57. What are the disadvantages of FIR FILTER
The duration
of impulse response
should be large to realize sharp cutoff filters.
The non integral delay can lead
to problems in some signal
processing
applications.
58. What is the necessary and
sufficient condition for
the
linear phase characteristic
of a FIR filter?
The phase function should be a linear function
of w, which inturn requires
constant group
delay and phase delay.
59. List the well
known design technique for
linear phase FIR filter
design?
Fourier series
method and window method
Frequency sampling method. Optimal filter design
method.
60. Define IIR filter?
The filter designed by considering
all the infinite samples of impulse response are
called IIR filter.
61. For what kind
of application , the antisymmetrical
impulse response can be used?
The ant symmetrical
impulse response can
be used to design Hilbert
transforms
and differentiators.
62. For what kind
of application , the symmetrical impulse response can be used?
The impulse
response ,which
is symmetric having odd number of samples can
be
used to design all types
of
filters ,i.e , lowpass,highpass,bandpass
and band reject. The
symmetric impulse
response having even
number of samples
can
be used
to design lowpass and bandpass filter.
63.What is the reason that FIR filter is always
stable?
FIR filter is
always stable because all its poles are at the
origin.
64.What condition on the FIR sequence h(n) are to
be imposed n order that
this filter can be called a liner phase filter?
The conditions are
(i) Symmetric condition h(n)=h(N-1-n)
(ii) Antisymmetric condition
h(n)=-h(N-1-n)
65. Under
what conditions
a finite duration sequence h(n) will yield constant group
delay in its frequency response characteristics and
not the phase delay?
If the impulse response
is anti symmetrical ,satisfying the condition
H(n)=-h(N-1-n)
The frequency response of FIR filter will have constant group delay and not the phase delay .
66. State the condition for
a digital filter to be
causal and stable?
A digital
filter is causal
if its impluse response
h(n)=0 for n<0.
A
digital filter is
stable if its
impulse response is absolutely summable ,i.e,
¥
∑ ½h(n)½< ¥
n=-¥
67. What are the properties of FIR filter?
1.FIR filter is
always
stable.
2.A realizable filter can always be obtained.
3.FIR filter has a linear phase response.
68. When cascade from realization
is
preferred in FIR filters?
The cascade from realization is preferred when complex zeros
with absolute
magnitude less
than
one.
69. What are the disadvantage of Fourier series method
?
In
designing FIR filter using Fourier series
method the infinite duration
impulse
response is truncated at
n= ± (N-1/2).Direct truncation of
the series will lead
to fixed percentage overshoots and undershoots
before and after an approximated
discontinuity in the frequency response
.
70. What is Gibbs phenomenon?
OR
What are
Gibbs oscillations?
One possible
way of finding
an FIR filter that approximates H(ejw)would be to truncate the infinite Fourier series at n= ±
(N-1/2).Abrupt
truncation of the series will lead
to oscillation both in pass band and
is stop band .This phenomenon is known as Gibbs phenomenon.
71. What are the desirable characteristics of the windows?
The desirable charaterstics of the window are
1.The central lobe
of the frequency response of the window
should contain most of the energy and should
be narrow.
2.The highest
side lobe level of the frequency response should be small.
3.The sides lobes
of the frequency response should decrease in
energy rapidly as w tends to p .
72. Compare Hamming window with Kaiser window.
Hamming window Kaiser window
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1.The main lobe width is equal to8ð/N
and
the peak side lobe level
is –41dB.
2.The low pass
FIR filter designed
will have first side lobe
peak of –53 dB
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The main lobe width ,the peak side lobe level can
be
varied by varying the parameter á and N.
The side
lobe peak
can be varied
by
varying the parameter á.
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73.What is the necessary and
sufficient condition
for linear phase characteristics in
FIR filter?
The necessary and
sufficient condition for linear phase characteristics in FIR filter
is the impulse
response h(n) of the system should
have the symmetry property,i.e,
H(n) = h(N-1-n)
Where N
is the duration of the sequence .
74.What are
the advantage of Kaiser
widow?
1.It provides
flexibility for the designer to select the
side lobe level and N .
2. It has the
attractive property that
the side lobe level can be varied continuously from the
low value in the Blackman window
to the high value in
the rectangle window
.
75.What is the principle of designing FIR filter
using
frequency sampling
method?
In frequency sampling method the
desired magnitude response
is sampled and a linear
phase response is
specified .The
samples of desired frequency response are defined as
DFT coefficients.
The filter coefficients are then determined as the IDFT
of
this set of samples.
76.For what
type of filters frequency sampling method is suitable?
Frequency sampling method is attractive
for narrow
band frequency selective
filters where only a few of the samples of the frequency response are non-zero.
77.What is meant by autocorrelation?
The autocorrelation of
a sequence is
the correlation of a sequence with
its shifted
version, and this indicates
how fast the signal
changes.
78.Define white noise?
A stationary random process
is said to be white noise if its power density
spectrum is constant. Hence the white
noise has flat frequency response spectrum.
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79.what do you understand
by a fixed-point
number?
In fixed
point arithmetic the position of the binary point is fixed. The
bit to the right
represent the
fractional part
of the number & those to
the left represent the
integer part.
For example,
the binary number 01.1100 has the value 1.75
in decimal.
80.What is the objective of spectrum estimation?
The main
objective of spectrum estimation is the determination
of the power
spectral
density of a random process. The
estimated PSD
provides information
about the structure of the random process
which can be used for modeling,
prediction or filtering of
the deserved
process.
81.List out the addressing
modes
supported by C5X processors?
1. Direct
addressing
2. Indirect
addressing
3. Immediate addressing
4. Dedicated-register addressing
5. Memory-mapped register addressing
6. Circular addressing
82.what is meant by block floating point
representation?
What
are its advantages?
In
block point arithmetic the set of signals to be
handled is divided into
blocks. Each
block
have the same value for the exponent. The
arithmetic operations
with in the block uses
fixed point arithmetic & only one exponent
per
block is stored thus saving memory. This representation
of numbers is more suitable in
certain FFT flow graph & in
digital audio applications.
83.what are the advantages
of floating point arithmetic?
1. Large dynamic
range
2. Over flow in floating point representation
is unlike.
84.what
are
the three-quantization errors to finite word
length registers in digital
filters?
1. Input
quantization
error 2. Coefficient
quantization error 3.
Product quantization
error
85.How the multiplication &
addition are carried out
in floating
point arithmetic?
In floating point
arithmetic,
multiplication are carried out as
follows,
Let f1
= M1*2c1 and f2
= M2*2c2. Then f3 = f1*f2
= (M1*M2) 2(c1+c2)
That is, mantissa is multiplied using
fixed-point arithmetic and
the exponents are added.
The sum of
two floating-point number is carried out
by
shifting the bits of
the mantissa of the smaller number to the right until the exponents of
the two numbers are equal and
then adding the mantissas.
86.What do you understand
by input quantization error?
In
digital signal
processing, the
continuous time input signals
are
converted into digital
using a b-bit ACD.
The
representation of
continuous signal amplitude by a fixed digit
produce an error,
which is known as input quantization
error.
87.List the on-chip peripherals in
5X.
The C5X
DSP
on-chip peripherals
available are as
follows:
1. Clock Generator
2. Hardware Timer
3. Software-Programmable Wait-State Generators
4. Parallel I/O
Ports
5. Host Port Interface (HPI)
6. Serial
Port
7. Buffered Serial
Port
(BSP)
8. Time-Division
Multiplexed (TDM) Serial
Port
9. User-Maskable Interrupts
88.what is the relationship
between truncation error e and the bits b for
representing
a decimal into binary?
For a 2's complement
representation,
the error due to
truncation for both positive and
negative values
of
x is 0>=xt-x>-2-b
Where b
is the number of bits and
xt is the truncated
value of x.
The equation
holds good for both
sign magnitude,
1's complement
if x>0
If x<0, then
for
sign magnitude and
for
1's complement the
truncation error satisfies.
89.what is meant rounding?
Discuss its effect on all types of number
representation?
Rounding a number to b bits is accomplished by choosing the rounded result
as the b
bit number closest to the original
number unrounded.
For fixed point arithmetic,
the error made by rounding a number to b bits
satisfy the inequality
-2-b 2-b
-----<=xt-x<= --------
2 2
for all three types of number systems,
i.e., 2's complement, 1's complement &
sign magnitude.
For floating point number the error made by rounding
a number to b bits satisfy the
inequality
-2-b<=E<=2-b where E=xt-x
-------- x
90.what is meant by A/D conversion noise?
A DSP contains
a device,
A/D converter that
operates on the analog input x(t) to
produce xq(t) which
is binary sequence of 0s
and
1s.
At first
the signal x(t) is sampled at
regular intervals
to produce a sequence x(n) is of infinite precision.
Each sample x(n) is
expressed
in terms of a finite number of bits
given
the sequence xq(n). The difference signal e(n)=xq(n)-x(n) is called A/D conversion noise.
91.what is the
effect of quantization on pole location?
Quantization of
coefficients in digital filters
lead
to slight changes in their value. This
change in
value of filter coefficients modify the pole-zero locations.
Some
times the pole locations
will be changed in such
a way that
the system may drive into
instability.
92.which realization is
less
sensitive to
the
process of quantization?
Cascade form.
93.what is meant by quantization step
size?
Let
us assume a sinusoidal
signal
varying between +1 and
-1 having a dynamic range
2. If the ADC used
to convert the sinusoidal
signal
employs b+1 bits including sign bit, the number of levels available for quantizing x(n) is 2b+1.
Thus the interval between
successive levels
q=
2 =2-b
--------
2b+1
Where q
is known as quantization step
size.
94.How would
you
relate the steady-state noise power
due
to quantization and
the
b bits representing
the
binary sequence?
Steady state noise power
Where b
is the number of bits excluding sign bit.
95.what is overflow oscillation?
The addition of two fixed-point
arithmetic numbers
cause over flow
the sum exceeds
the word size available to store the sum. This overflow caused
by
adder make the filter output to oscillate between maximum amplitude limits.
Such
limit cycles
have been referred
to as
over flow oscillations.
96.what are the methods used
to prevent overflow?
There are two
methods used to prevent
overflow
1. Saturation arithmetic 2. Scaling
97.what are the two kinds
of limit cycle behavior in DSP?
1.zero input limit cycle oscillations
2.Overflow limit cycle oscillations
98.What is meant by "dead
band" of the filter
The limit cycle occur as a result
of quantization effect
in multiplication. The
amplitudes of the output during a limit cycle are confined to a
range of values called the dead
band of the filter.
99.Explain briefly the need for
scaling in the digital filter implementation.
To prevent
overflow, the signal
level at
certain points in the digital filter must
be scaled so that no overflow
occurs in the adder.
100.What are the different
buses
of TMS320C5X and
their
functions?
The C5X
architecture has
four buses and their functions
are
as follows:
Program bus (PB):
It
carries
the instruction code and
immediate operands from
program
memory
space to the
CPU.
Program address
bus
(PAB):
It
provides addresses
to program memory space for both reads
and writes.
Data read bus (DB):
It
interconnects
various elements of
the CPU to data memory space.
Data read address bus (DAB):
It
provides the address to access
the data memory space.
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