Many factors can impact the effectiveness of the multi-antenna configurations implemented in today’s vehicles. Examples include blocking, reflecting or re-radiating energy, and co-site interference. In actual operating conditions, the motion of the vehicle platform and environmental factors like terrain and buildings also can reduce system effectiveness. In addition, radiation hazards may pose risks to nearby personnel. As explained in an eight-page white paper from Remcom, modeling and simulation are critical to understanding these issues and developing solutions that overcome them.
Titled “Using Simulation to Optimize Safety, Performance, and Cost Savings When Integrating an Antenna Onto a Platform,” the document explains that modeling and simulation can be used to assess options and tradeoffs. A small number of planned approaches can then be selected before any physical testing occurs. Modeling and simulation also eliminate the limitations of physical tests, such as the failure of a facility to handle the full range of frequencies for the system under test. With a comprehensive modeling and simulation toolset, any number of conditions can be simulated. Physical measurements can be used simply to confirm pre-test, simulation-based assessments.
To evaluate potential configurations until a successful option is identified, for instance, high-fidelity electromagnetic (EM) solvers can be used. Using the XFdtd software and an in-house ray-tracing tool, a radiation pattern has been simulated in free space without any vehicle or other obstruction to perturb the pattern. Once the antenna was mounted on a vehicle, that radiation pattern also was simulated. In this case, the antenna exhibited similar forward radiation and gain to the original design.
At higher frequencies, an electrically large scenario may require more computer memory or longer simulation times when performing an EM simulation. Here, a two-step hybrid approach may be used. The note cites an example in which the full-wave method from XFdtd determined the radiation pattern of the array on a metal groundplane. A solution based on the Uniform Theory of Diffraction (UFD) then calculated the radiation pattern resulting from mounting the array to the underside of the electrically large Global Hawk unmanned aerial vehicle (UAV).
Because military vehicles commonly incorporate several antenna systems in close proximity, interference between these systems can cause problems with simultaneous operation. Using simulation and power measurements, the power coupling between each transmit and receive antenna can be assessed to provide an idea of how much transmitted power propagates into the neighboring system. The paper ends by examining impact of the environment on antenna performance and potential radiation hazards. Overall, it builds a strong case for the use of EM modeling solutions to predict the performance of an antenna onto a vehicle platform—especially when intended for military operations.
Remcom, Inc., 315 S. Allen St., Ste. 416, State College, PA 16801; (814) 861-1299, www.remcom.com.