Frame set for shifted sinc-function

Abstract

We prove that frame set $\mathcal{F}_g$ for imaginary shift of sinc-function $$g(t)=\frac{\sin\pi b(t-iw)}{t-iw}, \quad b,w\in\mathbb{R}\setminus\{0\}$$ can be described as $\mathcal{F}_g=\{(\alpha,\beta): \alpha\beta\leq 1, \beta\leq|b|\}.$ \\ In addition, we prove that $\mathcal{F}_g=\{(\alpha,\beta): \alpha\beta\leq 1 \}$ for window functions $g$ of the form $\frac{1}{t-iw}(1-\sum\limits_{k=1}^{\infty}a_ke^{2\pi i b_k t})$, such that $\sum_{k\geq 1}|a_k|e^{2\pi|w|b_k}<1$, $wb_k<0$.