A Weil Sum Approach to Permutation Polynomials over Quadratic Extensions of Finite Fields

In this article, we introduce several classes of permutation polynomials over ${\mathbb{F}}_{q^2}$. More precisely, we characterize permutation polynomials of the forms $x^q+b{x}^2+cx+d$ and $x^{q+1}+b{x}^q+cx+d$ over ${\mathbb{F}}_{q^2}$. To this end, we determine the exact number of zeros of these polynomials using existing results on certain special Weil sums. We also present the compositional inverses of the permutation polynomials obtained in this paper.