Analysis and characterization of transponder antennae for radio frequency identification (RFID) systems

An investigation into the use of various radio frequency identification (RFID) antenna designs was performed. Passive RFID tag antennae with a resonant frequency range of 902–928 MHz were tested for robustness and efficiency in the Packaging Science RFID Laboratory at the University of Florida. Commercially available single‐ and dual‐dipole tags were examined for read performance. Electromagnetic modelling software was used to model the impedance matching and detuning effects of nearby conducting surfaces. s‐Parameters, current densities and polar plots of various dipole designs were estimated. Strategies used to shorten antenna length, such as capacitive loading, were evaluated. A simple half‐wave dipole antenna was modelled in order to determine the effect of length on resonant frequency and performance. Parameter sweeps showed that a length of 14.4 cm was required for resonance at 915 MHz and 50 Ω termination. Capacitive loads shortened the dipole to 8.4 cm while adding 4.2 cm to height. It was verified that a conducting surface, such as metal packaging, had strong detuning effects on RFID tag antennae. Different methods, such as tuning stubs, alleviated the detuning effects by allowing bandwidths twice as large as with a simple dipole. Finally, the rationale for commercially available RFID antenna designs was discussed. It was found that analysis of actual antenna tag structures in the laboratory and exploring different methods to improve efficiency can lead to improvements in RFID performance. Copyright © 2005 John Wiley & Sons, Ltd.     

Gain-Enhanced Metamaterial Based Antenna for 5G Communication Standards

Metamaterial surfaces play a vital role to achieve the surface waves suppression and in-phase reflection, in order to improve the antenna performance. In this paper, the performance comparison of a fifth generation (5G) antenna design is analyzed and compared with a metamaterial-based antenna for 5G communication system applications. Metamaterial surface is utilized as a reflector due to its in-phase reflection characteristic and high-impedance nature to improve the gain of an antenna. As conventional conducting ground plane does not give enough surface waves suppression which affects the antenna performance in terms of efficiency and gain etc. These factors are well considered in this work and improved by using the metamaterial surface. The radiating element of the proposed metamaterial based antenna is made up of copper material which is backed by the substrate, i.e., Rogers-4003 with a standard thickness, loss tangent and a relative permittivity of 1.524 mm, 0.0027 and 3.55, correspondingly. The proposed antenna with and without metamaterial surface operates at the central frequency of 3.32 GHz and 3.60 GHz, correspondingly. The traditional antenna yields a boresight gain of 2.76 dB which is further improved to 6.26 dB, using the metamaterial surface. The radiation efficiency of the proposed metamaterial-based 5G antenna is above 85% at the desired central frequency.     

Small modified monopole antenna for UWB application

In this paper, we present a novel modified printed monopole antenna (PMA) for ultra-wideband (UWB) applications. The proposed antenna consists of a truncated ground plane and radiating patch with two tapered steps, which provides wideband behaviour and relatively good matching. Moreover, the effects of a modified trapezoid-shaped slot inserted in the radiating patch, on the impedance matching and radiation behaviour is investigated. The antenna has a small area of 14 x 20 mm² and offers an impedance bandwidth as high as 100% at a centre frequency of 7.45 GHz for S₁₁ < -10 dB, which has a frequency bandwidth increment of 18% with respect to the previous similar antenna. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behaviour within the UWB frequency range.     

Theoretical and experimental study on a partially driven array antenna with simplified dipole elements

A novel design is proposed to reduce the number of driven elements by replacing them with passive elements or wires in an array antenna. The study is based on the analysis of electromagnetic wave fields by considering of the coupling between the half-wavelength dipoles. An array antenna of two driven elements and two passive elements is considered as a model. After optimising the element arrangement, the antenna gain can match that of the equivalent four-driven element case. The simulation result is confirmed by an experiment that uses dipoles with simplified matching technique. Feeding networks in a high-power radiating system are analysed in terms of the length and matching of feed lines, and the number of amplifiers.     

Application of gain-bandwidth bounds on loaded dipoles

Physical limitations based only on antenna volume, form factor and material parameters are applied to electrically small antennas in the form of single dipoles. The upper bound on the gain-bandwidth product is solely determined by the polarisability matrix that characterises the antenna when it is immersed in a uniform applied static field. The polarisability, and hence the bandwidth, is increased by loading the dipole arms close to their ends. The half-power impedance bandwidth is increased from 5 to 13% by moving the coils from the centre to the ends of the dipole arms. The introduction of a stub-matching further improves the bandwidth but the physical limit is not reached. Finally, a dual-resonance dipole antenna is analysed. It is observed that a second resonance hardly reduces the bandwidth of the first resonance if the resonances are separated more than 1.7 times in frequency.     

Microstrip-fed dual-frequency annular-slot antenna loaded by split-ring-slot

A compact dual-band annular-slot antenna loaded by a concentric split-ring-slot is presented. A stepped microstrip feedline enables the control of the coupling and provides good matching. The annular-slot is connected to the split-ring-slot by a rectangular slot, which increases the surface of the current path, thus notably reducing the resonant frequency for a given size. The embedded split-ring-slot structure allows many resonant modes to be realised. By tuning the key parameters, these operating modes and their bandwidths can be controlled. A wide bandwidth can be realised for either the lower band, upper band or both bands simultaneously, depending on the application. Measured results show that the bandwidths in the region of 45?15% and 32?8.4%, can be provided for the lower and upper bands, respectively. For the case where a wideband response is required for both bands, it is shown that 26 and 32% can be realised. A 30% miniaturisation is also achieved compared with conventional annular ring slot antennas.     

Triple-frequency meandered monopole antenna with shorted parasitic strips for wireless application

The performance of a triple-frequency meandered-strip monopole antenna for wireless application is presented. The proposed antenna comprises of a microstrip-fed monopole with an additional meandered strip and a ground plane with three protrudent strips on the opposite side of the substrate. By adding these shorted parasitic strips to this monopole, good impedance matching for multi-band application is obtained. Tuning effects of the additional shorted strips to the different resonant modes were examined and prototype of the proposed antenna had been constructed and experimentally studied. The measured results explore a broadband triple-frequency operation covering the required bandwidths of the PCS-1900/UMTS-2100 and the 2.4/5.2/5.8 GHz WLAN standards, a near-directive radiation pattern and a good antenna gain for this design.     

Design of multi-frequency microstrip antennas using multiple rings

An electromagnetically coupled feed arrangement is proposed for simultaneously exciting multiple concentric ring antennas for multi-frequency operation. This has a multi-layer dielectric configuration in which a transmission line is embedded below the layer containing radiating rings. Energy coupled to these rings from the line beneath is optimised by suitably adjusting the location and dimensions of stubs on the line. It has been shown that the resonant frequencies of these rings do not change as several of these singlefrequency antennas are combined to form a multi-resonant antenna. Furthermore, all radiators are forced to operate at their primary mode and some harmonics of the lower resonant frequency rings appearing within the frequency range are suppressed when combined. The experimental prototype antenna has three resonant frequencies at which it has good radiation characteristics.     

Dual-mode compact structure comprising of side-fed bifilar and quadrifilar helix antenna

A side-fed bifilar helix antenna can be integrated with a quadrifilar helix antenna in a piggy back configuration in order to achieve a dual-mode radiating structure. The overall length of the structure is 0.44 lambda at the resonant frequency (1.54 GHz) of the space mode antenna and 0.39 lambda at the resonant frequency (1.34 GHz) of the terrestrial mode antenna. The computed results are validated by experimental data.     

Matching radio frequency identification tag compact dipole antennas to an arbitrary chip impedance

A method for matching dipole antennas to capacitive or inductive arbitrary complex impedances is proposed for ultra high frequency radio frequency identification (RFID) tag antenna designs. It can be applied to straight, capacitive-loaded, meander or any small high-Q dipole topology. For this purpose, design stages are provided with the corresponding formulas. The reflection coefficient simulations and measurements of four implemented prototypes show the expected output when the RFID frequency band, bandwidth, chip impedance and maximum tag size are required as inputs for the method. The eventual S11 < 10 dB bandwidth depends on the chip impedance Q factor and the antenna size. How this bandwidth is manifested in terms of the read range is also discussed. A length ratio of up to 31.1% regarding the standard Λ/2 dipole at resonance is obtained.     

Broadband designs of coplanar capacitivelyfed shorted patch antennas

The author presents a coplanar capacitively fed shorted patch antenna for easy fabrication and providing a very wide impedance bandwidth. In this design, a feeding strip is located on the same plane as that of the radiating patch and used to excite the antenna by electromagnetic coupling. Experimental results reveal that the impedance bandwidth of the proposed antenna depends not only on the length and location of the feeding strip but also on the width of the radiating patch. For the optimal result obtained in the design, the 10 dB return-loss impedance bandwidth is as large as 78%. The radiation characteristics of the operating frequencies within the obtained wide bandwidth are also studied and presented.     

Theoretical and numerical analysis of the resonant behaviour of the Minkowski fractal dipole antenna

The resonant behaviour and the size reduction capabilities of the Minkowski fractal dipole antenna are investigated. The antenna is analysed at each resonant frequency by considering the radiation efficiency and the fractional bandwidth. Besides, a method for deriving the approximate positions of the resonant frequencies of the Minkowski dipole at each fractal iteration is proposed. The presented analysis is based on the inductive circuit model and is validated by simulations. Moreover, in order to quantify the advantages provided by the Minkowski geometry, the proposed study performs a comparison with the generalised Koch dipole in terms of fractal dimension and lacunarity.     

A simple dual-band microstrip-fed printed antenna for WLAN applications

A novel microstrip-fed dual-band printed antenna for wireless local area network (WLAN) is presented. The antenna comprises a rectangular and a circular radiating element, which generate two resonant modes to cover 2.4/5.2/5.8 GHz WLAN bands. The design was experimentally verified by constructing the antenna on a FR4 (ϵr = 4.4) dielectric substrate (47 mm x 26 mm x 0.76 mm) and measuring its impedance and radiation characteristics at both the bands. The measured 10 dB return loss (VSWR 2:1) bandwidth in the 2.4G Hz band is 550 MHz (2.1?2.65 GHz) and it covers the bandwidth required for 2.4 GHz WLAN. The 5.2/5.8 GHz resonant mode has a bandwidth of 950 MHz (5.15?6.1 GHz) covering 5.2/5.8 GHz WLAN bands. A rigorous experimental evaluation confirmed that the dual-band printed antenna maintained good radiation characteristics with minimum cross-polarisation levels.     

Dual frequency band antenna combined with a high impedance band gap surface

A compact dual-band antenna structure for automotive and aerospace applications is discussed. A bow tie dual-band electromagnetic band gap (EBG) element geometry is presented that has a reduced cell dimension compared to the wavelength yet has sufficient bandwidth for mobile communication applications. The EBG was combined with a printed planar monopole to produce a structure 8 mm thick. The return loss and radiation patterns gave satisfactory performance at two frequency bands with bandwidths of 11% at 1700 MHz and 7% at 2600 MHz. There was suppression of the back radiation at both bands of 5 dB or better even for the small 3 times 3 element EBG used and the antenna was platform tolerant.     

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%     

New CPW-fed monopole antennas with both linear and circular polarisations

A low-profile, planar, circularly polarised monopole antenna with a shorting sleeve strip fed using a coplanar-waveguide transmission line for wireless communication in the digital communication system and the global positioning system bands is studied. By utilising the coupling effect between the monopole antenna and sleeve, two excited resonant modes, including the monopole and travelling-wave modes, cover the 1.57- and 1.8-GHz bands. Through modification with antennas of various geometrical parameters, the proposed antenna exhibits the wide bandwidth in the desired frequency bands, which has a bandwidth of 45% at 1.6%GHz for an input reflection coefficient of less than %10%dB. Meanwhile, the antenna has a 3-dB axial ratio bandwidth of 5%. Details of the design considerations for the proposed antennas are described, and the results of the antenna performances obtained are presented and discussed.     

High-temperature superconductor antennas: Utilization of low rf losses and of nonlinear effects

The low radio frequency (r.f.) losses in epitaxial HTS thin films allow the realization of novel antenna structures which have to be excluded in conventional antenna techniques with normal conductors because of the highly reduced radiation efficiency. Thus, the design of miniaturized but nevertheless highly efficient antennas down to a lower limit determined by both the required order of radiation pattern and the frequency bandwidth becomes possible. For a bandwidth of more than about 1%, a considerable margin for a size reduction below the critical size is restricted to the case of electrically small antennas and of superdirective antennas with a relatively low order of the radiation pattern, e.g. antennas with a beam of less than 15 dB maximum gain. If the size approaches the lower limit, the antennas show a sharp bandpass frequency response. This is demonstrated by means of experimental results for a novel HTS meander antenna. These bandpass characteristics can be utilized in compact multiport antenna systems in order to decouple subantennas for adjacent frequency bands. Besides the low losses in HTS's, their nonlinear properties can be used in order to realize current-controlled HTS switches for antenna systems.     

声波测井偶极子发射换能器性能的实验研究

多极子声波测井是新一代声波测井技术,偶极子发射换能器制作技术是其关键技术。本文报道了对自行研发的偶极子声波测井换能器的一致性、耐温、指向性等进行的测试分析结果。本文对三个压电弯曲振子的实验测量结果表明,将偶极子声波测井换能器置于硅油中测量的谐振频率要比在空气中测量的谐振频率降低约20％：在室温到150℃范围内,换能器的谐振频率随着温度的升高略有降低;在偶极子声波测井发射换能器的指向性测量曲线中,换能器辐射声波能量最强方向的声压值与其最弱方向的声压值的比值超过12dB;初步现场测量结果说明．本文研制的偶极子声波测井发射换能器能够测得满意的偶极子声波测井波形。     

高频水声换能器匹配层技术研究

在复杂的海洋环境中,为提高对目标的探测效果以获得更多的信息,高频声呐常需要更宽的工作频带.首先,通过声透射原理对不同匹配层材料进行选取与设计;其次,通过有限元仿真对不同匹配层换能器的透射系数、电导谱和发送电压响应展开了分析计算;最后,在理论分析、解析计算和有限元仿真计算的基础上成功研制了单层、双层和三层匹配层高频宽带水...     

Low Profile UHF Antenna Design for Low Earth-Observation CubeSats

This paper reveals a new design of UHF CubeSat antenna based on a modified Planar Inverted F Antenna (PIFA) for CubeSat communication. The design utilizes a CubeSat face as the ground plane. There is a gap of 5 mm beneath the radiating element that facilitates the design providing with space for solar panels. The prototype is fabricated using Aluminum metal sheet and measured. The antenna achieved resonance at 419 MHz. Response of the antenna has been investigated after placing a solar panel. Lossy properties of solar panels made the resonance shift about 20 MHz. This design addresses the frequency shifting issue after placing the antenna with the CubeSat body. This phenomenon has been analyzed considering a typical 1U and 2U CubeSat body with the antenna. The antenna achieved a positive realized gain of 0.7 dB and approximately 78% of efficiency at the resonant frequency with providing 85% of open space for solar irradiance onto the solar panel.