DISCRETE TIME SIGNALS Flashcards
By the term** continuous-time (CT) signal**, a function of time x(t), where the independent variable t is ____________. If t is a discrete variable, then the ____________ is a discrete-time signal (DT). A discrete-time signal is often identified as a sequence of numbers, denoted by ____________, where n is an integer.
The discrete-time signal x[n] was obtained from sampling an analog signal x(t), then
**x[n] = x(nT)
**
where T is the sampling period
continuous, signal x(t), x[n]
When we process a sequence, this sequence may undergo several manipulations involving the ________or the ____________ of the signal.
time, amplitude
The basic operations on sequences are as follows:
Time shifting
Time reversal
Time scaling
Amplitude scaling
Signal addition
Signal multiplication
The time shifting of a signal may result in ________ or _______
time delay or time advance.
The time shifting operation of a discrete-time signal x[n] can be represented by
y[n] = x[n – k]
The signal y[n] can be obtained by time shifting the signal x[n] by k units. If k is ________, it is delay and the shift is to the right, and if k is ________, it is advance and the shift is to the left.
positive, negative
The time reversal also called ____________ of a discrete-time signal x[n] can be obtained by folding the sequence about n = 0. The time reversed signal is the reflection of the ____________. It is obtained by replacing the independent variable n by –n.
y[n] = x[-n]
time folding, original signal
This transformation is estimated by the statement y[n] = x[-n] which involves ________ the signal x[n] concerning the _________.
flipping, index n
The ____________ may be time expansion or time compression.
time scaling
The time scaling of a discrete time signal x[n] can be accomplished by replacing n by ____ in it. Mathematically, it can be expressed as
y[n] = x[kn]
Where k is any positive number. If k > 1, it is time ____________ and if k < 1, it is time ____________.
kn, compression, expansion
The amplitude scaling of a discrete-time signal can be represented by
y[n] = k*x[n]
where k is any positive integer. Amplitude scaling of a signal by a constant k is accomplished by multiplying the value of every signal sample by k.
If k > 1, it is ____________ and if a < 1, it is ____________. Hence the amplitude is __________.
amplification, attenuation, rescaled
In ____________________, the sum or difference of two signals a[n] and b[n] can be obtained by adding or subtracting the corresponding sample values.
y[n] = a[n] + b[n] = b[n] + a[n]
discrete-time domain
The multiplication of two discrete-time sequences can be performed by multiplying their values at the sampling instants as shown below.
y[n] = a[n] * b[n] = b[n] * a[n]
