DSP Lab Manual2

7/31/2019 DSP Lab Manual2

1/21

L a b m a n u a l o n

D i g i t a l S i g n a l P r o c e s s i n g

Submitted to:

E n g r . M . A b b a s A b b a s i

Su b m i t t e d b y :

0 8 E L - 6 0

Sh a f q a t H u s s a in Sa b a a q

Se m e s t e r :

6 t h , 2 0 0 8 - 2 0 1 2

University College Of Engineering And Technology

Islamia University Of Bahawalpur, Pakistan.
http://www.tracker-software.com/buy-nowhttp://www.tracker-software.com/buy-nowhttp://www.tracker-software.com/buy-now


2/21

2

08EL-60 Shafqat Hussain Sabaaq Digital Signal Processing

S.No Lab Experiments Page No

1To become familiar with the different types of discrete signaland plot them in the matlab. 3

2 Generating Tunes with Music Notes in MATLAB 11

3Working with Audio Signals in MATLAB

13

4 Introduction to SimPowerSystem 16

5To See the Frequency Response of a Signal in MATLAB

18

6To Implement a Discrete System in Simulink.

20


3/21

3


Lab No 1

Objective:

To become familiar with the different types of discrete signal and plot them in the matlab.

Apparatus:

MATLAB software.Theoretical background:

Discrete signals are those signals which have discrete values at particular

interval of time. We study some of the basic discrete time signals.

(1) Unit sample signal:The unit step signal can be expressed as

x(n) = (n)

And(n) = 1 for n = 0

(n) = 0 for all n 0

-3 -2 -1 0 1 2 30

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

(n)

(xn

)

(FIG: UNIT IMPULSE SIGNAL)


4/21

4


(2) Unit step signal:The unit step signal can be expressed as

x(n) = u(n)

And u(n) = 1 for n 0

u(n) =0 for n < 0

(3) Ramp signal:Ramp signal can be expressed as

r(n) = n for n 0

r(n) = 0 for n < 0

-10 -8 -6 -4 -2 0 2 4 6 8 100

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

(n)

(xn

)

(FIG: UNIT STEP SIGNAL)


5/21

5


(4) Sinusoidal signal:The sinusoidal signal can be expressed as

x(n) = A cos (2fn)

-10 -8 -6 -4 -2 0 2 4 6 8 100

1

2

3

4

5

6

7

8

9

10

(n)

(xn

)

(FIG: RAMP SIGNAL)

-10 -8 -6 -4 -2 0 2 4 6 8 10-10

-8

-6

-4

-2

0

2

4

6

8

10

(n)

(xn

)

(FIG: SINUSOIDAL SIGNAL)


6/21

6


(5)Exponential signal:The exponential signal can be expressed as

x(n) = A ean

(6) Complex exponential signal:The complex exponential signal can be expressed as

x(n) = A ej2fn

-10 -8 -6 -4 -2 0 2 4 6 8 100

10

20

30

40

50

60

70

80

(n)

(xn)

(FIG: EXPONENTIAL SIGNAL)

-10 -8 -6 -4 -2 0 2 4 6 8 10-10

-5

0

5

10

(n)

xr

FIG: COMPLEX EXPONENTIAL SIGNAL(REAL PART)

-10 -8 -6 -4 -2 0 2 4 6 8 10-10

-5

0

5

10

(n)

(xi)

FIG: COMPLEX EXPONENTIAL SIGNAL(IMAGINARY PART)


7/21

7


(7) Square wave signal:This signal obtained on the graph which shows that it has the wave like a square

It can be expressed as

x(n) = square (2fn)

(8) Sawtooth wave signal:On the graph its behavior like a sawtooth. It is very common type of wave signal.

It can be expressed as

x(n) = sawtooth (2fn)

-10 -8 -6 -4 -2 0 2 4 6 8 10

-8

-6

-4

-2

0

2

4

6

8

(n)

(xn

)

(FIG: SQUARE WAVE SIGNAL)


8/21

8


(9) Sinc signal:It is the signal which can be expressed mathematically as

x(n) = sinc (2fn)

-20 -15 -10 -5 0 5 10 15 20-20

-15

-10

-5

0

5

10

15

20

(n)

(xn

)

(FIG: SAWTOOTH WAVE SIGNAL)

-10 -8 -6 -4 -2 0 2 4 6 8 10-2

-1

0

1

2

3

4

5

6

7

8

(n)

(xn

)

(FIG: SINC WAVE SIGNAL)


9/21

9


Cell structure matlab code for all signals listed above:

%%

%(1)unit impulse signal

n=-3:3;

x_n=[0 0 0 1 0 0 0];

stem(n,x_n);xlabel('(n)');ylabel('(x_n)');grid ontitle('(FIG: UNIT IMPULSE SIGNAL)');

%%

%(2)unit step signal

n=-10:10;

x_n=zeros(1,length(n));

x_n(find(n>=0))=1;

stem(n,x_n);xlabel('(n)');ylabel('(x_n)');

title('(FIG: UNIT STEP SIGNAL)');grid on

%%

%(3)ramp signal

n=-10:10;

x_n=n; x_n(find(n


10/21

10


%%

%(7) square wave signal

n=-10:10;

A=8; f=0.1;

x_n=A*square(2*pi*f*n);


title('(FIG: SQUARE WAVE SIGNAL)');grid on%%

%(8) sawtooth wave signal

n=-20:20;

A=20; f=0.1;

x_n=A*sawtooth(2*pi*f*n);


title('(FIG: SAWTOOTH WAVE SIGNAL)');grid on

%%

%(9) sinc wave signal

n=-10:10;

A=8; f=0.1;

x_n=A*sinc(2*pi*f*n);


title('(FIG: SINC WAVE SIGNAL)');grid on


11/21

11


Lab No 2

Objective:

Generating Tunes with Music Notes in MATLAB

Apparatus:


Introduction:The music tunes are composed of several sinusoidal and exponential signals. Each music

note is defined as a function of time. So by the combination of different music notes, a tune can be

generated. This lab session is to generate the music tune and to work with several discrete signals by

getting familiarity with several parameters.

Upsampling and Downsampling:The process of increasing the sampling frequency of the sampler is called upsampling while the process

of decreasing the sampling frequency is called downsampling.

Downsampling is done in MATLAB by the following code:

tdown=downsample(t,N)

here t is the sampling time that is reciprocal of sampling frequency and N is the number by which the

downsampling is required. This command reduces the sampling frequency by a factor of N. tdown is the

new sampling time.

Similarly the command for upsampling is:

tup=upsampling(t,N)

Matlab code for sampling:

%sampling

A=5;

F=300;

F_s=8000;

T_s=1/F_s;

t=0:T_s:0.01;

x_t=A*sin(2*pi*F.*t);

tup=upsample(t,4);

x_tup=upsample(x_t,4);

stem(tup,x_tup)


12/21

12


Output results:

F ig : S a m p l i n g

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01-5

-4

-3

-2

-1

0

1

2

3

4

5


13/21

13


Lab No 3

Objective:

Working with Audio Signals in MATLAB

Apparatus:


Section AThere are four ways to transmit or receive data.

1) Text Keypad2) Audio Microphone3) Image Camera4) Video Web Cam/VID Cam

Sound command is used to listen a defined function in MATLAB. This function will be played at the

frequency of 8 kHz, which is the default frequency of sound card. In addition, the transmission system is

also transmitting signals on this frequency.

The Maximum frequency that can be achieved from sound card is 48 kHz. To hear the maximum sound

of sound card, the command soundsc is used.

Lab Work:

Consider the following program

t=0:0.01:1;y1=5*sin(40*pi.*t);

y2=10*square(40*pi.*t);

y3=15*sawtooth(40*pi.*t);

Q1. Listen the following signals at specified frequency

i) y1ii) y2iii) y3iv) y1+y2+y3v) y1y2y3vi) y1y2+y3vii) y1-y2-y3viii) y1-y2y3

sound(signal name) command is used to listen these signals.


14/21

14


Q2. Listen y2 at 8 kHz, 4 kHz, 2 kHz and 5 Hz

sound(y2, 8000) is used to listen y2 at 8 kHz. Similarly by changing the frequency, y2 can be heard at any

frequency.

Q3. Listen y3 at 9 kHz

sound(y3, 9000) is used here.

All signals given in above questions have been successfully listened during the lab session.

Matlab code:

t=0:0.01:1;

y1=5*sin(40*pi.*t);

y2=10*square(40*pi.*t);

y3=15*sawtooth(40*pi.*t);

play(y1,8000)

play(y2,8000)

play(y2,4000)

play(y2,3000)play(y2,2000)

play(y3,9000)

play(y1+y2+y3)

play(y1y2y3)

play(y1y2+y3)

play(y1+y2y3)

play(y1-y2-y3)

Section B

Recording:

Recording in MATLAB can be static or dynamic.

The difference in two types is that the static recording cant be plotted and also it is difficult to save it in

memory. To view the recording graphically and to save it, we have to convert the recording into Dynamic

Type.

How to record a static file?

Static recording can be accomplished using audiorecorder and record command. In order to record a

signal y for 10 seconds, following MATLAB code is written:

y=audiorecorder;

record(y,10)

To play this signal, use play command as shown below:play(y)

To pause the playing signal, use pause command as shown below:

pause(y)

To stop the signal, use stop command as shown below:

stop(y)

How to covert Static Recording into Dynamic Recording?


15/21

15


Static recording can be converted into dynamic recording by using the getaudiodata command as shown

below:

x= getaudiodata(y);

Now it is a dynamic file and cant be played with a play command. To listen this, use wavplay

command as shown below:

wavplay(x)How to save a wav file?

wav file x can be saved by using the command wavwrite as shown below:

wavwrite(x, desired frequency, Name of the file)

This file will be saved in work folder of MATLAB.

How to play a wav file from local disk?

If a wav file is located in the local disk of computer, then it can be listened in MATLAB using the

command wavread. Suppose a wav file format of 3idiots ringtone is located in tones folder in local disk

D, then following code will be used to play this file in MATLAB:

wavread(d:\tones\3idiots.wav)

Matlab code for recording:y=audiorecorder;

record(y)

play(y,70)

pause(y)

stop(y)

yd=getaudiodata(y);

wavplay(yd)

wavplay(yd,8000)

wavwrite(yd,8000,'Sabaaq.wav')


16/21

16


Lab No 4

Objective:

Introduction to SimPowerSystem

Apparatus:


Introduction:

SimPowerSystem is a library in simulink and is the core tool for Power Engineers for

implementing and simulating the Power Devices and Projects. This library covers almost all of the

practical modeling in simulation. This lab session is to learn techniques of simulink modeling of physical

and power devices.

Lab Work:

Implement the following model in simpower and observe the output

Fig: Simpower model

powergui

Continuous

Voltage Measurement

v+-

Universal Bridge

A

B

C

+

-Scope

Sada source

N

A

B

C


17/21

17


Output Results:

Fig: Output Results for simpower model


18/21

18


Lab No 5

Objective:

To See the Frequency Response of a Signal in MATLAB

Apparatus:


Introduction:Discrete-Time Fourier Transform (DTFT) is used to see the behavior of a signal with

respect to Frequency that is often called as Frequency Response of a Signal.

Discrete-Time Fourier Transform is denoted as X(j).

Mathematically it is written as

() = ()

Lab Work:

() = () Then

|()|^2 = 1/ (1 2 + ^2 )

Sketch X(j) for

i) a=1/4ii) a=-1/4iii) a=1/2iv) a=-1/2

a1=1/4;

a2=-1/4;

a3=1/2;

a4=-1/2;

w=-pi:0.001:pi;

E1=1./(1-2*a1*cos(w)+a1^2);

E2=1./(1-2*a2*cos(w)+a2^2);

E3=1./(1-2*a3*cos(w)+a3^2);


19/21

19


E4=1./(1-2*a4*cos(w)+a4^2);

plot(w,E1,w,E2,w,E3,w,E4);

grid on

legend('a=1/4','a=-1/4','a=1/2','a=-1/2')

Output Results:

Fig: Frequency Response of a signal

-4 -3 -2 -1 0 1 2 3 40

0.5

1

1.5

2

2.5

3

3.5

4

a=1/4

a=-1/4

a=1/2

a=-1/2


20/21

20


Lab No 6

Objective:

To Implement a Discrete System in Simulink.

Apparatus:


Introduction:This lab session is to implement a discrete system in Simulink and to be familiar with

different simulink tools.

The general equation of a system is given by

() = ( 1) + () Lab Work:Let = 1 / = /And let

= 10 = 1 = 0.5Now we will implement this model in simulink as shown below

Fig: Model A

Unit Delay

z

1

Sine Wave

Scope

Gain 1

a

Gain

b

First-Order

Hold 1

First-Order

Hold


21/21

21


Output Results:

Fig: Results for model A

Date post:	04-Apr-2018
Category:	Documents
Upload:	xp2009
View:	279 times
Download:	0 times

DSP Lab Manual2

Documents