Near-Field Versus UWB Ranging

Siwiak, Kazimierz;
RFID Symposium, 2009 IEEE
27 April 2009

Ultra-wideband (UWB) systems have the potential to achieve high precision spatial resolution. Their performance, however, can be severely limited by multipath interference, low actual utilized bandwidth, and low SNR. But, the time-of-arrival or time-difference-of-arrival approach to real-time location systems (RTLS) are not the only answer. Spatial precision can also result from precise phase measurement of narrow band or CW signals. Furthermore, near-field electromagnetic ranging operates at frequencies too low for multipath to be relevant. This paper compares near-field electromagnetic ranging with UWB and simple RSSI technology for RTLS.

  A Fundamental Limit on Antenna Gain for Electrically Small Antennas

Compston, A.J.; Fluhler, J.D.; Schantz, H.G.;
Sarnoff Symposium, 2008 IEEE
28-30 April 2008 Page(s):1 - 5

A fundamental limit on an antenna's gain is derived and compared to measurements taken on a number of different antennas. First, a propagation formula applicable in both the near and far fields is developed, and that result is used to demonstrate that the gain of an antenna is limited by its electrical size.

Low-probability of intercept of ultra-low-power, near-field signals

Schantz, H.G.;
Antennas and Propagation International Symposium, 2007 IEEE
9-15 June 2007 Page(s):3804 - 3807

Long considered a technical backwater, low-power, near-field systems are emerging as the preferred solution for a variety of useful applications. These applications include short-range communication, radio frequency identification (RFID), and real-time locating systems (RTLS). This paper explores the ultra-low-power and thus low-probability of intercept nature of near-field signals operating within the AM broadcast band under part 15 constraints.

Schantz, H.G.;
Antennas and Propagation International Symposium, 2007 IEEE
9-15 June 2007 Page(s):3792 - 3795

Near-field electromagnetic ranging (NFER) technology is emerging as a preferred real-time locating system (RTLS) solution for operation in complicated indoor propagation environments [H. Schantz and R. DePierre, 2005]. Operating at low frequencies, typically within the AM broadcast band (530-1710kHz), NFER systems exploit the near-field behavior of radio signals within about one-third of a wavelength. This paper explores the performance of NFER systems and the propagation of NFER signals.

Near-Field Technology – An Emerging RF Discipline

Schantz, H.; Fluhler, J.
Proceedings of The European Conference on Antennas and Propagation: EuCAP 2006 (ESA SP-626).
6-10 November 2006, Nice, France. Page(s): 2.1

This paper explains and surveys the emerging RF discipline of near-field technology. First, this paper defines what is meant by the “near field.” Then, this paper presents a brief history of near-field technology from Faraday to the present day. In particular, this paper focuses on recent advances in near-field technology for applications like Near Field Communications (NFC), Radio Frequency Identification (RFID), and Real Time Location Systems (RTLS). Finally, this paper will discuss the extension of propagation laws and antenna gains to the near-field regime.

Near field phase behavior

Schantz, H.G.;
Antennas and Propagation Society International Symposium, 2005 IEEE
Volume 3B,  3-8 July 2005 Page(s):134 - 137 vol. 3B

This paper presents a theoretical analysis of near field phase behavior in free space. Then this paper validates the theoretical model by numerical modeling and comparison to experimental data. Near field phase behavior is the basis of a novel RF tracking technology, with a demonstrated accuracy of 30 cm at ranges up to 70 m.

Schantz, H.G.;
Antennas and Propagation Society International Symposium, 2005 IEEE
Volume 3A,  3-8 July 2005 Page(s):237 - 240 vol. 3A

The paper presents a theoretical analysis of the near field channel in free space. The theoretical model is then validated by comparison to data measured in an open field. The results are important for low frequency RF systems, such as those operating at short range in the AM broadcast band (525-1715 kHz). Finally, the paper establishes a novel fundamental limit for antenna gain versus size.