sinc interpolator
Perfect interpolator to recover a continuous signal \(x_r(t)\) from sampled sequence \(x[n]\) when the criterion in the shannon-nyquist theorem is fulfilled.
\begin{equation}
x_r(t) = \sum_{n=-\infty}^{\infty}x[n] sinc(\frac{\pi(t-nT)}{T})
\end{equation}
where \(sinc\) is the sinc function, \(T\) is the sampling period.
This is nonrealizable because the sinc function is infinite in the time domain, and you need an infinite number of sinc functions.
The idea of resampling refers to manipulating the sampling rate.