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8/7/2019 Signals and Systems Note1
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6.003:
Signals and
Systems
Signals and Systems
February 2,
2010
8/7/2019 Signals and Systems Note1
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6.003:
Signals and
Systems
Todays handouts:
Lecturer: Instructors:
Website:
Text:
Single package
containing
Slides for Lecture 1 Subject Information & Calendar Denny
Freeman
Peter Hagelstein
Rahul
Sarpeshkar
mit.edu/6.003
Signals and
Systems
Oppenheim
and
Willsky
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6.003:
Homework
Doing the
homework
is
essential
for
understanding
the
content.
where subject matter is/isnt learned equivalent to practice in sports or music
Weekly Homework
Assignments
Conventional Homework Problems plus Engineering Design Problems (Python/Matlab)
Open Office
Hours
!
Stata
Basement
Mondays and Tuesdays, afternoons and early evenings
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6.003:
Signals and
Systems
Collaboration Policy
Discussion of concepts in homework is encouraged Sharing of homework or code is not permitted and will be re
ported to
the
COD
Firm Deadlines Homework must be submitted in recitation on due date Each student can submit one late homework assignment without
penalty.
Grades on other late assignments will be multiplied by 0.5 (unless excused
by
an
Instructor,
Dean,
or
Medical
Official).
8/7/2019 Signals and Systems Note1
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spring spring spring spring spring
nals nals nals nals nals
6.003 At-A-Glance
Tuesday
Wednesday
Thursday
Friday
Feb
2
L1:
Signals and
Systems
R1:
Continuous &
Discrete
Systems
L2:
Discrete-Time
Systems
R2:
Difference
Equations
Feb 9
L3:
Feedback,
Cycles,
and
Modes
HW1
due
R3:
Feedback,
Cycles, and
Modes
L4:
CT Operator
Representations
R4:
CT
Systems
Feb 16
Presidents
Day:
Monday
Schedule
HW2
due
R5:
CT Operator
Representations
L5:
Second-Order
Systems
R6:
Second-Order
Systems
Feb 23
L6:
Laplace
and
Z
Transforms
HW3
due
R7:
Laplace and
Z
Transforms
L7:
Transform
Properties
R8:
Transform
Properties
Mar 2
L8: Convolution; Impulse
Response
EX4
Exam 1 no
recitation
L9: Frequency Response
R9: Convolution and
Freq.
Resp.
Mar 9
L10:
Bode
Diagrams
HW5
due
R10:
Bode
Diagrams
L11:
DT Feedback
and
Control
R11:
Feedback and
Control
Mar 16
L12:
CT
Feedback
and
Control
HW6
due
R12:
CT Feedback
and
Control
L13:
CT Feedback
and
Control
R13:
CT Feedback
and
Control
Mar 23
Spring
Week
Mar 30
L14:
CT
Fourier
Series
HW7
R14:
CT
Fourier
Series
L15:
CT Fourier
Series
R15:
CT Fourier
Series
Apr 6
L16:
CT
Fourier
Transform
EX8
due
Exam 2
no
recitation
L17:
CT Fourier
Transform
R16:
CT Fourier
Transform
Apr 13
L18:
DT
Fourier
Transform
HW9
due
R17:
DT Fourier
Transform
L19:
DT Fourier
Transform
R18:
DT Fourier
Transform
Apr 20
Patriots Day Vacation
HW10
R19: Fourier Transforms
L20: Fourier Relations
R20: Fourier Relations
Apr 27
L21:
Sampling
EX11
due
Exam 3
no
recitation
L22:
Sampling
R21:
Sampling
May 4
L23:
Modulation
HW12
due
R22:
Modulation
L24:
Modulation
R23:
Modulation
May 11
L25:
Applications
of 6.003 EX13 R24: Review
Breakfast
with
Staff Study Period
May 18
Final
Examination
Period
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6.003:
Signals and
Systems
Weekly meetings
with
class
representatives
help staff understand student perspective learn about teaching One
representative
from
each
section
(4
total)
Tentatively
meet
on
Thursday
afternoon
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The Signals
and
Systems
Abstraction
Describe
a
system
(physical,
mathematical,
or
computational)
by the
way
it
transforms
an
input
signal
into
an
output
signal .
systemsignal
in
signal out
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Example:
Mass and
Spring
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Example:
Mass and
Spring
x(t)
y(t)
mass & spring system
x(t)
y(t)
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Example:
Mass and
Spring
x(t)
y(t)
x(t)
y(t)
mass & spring system
t
t
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r 0 (t )
t
Example:
Tanks
r 0 (t)
h1 (t) r 1 (t)
h2 (t)
r 2 (t)
r 0 (t)
tank system
r 2 (t)
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Example:
Tanks
r 0 (t)
h1 (t) r 1 (t)
h2 (t)
r 2 (t) r 0 (t)
r 2 (t)
tank systemt t
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Example:
Cell Phone
System
sound out
sound in
sound in
cell
phone system
sound out
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Example:
Cell Phone
System
sound out
sound in
sound in sound out
cell
phone system
t t
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Signals and
Systems:
Widely
Applicable
The
Signals
and
Systems
approach
has
broad
application:
electrical,
mechanical, optical, acoustic, biological, nancial, ...
x(t)
y(t)
t
mass &
spring system
t
r 0 (t)
r 1 (t)
r 2 (t)
h1 (t)
h2 (t)
tank system
r 0 (t)
r 2 (t)
t
t
cell phone
system
sound in
sound
out
t
t
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tower
E/M tower
sound E/M optic cell sound in phone
out
cellphone ber
focuses on
the
ow
of
information ,
abstracts
away
everything
else
Signals and
Systems:
Modular
The
representation
does
not
depend
upon
the
physical
substrate.
sound in
sound ou
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Signals and
Systems:
Hierarchical
Representations
of
component
systems
are
easily
combined.
Example:
cascade of
component
systems
cell phone
tower tower cell phone sound in
E/M
optic ber
E/M sound out
Composite system
cell phone
system
sound
in
sound
out
Component and composite systems have the same form, and are analyzed
with
same
methods.
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Signals and
Systems
Signals
are
mathematical
functions.
independent variable = time dependent variable = voltage, ow rate, sound pressure
mass &
spring system
x(t)
y(t)
t
t
r 0 (t) r2 (t)
tank systemt
t
sound in
sound
out
cell phone
system
t
t
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Signals and
Systems
continuous
time
(CT)
and
discrete
time
(DT)
x(t) x[n]
nt 0 2 4 6 8 10 0 2 4 6 8 10
Many physical
systems
operate
in
continuous
time.
mass
and
spring
leaky tank Digital
computations
are
done
in
discrete
time.
state machines: given the current input and current state, what is the
next
output
and
next
state.
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Signals and
Systems
Sampling:
converting
CT
signals
to
DT
x(t)
x[n] = x(nT
)
nt 0T 2T 4T 6T 8T 10T 0 2 4 6 8 10
T =
sampling
interval
Important for
computational
manipulation
of
physical
data.
digital representations of audio signals (e.g., MP3) digital representations of pictures (e.g., JPEG)
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Signals and
Systems
Reconstruction:
converting
DT
signals
to
CT
zero-order hold
x[n]
x(t)
n
t 0 2 4 6 8 10
0 2T
4T
6T
8T
10T
T =
sampling
interval
commonly used
in
audio
output
devices
such
as
CD
players
Si l d S
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Signals and
Systems
Reconstruction:
converting
DT
signals
to
CT
piecewise linear
x[n]
x(t)
n
t 0 2 4 6 8 10
0 2T
4T
6T
8T
10T
T =
sampling
interval
commonly used
in
rendering
images
Ch k Y lf
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Check Yourself
Computer generated speech (by Robert Donovan)
t
f (t)
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
f 1 (t) = f (2t) f 2 (t) = f (t) f 3 (t) = f (2t)
f 4 (t) = 2 f (t)
Ch k Y lf
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Check Yourself
Computer generated speech (by Robert Donovan)
t
f (t)
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
f 1 (t) = f (2t) f 2 (t) = f (t) f 3 (t) = f (2t)
f 4 (t) = 2 f (t)
Check Yourself
8/7/2019 Signals and Systems Note1
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Check Yourself
Computer generated speech (by Robert Donovan)
t
f (t)
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
f 1 (t) = f (2t) f 2 (t) = f (t) f 3 (t) = f (2t)
f 4 (t) = 2 f (t)
Check Yourself
8/7/2019 Signals and Systems Note1
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Check Yourself
Computer generated speech (by Robert Donovan)
t
f (t)
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
f 1 (t) = f (2t) f 2 (t) = f (t) f 3 (t) = f (2t)
f 4 (t) = 2 f (t)
Check Yourself
8/7/2019 Signals and Systems Note1
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Check Yourself
Computer generated speech (by Robert Donovan)
t
f (t)
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
f 1 (t) = f (2t) f 2 (t) = f (t) f 3 (t) = f (2t)
f 4 (t) = 2 f (t)
Check Yourself
8/7/2019 Signals and Systems Note1
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Check Yourself
Computer generated speech (by Robert Donovaf (t)
n)
t
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
f 1 (t) = f (2t) f 2 (t) = f (t) f 3 (t) = f (2t)
f 4 (t) = 2 f (t)
Check Yourself
8/7/2019 Signals and Systems Note1
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Check Yourself
Computer generated speech (by Robert Donovan) f (t)
t
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
f 1 (t) = f (2t) f 2 (t) = f (t) f 3 (t) = f (2t)
f 4 (t) = 2 f (t)
Computer generated speech (by Robert Donovan)
Check Yourself
8/7/2019 Signals and Systems Note1
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Check Yourself
Computer generated speech (by Robert Donovan)
t
f (t)
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
f 1 (t) = f (2t) f 2 (t) = f (t) f 3 (t) = f (2t)
f 4 (t) = 2 f (t)
Check Yourself
8/7/2019 Signals and Systems Note1
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Check Yourself
Computer generated speech (by Robert Donovan)
t
f (t)
Listen to the following four manipulated signals: f 1 (t),
f 2 (t),
f 3 (t),
f 4 (t).
How
many
of
the
following
relations
are
true?
2
f 1 (t) = f (2t) f 2 (t) = f (t) X f 3 (t) = f (2t) X
f 4 (t) = 2 f (t)
Check Yourself
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y f (x,
y)
250 0 250
250
0
250
x
How many
images
match
the
expressions
beneath
them?
250
0
250
y
x
250
0
250
y
x
250
0
250
y
x
250
0
250
250
0
250
250
0
250 f 1 (x,
y)= f (2x,
y)
?
f 2 (x,
y)= f (2x250, y) ? f 3 (x, y)= f (x250, y) ?
Check Yourself
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y y y y
250
0
250
250
0
250
250
0
250
250
0
250
250 0 250 x
250 0 250 x
250 0 250 x
250 0 250 f (x, y )
f 1 (x, y ) = f (2x, y)
?
f 2 (x, y ) =
f (2x250, y) ? f 3 (x, y ) = f (x250, y) ?
x = 0
f 1 (0, y) =
f (0, y)
x =
250
f 1 (250, y) = f (500, y) X x
= 0
f 2 (0, y) = f (250, y) x = 250 f 2 (250, y) = f (250, y) x
= 0
f 3 (0, y) = f (250, y) X x
=
250
f 3 (250, y) = f (500, y) X
x
Check Yourself
8/7/2019 Signals and Systems Note1
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y f (x,
y)
250 0 250
250
0
250
x
How many
images
match
the
expressions
beneath
them?
250
0
250
250
0
250
y
x
f 1 (x, y)= f (2x,
y)
?
250
0
250
250
0
250
y
x
f 2 (x, y)= f (2x250, y) ?
250
0
250
250
0
250
y
x
f 3 (x, y)= f (x250, y) ?
The Signals and Systems Abstraction
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Describe
a
system
(physical,
mathematical,
or
computational)
by
the way it transforms an input signal into an output signal .
systemsignal in
signal out
Example System: Leaky Tank
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Formulate
a
mathematical
description
of
this
system.
r 0 (t)
h1 (t) r 1 (t)
What determines
the
leak
rate?
Check Yourself
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The holes
in
each
of
the
following
tanks
have
equal
size.
Which
tank
has
the
largest
leak
rate
r 1 (t)?
3.
4.
1. 2.
Check Yourself
8/7/2019 Signals and Systems Note1
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The holes
in
each
of
the
following
tanks
have
equal
size.
Which
tank
has
the
largest
leak
rate
r 1 (t)?
2
3.
4.
1. 2.
Example System: Leaky Tank
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Formulate
a
mathematical
description
of
this
system.
r 0 (t)
r 1 (t)
h1 (t)
Assume linear
leaking:
r 1 (t)
h1 (t)
What determines the height h1 (t)?
Example System: Leaky Tank
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Formulate
a
mathematical
description
of
this
system.
r 0 (t)
r 1 (t)
h1 (t)
Assume linear
leaking:
r 1 (t)
h1 (t)
Assume water is conserved: dh 1 (t)
r0 (t) r 1 (t)dt
Solve:
dr 1 (t)
r 0 (t) r 1 (t)dt
Check Yourself
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What are
the
dimensions
of
constant
of
proportionality
C ?
dr1
(t) dt
= C r 0 (t) r 1 (t)
Check Yourself
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What are
the
dimensions
of
constant
of
proportionality
C ?
inverse
time
(to
match
dimensions
of
dt )
dr 1 (t) dt
=
C
r 0 (t)
r 1 (t)
Analysis of the Leaky Tank
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Call
the
constant
of
proportionality
1/
.
Then
is called
the
time
constant
of
the
system.
dr 1 (t)
r 0 (t)
r 1 (t)=
dt
Check Yourself
8/7/2019 Signals and Systems Note1
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Which of
the
following
tanks
has
the
largest
time
constant
?
3.
4.
1. 2.
Check Yourself
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Which of
the
following
tanks
has
the
largest
time
constant
?
4
3.
4.
1. 2.
Analysis of
the
Leaky
Tank
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Call the
constant
of
proportionality
1/
.
Then is called the time constant of the system.
dr 1 (t)
r 0 (t)
r 1 (t)=
dt Assume
that
the
tank
is
initially
empty,
and
then
water
enters
at
a
constant
rate
r 0 (t) = 1 .
Determine
the
output
rate
r 1 (t).
r 1 (t)
time (seconds)
1 2 3
Explain the
shape
of
this
curve
mathematically.
Explain
the
shape
of
this
curve
physically.
Leaky Tanks
and
Capacitors
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Although derived
for
a
leaky
tank,
this
sort
of
model
can
be
used
to
represent a variety of physical systems. Water
accumulates
in
a
leaky
tank.
r 0 (t)
h1 (t)
r1
(t) Charge accumulates
in
a
capacitor.
i i
io
+ vC
dv i i io dh = i i io analogous to r 0 r 1dt C dt
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