2,192 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
Power margin reduction in linear passive UHF RFID tag arrays
This paper studies the power margin reduction
in linear passive UHF RFID tag arrays due to proximity effects.
It is shown experimentally that a 40% reduction in tag power
margin occurs when two tags are placed with a separation of
less than 2cm. Major causes of tag sensitivity degradation due
to proximity in arrays are analyzed by experiment and
simulation, including tag detuning, shadowing and re-emission
cancellation. It is shown that tag detuning has a significant
effect when tags are separated by less than 7mm. At larger
separations in excess of 1cm, the tag shadowing effect and
interactions between the backscattered waves cause more
significant degradation for large tag arrays.This work has been supported by UK Engineering and
Physical Science Research Council via the COPOSII project.This is the author accepted manuscript. The final version is available at http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=6934248
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SPAD-Array Contention Signal and Noise Model Suitable for Multilevel Modulation Schemes with Signal Processing
The first signal model for a single photon avalanche diode (SPAD)-array communication receiver for multilevel modulation schemes is reported. This paper proposes a novel, generalised SPAD array signal and noise model for both digital and analogue, synchronous and asynchronous SPAD readout arrays, which includes the competition between the input photons, dark counts and after-pulsing counts. With this contention signal and noise model, multilevel signals including the signal variation after distortion or equalisation can be evaluated. Also, we report the first numerical investigation for SPAD-based, high data rate, free space, visible light communication using higher order pulse amplitude modulation (PAM) with matched filter, linear and non-linear Volterra post-equalization. Simulations have been carried out to analyze and compare the bit error rate (BER) performances under a variety of conditions. The model is
verified by comparison with published experimental results.UK EPSRC via the TOWS project (EP/S016570/1
Low-energy, high-performance lossless 8×8 SOA switch
We demonstrate the first monolithically-integrated active-passive lossless 8×8 SOA
switch. A wide IPDR of 14.5dB for penalty <1dB is achieved. The switch paths through the device
exhibit excellent uniformity.The research leading to these results has received funding from the UK EPSRC through the
INTERNET, STAR and COPOS II grants and the European Commission under FP7 grant agreement ICT 257210
PARADIGM.This is the accepted manuscript. The final version is available from OSA at http://www.opticsinfobase.org/abstract.cfm?uri=OFC-2015-Th4E.6
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