# Linear Filtering Methods Based on DFT

This set of Digital Signal Processing Interview Questions & Answers focuses on “Linear Filtering Methods Based on DFT”.

1. By means of the DFT and IDFT, determine the response of the FIR filter with impulse response h(n)={1,2,3} to the input sequence x(n)={1,2,2,1}?

a) {1,4,11,9,8,3}**b) {1,4,9,11,8,3}**

c) {1,4,9,11,3,8}

d) {1,4,9,3,8,11}

2. What is the sequence y(n) that results from the use of four point DFTs if the impulse response is h(n)={1,2,3} and the input sequence x(n)={1,2,2,1}?

a) {9,9,7,11}

b) {1,4,9,11,8,3}

c) {7,9,7,11}**d) {9,7,9,11}**

3. Overlap add and Overlap save are the two methods for linear FIR filtering a long sequence on a block-by-block basis using DFT.**a) True**

b) False

4. In Overlap save method of long sequence filtering, what is the length of the input sequence block?

a) L+M+1

b) L+M**c) L+M-1**

d) None of the mentioned

5. In Overlap save method of long sequence filtering, how many zeros are appended to the impulse response of the FIR filter?

a) L+M

b) L

c) L+1**d) L-1**

6. The first M-1 values of the output sequence in every step of Overlap save method of filtering of long sequence are discarded.**a) True**

b) False

7. In Overlap add method, what is the length of the input data block?

a) L-1**b) L**

c) L+1

d) None of the mentioned

8. Which of the following is true in case of Overlap add method?

a) M zeros are appended at last of each data block

b) M zeros are appended at first of each data block**c) M-1 zeros are appended at last of each data block**

d) M-1 zeros are appended at first of each data block

9. In which of the following methods, the input sequence is considered as shown in the below diagram?**a) Overlap save method**

b) Overlap add method

c) Overlap add & save method

d) None of the mentioned

10. In which of the following methods, the output sequence is considered as shown in the below diagram?

a) Overlap save method**b) Overlap add method**

c) Overlap add & save method

d) None of the mentioned

11. What is the value of x(n)*h(n), 0≤n≤11 for the sequences x(n)={1,2,0,-3,4,2,-1,1,-2,3,2,1,-3} and h(n)={1,1,1} if we perform using overlap add fast convolution technique?

a) {1,3,3,1,1,3,5,2,2,2,3,6}

b) {1,2,0,-3,4,2,-1,1,-2,3,2,1,-3}

c) {1,2,0,3,4,2,1,1,2,3,2,1,3}**d) {1,3,3,-1,1,3,5,2,-2,2,3,6}**

12. What is the value of x(n)*h(n), 0≤n≤11 for the sequences x(n)={1,2,0,-3,4,2,-1,1,-2,3,2,1,-3} and h(n)={1,1,1} if we perform using overlap save fast convolution technique?**a) {1,3,3,-1,1,3,5,2,-2,2,3,6}**

b) {1,2,0,-3,4,2,-1,1,-2,3,2,1,-3}

c) {1,2,0,3,4,2,1,1,2,3,2,1,3}

d) {1,3,3,1,1,3,5,2,2,2,3,6}