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 Electrically Small Antenna Design For Low Frequency Systems
Richards, Eric A.; Schantz, Hans Gregory; Unden, John A.; von Laven, Kurt; Compston, Drew; Weil, Christian
34th Annual Antenna Applications Symposium (submitted)
21-23 Sept., 2010 We report on our design of a compact, omnidirectional transmitter that operates in the AM broadcast band (550-1710 kHz). Careful design of the magnetic antennas provides gains of -75 dBi despite being only 0.0002λ in dimension, in good agreement with theoretical predictions and FEMM simulations. Furthermore, we have developed a compact (1 m) near-field antenna testing range that allows us to characterize magnetic antennas. This transmitter has been deployed at a variety of sites, showing a tracking accuracy of 1-3 feet over areas as large as 100,000 sq. ft. Recent work has focused on reducing the size, weight, and cost of our tag by utilizing printed circuit board (PCB) methodologies. We report on a recent breakthrough that allows us to achieve almost an order of magnitude decrease in size while retaining performance.
Characterization of Error in a NFER Real-Time Location System Schantz, Hans Gregory; Weil, Christian; Unden, John
Radio and Wireless Symposium (submitted), 2011 IEEE
16-20 Jan., 2011 We provide results and error analysis for over four hundred individual measurements of a Near-Field Electromagnetic Ranging (NFER®) Real-Time Location System (RTLS). The system operated over ranges from 1.41m to 23.4m and the bulk of the points were taken “through wall” in a non-line-of-sight configuration. We break the error down into orthogonal range and transverse components in order to assess the relative impact of range versus bearing errors in the system. We found an average range error of 34.0cm, an average transverse error of 35.5cm, and a corresponding total location error of 55.1cm. These error values are on a per receiver basis, and will tend to reduce by 1 / Sqrt(N) as measurements from N receivers are combined to yield a solution.
Origins of RF Based Location Technology Schantz, Hans Gregory
Radio and Wireless Symposium (submitted), 2011 IEEE
16-20 Jan., 2011 This paper will provide a brief survey of the origins of RF-based location technology through the beginning of the Second World War. Direction finding (DF) was invented by John Stone Stone in 1902 and improved upon by Lee de Forest, Ettore Bellini and Alessandro Tosi. Both radar and amplitude ranging date to 1904, although these concepts were in advance of the ability of RF technology to implement. DF played a critical role in the First World War, most notably in the naval Battle of Jutland. The requirement for accurate night-time direction led classicist and cryptographer Frank Adcock to invent an improved DF system. In the 1920’s, DF and related concepts came of age for civilian applications like navigation. Inventors of the period introduced a variety of other techniques were introduced including time-of-flight or transponder ranging. By the time of the Second World War, DF was a mature field and additional novel RF-based technologies were ready to be developed.
RF Based Location Technology Since World War II Schantz, Hans Gregory
Radio and Wireless Symposium (submitted), 2011 IEEE
16-20 Jan., 2011 This paper presents a brief historical overview of RF-based location technologies since the Second World War. Although direction-finding (DF) was critical to the Allied victory over German U-Boats in the north Atlantic, this paper focuses on more recent RF-based location technologies including Time-Difference of Arrival (TDOA), and ultra-wideband (UWB) technologies. More recent advances, including satellite navigation, RF fingerprinting, and near-field electromagnetic ranging technologies are also considered.
Testing a Novel Firefighter Location System Using Near-Field Electromagnetic Ranging Schantz, Hans Gregory; Meares, Michael Jason; Werner, Stephen; Unden, Alfred Hans; Della Silva, Clark; Kang, Jason
Radio and Wireless Symposium (submitted), 2011 IEEE
16-20 Jan., 2011 We provide a brief system description and real-world test results for a novel firefighter location system using a Near-Field Electromagnetic Ranging (NFER®) Real-Time Location System (RTLS). The “Firefighter Location And Rescue Equipment” or “FLARE” system employs a unique RF signature breadcrumb approach to calibrate specific paths within an emergency incident scene and route rescuers to the location of firefighters needing assistance. Despite a relatively crude GUI, the prototype FLARE system delivered results comparable to or better than the best available inertial based systems in a real-world simulated rescue..
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.
A real-time location system using near-field electromagnetic ranging 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.
Near field propagation law & a novel fundamental limit to antenna gain versus size 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.
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