Joint Communication/MTT/APS Society Meeting


Speaker:

Hans Schantz, Ph.D., Time Domain Corporation

Subject:

"Ultra-wideband Antenna Efficiency"

Date:

Wednesday, September 26, 2001

Time:

11:30 am to 1:00 pm

Place:

Redstone Officers’ & Civilians' Club

Reservations:

Please contact Sonya Hutchinson at 544-3312, if you plan to attend. You may also email her at: Sonya.Hutchinson@msfc.nasa.gov.

Abstract: The usual narrowband or resonant techniques for measuring antenna efficiency are ill-suited for use with ultra-wideband (UWB) or a-resonant antennas. This talk will survey traditional approaches to measure antenna efficiency and develop an extension of the "Wheeler Cap" technique that can be applied to UWB antennas. Experimental results from Time Domain's BroadSpecâ UWB antennas will be presented. These antennas are electrically small at the low frequency end of operation, yet >90% efficient across as much as two octaves of bandwidth. The second half of the talk looks at theoretical constraints on UWB antenna size and efficiency. The conventional prediction (the "Chu-Harrington Limit") is shown to break down for small Q, large bandwidth antennas. An alternate approach to ideal antenna efficiency is presented, one that explicitly considers the ratio of radiative to total (radiative plus reactive) energy emitted by an ideal dipole antenna. This approach leads to the conclusion that it is possible to construct a dipole antenna of characteristic size 0.096 l at the lower end of the operating band. This is smaller than would be allowed by the Chu-Harrington limit for Q < ~5.

Biographical Sketch: Hans Schantz was born in Detroit, Michigan in 1966. He received his BSIE in industrial engineering from Purdue University in 1988, a BS in the honors curriculum in physics from Purdue in 1990, and his PhD from the University of Texas at Austin in 1995. He also undertook additional graduate course work from the Ohio State University. His work experience includes stints with IBM, the Lawrence Livermore National Laboratory, and ITT Technical Institute in Austin, Texas. Since 1999 he has been employed as an antenna engineer with Time Domain Corporation in Huntsville, Alabama (http://time-domain.com) where his responsibilities include designing ultra-wideband antennas for a variety of radar, positioning, and communications systems.

NOTES:

  1. We will eat from 11:00 - 11:45am and the talk will begin at 11:45am. All lunch will be Dutch treat. The price for lunch is about $5.95 (cost subject to food selection), and there is a $2 meeting room fee for all participants.

  2. The Redstone Officer's Club is located off of Goss Road on the Redstone Arsenal. Turn left before entering Gate 9 (Rideout Road entrance). Go about 1 mile on Goss road and you will see the sign. Turn left and continue about ¼ mile and you will see the building on your right.

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