Up-sampling in MATLAB

Interpolation or up-sampling is the specific inverse of decimation. It is a data saving operation, in that all examples of x[n] are available in the extended signal y[n]. Interpolation works by adding (L–1) zero-valued examples for each input sample. 

We will be using the interp() function to interpolate a signal. It is used to increase the sample rate of a signal by an integer factor.

Syntax: a = interp(x, r) 
Parameter: 

• x: input signal
• r: interpolation factor

Return Value: Returns interpolated signal 

MATLAB code for interpolation of a signal:

MATLAB

% time vector
t = 0 : .00025 : 1;

# input signal
x = sin(2 * pi * 50 * t) + sin(2 * pi * 100 * t);

% increase the sample rate of i/p signal by factor of 4
y = interp(x, 4);

subplot(2, 2, 1);

% plot few samples of the Original signal
stem(x(1 : 75))
title('Original Signal');

subplot(2, 2, 2);

% plots few samples of the up-sampled signal
stem(y(1 : 75));
title('Interpolated Signal');

Output: