Test: Shifting and Time Reversal of Signals - Electronics and Communication Engineering (ECE) MCQ

In time signal finite time value is added or subtracted from it.

• Time scaling involves compressing or stretching a signal in time. For example, replacing t with at where a >1  compresses the signal, and 0<a<1 stretches it.
• Time reversal is similar because it modifies the time axis by replacing t with −t, flipping the signal in time.
• Both operations involve transformations of the time axis, unlike amplitude scaling or multiplication.
• Correct answer: a) Time reversal.

Amplitude scaling is represented with the equation Y(t) = α X(t)

When the α value is less than one in time scaling then the signal is said to be expanded or dilated

In time scaling the signal is compressed or expanded by multiplying the time variable

In time reversal only the time variable is affected and not the amplitude.

when a finite time value is added to the time variable of the original signal then it is called as negative time shift.

Time scaling is done on independent variables.

The system needs to give a zero output for a zero input so as to conserve the law of additivity, to ensure linearity.

Time-shifting property: When a signal is shifted in time domain it is said to be delayed or advanced based on whether the signal is shifted to the right or left.
For example: