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Digital Signal Processing - Applications of DSP - Important Short Questions and Answers: Applications of DSP

**APPLICATIONS OF DSP**

**1. What
is the need for multirate signal processing?**

In real
time data communication we may require more than one sampling rate for processing
data in such a cases we go for multi-rate signal processing which increase
and/or decrease the sampling rate.

**2. Give
some examples of multirate digital systems. **

Decimator
and interpolator

**3. Write
the input output relationship for a decimator. **

Fy = Fx/D

**4. Write
the input output relationship for an interpolator. **

Fy = IFx

**5. What
is meant by aliasing?**

The
original shape of the signal is lost due to under sampling. This is called
aliasing.

**6. How
can aliasing be avoided? **

Placing a
LPF before down sampling.

**7. How
can sampling rate be converted by a factor I/D. **

Cascade
connection of interpolator and decimator.

**8. What
is meant by sub-band coding?**

It is an
efficient coding technique by allocating lesser bits for high frequency signals
and more bits for low frequency signals.

**9. What
is meant by up sampling? **

Increasing
the sampling rate.

**10. What
is meant by down sampling? **

Decreasing
the sampling rate.

**11. What
is meant by decimator?**

Down
sampling and a anti-aliasing filter.

**12. What
is meant by interpolator?**

An
anti-imaging filters and Up sampling.

**13. What
is meant by sampling rate conversion?**

Changing
one sampling rate to other sampling rate is called sampling rate conversion.

**14. What
are the sections of QMF. **

Analysis
section and synthesis section.

**15.
Define mean.**

Mxn=E[xn]=intg
xpxn(x,n) dx

**16.
Define variance. **

Zxn2=E[{xn=mxn}2]

**17.
Define cross correlation of random process. **

R xy
(n.m)= intxy*pxn,ym(x,n,y,m)dxdy.

**18.
Define DTFT of cross correlation**

Txy(e jw)
= x rxy(l) e jwl

**19. What
is the cutoff frequency of Decimator? **

Pi/M
where M is the down sampling factor

**20. What
is the cutoff frequency of Interpolator? **

Pi/L
where L is the UP sampling factor.

**21. What
is the difference in efficient transversal structure? **

Number of
delayed multiplications are reduced.

**22. What
is the shape of the white noise spectrum? **

Flat
frequency spectrum.

**Glossary:**

**Sampling Rate:**

The No.
of samples per cycle given in the signal is termed as sampling rate of the
signal .The samples occur at T equal intervals of Time.

**Sampling Theorem:**

Sampling
Theorem states that the no. of samples per cycle should be greater than or
equal to twice that of the frequency of the input message signal.

**Sampling Rate Conversion:**

The
Sampling rate of the signal may be increased or decreased as per the
requirement and application. This is termed as sampling rate Conversion.

**Decimation:**

The
Decrease in the Sampling Rate are termed as decimation or Downsampling. The No.
of Samples per Cycle is reduced to M-1 no. of terms.

**Interpolation:**

The
Increase in the Sampling rate is termed as Interpolation or Up sampling. The
No. of Samples per Cycle is increased to L-1 No. of terms.

**Polyphase Implementation:**

If the
Length of the FIR Filter is reduced into a set of smaller filters of length k.
Usual upsampling process Inserts I-1 zeros between successive Values of x(n).
If M Number of Inputs are there, Then only K Number of Outputs are non-zero.
These k Values are going to be stored in the FIR Filter.

**Narrow band Filters:**

If we
want to design a narrow passband and a narrow transition band, then a lowpass
linear phase FIR filters are more efficiently implemented in a Multistage
Decimator – Interpolator.

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