# MATLAB Questions and Answers – Fourier Analysis and Filtering – 2

This set of MATLAB MCQs focuses on “Fourier Analysis and Filtering – 2”.

1. What is the output of the following code?

`buttord[2,1,3,4]`

a) Error
b) Returns order of the filer
c) 1
d) 0

Explanation: The input to the buttord command should be given within parentheses. Since we have used third brackets, MATLAB will generate an error.

2. What is the output of the following code?

`Buttord(1,2,3,4)`

a) 1
b) Syntactical Error
c) Frequency Error
d) Error

Explanation: The passband frequency should be in the interval 0 to 1. Hence MATLAB returns an error when we give 2 as the passband corner frequency.
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3. The order of the type 1 Chebyshev filter is obtained from the ________
a) cheb1ord()
b) chebord()
c) chebyord()
d) chebshev()

Explanation: The cheb1ord() command is inbuilt in MATLAB. It helps to generate the order of the type-1 chebyshev filter and also it’s cut-off frequency.

4. The cut-off frequency of the type-2 Chebyshev filter is produced by the ________
a) cheby2ord()
b) chebyord2()
c) chebyshevord2()
d) cheby2order()

Explanation: The cheby2ord() command is used to generate the order and the cut-off frequency of the type-2 Chebyshev filter. Hence only cheby2ord() is correct.

5. The ellipord command is used for _________
a) FIR Filter design
b) IIR Filter design
c) Both IIR and FIR filter design
d) No such command

Explanation: The ellipord command is used to generate the minimum order of a filter based on certain design specifications. The specifications include cut-off frequencies, passband ripple and the attenuation factor.

6. The freqz() command returns __________
a) No such command
b) A set of frequencies
c) Frequency Response
d) Phase plot

Explanation: The freqz() command returns the frequency response of a filter. The input to the command are the numerator and the denominator polynomial.

7. The fftfilt command filters data based on ____________
a) Convolution
b) Overlap save method
c) No such command

Explanation: The overlap add method is used by the fftfilt command to generate the filtered sequence. This command is only allowed for FIR filters.

8. The bilinear transformation is done by the ________
a) bilin()
b) bilinear()
c) no such command
d) bilineartran()

Explanation: The bilinear() command is pre-defined in MATLAB and is used to convert analog filters to digital filters with the help of the bilinear transformation. Hence, only bilinear() is correct.

9. The bilinear command returns column vectors.
a) True
b) False

Explanation: The bilinear command returns row vectors. They comprise of descending powers of z of the numerator and denominator polynomial.

10. In chebwin(L,r), what is the default value of r?
a) 150 dB
b) 90 dB
c) 100 dB
d) 110 dB

Explanation: The default value of r is 100dB. R is the amount by which the the Fourier Transform of the side-lobe magnitude should be below the main-lobe magnitude.

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