Efficient Design Procedures for Wideband, Low-profile Antennas Using Altair FEKO Electromagnetic Simulation Technology

The Antenna Research Group (ARG) at the University of Colorado-Boulder is a leading research center housed in the Department of Electrical, Computer, and Energy Engineering. ARG is committed to research directed toward antenna theory and design with emphasis on applications of electrically small antennas, simultaneous transmit and receive techniques, and wideband microwave and millimeter wave antennas for electronic attack, electronic support and communications. Under the direction of Dr. Dejan Filipovic, the ARG team has designed and delivered many wideband and narrowband antenna systems operating as low as 2 MHz and as high as 220 THz. The ARG at the University of Colorado Boulder has a 15-year history of dedication to antenna research and design. The research group has 8 post-doctoral research associates, 14 doctoral students, 2 undergraduate research students, and 2 research administrators. To date, the group has published over 225 peer reviewed journal publications, conference papers, short courses, and tutorials.

The Antenna Research Group (ARG) at the University of Colorado-Boulder was tasked with evaluating the bottom side of a vehicle as an alternative to more conventional antenna placement positions for mounting high-frequency VHF antenna systems. The challenge was to develop a procedure for evaluating the feasibility of bottom placement of HF-VHF antennas on military vehicles. Low profile concealed antennas are often desired for diverse applications across many military and commercial vehicle platforms. However, these tall antennas increase vehicles’ vertical clearance and constitute an easy to identify visual signature, which is undesirable. A vehicle underside can be considered as a viable alternative place for concealment, since it provides enough space to avoid extreme antenna miniaturization. The challenge was to assess and compare propagation losses for antennas at various vehicle positions.

The solution was to apply FEKO electromagnetic field simulation methods to assess bottom placement antenna performance. The numerical study was conducted with the vehicle model. An all metallic structure was assumed to be a perfect electric conductor, whereas antenna sources were approximated as Hertzian electric dipoles placed 0.05 m away from the vehicle surface for top and bottom positions. FEKO accounts for the ground loss by means of Sommerfeld integrals implemented in the code. Three types of grounds including dry sand, asphalt and wet soil were considered. The ARG project team heavily relied on FEKO results to validate their analytical procedure for the propagation loss calculations and then use the developed FEKO models to accurately determine impact ranges for various antenna/platform systems. The performance of the vehicle mounted antennas at various locations was evaluated in terms of omnidirectionality, efficiency, and propagation loss.

• The application of FEKO electromagnetic field simulation methods provided a comprehensive solution to the challenge of assessing bottom placement antenna performance. The numerical study conducted with the vehicle model allowed for accurate approximation of antenna sources and accounted for ground loss. The ARG project team was able to heavily rely on FEKO results to validate their analytical procedure for the propagation loss calculations and then use the developed FEKO models to accurately determine impact ranges for various antenna/platform systems. The performance of the vehicle mounted antennas at various locations was evaluated in terms of omnidirectionality, efficiency, and propagation loss. This study showed that propagation loss upper bound for bottom, top, and rear antenna source placements are comparable at most frequencies below 100 MHz and at distances less than 10 m. Thus, bottom-side located antennas can be considered as an alternative to conventionally used positions.

• FEKO-based computational studies can be applied to accurately and efficiently assess antenna system mounting location in terms of omni-directionality, efficiency, and propagation loss.
• FEKO electromagnetic modeling capability accounts for all of these needed effects.
• FEKO accounts for the ground loss by means of Sommerfeld integrals implemented in the code.