Multirate Digital Signal Processing, Oversampling of Analog-to-Digital Conversion, and Undersampling of Bandpass Signals - Digital Signal Processing: Fundamentals and Applications - page 564

w () y ()

x ()

Interpolation
filter H(z)

L

f f
sL

f s

Lf s

s

X ()

f s f s /2 f s /2 f s

0

W ()

f s /2 f s /2 f f

sL

Lf s f s f s

0

s

H ()

1

f s /2 f s /2

f sL f s 0 f s f sL

Y ()

f sL f sL /2 f s /2 f sL /2 f sL

0 f s /2

FIGURE 12.5B

Spectra before and after upsampling

The bottom plot in Figure 12.6 shows the spectrum for yðmÞ after applying the interpolation filter,
where only the original signals with frequencies of 1 kHz and 2.5 kHz are presented. Program 12.2
shows the implementation details in MATLAB.
Program 12.2. MATLAB program for interpolation.

close all; clear all
% Upsampling filter (see Chapter 7 for FIR filter design)
B ¼ [-0.00012783931504 0.00069976044649 0.00123831516738 0.00100277549136 .
-0.00025059018468 -0.00203448515158 -0.00300830295487 -0.00174101657599 .
0.00188598835011 0.00578414933758 0.00649330625041 0.00177982369523 .