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Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

EE 350

Continuous-Time Linear Systems

Recitation 3

1

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 1• Consider the following circuit that contains an ideal diode

1. Sketch the output y(t) as a function of the input f(t)2. Is the system zero-state linear or nonlinear?3. Is the system instantaneous (memoryless) or dynamic?

2

R R

f(t)

2V

y(t)

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 1 Solution

3

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 1 Solution

4

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 1 Solution

5

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2• Consider the circuit below with input f(t) and output y(t)

1. Is the system linear or nonlinear? 2. Is the system time-invariant or time-varying?3. Is the system instantaneous (memoryless) or dynamic?4. Is the system causal or noncausal?

6

Rf(t)

y(t)C

v ( )C

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

7

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

8

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

9

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

10

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

11

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

12

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3• The relationship between the input f(t) and zero-state

response y(t) of two systems are given below. Determine if each system is

1. Zero-state linear or nonlinear2. Time-invariant or time-varying3. Causal or noncausal4. Instantaneous (memoryless) or dynamic

13

| | 2(a) ( ) ( 1)

(b) ( ) ( )e

ty t e f t

y t f t d

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

14

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

15

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

16

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

17

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

18

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

19

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 4• Consider a linear time-invariant (LTI) system with input f(t)

and zero-state response y(t)

1. Can we use f1(t) = 2f(t/2) to find y1(t) in terms of y(t)?2. Sketch the zero-state response y1(t) to the input f1(t)3. Sketch the input f2(t) yielding the zero-state response y2(t)

20

f(t)

t

1

10

y(t)

t

1

1

LTISystem

f(t)y(t)

0

1f (t)

t2

20

2y (t)

t

3

11

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 4 Solution

21

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 4 Solution

22

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 4 Solution

23

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Complex Number Review• A complex number is a number that can be expressed in

the form a + j b, where a and b are real numbers and jsatisfies the equation j2 = 1

• Notation

• Complex numbers extend the concept of the one-dimensional number line to the two-dimensional complex plane by using the horizontal axis for the real part and the vertical axis for the imaginary part

24

Complex Number:

Real part of Re , Imaginary part of Im

z a jb

z z a z z b

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Rectangular and Polar Form• A complex number z can be represented either in

rectangular or polar form

25

z

Re

Im

a

b

Rectangular Form z a jb

z

Re

Im

Polar Form r z

r

2 2

1

cos( ) | |

sin( ) = z = Tan

a r r z a bbb ra

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Polar Form and Euler’s Identity

26

Rectangular Form:

cos( ) sin( )

r cos( ) sin( )

Polar Form: j

z a jb

z r jr

z j

z re

Euler's Identity: cos( ) sin( )je j

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Operations on Complex Numbers• Use rectangular form for addition and subtraction

• Use polar form for multiplication and division

• The complex conjugate of the complex number z = a + jb is defined as z* = a – jb

27

1 2

1 2

1 2

If and , then z ( ) ( ) z ( ) ( )

z a jb z c jdz a c j b dz a c j b d

1 2

1 2 1 2

11 2

2

1 1 2 2

( )1 2 1 2 1 2

( )1 1 1

2 2 2

If e and e , then z e e

e e

j j

j j j

jj

j

z r z r

z r r r r e

z r r ez r r

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 5

• Given z = a + jb = r ej show that1. z* = r e-j

2. z + z* = 2a = 2Re{z}3. z z* = 2jb = j2Im{z}4. z z* = a2 + b2 = r2

28

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 5 Solution

29

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Entering Complex Numbersin MATLAB

30

• The complex number z = 2 + j3 may be entered into MATLAB as

>> z = 2 + 3*i>> z = 2 + 3i

>> z = 2 + 3*j>> z = 2 + 3j

>> z = 2 + 3*1i

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Complex Functions in MATLAB

31

Operation Functionmagnitude (r) of z abs(z)angle (q) of z in radians angle(z)construct z from a and b complex(a,b)conjugate of z conj(z)imaginary part of z imag(z)real part of z real(z)

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 6• Use MATLAB to determine

• Explain the difference between the results in parts 3 and 4

32

1 21. The rectangular form of 1 2

2 2 32. The polar form of

1 3

3. Execute the MATLAB command >>exp(pi/2*i)

4. Execute the MATLAB command >>exp(pi/2i)

jj

j j

j j

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 6 Solution

33

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

EE 350

Continuous-Time Linear Systems

Recitation 3

1

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 1• Consider the following circuit that contains an ideal diode

1. Sketch the output y(t) as a function of the input f(t)2. Is the system zero-state linear or nonlinear?3. Is the system instantaneous (memoryless) or dynamic?

2

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 1 Solution

3

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 1 Solution

4

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 1 Solution

5

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2• Consider the circuit below with input f(t) and output y(t)

1. Is the system linear or nonlinear? 2. Is the system time-invariant or time-varying?3. Is the system instantaneous (memoryless) or dynamic?4. Is the system causal or noncausal?

6

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

7

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

8

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

9

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

10

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

11

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 2 Solution

12

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3• The relationship between the input f(t) and zero-state

response y(t) of two systems are given below. Determine if each system is

1. Zero-state linear or nonlinear2. Time-invariant or time-varying3. Causal or noncausal4. Instantaneous (memoryless) or dynamic

13

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

14

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

15

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

16

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

17

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

18

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 3 Solution

19

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 4• Consider a linear time-invariant (LTI) system with input f(t)

and zero-state response y(t)

1. Can we use f1(t) = 2f(t/2) to find y1(t) in terms of y(t)?2. Sketch the zero-state response y1(t) to the input f1(t)3. Sketch the input f2(t) yielding the zero-state response y2(t)

20

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 4 Solution

21

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 4 Solution

22

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 4 Solution

23

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Complex Number Review• A complex number is a number that can be expressed in

the form a + j b, where a and b are real numbers and jsatisfies the equation j2 = 1

• Notation

• Complex numbers extend the concept of the one-dimensional number line to the two-dimensional complex plane by using the horizontal axis for the real part and the vertical axis for the imaginary part

24

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Rectangular and Polar Form• A complex number z can be represented either in

rectangular or polar form

25

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Polar Form and Euler’s Identity

26

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Operations on Complex Numbers• Use rectangular form for addition and subtraction

• Use polar form for multiplication and division

• The complex conjugate of the complex number z = a + jb is defined as z* = a – jb

27

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 5

• Given z = a + jb = r ej show that1. z* = r e-j

2. z + z* = 2a = 2Re{z}3. z z* = 2jb = j2Im{z}4. z z* = a2 + b2 = r2

28

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 5 Solution

29

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Entering Complex Numbersin MATLAB

30

• The complex number z = 2 + j3 may be entered into MATLAB as

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Complex Functions in MATLAB

31

Operation Functionmagnitude (r) of z abs(z)angle (q) of z in radians angle(z)construct z from a and b complex(a,b)conjugate of z conj(z)imaginary part of z imag(z)real part of z real(z)

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 6• Use MATLAB to determine

• Explain the difference between the results in parts 3 and 4

32

Recitation 3.School of Electrical Engineering and Computer Science

Jeffrey Schiano 2015-2017 All rights reserved.

Problem 6 Solution

33

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