首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 68 毫秒
1.
A wideband cavity-backed slot antenna operated in the ultra-high frequency(UHF)band is introduced.The antenna has a compact structure and low profile with the size ratio of the ground plane to the slot only 1.6:1.The measured impedance bandwidth of VSWR≤3 achieves 85.3%,covering a frequency range from 390 MHz to 970 MHz.The measured gain is about 5.5～7.5 dB.  相似文献   

2.
为了广泛应用射频识别(RFID)技术,设计了一种标签天线。利用计算电磁场时域有限差分/矩量法的混合方法,分析了复杂环境中RFID天线的性能。将计算结果和实验进行比较,验证了混合方法计算结果的准确性,对RFID天线的工程设计有一定参考价值。  相似文献   

3.
The surface acoustic wave (SAW) identification (ID)-tags have great potential for application in radio frequency identification (RFID) due to their characteristics of wireless sensing and passive operation. In the measurements based on the frequency domain sampling (FDS), to expand the range of detection and allow the system work in harsh environments, it is necessary to enhance the identification capability at low SNR. In addition, to identify the tags in real time, it is important to reduce identification time. Therefore, estimation of signal parameters based on the Procrustes rotations via the rotational invariance technique (PRO-ESPRIT) is adopted. Experimental results show that good identification capability is achieved with a relatively faster measurement speed.  相似文献   

4.
高频和超高频RFID在图书馆中的应用比较   总被引：2，自引：0，他引：2  
通过分析高频RFID和超高频RFID在图书馆的使用情况,对比它们在图书馆工作中的应用,总结了两种标签在图书馆中的不同功能以及各自存在的问题,旨在为同行选择RFID提供一些参考。  相似文献   

5.
To address security and privacy issues in radio frequency identification (RFID) traceability networks, a multi-layer privacy and security framework is proposed, which includes four facets: a security model, a communication protocol, access permission and privacy preservation. According to the security requirements that are needed in an RFID system, a security model that incorporates security requirements that include privacy of tag data, privacy of ownership, and availability of tag identity is introduced. Using this model, a secure communication protocol that can be used for anti-counterfeiting, automatic identification and privacy preservation is then developed. In order to manage the number of parties, data records of items, and complicated transitions of access permissions in an item-level traceability context, a well-designed access control protocol is proposed to parties that can prove the physical possession of an item;meanwhile, to address the privacy issues during data sharing in an RFID network, a vision of database systems that take responsibility for the privacy of the data they manage is also presented.  相似文献   

6.
Refined empirical line method to calibrate IKONOS imagery   总被引：1，自引：0，他引：1  
INTRODUCTION To extract quantitative biophysical parameter such as leaf biomass and leaf chlorophyll concentra- tion from the remotely sensed imagery accurately, the effects of atmospheric scattering and absorption must be removed. Atmospheric effects add to or diminish true ground reflectance, if the atmospheric spectral features are not properly removed. A significant analytical bias could be introduced for data interpre- tation (Ben-Dor and Levin, 2000). Many approaches have been deve…  相似文献   

7.
Using composite field arithmetic in Galois field can result in the compact Rijndael S-Box. However, the power con- sumption of this solution is too large to be used in resource-limited embedded systems. A full-custom hardware implementation of composite field S-Box is proposed for these targeted domains in this paper. The minimization of power consumption is implemented by optimizing the architecture of the composite field S-Box and using the pass transmission gate (PTG) to realize the logic functions of S-Box. Power simulations were performed using the netlist extracted from the layout. HSPICE simulation results indicated that the proposed S-Box achieves low power consumption of about 130 μW at 10 MHz using 0.25 μm/2.5 V technology, while the consumptions of the positive polarity reed-muller (PPRM) based S-Box and composite field S-Box based on the conventional CMOS logic style are about 240 μW and 420 μW, respectively. The simulations also showed that the presented S-Box obtains better low-voltage operating property, which is clearly relevant for applications like sensor nodes, smart cards and radio frequency identification (RFID) tags.  相似文献   

8.
给出了一种紧凑的可用于WUSB的新型带陷超宽带印刷单极子天线．天线由内嵌条带的U形环组成并采用部分接地技术,从而使天线具有带陷超宽带特性．实测结果表明该天线输入端驻波比小于2的绝对阻抗带宽为7．88GHz,覆盖了3．12～11GHz的频率范围,其中5．06～5．89GHz范围内具有带阻特性．讨论了各几何参数对天线性能的影响,同时获得了该天线相对稳定的、近似全向且对称的测试方向图．由于此种天线无需额外的带阻滤波器来隔离天线与其他通信系统的干扰,从而大大简化了WUSB系统的设计．  相似文献   

9.
A bidirectional deployable parabolic cylindrical reflector for an L-band synthetic aperture radar is presented in this study, in which a self-deployed antenna with low weight was designed. The antenna consists of four curved surfaces formed from thin sheets of composite materials connected by hinges along the edges, and the reflective surface is provided by the front surface. The edge profiles of connecting lines were obtained through geometric analysis. A scaled model, including design and manufac- ture, was demonstrated to validate the process from the folded state to the fully deployed state. The non-contact synchronous vision measuring method was used to test the basic frequency of the scaled model, and the test results gave the verification of the analyses. Compared with the existing unidirectional deployable antenna, this new type of bidirectional deployable antenna can be applied to larger-size antennas and has better performance because the glass-woven tape connections were substituted with more reliable hinges. Static, modal, harmonic response, and transient response analyses of the full-sized reflector structure were mod- eled with the commercial finite element （FE） package ABAQUS. The modeling techniques were developed to predict the struc- tural dynamic behavior of the reflector and the results showed that the first natural frequency was 0.865 Hz, and the reflector structure had good stiffness in three directions. This proposed structure has very high stiffness-to-mass ratio because of its hollow solid construction. A preliminary simulation of radiation properties of the parabolic cylindrical antenna, fed by an off-set linear feed horn array, was conducted to obtain the radiation pattern of the feed and the reflector.  相似文献   

10.
INTRODUCTIONInvestigationofphotonicbandgap(PBG)materialsiscurrentlyoneofthemostactivefron-tiersinengineeringandphysics.PBGmaterialshaverecentlyemergedasanewmultidisciplinaryfieldofstudy(Kesleretal.,1996;Yablonovitch,1994;SimovskiandHe,2001).APBGstructurecanhaveabandgapwithinwhichelectromagnetic(EM)wavepropagationispreventedinalldirec-tions(Joannopoulosetal.,1997;Ozbayetal.,1994).Foratwo-dimensionalPBGmaterial,thepropagationofanEMwavewithinitsbandgapispreventedinalldirectionswithin…  相似文献   

11.
INTRODUCTION Veselago (1968) showed that if both the permit- tivity ε and the magnetic permeability μ of a material are negative, the propagation direction of an elec- tromagnetic (EM) wave will be opposite to its energy flow direction. Such media are called left-handed materials (LHMs) since the electric field E, magnetic field H, and wave vector k in these media form a left-hand triplet of vectors, instead of a right-hand triplet observed in conventional materials. For a long time, …  相似文献   

12.
A new photonic bandgap (PBG) cover for a patch antenna with a photonic bandgap substrate is introduced. The plane wave expansion method and the FDTD method were used to calculate such an antenna system. Numerical results for the input return loss, radiation pattern, surface wave, and the directivity of the antennas are presented. A comparison between the conventional patch antenna and the new PBG antenna is given. It is shown that the new PBG cover is very efficient for improving the radiation directivity. The physical reasons for the improvement are also given. Project supported by the National Natural Science Foundation of China (No. 90101024) and the Science and Technologies of Zhejiang Provinc (No. ZD0002)  相似文献   

13.
Antenna is very crucial to radiotelemetry capsules which can measure the physiological parameters of the gastroin- testinal (GI) tract. The objective of this paper is to design a novel spiral slots microstrip patch antenna for the radiotelemetry capsules communicating with external recorder at 915 MHz located in ISM (Industry, Science, and Medical) bands. The microstrip patch antenna is designed and evaluated using the finite-difference time-domain (FDTD) method. Return loss characteristics and the effect of the human body on resonant frequency are analyzed, and the performances of radiation patterns at different positions of the human alimentary tract are also estimated. Finally, specific absorption rate (SAR) computations are performed, and the peak 1-g and 10-g SAR values are calculated. According to the peak SAR values, the maximum delivered power for the designed antenna was found so that the SAR values of the antenna satisfy the ANSI (American National Standards Institute) limitations.  相似文献   

14.
RFID隶属于非接触的自动识别技术。RFID系统在工业和商业中得到广泛的应用，系统基本原理是利用射频信号和空间电磁场耦合传输特性，来实现对监控物体的信息交换及自动识别。系统一般包括两部分，即电子标签（Tag）和阅读器（Reader）。标签激活距离是衡量一个RFID系统性能的重要因素。该文详细解释了RFID工作原理和推导出影响标签激活距离的参数。研究对象是高频（HRF）13．56MHz的RFID系统。  相似文献   

15.
A low-sidelobe circularly-polarized （CP） microstrip patch array for 2.4 GHz radio frequency identification （RFID） readers is presented. The antenna array with a Chebyshev current distribution is composed of 6 microstrip elements. The CP operation is obtained by the quasi-square patch with difference in lengths of the two sides. The antenna has been investigated numerically and experimentally. Measured results show that the array has a Chebyshev pattern with the sidelobe level of -23 dB, the half-power beamwidth of 16° and an impedance bandwidth （S11 ≥-10 dB） of 130 MHz, which is suitable for RFID reader applications.  相似文献   

16.
1IntroductionMultiple-input multiple-output(MIMO)systems canoffer significant capacity gains,compared to single-input single-output(SISO)systems.The extra degreesof freedom offered by multiple antennas can be usedfor increasing bit rates through spatial m…  相似文献   

17.
A simple and compact ultra wideband (UWB) printed monopole antenna with band-notched performance is proposed in this paper. The antenna is partially grounded so that the Q value is depressed and the impedance bandwidth is broadened. A small strip bar is loaded on each arm of the similar U-shaped radiator. The impedance bandwidth of the antenna overlap with IEEE 802.11a is rejected consequently. The geometry parameters of the antenna are investigated and optimized with HFSS. The measured bandwidth of the proposed antenna occupies about 7.89 GHz covering from 3.05 GHz to 10.94 GHz with expected notched band from 4.96 GHz to 5.98 GHz. A quasi-omnidirectional and quasi-symmetrical radiation pattern in the whole band is also obtained. As a result, a UWB wireless communication system can be simplified with the band-notched UWB antenna presented.  相似文献   

18.
INTRODUCTION Metamaterials are periodic metallic structures exhibiting unique properties not existing in natural materials. They are also called backward wave mate- rials, double negative materials, or left-handed mate- rials (LHM) in particular, in which the vectors E, H and k form a left-handed system. Since the idea pro- posed by Veselago (1968), metamaterials have at- tracted great interest in the last years (Smith et al., 2000; Pendry, 2000; Smith and Kroll, 2000; Shelby et al., …  相似文献   

19.
用于通信的超宽带印刷天线   总被引：1，自引：1，他引：1  
1IntroductionUltra-wideband(UWB)microwave antennas are ofinterest for a variety of applications such as electroniccountermeasure,transient radars,mine detection,andunexploded ordnance(UXO)location and identifica-tion.In the early2002,the release of the UWB forcommercial communications by the Federal Communi-cation Commission(FCC,USA)sparked renewed in-terest in the subject of UWB antennas.Conventional UWB antennas such as log-periodic orspiral antennas exhibit good UWB characteristi…  相似文献   

20.
INTRODUCTION The rapidly increasing application of radio fre- quency identification (RFID) includes supply chain management, access control to buildings, public transportation, airport baggage, and express parcel logistics (Karthaus and Fischer, 2003; Feldhofer, 2004; Glidden et al., 2004). Using an RFID system is a good approach for automated identification of products. RFID system consists of two major components, an interrogator (reader) and a transponder (tag), composed of an ant…  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号