Question

Time scaling operation is also known as ___________

(a) Down-sampling

(b) Up-sampling

(c) Sampling

(d) None of the mentioned

The question was posed to me by my college professor while I was bunking the class.

My enquiry is from Discrete Time Signals in section Discrete Time Signals and Systems of Digital Signal Processing

Answer 1

The correct choice is (a) Down-sampling

Explanation: If the signal x(n) was originally obtained by sampling a signal xa(t), then x(n)=xa(nT). Now, y(n)=x(2n)(say)=xa(2nT). Hence the time scaling operation is equivalent to changing the sampling rate from 1/T to 1/2T, that is to decrease the rate by a factor of 2. So, time scaling is also called as down-sampling.