Impact Of Creeping Waves On Antenna Performance

Savant includes creeping-wave physics, a powerful feature that works with and augments Savant’s baseline shooting-and bouncing rays (SBR) solution to improve accuracy for antennas mounted directly on curved structures. In this example, the radiation pattern of a wire monopole mounted atop the fuselage of an Airbus A320 is predicted using Savant and compared with a full-wave method-of moments (MoM) solution. This is representative of many different scenarios where an antenna is mounted on a large, metallic, curved surface. Being able to quickly predict the installed radiation performance is of great importance in the design and platform integration of such antennas.

The A320 aircraft is modeled by a collection of curved surfaces specified in IGES format, one of the many CAD formats supported by Savant. The mounted monopole is of height 7.5 cm, operating at 400 MHz. It is placed on top of the fuselage. The monopole currents are represented by several current sources. The current source positions and weights are extracted from a full-wave solution of the monopole radiating above an infinite ground plane.

SBR (geometric optics) rays are not sufficient to represent the radiation physics in this example since significant energy is expected to propagate down-ward along the surface of the fuselage and into the shadow region. Savant’s creeping-wave formulation provides a rigorous framework to account for this. It can be switched on by user choice to augment the baseline SBR solution. To deploy the creeping wave, Savant traces creeping rays in all directions along surface geodesics.