Interpolating Spherical Harmonics for Computing Antenna Patterns

摘要

This report reviews spherical harmonic expansions to compute wideband antenna patterns. Some 'antenna' patterns, such as the far-field of a ship, require lots of computer time per each frequency. Consequently, computing such a pattern across a wide frequency band at each frequency is prohibitive. Spherical harmonics offer an alternative-compute the pattern over a coarse sampling across the frequency band, interpolate the spherical harmonics, and use these harmonics to recover the pattern at a fine frequency sampling with small CPU. This report develops an adaptive spline interpolation algorithm with error control. The development used antennas with smooth analytic patterns for verification. Further developments must test this algorithm on a suite of tactical antenna patterns.