Let $S \subset \mathbb R$ be a separated subset of the real line (meaning that $\inf_{x \neq y \in S} |x-y| > 0$) such as a uniform grid, $S = \alpha \mathbb Z$. Let $K$ be a square integrable function and $A$ the operator which maps $f \in L^2(\mathbb R)$ to the sequence $$ Af = (K*f(x))_{s \in S} $$ I.e. $A$ maps $f$ to the samples of the convolution of $f$ with $K$.

Problem:

Restrict $A$ to the space of compactly supported $L^2$-functions, say $L^2[0,1]$. For which $K$ can we choose a separated sampling set $S$ such that the resulting operator $A$ is injective? In formulas: $$ \forall f,g \in L^2[0,1] : (K*f(x)=K*g(x) \ \forall x \in S \implies f=g). $$

There are obvious candidates of $K$ where this is not true, e.g. compactly supported $K$.

I was wondering if anyone of you came accross such problems or knows if there's a characterization of such functions $K$. The papers I found so far mainly deal with situation where the domain of $A$ equals to $L^2(\mathbb R)$. Here, I'm intersted in functions with compact support.