The spherical Dirichlet or Christoffel-Darboux kernel has the unique property of being a convergent finite series in Fourier coefficients with an integral of one. This kernel is recommended for calculating physical properties as the Fourier coefficients always have a value of one for a given bandwidth.
It is defined by its Legendre series
\[ \psi_N(t) = \sum\limits_{n=0}^N (2n+1) \, \mathcal P_{n}(t)\].
Syntax
psi = S2DirichletKernel(N)Input
| N | polynomial degree / bandwidth |