Signal Classification

Question 1

Signal

Answer 1

Communication between devices

A set of data

A function that varies with an independent variable

Question 2

Signal examples

Answer 2

1. Voltage across a capacitor in a circuit. The signal is a function of time
2. Average high temperature in Ruston over different months. The signal is a function of month
3. Current through an inductor
4. Average number of children per family
5. Batting average

Question 3

Signal classifications

Answer 3

1. Continuous time vs. discrete time
2. Energy vs. power
3. Periodic vs. aperiodic
4. Even vs. odd

Question 4

Continuous-time signal

Answer 4

If the independent variable is a continuous variable

Between two values of the independent variable, there are infinite number of values

Question 5

Discrete-time signal

Answer 5

If the independent variable is a discrete variable

T —> 1,2,3,4,5,…
t —> 1.1,2.1,3.1,4.1,…

Between two consecutive values of a discrete variable, there are no other possible values

Question 6

Periodic signal

Answer 6

If a signal repeats its pattern at regular intervals

If x(t) is a periodic signal, then x(t+T) = x(t)
T-fundamental period of x(t)

Question 7

The fundamental period of x(t)

Answer 7

The smallest positive integer T for which x(t) = x(t+T) holds

Question 8

Aperiodic signal

Answer 8

A signal that is not periodic

Question 9

Cos(x) =

Answer 9

1

Question 10

Jsin(x) =

Answer 10

0

Question 11

Exp(jx) =

Answer 11

1

Question 12

Cos(x) + jsin(x) =

Answer 12

1

Question 13

Cos(2pi n) =

Answer 13

1

Question 14

Sin(2pi n) =

Answer 14

0

Question 15

For a sum of many periodic signals, the fundamental period is…

Answer 15

The least common multiple of the individual fundamental periods

Question 16

Energy signal

Answer 16

If a signal has a finite energy

The power of an energy signal is always 0

Question 17

Power signal

Answer 17

If a signal has a finite and non-zero power

The energy of a power signal is always infinity

All periodic signals are power signals, which means they have infinite energy

Question 18

Even signal

Answer 18

A signal x(t) is called even if x(t) = x(-t)

Flipping the signal about the vertical axis results in the same signal

Question 19

Odd signal

Answer 19

A signal x(t) is called an odd signal if x(t) = -x(-t)

Flipping the signal about both vertical and horizontal axes results in the same signal