Let $n \in \mathbb{N}$ and let $h > 0$. Let $\mathcal{S}(\mathbb{R}^n)$ denote the Schwartz space on $\mathbb{R}^n$, and write $\hat{u}$ for the Fourier transform of $u \in \mathcal{S}(\mathbb{R}^n)$. For $t \in \mathbb{R}$, define the Fourier multiplier