1.List out the advantages and disadvantages of FIR filter. (May/June 2013)
Advantages of FIR filter :
(i) Linear phase FIR filters can be easily designed.
(ii) Efficient realizations of FIR filter exist as both recursive and nonrecursive structures.
(iii) FIR filters realized nonrecursively are always stable.
(iv) The roundoff noise can be made small in nonrecusrsive realization of FIR filters.
Disadvantages of FIR filter:
(i) The duration of impulse response should be large to realize sharp cutoff filters.
(ii) The non integral delay can lead to problems in some signal processing applications.
2.What is product quantization error? (NOV/DEC 2010)
In digital computations, the output of multipliers i.e, the products are quantized to finite word length in order to store them in registers and to be used in subsequent calculations. The error due to the quantization of the output of multiplier is referred to as product quantization error.
3. What is prewarping? (NOV/DEC 2010)
In IIR filter design using bilinear transformation, the conversion of the specified digital frequencies to analog frequencies is called prewarping. The prewarping is necessary to eliminate the effect of warping on amplitude response.
4. Define zero input limit cycle oscillations. (May/June 2013)
In recursive system, the product quantization may create periodic oscillations in the output. These oscillations are called limit cycles. If the system output enters a limit cycle, it will continue to remain in limit cycle even when the input is made zero. Hence these limit cycles are also called zero input limit cycles.
5.What are the two types of quantization employed in digital system.(May/June 2013)
The two types of quantization employed in digital system are
(i) Truncation
(ii) Rounding
6.Mention the advantages of cascade realization. (May/June 2013)
In digital implementation of LTI system , the filter coefficients are quantized. While quantizing the filter coefficient the value of poles may change. This will end up in a frequency response different to that of desired frequency response. These effects can be avoided or minimized, if the LTI system is realized in cascade structure.
(or)
The sensitivity of frequency response characteristics to quantization of the coefficients is minimized by realizing the system in cascade form.
7.What is zero padding? what are its uses?(NOV/DEC 2011)
Appending zeros to a sequence in order to increase the size or length of the sequence is called zero padding.
In circular convolution, when the two input sequences are of different size, then they are converted to equal size by zero padding.
8. What is truncation? (NOV/DEC 2010)
The truncation is the process of reducing the size of binary number by discarding all bits less significant bit that is retained.
9. How many multiplications and additions are involved in radix-2 FFT?(NOV/DEC 2013)
For performing radix-2 FFT, the value of N should be such that, N=2^m. The total number of complex additions are Nlog2N and the total number of complex multiplications are (N/2)log2N.
10. Explain the meaning of limit cycle oscillator.(APR/MAY 2011)
In recursive systems when the input is zero or some nonzero constant value, the nonlinearities due to finite precision arithmetic operations may cause periodic oscillations in the output. These oscillations are called limit cycles.
11. What is meant by Gibb's phenomenon? (APR/MAY 2011)
In FIR filter design by fourier series method , the infinite duration impulse response is truncated to finite duration impulse response. The abrupt truncation of impulse response introduces oscillations in the passband and stopband. This effect is known as Gibb's phenomenon(or) Gibb's oscillations.
12. What are the properties of Chebyshev filter?
1. The magnitude response of the chebyshev filter exhibits ripple either in passband or in stopband according to type.
2. The poles of the chebyshev filter lies on an ellipse.
13. What are the desirable characteristics of the window?
The desirable chracteristics of the window are
i. The central lobe of the frequency response of the window should contain most of the energy and should be narrow.
ii. The highest side lobe level of the frequency response should be small.
iii. The side lobes of the frequency response should decrease in energy rapidly as w tends to π.
Advantages of FIR filter :
(i) Linear phase FIR filters can be easily designed.
(ii) Efficient realizations of FIR filter exist as both recursive and nonrecursive structures.
(iii) FIR filters realized nonrecursively are always stable.
(iv) The roundoff noise can be made small in nonrecusrsive realization of FIR filters.
Disadvantages of FIR filter:
(i) The duration of impulse response should be large to realize sharp cutoff filters.
(ii) The non integral delay can lead to problems in some signal processing applications.
2.What is product quantization error? (NOV/DEC 2010)
In digital computations, the output of multipliers i.e, the products are quantized to finite word length in order to store them in registers and to be used in subsequent calculations. The error due to the quantization of the output of multiplier is referred to as product quantization error.
3. What is prewarping? (NOV/DEC 2010)
In IIR filter design using bilinear transformation, the conversion of the specified digital frequencies to analog frequencies is called prewarping. The prewarping is necessary to eliminate the effect of warping on amplitude response.
4. Define zero input limit cycle oscillations. (May/June 2013)
In recursive system, the product quantization may create periodic oscillations in the output. These oscillations are called limit cycles. If the system output enters a limit cycle, it will continue to remain in limit cycle even when the input is made zero. Hence these limit cycles are also called zero input limit cycles.
5.What are the two types of quantization employed in digital system.(May/June 2013)
The two types of quantization employed in digital system are
(i) Truncation
(ii) Rounding
6.Mention the advantages of cascade realization. (May/June 2013)
In digital implementation of LTI system , the filter coefficients are quantized. While quantizing the filter coefficient the value of poles may change. This will end up in a frequency response different to that of desired frequency response. These effects can be avoided or minimized, if the LTI system is realized in cascade structure.
(or)
The sensitivity of frequency response characteristics to quantization of the coefficients is minimized by realizing the system in cascade form.
7.What is zero padding? what are its uses?(NOV/DEC 2011)
Appending zeros to a sequence in order to increase the size or length of the sequence is called zero padding.
In circular convolution, when the two input sequences are of different size, then they are converted to equal size by zero padding.
8. What is truncation? (NOV/DEC 2010)
The truncation is the process of reducing the size of binary number by discarding all bits less significant bit that is retained.
9. How many multiplications and additions are involved in radix-2 FFT?(NOV/DEC 2013)
For performing radix-2 FFT, the value of N should be such that, N=2^m. The total number of complex additions are Nlog2N and the total number of complex multiplications are (N/2)log2N.
10. Explain the meaning of limit cycle oscillator.(APR/MAY 2011)
In recursive systems when the input is zero or some nonzero constant value, the nonlinearities due to finite precision arithmetic operations may cause periodic oscillations in the output. These oscillations are called limit cycles.
11. What is meant by Gibb's phenomenon? (APR/MAY 2011)
In FIR filter design by fourier series method , the infinite duration impulse response is truncated to finite duration impulse response. The abrupt truncation of impulse response introduces oscillations in the passband and stopband. This effect is known as Gibb's phenomenon(or) Gibb's oscillations.
12. What are the properties of Chebyshev filter?
1. The magnitude response of the chebyshev filter exhibits ripple either in passband or in stopband according to type.
2. The poles of the chebyshev filter lies on an ellipse.
13. What are the desirable characteristics of the window?
The desirable chracteristics of the window are
i. The central lobe of the frequency response of the window should contain most of the energy and should be narrow.
ii. The highest side lobe level of the frequency response should be small.
iii. The side lobes of the frequency response should decrease in energy rapidly as w tends to π.
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