(1) Complete Title of One or More Papers: Genetic Hybrid Antenna Fills the Gap (2) The Authors: LtCol Terry O'Donnell, USAFR AFRL/VSB 29 Randolph Road Hanscom AFB, MA 01731 teresa.odonnell2@hanscom.af.mil terry@arcon.com 781-377-1720 Major Jim Hunter AFRL/VSBX 29 Randolph Road Hanscom AFB, MA 01731 james.hunter@hanscom.af.mil 781-266-9283 1Lt Richard Barton AFRL/VSBXI 29 Randolph Road Hanscom AFB, MA 01731 richard.barton@hanscom.af.mil 781-377-7367 Dr. Terence Bullett AFRL/VSBXI 29 Randolph Road Hanscom AFB, MA 01731 terence.bullett@hanscom.af.mil 781-377-3035 Dr. Steven Best AFRL/SNHA 80 Scott Drive Hanscom AFB, MA 01731 steven.best@hanscom.af.mil 781-377-3780 (3) Name of Corresponding Author: (prior to 24 June 05, after 02 July 05): Teresa H. O'Donnell (24 Jun -02 Jul 05): Major James Hunter (4) Abstract: The genetic DISS hybrid transmit antenna is a genetically-engineered hybrid transmit antenna designed and developed by Air Force Research Laboratory at Hanscom AFB to improve the measurement capability of the Digital Ionospheric Sounding System (DISS). The DISS network consists of 18 fully automated digital ionosondes deployed around the world to measure the ionosphere. The ionospheric measurements are used to predict many factors important to the military, including GPS error, SATCOM outages, and environmental conditions for spacecraft. The original DISS transmit antenna, a TCI-613F off-the-shelf communications antenna, exhibited "holes" in vertical gain coverage across the wide-bandwidth (2-30MHz) required for ionospheric measurements. At some frequencies, it was impossible to get good measurements of the ionosphere. In March 2003, attempts were made to augment the antenna with a human-engineered hybrid solution, consisting of the addition of a log-periodic array to the original TCI-613F antenna. While this design looked like a good fix on paper and via simulation, it was not mechanically sound. During construction, it broke apart, resulting in a near-injury at the site. Measurements using this configuration were not obtained. In 2003-2004, work began on a joint project between the AFRL Space Weather Center of Excellence and the AFRL Antenna Technology Branch to apply genetic antenna design and optimization techniques to the DISS transmit antenna problem. The team initially trying to duplicate the performance of the unstable TCI-613F + log-periodic antenna configuration which had mechanically failed in 2003 with a genetically-optimized bent-dipole configuration. However, during optimization, the genetic DISS hybrid team realized that the genetically-proposed solutions were capable of obtaining greater gain across the bandwidth than had been possible with the human-engineered solution. The optimization cost functions were therefore modified to achieve higher gain and the resulting genetically-design hybrid antenna out-performed in simulation the human-designed solution. Even more important, the genetic design was simple to build and robust to the harsh DISS operating environments. The genetic hybrid took only 10 hours and $500 worth of material to build and instantly started exhibiting gain up to 10x better than its predecessor across the bandwidth. The critical frequency measurement error was reduced from 16% to only 1.6%, which was now within the 5% acceptable operational error margin. The genetic DISS hybrid antenna has been operational on Ascension Island throughout 2004, demonstrating both its electromagnetic utility above its predecessor and robustness to the operational environment. (5) A,D,E,G (6) Statement Identifying why Result Satisfies Eligibility Criteria (A) A patent application has been created by the authors for this hybrid antenna configuration and will be submitted by the USAF patent attorney after final schematics are complete. (D) The result is publishable in its own right as a new scientific result. Initial publication of two potential genetic DISS hybrid designs and simulated results was accepted and presented at the IEEE Antennas and Propagations International Symposium, June 2004, Monterey, CA. After the antenna was physically built and tested, more detailed results were presented at the September 2004 AFRL STARs (Sensor Technology and Algorithms Research Workshop) in Dayton, OH; however those results have not been cleared for public release. The recent December 2004 AFRL Technology Horizons article shows the implemented antenna configuration and those results which have been cleared for public release. (E&G) The result is significantly better than both the originally fielded DISS transmit antenna solution and also better than the human-created solution to replace the fielded solution that was proposed and partially-built in 2003, prior to mechanical failure. It is interesting to note that the initial attempts at a genetic solution were solely to duplicate the performance of the human-engineered solution, but with a design that was mechanically more-stable (i.e. bent dipoles anchored via insulator to ground, rather than a large horizontal log-periodic array). However, during optimizations it became clear that the emerging genetic solutions could perform even better than the human-engineered solution, not only mechanically, but even more importantly, electromagnetically! (7) Title of at least one paper R. Barton, T. O'Donnell, T. Bullett, J. Hunter, and S. Best, "Genetic Hybrid Antenna Fills the Gap", AFRL Technology Horizons, Associated Business Publications Co., Vol 5, No 6, December 2004, pg 16-18.