465 research outputs found
Reduction of Proximity Effects on UHF Passive RFID Systems by Using Tags with Polarization Diversity
A new technique that enables passive ultra high fre-
quency (UHF) radio frequency identification (RFID) tags to be
read when they are placed in close proximity in an array is pre-
sented. This paper demonstrates that, in a linear tag array with
a tag separation of 1 cm, the interaction between the backscat-
tered waves and incident wave causes a significant degradation in
tag sensitivity. It is found that the use of tags that have polariza-
tion diversity can improve the read performance when they are
placed in close proximity to one another compared with conven-
tional linear tags. Two ways of achieving polarization diversity are
studied in this paper, namely: 1) using a circularly polarized tag
and 2) using a cross-polarized tag pair. Both methods show an
improvement in close proximity read performance and it is exper-
imentally demonstrated that by using cross-polarized tag pairs in
an array, one achieves on average a 2.6-dB increase in read power
margin for a 57-tag array with 1 cm separation compared with
using conventional linearly polarized tags.This work has been supported by UK Engineering and
Physical Science Research Council
via the COPOSII project.This is the final published version. It first appeared at http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7042269
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Low-Cost MIMO radio over fiber system for multiservice das using double sideband frequency translation
In this paper, a novel low-cost DSB frequency translation system is experimentally demonstrated and its theory is mathematically proved. The new system is capable of transmitting wideband LTE MIMO signals and supporting multiple services. Experimentally, 2×2 LTE MIMO channels with 20MHz bandwidth, and a 700MHz carrier frequency, are transmitted simultaneously along with an IEEE 802.11g signal (54Mbps) over a 300m length of multi-mode fiber (MMF). The MIMO channel matrix of the system is retrieved and the condition number is calculated. It can be seen in the experimental results that the system is well conditioned, has a low error vector magnitude (EVM) and the transmission of the MIMO signals has negligible effect on the IEEE 802.11g signal. The use of a preamplifier minimizes the non-linearity introduced by the frequency mixers, resulting in a high spurious-free dynamic range (SFDR). Compared to a single sideband (SSB) system, where multiple filters are used and two channels encounter different EVMs, the new DSB system avoids unnecessary filtering and the impairments introduced will be the same for both channels. Therefore it can be concluded that the improved MIMO over fiber system using DSB frequency translation technology is a potential low-cost solution for multiservice MIMO-enabled distributed antenna systems (DAS).This work was supported in part of the UK Engineering and Physical Sciences Research Council via the COPOS II grant and the European Community via the FP7 programme Quaternian project.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/JLT.2016.258208
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MIMO capable RoF system with improved SFDR using quadruple sidebands
© 2017 IEEE. An RoF system using a quadrature-multiplexing technique is shown experimentally to improve the 3rd order SFDR by 2.7dB over an intrinsic optical link. As a result of orthogonality between quadrature sidebands, the system can support MIMO
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Long distance passive UHF RFID system over ethernet cable
This paper proposes a new antenna remoting system for ultra-high frequency (UHF) radio frequency identification (RFID). The system consists of a central baseband controller and a remote antenna subsystem, which are connected using twisted-pair cable. During the inventory session, only baseband signals are transmitted over the twisted-pair cable, whilst the transmitted radio frequency (RF) signals are up and down converted in the antenna subsystem. This new RFID system provides -94.5 dBm of reader sensitivity, and can fulfill long-distance detection tasks with very low performance degradation over up to 150 m of Cat5et cable. Compared with conventional RFID systems using coaxial cables between reader and antenna, the presented RFID system is more flexible and cost-efficient due to its low deployment cost and ease of cable routing
Enhanced RFID tag detection accuracy using distributed antenna arrays
© 2018 IEEE. An Ultra High Frequency (UHF) Radio Frequency Identification (RFID) system using distributed antenna arrays for interrogating RFID tags in a highly multipath environment is demonstrated. The system makes use of phase diversity and beam steering to overcome fading. The tag detection accuracy is compared to a standard fixed antenna system, showing that the presented system is able to deliver more power to the more challenging tags, and therefore is capable of a higher tag read success rate. It is also shown that, whereas a fixed antenna is capable of scanning a single cell, the ability of a phased array to scan through 360° azimuth leads to a reduction in number of antennas required for a multicell system. The experimental results are validated using a 3D field-based propagation model, which enables visualisation of the power distribution in the field of interest, and provides insight into the improved system performance
A critique of Rossberg et al.: noise obscures the genetic signal of meiobiotal ecospecies in ecogenomic datasets
Non-beneficial pediatric research : individual and social interests
Biomedical research involving human subjects is an arena of conflicts of interests. One of the most important conflicts is between interests of participants and interests of future patients. Legal regulations and ethical guidelines are instruments designed to help find a fair balance between risks and burdens taken by research subjects and development of knowledge and new treatment. There is an universally accepted ethical principle, which states that it is not ethically allowed to sacrifice individual interests for the sake of society and science. This is the principle of precedence of individual. But there is a problem with how to interpret the principle of precedence of individual in the context of research without prospect of future benefit involving children. There are proposals trying to reconcile non-beneficial research involving children with the concept of the best interests. We assert that this reconciliation is flawed and propose an interpretation of the principle of precedence of individual as follows: not all, but only the most important interests of participants, must be guaranteed; this principle should be interpreted as the secure participant standard. In consequence, the issue of permissible risk ceiling becomes ethically crucial in research with incompetent subjects
Flammable biomes dominated by eucalypts originated at the Cretaceous-Palaeogene boundary
Fire is a major modifier of communities, but the evolutionary origins of its prevalent role in shaping current biomes are uncertain. Australia is among the most fire-prone continents, with most of the landmass occupied by the fire-dependent sclerophyll and savanna biomes. In contrast to biomes with similar climates in other continents, Australia has a tree flora dominated by a single genus, Eucalyptus, and related Myrtaceae. A unique mechanism in Myrtaceae for enduring and recovering from fire damage likely resulted in this dominance. Here, we find a conserved phylogenetic relationship between post-fire resprouting (epicormic) anatomy and biome evolution, dating from 60 to 62 Ma, in the earliest Palaeogene. Thus, fire-dependent communities likely existed 50 million years earlier than previously thought. We predict that epicormic resprouting could make eucalypt forests and woodlands an excellent long-term carbon bank for reducing atmospheric CO2 compared with biomes with similar fire regimes in other continents
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