Smooth Kernel Estimation of a Circular Density Function: A Connection to   Orthogonal Polynomials on the Unit Circle
  In this note we provide a simple approximation theory motivation for the circular kernel density estimation and further explore the usefulness of the wrapped Cauchy kernel in this context. It is seen that the wrapped Cauchy kernel appears as a natural candidate in connection to orthogonal series density estimation on a unit circle. This adds further weight to the considerable role of the wrapped Cauchy in circular statistics. 
Yogendra P. Chaubey
math.ST stat.TH