrated Microstrip Antenna

A three-dimensionally integrated microstrip antenna (3DIMA) is a microstrip antenna woven into the three-dimensional woven composite for load bearing while functioning as an antenna. In this study, the effect of weaving direction of conductive yarns on electromagnetic performance of 3DIMAs are investigated by designing, simulating and experimental testing of two microstrip antennas with different weaving directions of conductive yarns: one has the conductive yarns along the antenna feeding direction (3DIMA-Exp1) and the other has the conductive yarns perpendicular the antenna feeding direction (3DIMA-Exp2). The measured voltage standing wave ratio (VSWR) of 3DIMA-Exp1 was 1.4 at the resonant frequencies of 1.39 GHz; while that of 3DIMA-Exp2 was 1.2 at the resonant frequencies of 1.35 GHz. In addition, the measured radiation pattern of the 3DIMA-Exp1 has smaller back lobe and higher gain value than those of the 3DIMA-Exp2. This result indicates that the waving direction of conductive yarns may have a significant impact on electromagnetic performance of textile structural antennas.     

Effect of conductive yarn crimp in radiation patch on electromagnetic performance of 3D integrated microstrip antenna

A three-dimensionally integrated microstrip antenna (3DIMA) is a microstrip antenna woven into the three-dimensional woven composite for load bearing while functioning as an antenna. In this study, the effect of conductive yarn crimp on electromagnetic performance of 3DIMAs are investigated by designing, simulating and experimental testing of two microstrip antennas with different patch woven structures: one woven in plain weave pattern with most yarn crimp and the other woven orthogonally without yarn crimp. The measured voltage standing wave ratio (VSWR) of the crimp free 3DIMA was 1.05 at the resonant frequency of 1.31 GHz; while that of the crimped 3DIMA was 1.78 at the resonant frequency of 1.41 GHz. In addition, the measured radiation pattern of the crimp free 3DIMA in its radiating patch has smaller back lobe and side lobes than those of the crimped 3DIMA. This result indicates that yarn crimp may have a negative impact on electromagnetic performance of textile structural antennas.     

Design and fabrication of microstrip antennas integrated in three dimensional orthogonal woven composites

During the last 10 years, there has been considerable interest in the development of conformal load-bearing antenna structure (CLAS) for communication and aerospace applications. CLAS combines the antenna into a composite structure such that it can carry the designed load while functioning as an antenna. In this paper, a 3D integrated microstrip antenna (3DIMA) was designed and fabricated. The input return loss and radiation pattern of the antennas were simulated using a computer aided design tool (HFSS) and also measured experimentally. The swept input return loss curve in the range of 1–2 GHz of the 3DIMA showed a return loss of ?13.15 dB at the resonant frequency of 1.872 GHz with a voltage standing wave ratio (VSWR) of 1.56; the radiation pattern has a maximum at 180° and agrees well with the simulation results, indicating that 3DIMA can be an effective approach for a CLAS.     

Performance and impact damage of a three dimensionally integrated microstrip feeding antenna structure

A three dimensionally integrated microstrip antenna (3DIMA) with microstrip feeding was fabricated and analyzed. In this design concept, a microstrip antenna was woven into the three-dimensional orthogonal woven composite for the load-bearing while functioning as an antenna. The simulation work was done using the antenna simulation software before fabrication. The measured voltage standing wave ratio (VSWR) of the antenna was 1.18 at the resonant frequency of 1.31 GHz. The measured radiation pattern had a maximum value at 0°, which agreed well with the simulation results. In addition, impact tests were performed with the impact energy ranging from 0 J to 15 J. The results showed that the VSWR changed little even at 15 J impact energy demonstrating good impact resistance and structural integrity of the antenna structure.     

Effect of adhesive bonds on electrical performance in multi-layer composite antenna

We study experimentally the effect of adhesive bonds in a multi-layer composite antenna. Changes in the antenna performance after the bonding process were determined. Three types of antennas were designed and fabricated, with different resonant frequencies. The measured electrical performances of these fabricated structures reveal that all antennas undergo a fall in their resonant frequencies and a reduction in the gain. The change in resonant frequency is related to a change in the effective dielectric constant of the assembly, and the gain falls due to loss in the adhesive. Corrections were then introduced in the design process so as to compensate for the effect of the adhesive. The measured results for the modified antenna show excellent agreement with the target performance.     

Analysis and design of broadband U-slot cut rectangular microstrip antennas

Broadband microstrip antenna using variations of U-slot has been widely reported. However, in most of the reported work, an in-depth explanation about the mode introduced by U-slot and procedure to design U-slot cut antennas at any given frequency is not explained. In this paper, first an extensive analysis to study the broadband response in symmetrical and a new configuration of asymmetrical U-slot cut rectangular microstrip antennas is presented. The U-slot tunes higher-order orthogonal mode resonance frequency of the patch with respect to fundamental mode to realise wider bandwidth. Further formulation in resonant length at modified patch modes in symmetrical U-slot cut antenna is proposed. Frequencies calculated using these formulations show closer agreement with simulated and measured results. Using proposed formulations, a procedure to design U-slot cut antenna at different frequencies over 800–4000 MHz range which shows broadband response is explained. Thus, the proposed work gives an insight into the functioning of widely used U-slot cut antennas and the formulations will be helpful for designing at any given frequency.     

Application of dual-mode filter techniques to the broadband matching of microstrip patch antennas

Structures such as square or circular microstrip patch antennas may support two orthogonal resonant modes. The paper presents a new method of utilising the dual-mode property to increase the bandwidth of microstrip antennas. The input impedance of such a dual-mode antenna may be represented as a second-order ladder network of coupled resonators, where each resonator is coupled to a load resistor. A theoretical method for evaluating the coupling values in the network is presented, enabling the bandwidth of a dual-mode antenna to be maximised. A theoretical bandwidth improvement of up to 3:1 is achieved when compared to a single-mode antenna. This is confirmed with an experimental dual-mode circular microstrip patch antenna     

Effect of Wire Space and Weaving Pattern on Performance of Microstrip Antennas Integrated in the Three Dimensional Orthogonal Woven Composites

A conformal load-bearing antenna structure (CLAS) combines the antenna into a composite structure such that it can carry the designed load while functioning as an antenna. Novel microstrip antennas woven into the three dimensional orthogonal woven composite were proposed in our previous study. In order to determine the effect of the space between the conductive wires on the antenna performance, different space ratios of 1.7, 2.3 and 4.6 were considered in the design. Simulation results showed that when the space ratio increased, the frequency shift and return loss of the corresponding antenna became larger. And the antenna had relatively good performance when the space ratio reached 1.7. Two types of antennas were designed and fabricated with the ratio of 1.7 and 1 respectively and both of them obtained agreeable results. It was also demonstrated by the experimental that the orthogonal structure patch antenna had similar radiation pattern with the traditional copper foil microstrip antenna. However, the interlaced patch antenna had large back and side lobes in the radiation pattern because the existence of the curvature of copper wires in interlaced coupons lowered the reflective efficiency of the ground.     

新型宽频带微带贴片天线的设计

提出了一种新颖的展宽三角形微带贴片天线工作频带的设计方法．通过在三角形微带贴片侧边附近加载与之平行的缝隙来实现双频工作,并添加一对平行于底边的缝隙使两个频点靠近,利用仿真软件进行优化,有效地展宽了贴片天线的频带．制作了实际的贴片天线,结果表明所设计天线的工作带宽(VSWR<2)是普通三角形微带天线的4.46倍,且天线尺寸与同频率的常规贴片天线相比缩小了9.3%．测量结果与仿真结果吻合,证明了所提方法的有效性．     

Wideband microstrip antennas with sandwich substrate

A broadband microstrip antenna with low?high?low (sandwich) dielectric constant substrate combination using a microstrip line-via feed is presented for ultra-wideband applications. The proposed antenna consists of three dielectric substrates; low dielectric constant substrates that contain the microstrip feed line as well as parasitic patches and a high dielectric constant substrate that contains the driven patch. To achieve a large impedance bandwidth, parasitic patches and microstrip line-via combination feed to the driven patch in the multilayered microstrip antenna are used. The proposed antenna designed, fabricated and measured on the sandwich substrate. The antenna has measured 10 dB return loss bandwidth of 46.9% and directive gain .5.2 dBi at boresight across the impedance bandwidth. The total height of antenna is 5.77 mm or 0.077λ ^{at 4 GHz.}     

Size reduction of microstrip patch antennas with left-handed transmission line loading

A procedure for designing an electrically small microstrip patch antenna (MPA) is developed, wherein the length of a side of the MPA is reduced to significantly less than a half-wavelength. The MPA is loaded with a resonant circuit equivalent to that of a left-handed transmission line to artificially increase the effective wavelength of the device, thus creating a resonance equivalent to, but at a lower frequency than the unloaded {10} mode. The field distribution in the loaded MPA remains relatively unperturbed, unlike the {0} mode case that attempts to decrease the size by introducing a shorting-post; consequently, very low cross-polarisation behaviour is observed. The theory to predict the full spectrum of resonant frequencies of the antenna is developed, with finite-difference time-domain simulations used to finalise the antenna design. Finally, an electrically small ((lambda/6)times(lambda/4)) and thin (相似文献   

Compact dual-band tunable microstrip antenna for GSM/DCS-1800 applications

A compact single feed dual-band electronically tunable microstrip antenna for operation in GSM/DCS-1800 system is presented. The antenna consists of two resonant elements designed separately and integrated while preserving their designed bands. The two bands are separately tuned using two biasing control circuits. A significant size reduction and bandwidth selection are achieved using a varactor diode as a voltage control capacitance. The design and implementation is carried out on a foam substrate of thickness 2.44 mm and with a dielectric constant 1.2. Simulation and experimental results show that the required bandwidth of the GSM/DCS-1800 system can be easily covered with voltage changes from 1 to 3 V, which is suitable for mobile hand phones.     

一种新型复合左右手负阶谐振天线的设计

为了获得高增益小尺寸天线,通过在基片集成波导上引入二阶Hilbert分形缝隙,提出了一种新型复合左右手传输线.在等效电路模型的基础上,利用HFSS和Serenade软件对该传输线的电路参数进行了提取;利用MATLAB语言给出了该传输线的色散曲线;最后,由该传输线设计了终端短路的缝隙天线.实验结果表明：该天线馈电网络简单,工作在复合左右手传输线的-1阶模式上,比之前报道的复合左右手谐振天线具有更小的电尺寸和更高的增益.由于这些性能,使得该天线可以用于无线通信系统中.     

Wideband circularly polarised slot antenna

A wideband circularly polarised slot antenna is presented. The slot antenna is fed by four microstrip line feeds orientated to have relative phases of 0deg, 90deg, 180deg and 270deg using a feed network comprising a pair of broadband 90deg hybrid. The proposed antenna delivers measured and simulated impedance bandwidths of 77.8% (1.02-2.32 GHz) and 89.1% (1.02-2.66 GHz), respectively, for standing wave ratio (SWR) < 2, measured and simulated axial-ratio bandwidths of 88.9% (1-2.6 GHz) and 81% (1.1-2.6 GHz), respectively, for axial ratio < 3 dB and measured and simulated gain bandwidths of 33% (1.5-2.1 GHz) and 27% (1.6-2.1 GHz), respectively, for gain >3 dB. A good agreement is observed between simulation and measurement.     

Compensated circuit with characteristics of lossless double negative materials and its application to array antennas

A compensated circuit showing the characteristics of lossless double negative (DNG) materials is proposed and applied to an active integrated antenna array. A properly selected matching circuit produces the phase advance, which is characteristic of a left-handed wave (backward-wave), and the lossy resonant circuit generates the negative group velocity. An amplifier is used to compensate for the inherent loss of the resonant circuit, including its resistor. Then, a series-fed antenna array with a proposed DNG circuit is also designed and fabricated. It consists of two subarrays, each made of two aperture-coupled patch antennas, and the DNG circuit block inserted between the subarrays. In comparison to a conventional array, without the DNG circuit whose two subarrays are connected directly by a microstrip line, the proposed array shows a negligible beam squint and flat gain, over a considerable bandwidth of 11%     

An investigation into measurement of handset antennas

This paper describes the investigation into the effects of signal cables on the operating frequencies, radiation patterns, and gains of handset antennas under test by using a proposed testing scheme. In this simple testing method, a coaxial signal cable feeds the handset antenna under test through a microstrip transmission-line etched onto a printed circuit board. The studies of the influences of different feeding schemes and cable arrangements on two commonly used handset antennas are carried out experimentally and numerically. Also, the distributions of the fields close to the antenna, handset chassis, and the cable are measured and simulated to explore the cable-related influences.     

Design of a novel dielectric resonator antenna using MgTiO3–CoTiO3 for wideband applications

In this work, a novel low profile design of a cylindrical dielectric resonator (DR) antenna with two different permittivity materials is proposed for wideband applications. The multi-permittivity cylindrical DR (MPCDR) was formed by combining four 90° sectors whereby sectors with the same permittivity were positioned in opposite quadrants. Simulation of the antenna was performed in the time domain using computer simulation technology (CST 2014). A systematic analysis was carried out to optimize the antenna's sector size and permittivity. The prototype was fabricated using MgTiO₃ (MTO) and CoTiO₃ (CTO) dielectric materials prepared via solid state reaction. MTO and CTO were sintered at 950 °C (4 h) and subsequently analyzed by XRD to confirm the presence of a single phase. The dielectric properties of MTO and CTO were studied by electrical characterization; it was found that MTO and CTO have permittivity values of 15.72 and 9.85, respectively. The antenna performance was analyzed by placing the MPCDR on top of a microstrip line with an angular position (θ) of 27.5° with respect to the longitudinal axis of the feed-line. An impedance bandwidth up to 56% with stable broadside radiation pattern was achieved in both the simulation and measured.     

Crystal structure,microwave dielectric properties,and dielectric resonant antenna studies of novel low-permittivity CoAl2O4 spinel ceramics

CoAl₂O₄ spinel ceramics were prepared via a standard solid-state reaction method, and their crystal structure, microwave dielectric properties, and dielectric resonant antenna applications were systematically investigated in this study. X-Ray diffraction patterns and Raman spectra confirmed that CoAl₂O₄ belongs to the Fd-3 m space group with cubic crystal symmetry. ε_r and Qf values increased with the increasing sintering temperature, where an ever-improving microstructure was also observed from the scanning electron micrographs. The optimal microwave dielectric properties were achieved as follows: ε_r?=?9.34, Qf?=?30,500 GHz, and τ_f?=??54 ppm/^°C. Moreover, a dielectric resonant antenna was designed and simulated to demonstrate the application prospects of CoAl₂O₄ ceramics towards microwave antennas. The CoAl₂O₄-based antenna resonating at 14.33 GHz exhibited a high return loss of??40.9 dB, a wide impedance bandwidth of 940 MHz, and an exceptionally high total efficiency of 96.6%. The remarkable antenna performances suggested that CoAl₂O₄ ceramics were promising candidates for wireless communication devices operating at the Ku-band, provided τ_f can be further tuned toward zero.

     

Design of a Compact Monopole Antenna for UWB Applications

In this paper, a low cost, highly efficient and low profile monopole antenna for ultra-wideband (UWB) applications is presented. A new inverted triangular-shape structure possessing meander lines is designed to achieve a wideband response and high efficiency. To design the proposed structure, three steps are utilized to achieve an UWB response. The bandwidth of the proposed antenna is improved with changing meander lines parameters, miniaturization of the ground width and optimization of the feeding line. The measured and simulated frequency band ranges from 3.2 to 12 GHz, while the radiation patterns are measured at 4, 5.3, 6 and 8 GHz frequency bands. The overall volume of the proposed antenna is 26 × 25 × 1.6 mm3 ; whereas the FR4 material is used as a substrate with a relative permittivity and loss tangent of 4.3 and 0.025, correspondingly. The peak gain of 4 dB is achieved with a radiation efficiency of 80 to 98% for the entire wideband. Design modelling of proposed antenna is performed in ANSYS HFSS 13 software. A decent consistency between the simulated and measured results is accomplished which shows that the proposed antenna is a potential candidate for the UWB applications.     

At and below the chu limit: passive and active broad bandwidth metamaterial-based electrically small antennas

The solution to the canonical problem of a radiating infinitesimal electric dipole antenna that is centred in a multilayered, concentric metamaterial-based spherical shell system is presented. It is demonstrated that when this system is electrically small, a specifically designed homogenous and isotropic epsilon-negative (ENG) layer can function as a distributed matching element to the antenna enabling a resonant radiation behaviour. A finite element model of the corresponding centre-fed cylindrical dipole antenna-based resonant system confirms that such designed ENG-based spherical layers can act as a distributed matching element, which can be optimised to produce a reactance free, resistively matched and, hence, efficient radiating system. Several limits on the dispersion properties of the homogenous and isotropic ENG media used in these matching layers are considered and their impact on the bandwidth of these resonant systems is established. Although the dispersionless resonant antenna-ENG system has a bandwidth substantially below the Chu limit, the bandwidths of the corresponding dispersive systems are shown to be at or just slightly below the Chu limit. An analytical model of an idealised gaseous plasma-based ENG layer sandwiched between two glass layers, a potential realisation of these metamaterial-based ENG spherical shell systems, is introduced and its solution is used to study these efficiency and bandwidth issues further. Resonant systems based on active ENG metamaterial layers realised with two types of idealised gain medium models are shown to have bandwidths that approach the idealised dispersionless medium values and, consequently, are substantially below the Chu limit