A combined Smith-Carter chart shows the impedance of ideal electric and magnetic dipole fields normalized to free-space impedance.

This week, I’ll be presenting my paper on “A simple procedure for measuring gain of very electrically small antennas” at the 2014 Loughborough Antenna and Propagation Conference.

Gain measurements of very electrically small antennas (VESAs) present special challenges. These antennas radiate with poor efficiency, and great care is needed to make a suitable gain measurement using radiative techniques. This paper presents a novel gain measurement technique based upon the observation that the gain of well-matched VESAs is proportional to electrical volume and antenna quality factor (Q) for antennas of similar shape factor. Thus, antenna gain may be determined by a measurement of antenna quality factor and antenna size. This paper presents three distinct derivations for the antenna gain relation. Finally this paper validates the theoretical prediction using a NEC model and demonstrates that a “Brooks Coil” with a diameter three times the length yields optimal results.

I originally derived and presented the gain result in my 2013 Allerton Antenna Applications Symposium paper, “Simple formulas for near-field transmission gain and fields.” The novelty of this paper lies in using Schelkunoff’s dipole impedance formulas to understand power flow of electrically small antennas. We can define a power factor based on the impedance phase. Just as the phase difference between current and voltage defines the power factor for an AC circuit, the ratio of electric to magnetic field phase defines the power factor for energy flow in fields. The Smith chart to the right plots the dipole impedance normalized to free-space impedance. The blue arcs are lines of constant phase – an enhancement suggested by Phillip S. Carter. The larger the size of the ideal dipole, expressed here in terms of wave number and boundary sphere radius, the smaller the phase difference and the larger the power factor.

This analysis ties together lots of fascinating small antenna physics because the power factor is the inverse of the quality factor – a parameter of considerable interest in the study of electrically small antennas.

Here are my slides:

Here is a video of my presentation:

My full paper, “A simple procedure for measuring gain of very electrically small antennas,” is available through ResearchGate.

 

Today, I am presenting a seminar on some diverse topics for the folks in the Antennas and Electromagnetics Research Group at Queen Mary University, London. Here are links to some slides:

A couple of these are previews of upcoming presentations. I’ll publish videos of the talks in a couple of months, when I’m fully satisfied with the results.

Oct 022014
 

The Allerton Park and Retreat Center in Monticello, IL was the site of the 2014 Antenna Applications Symposium.

Last week, I traveled to the Allerton Park and Retreat Center to present a new paper on fundamental electromagnetic physics at the 2014 Antenna Applications Symposium. My paper, “On Energy Flow in Standing Waves,” analyzes and explains the propagation of energy in a variety of standing waves. The conventional point of view in electromagnetics holds that near fields only matter close to sources, sinks, or scatterers of electromagnetic energy. I argue that near-fields arise whenever multiple electromagnetic waves interact. Although fields pass through each other, in so doing, the individual waves exchange energy with each other. These insights have helped Q-Track create better precision location systems, and may be helpful in making antennas work better in multipath environments. The standing wave perspective also has fascinating implications. The propagation of electromagnetic energy from source to destination follows, not ideal optical rays, but rather a complicated meander or drift as particular fields perturb the energy of the collective electromagnetic superposition one way or another. Also, it appears that although electromagnetic signals and fields propagate at the speed of light, electromagnetic energy only rarely propagates so quickly and instead ebbs and flows at a drift velocity less than the speed of light. The full text of my paper, “On Energy Flow in Standing Waves,” is available if you sign up on ResearchGate.net.

A video of my talk is also available.

 

The Heaviside Memorial Project recently completed the restoration of the memorial to Oliver Heaviside and his family in the Paignton Cemetary near Torquay, Devon.

The Heaviside Memorial Project successfully raised funds and completed the restoration of the memorial to Oliver Heaviside and his family in the Paignton Cemetary near Torquay, Devon. Details and additional photos of the unveiling ceremony are available at their web site.

The group, organized by the Newcastle Electromagnetics Interest Group and spearheaded by Christopher Spargo, is on to their next challenge. Their goal is to republish Searle’s 1950 biography of Heaviside. G.F.C. Searle (1864-1950) was a friend and professional colleague of Heaviside and shared many fascinating insights to Heaviside’s character and thinking in his posthumously published biography. The Heaviside Memorial Project is accepting donations to aid in the publication.

Update: A $50 donation now entitles you to a signed copy when available.

Jul 202014
 

Heaviside's barely legible monument tilts atop the family plot where he lies with his parents in Paignton Cemetary, Torquay, Devon, UK.

He developed the theory of transmission lines, coined such terms as inductance, impedance, and admittance, and rewrote James Clerk Maxwell’s awkwardly expressed equations into the vector form familiar to any student of electromagnetics. Today, Oliver Heaviside’s neglected tombstone is barely legible and is beginning to lean.

Chris Spargo and Professor Alex Yakolev aim to restore the monument, and they could use our help.

Founders of The Heaviside Memorial Project, the two have set up a website aiming to collect £800 in donations for the £660 repair and £140 for any unexpected costs. The restoration will relevel, clean, and repair the monument. Their campaign has already raised nearly half of the required funds. Please go to their website and donate what you can to this worthy cause.

Jul 162014
 

Yesterday, UWB pioneer Time Domain announced their acquisition by a private equity group led by Bonaventure Capital and Fidelis Capital. Time Domain did not disclose the terms of the transaction. Additional details are available in a statement from the company and in coverage from the Huntsville Times.

Jul 032014
 

I’ll be presenting my short course on UWB antennas at the IEEE Antennas and Propagation Symposium (APS) in Memphis, TN on Sunday July 6. This is the first time I’ve been back to IEEE APS since 2007, and my short course includes some interesting revisions from the second edition of my book, underway. Here’s a summary.

The wide scale commercial deployment of ultra-wideband (UWB) systems has led to increased interest in UWB antenna designs. In many cases, though, investigators have unknowingly resurrected already known designs rather than developing new ones. Also, the subtleties of UWB antenna physics and design are not always obvious to those more familiar with narrowband antennas. For instance, the spectral and impedance matching properties of a UWB antenna exert a profound influence on an overall UWB system design.

This workshop will enable attendees to:

  • Understand basic antenna physics as applied to UWB antennas
  • Quickly and correctly apply UWB antennas to current projects
  • Design and analyze UWB antennas
  • Integrate these antennas in an RF system
Jul 032014
 

Mark Brown (N4BCD) Participates in ARRL's Field Day.

One benefit of working at Q-Track is the opportunity to collaborate with talented people for whom  radio is a passion, not just a profession. This past weekend, my Q-Track colleague, Mark Brown [N4BCD], participated in the American Radio Relay League (ARRL) “Field Day.” The weekend-long exercise tests the ability of amateur radio operators to maintain communications in the event of an emergency like the tornadoes that struck Northern Alabama in 2011. Mark was featured in the footage from WHNT Channel 19.

 

 

 

 

 

 

Near-field wireless technology is an emerging area of great importance in Radio Frequency Identification (RFID). Specific applications include low frequency (LF) and high frequency (HF) RFID, Near-Field Communications (NFC), Near-Field Electromagnetic Ranging (NFER), and wireless power transfer. This talk discusses the origins of near-field wireless, surveys applications, presents near-field links laws, and reviews the properties and performance of electrically-small antennas. This March 31, 2014 presentation to the Huntsville, AL section of the IEEE previews the full three hour workshop presented April 8, 2014 at the 8th Annual IEEE International Conference on RFID held in conjunction with 2014 RFID Journal Live.

 A couple of misstatements I caught in reviewing this: first, Preece transmitted near field wireless signals across the Bristol Channel not the “British” Channel; and second, “unlike” links go as 40dB/decade, not 20dB/decade in the near-field. Prezi slides are available here: http://bit.ly/1x0FY7W if you’d like to take a closer look. In some of the views, you can’t see all the details.

 

 

James Clerk Maxwell (1831-1879) formalized a set of equations that describe the behavior and interaction of electricity and magnetism.

From Scientific Papers of James Clerk Maxwell, vol 2, LIV, p.311 (Proceedings of the Royal Institution of Great Britain, vol. VII, 1876). Emphasis added inn bold.

I HAVE no new discovery to bring before you this evening. I must ask you to go over very old ground, and to turn your attention to a question which has been raised again and again ever since men began to think. The question is that of the transmission of force. We see that two bodies at a distance from each other exert a mutual influence on each others’ motion. Does this mutual action depend on the existence of some third thing, some medium of communication, occupying the space between the bodies, or do the bodies act on each other immediately, without the intervention of anything else?The mode in which Faraday was accustomed to look at phenomena of this kind differs from that adopted by many other modem inquirers, and my special aim will be to enable you to place yourselves at Faraday’s point of view, and to point out the scientific value of that conception of lines of forcewhich, in his hands, became the key to the science of electricity.When we observe one body acting on another at a distance, before we assume that this action is direct and immediate, we generally inquire whether there is any material connection between the two bodies; and if we find strings, or rods, or mechanism of any kind, capable of accounting for the observed action between the bodies, we prefer to explain the action by means of these intermediate connections, rather than to admit the notion of direct action at a distance.Thus, when we ring a bell by means of a wire, the successive parts of the wire are first tightened and then moved, till at last the bell is rung at a distance by a process in which all the intermediate particles of the wire have taken part one after the other. We may ring a bell at a distance in other ways, as by forcing air into a long tube, at the other end of which is a cylinder with a piston which is made to fly out and strike the bell. We may also use a wire; but instead of pulling it, we may connect it at one end with a voltaic battery, and at the other with an electro-magnet, and thus ring the bell by electricity.

Continue reading »

© 2010-14 Hans Schantz except as noted. Suffusion theme by Sayontan Sinha

Switch to our mobile site