from
the signal 
.
and the discrete time Fourier transform
(DTFT) of the discrete signal 
generated from 
by sampling.
This Demonstration also illustrates the use of different algorithms to reconstruct the signal from
the signal .
The time domain signal 
is made of two harmonics. You can vary the amplitude and the
frequency of each harmonic as well as the sampling frequency, the duration of 
, and
the delay time. The spectrum of 
and of 
are also displayed (the magnitude and
the phase spectra). A number of plotting options are available to help analyze the results
generated.
The following important relation between the CTFT and the DTFT is observed: The CTFT is an
aperiodic and continuous function. The DTFT is also a continuous function, but it is a periodic function
with a period of 
. The maximum frequency present in the DTFT is 
in radians (or 
in cycles).
In addition, there is a scaling effect: the magnitude spectrum of 
is 
of the magnitude spectrum
of 
, where 
is the sampling period. The units of the DTFT are radians, while the units of the
CTFT are in radians per second.