Application of the Savant/WIPL-D Hybrid Solver to Analyze the Installed Performance of a Monopulse Antenna Array Mounted on a Widebody Aircraft

Amplitude comparison monopulse antenna arrays produce a sum pattern and a difference pattern, which allow for highly accurate angular measurements to be performed with tracking radars. When a monopulse antenna array is mounted on a platform such as an aircraft, the radiation pattern of the antenna array can change relative to the free space pattern. In particular, the angle and depth of the null of the difference pattern can be significantly different from the free space pattern. It is critical for system designers to understand the changes in the null of the difference pattern as the array is steered (electronically or mechanically). Often, the installed patterns are simulated with computational electromagnetic (CEM) software tools given the cost of measurements and the insight provided by simulation tools. The simulation of monopulse antenna arrays as installed on electrically large platforms can greatly benefit from a hybrid CEM approach. A hybrid approach that combines method of moments (WIPL-D) and shooting and bouncing rays (Savant) is used to predict difference pattern null characteristics for a linear array of Yagi-Uda elements mounted on an Airbus A320 aircraft. Hybrid solutions are compared with WIPL-D solutions and excellent agreement is achieved. A graphics processing unit (GPU) acceleration feature for the hybrid approach is used to rapidly generate installed null characteristics for many orientations of the linear array as mounted on the A320 aircraft. This null error information can then be used to either directly generate calibration tables for downstream signal processing or to identify particularly problematic array orientations for which pure full-wave solutions or measurements are required.