Signals and Systems Flashcards Preview

Electrical > Signals and Systems > Flashcards

Flashcards in Signals and Systems Deck (161)
Loading flashcards...
1

What are samples? 

Points of data

2

What are sampling intervals

The distance between the sample points

3

Discrete-time signals can be defined in 2 ways...

  1. As a function
  2. As a list of values of a sequence 

4

In this picture, the arrow indicates....?

And if the arrow  is not shown, where is the ____ point? 

The n=0 point

The first value in the sequence is the n=0 point

5

Define analog signals 

Analog Signals: An analog signal is a continuous-time signal x(t) that can take on any value in the continuous interval (a, b), where a may be - ∞ and b may be +∞.

6

Define Digital Signals

Digital Signals: A digital signal is a discrete-time signal x[n] that can only take on only a finite number of distinct values.

 

7

What is a real signal?

Real Signals: A signal x(t) is said to be a real signal if its value is a real

number

8

What is a complex signal?

Complex Signals: A signal x(t) is said to be a complex signal if its value is a complex number

9

A general (continuous- or discrete-time) complex signal x(t) is a function of the form

where x1(t) and x2(t) are real signals and j = √−1

10

Define Deterministic Signals

Deterministic Signals: Those signals whose values are exactly specified for any given time in the time span of interest are called deterministic signals. Such signals may be represented by a known function of time t.

11

Define Random Signals

Random Signals: Those signals that take random values at any given time are called random or non-deterministic signals. Such signals must be characterized statistically (that is, represented in probabilistic terms)

12

Any signal x(t) or x[n] can be expressed as a sum of ____ ____, one of which is ____ and one of which is ____

Any signal x(t) or x[n] can be expressed as a sum of two signals, one of which is even and one of which is odd

13

The product of two even signals or of two odd signals is a...?

...even signal

14

The product of an even signal and an odd signal is an...?

...odd signal

15

Define Periodic continuous-time signals

Periodic Continuous-time Signals: A continuous-time signal x(t) is said to be a periodic signal with period T if there is a unique positive nonzero value of T for which the following expression is valid

16

A dc signal is a signal in which x(t) is ____; such a signal is not periodic since its fundamental period is ____

A dc signal is a signal in which x(t) is constant; such a signal is not periodic since its fundamental period is undefined

17

Define Aperiodic Continuous-time Signals

Aperiodic Continuous-time Signals: Any continuous-time signal which is not periodic is called a non-periodic signal or an aperiodic signal

18

Define Periodic Discrete-time Signals

Periodic Discrete-time Signals: A sequence (discrete-time signal) x[n] is periodic with period N if there is a unique positive integer N for which the following expression is valid

19

Define Aperiodic Discrete-time Signals

Aperiodic Discrete-time Signals: Any sequence which is not periodic is called a non-periodic sequence or an aperiodic sequence

20

A sequence obtained by uniform sampling of a periodic continuous-time signal may...

...not be periodic

21

The sum of two continuous-time periodic signals may...

... not be periodic

22

The sum of two periodic sequences is...

...always periodic

23

For any continuous-time signal x(t), the total energy of the signal over the interval     t1 ≤ t ≤ t2 is defined as

24

The average power of the signal x(t) over the interval t1 ≤ t ≤ t2 is defined as

25

|x(t)| denotes the ____ of x(t) and the signal x(t) could be a ____ or ____ signal.

|x(t)| denotes the magnitude of x(t) and the signal x(t) could be a real or complex signal.

26

For any discrete-time signal x[n], the total energy of the signal over the interval n1 ≤ n ≤ n2 is defined as

27

The average power of the signal x[n] over the interval n1 ≤ n ≤ n2 is defined as

28

A signal x(t) (or x[n]) is said to be an ____ ____ (or sequence) if and only if 0 < E∞ < ∞, in which case, P∞ = 0.

A signal x(t) (or x[n]) is said to be an energy signal (or sequence) if and only if 0 < E∞ < ∞, in which case, P∞ = 0.

29

A signal x(t) (or x[n]) is said to be a ____ signal (or sequence) if and only if 0 < P∞ < ∞, in which case, E∞ = ∞

A signal x(t) (or x[n]) is said to be a power signal (or sequence) if and only if 0 < P∞ < ∞, in which case, E∞ = ∞

30

A signal that does not satisfy 0 < E∞ < ∞ and 0 < P∞ < ∞ is not an ____ or a ____ signal

A signal that does not satisfy 0 < E∞ < ∞ and 0 < P∞ < ∞ is not an energy or a power signal