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312:). Therefore, since higher frequencies have smaller wavelengths, high frequency antennas are typically smaller than low frequency antennas. The larger size of practically efficient low frequency antennas is a significant hurdle that near-field electromagnetic ranging systems cannot overcome without decreasing gain. Applying fractal antennae to NFC requires complex adaptive controls
261:, and the EH phase difference changes about 45 degrees between 30 m (98 ft) to 60 m (200 ft). Thus, a 1 degree EH phase difference in a 1 MHz signal corresponds to a range difference of about 67 cm (26 in) and 1/360 of the period or 27.78
329:(UWB). Systems deployed in complicated indoor propagation environments reportedly achieve 60 cm (24 in) accuracy or better at ranges of 46 m (151 ft) or more. There is also an indication that multiple frequency implementations may yield increased accuracy.
219:, the EH phase difference goes to zero. Thus a receiver that can separately measure the electric and magnetic field components of a near-field signal and compare their phases can measure the range to the transmitter.
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The low-frequency, multipath-resistant characteristics of NFER make it well suited for tracking in dense metallic locations, such as typical office and industrial environments. Low frequencies also readily
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Operation at low frequencies faces challenges as well. In general, antennas are most efficient at frequencies whose wavelengths are comparable to the antennas' dimensions (e.g., a quarter-wavelength
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Using relatively low frequencies also conveys additional advantages. First, low frequencies are generally more penetrating than higher frequencies. For instance, at 2.4
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Second, precise synchronization is not required between different receivers: in fact, a local range measurement can be made with just a single receiver.
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Kim, C.w.; Chin, F.p.s.; Garg, H.K. (2006). "Multiple
Frequencies for Accuracy Improvement in Near Field Electromagnetic Ranging (NFER)".
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ranging is an emerging RTLS technology that employs transmitter tags and one or more receiving units. Operating within a half-
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out of phase. As the distance from the antenna increases, the EH phase difference decreases. Far from a small antenna in the
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around the human body, which makes tracking people possible without the body blockage experienced by microwave systems like
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NFER technology is a different approach for locating systems. It has several inherent advantages over other RTLS systems.
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signal, the period becomes 1 ms, and the time difference required to measure becomes 27.78 μs. A comparable
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Electric Waves: Being
Researches on the Propagation of Electric Action with Finite Velocity Through Space
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signals to be used for reliable positioning. Low frequencies are less affected by this problem.
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difference in time between the electric and magnetic signals. Down-converted to a 1 kHz
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Close to a small antenna, the electric and magnetic field components of a radio wave are 90
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2006 IEEE 17th
International Symposium on Personal, Indoor and Mobile Radio Communications
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Capps, Charles. “Near Field or Far Field,” EDN, August 16, 2001, pp. 95-102.
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277:(TDOA) system would require 2 ns to 4 ns to make the same measurement.
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of 30 cm (12 in) and ranges up to 300 m (980 ft).
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Hz a reinforced concrete wall might attenuate signals as much as 20
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2005 IEEE Antennas and
Propagation Society International Symposium
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Third, since EH phase differences are preserved when a signal is
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For instance, a radio wave at 1 MHz has a period of 1
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549:"Q-Track Demonstrates Novel Indoor Wireless Tracking Product"
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is required, so baseband signals with an arbitrarily small
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relations between the EH components of an electro-magnetic
502:"Automatic impedance matching for 13.56 MHZ NFC antennas"
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Local
Positioning Systems: LBS Applications and Services
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of a receiver, transmitter tags must use relatively low
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341:, a definition with the Hertz and Maxwell wave models
432:Schantz, H.G. (2005). "Near Field Phase Behavior".
46:. Unsourced material may be challenged and removed.
622:Introduction to Near Field Electromagnetic Ranging
388:"Novel approach to tracking shows its accuracy"
473:Kolodziej, Krzysztof W.; Hjelm, Johan (2006).
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106:Learn how and when to remove this message
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479:. Taylor & Francis. p. 95.
55:"Near-field electromagnetic ranging"
44:adding citations to reliable sources
347:, a short-range wireless technology
192:)) vary with distance around small
436:. Vol. 3B. pp. 134–137.
119:Near-field electromagnetic ranging
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357:Real Time Locating Systems (RTLS)
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386:Mannion, Patrick (2004-10-25).
196:. This was first discovered by
184:((E and H are the components E=
31:needs additional citations for
417:. Dover Publications. p.
351:Radio Frequency Identification
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135:Real Time Location System
125:technology employing the
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411:Hertz, Heinrich (1893).
345:Near Field Communication
239:may be used for ranging.
200:and is formulated with
121:(NFER) refers to any
511:. pp. 288–291.
172:Technical Discussion
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486:978-0-8493-3349-1
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131:radio waves
559:2019-10-06
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374:References
339:Near-field
231:First, no
223:Advantages
166:resolution
151:wavelength
127:near-field
66:newspapers
294:microwave
290:multipath
273:(TOF) or
237:bandwidth
217:far-field
96:July 2007
636:Category
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333:See also
323:diffract
251:baseband
194:antennas
190:magnetic
186:electric
141:Overview
137:(RTLS).
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392:EETimes
213:degrees
202:Maxwell
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178:phase
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