A comparison between the SEM method and the Slepian expansion for modeling the frequency dependency of an antenna transfer function

In order to account for this frequency dependency, various antenna models, which can be roughly grouped into two categories, have been proposed. First, the singularity expansion method (SEM) models the antenna using a pole/residue technique. Second, the Slepian expansion expands the frequency dependency into Discrete Prolate Spheroidal Sequences (DPSSs) or Prolate Spheroidal Wave Functions (PSWFs).