The Sinc Function
The sinc function, or cardinal sine function, is the famous ``sine x over x'' curve, and is illustrated in Fig.D.2. For bandlimited interpolation of discrete-time signals, the ideal interpolation kernel is proportional to the sinc function
sinc
where ![$\displaystyle (f_st) \isdef \frac{\sin(\pi f_st)}{\pi f_st}.
$](http://www.dsprelated.com/josimages_new/mdft/img1769.png)
![$ f_s$](http://www.dsprelated.com/josimages_new/mdft/img607.png)
![$ t$](http://www.dsprelated.com/josimages_new/mdft/img366.png)
![$ f_s$](http://www.dsprelated.com/josimages_new/mdft/img607.png)
![$ (f_st)$](http://www.dsprelated.com/josimages_new/mdft/img1770.png)
![$ f_s$](http://www.dsprelated.com/josimages_new/mdft/img607.png)
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