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naresh850
Joined: 09 Jun 2006
Posts: 162
Helped: 1
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 08 Aug 2006 12:32 dsp interview questions |
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hi,
Most of you must've already passed that interview stage and some others could be the Interviewers themselves. So, I thought this thread should be helpful to everyone and anyone who is not just attending an interview but wants to know more about DSP.
The aim is simple:
If you've come across some question that you think is tricky, please post it here along with its solution by maintaining a number to it...
Just put the question in the quote tags like this
"what is the convolution"
"y we use Forrier transform in DSP"
the answer should be that mush short. we can tell the interviwer in quik.
Please contribute as even one question from you might change someone'e life out there...
hopw we do the good job.
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amit_8561
Joined: 18 Apr 2006
Posts: 56
Helped: 8
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08 Aug 2006 13:53 dsp interview question and answers |
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| "what is use of windowing in digital filters"
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radheshbhat
Joined: 14 Mar 2006
Posts: 106
Helped: 7
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09 Aug 2006 12:11 signal processing interview questions |
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| "What are basis vectors in a transofrm?"
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sarkararghya
Joined: 18 May 2006
Posts: 102
Helped: 3
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10 Aug 2006 11:19 digital signal processing interview questions |
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| In signal processing, why we are much more interested in orthogonal transform?
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itsthetimetodisco
Joined: 21 Jul 2006
Posts: 82
Helped: 2
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11 Aug 2006 17:25 interview questions on dsp |
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| "What are the pros and cons of Discrete Cosine Transform?"
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itsthetimetodisco
Joined: 21 Jul 2006
Posts: 82
Helped: 2
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13 Aug 2006 10:41 dsp interview question |
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| "What is Gibbs phenomenon?"
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nagacnu
Joined: 08 Sep 2005
Posts: 25
Helped: 4
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14 Aug 2006 0:23 dsp engineer interview questions |
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| what is the special about minimum phase filter ?
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naresh850
Joined: 09 Jun 2006
Posts: 162
Helped: 1
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14 Aug 2006 12:25 dsp interview |
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Thank u all friends,
for sending the questions & spending yr valuable time.
But this forum is not only for questions.U have to share your incridible answer to others. So everyone will get benifit from it.
Post as many questions as u know.
Hope we will do that.
regards
Added after 6 minutes:
Hi,
"What is Gibbs phenomenon?"
transfer function h(n) in time domain is infinite.
We can not implement it on DSP processor. We have to truncate it to finite lenth.
so when we truncate it. in freq domain we get the ringging at the edges.
this is called the gibbes Phenomena.
if someone have better answer then plz share to otheres.
Added after 11 minutes:
"what is use of windowing in digital filters"
because of gibbes phenomena, we get pass band ripples & stop band attenuation.
we have to remove this, we use window function.
so, different type of window we multiply with h(n).
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naresh850
Joined: 09 Jun 2006
Posts: 162
Helped: 1
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30 Aug 2006 8:33 dsp programming interview questions |
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Hi friends,
plz share yr experince.
regards,
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farhadtehrani1
Joined: 30 Aug 2006
Posts: 2
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30 Aug 2006 22:19 interview question on dsp |
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use this program: [x,fs]=wavread('1.wav');
o(1:100,1)=0
a=100*ceil (length(x)/100)
l=a+200
sum(1:l,1)=0
b=a-length(x)+100
oo(1:b,1)=0
x=[o;x;oo]
ham2=hamming(200)
ham2(201:l)=0
u=x.*ham2
u=u(1:200)
fff=fft(u,1024)
fff(129:897)=0
iff=ifft(fff,1024)
iff=iff(1:200)
sum(1:200)=iff
ham=hamming(200)
m(1:a-100,1)=0
for k=1 a/100+1)
n((100*k-99):100*k,1)=0
m=m(1l-100*k-200),1)
ham1=[n;ham;m]
y=x.*ham1
y=y(100*k+1:(100*k+200))
fff=fft(y,1024)
fff(129:897)=0
iff=ifft(fff,1024)
iff=iff(1:200)
sum((100*k+1):(100*k+200))=sum((100*k+1):(100*k+200))+iff(1:200)
for k=1a/100+1)
z=x(100*k+1:100*k+200)
y=z.*ham
fff=fft(y,1024)
fff(129:897)=0
iff=ifft(fff,1024)
iff=iff(1:200)
sum((100*k+1):(100*k+200))=sum((100*k+1):(100*k+200))+iff(1:200)
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smileysam
Joined: 19 Feb 2006
Posts: 87
Helped: 8
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19 Sep 2006 6:59 dsp engineer interview |
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why we use DCT extensilvely in compression?
why after DCt we use a zig zag manner for run length coding?
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icyabhi
Joined: 10 May 2006
Posts: 12
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19 Sep 2006 8:21 interview dsp questions |
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| Why do we need I&Q signals?
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asnivas
Joined: 07 Dec 2005
Posts: 5
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20 Sep 2006 10:48 interview questions on digital signal processing |
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| Why is FFT faster than DFT? what is the actual concept behind this?
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shameem
Joined: 27 Oct 2005
Posts: 139
Helped: 2
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21 Sep 2006 3:02 interview questions in digital signal processing |
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What is the basic difference blw FIR and IIR filters?
If a have two vectors, how will i check the orthogonality of those vectors?
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narfnarf
Joined: 07 Sep 2006
Posts: 71
Helped: 4
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21 Sep 2006 16:56 dsp interview questions and answers |
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| "differences b/w butterworth, chebyshev, elliptical filter and advantages/disadvantages of each"
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joi
Joined: 02 Aug 2006
Posts: 53
Helped: 1
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24 Sep 2006 12:59 dsp filters interview questions |
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| "What is the concept of stability of an LTI system? How to check if a given system is stable?"
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electricpete
Joined: 04 Jun 2006
Posts: 262
Helped: 5
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24 Sep 2006 14:58 digital signal processor interview questions |
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The original poster asked for answers so I repeat some of the earlier questions (and add some new) with answers.
Q. How can you determine the stability of an LTI system
A. Determine the roots of the system. If all roots have real part < 0, the system is stable. Any root has real part > 0, the system is unstable.
Q. What is aliasing and how do we prevent it.
A. Aliasing is frequency shifting of content of input signal above half the sample frequency. We avoid it by using antialiasing filters to limit signal content below 1/2 sample frequency and/or by sampling at high enough frequency to avoid antialiasing.
Q. Explain using convolution the effects of taking an FFT of a sampe with no windowing (rectangular window).
A. The signal is multiplied by a rectangular window in the time domain. This corresponds to convolution by a sync function in the frequency domain. The wide center lobe of the sync function spreads frequencies and the side lobes shift frequencies.
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Robinenemy
Joined: 10 Jul 2006
Posts: 119
Helped: 15
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24 Sep 2006 17:15 dsp firmware interview questions |
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1. What is the need of Digital Signal Processing?
2. Why is the need of FFT ?
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naresh850
Joined: 09 Jun 2006
Posts: 162
Helped: 1
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08 Oct 2006 7:53 signal processing interview question |
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hi
1. wat care should be taken when we doing camulative decimation
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111111
Joined: 17 Nov 2005
Posts: 103
Helped: 3
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13 Oct 2006 9:02 digital signal processing question for interview |
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I have a very important question.
What is the importance of time frequency resolution? Can this be explained with respect to some application eg when we need to determine the stationary and dynamic characteristic of a signal, how do transform with different time frequency resolution, affects it. I do not want simple and vague explanation given in textbooks. I require correct and precise information.
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Google
AdSense
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13 Oct 2006 9:02 Ads |
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rsrinivas
Joined: 10 Oct 2006
Posts: 419
Helped: 36
Location: bengalooru
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13 Oct 2006 11:46 dsp interview questions and answer |
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Hi
Time and frequency are two important aspects in which time and frequency are the inverse of each other.Hence if u have a small frequency it is spread out in large time and vice versa. Just u can analyze a time frequency plot.
So when we try to analyze non stationary signals these values continuously change and the properties of FFT do not hold for non stationary signals for which u need to go to either Short term Fourier trnasform or the wavelet analysis.
Each has it's own adv and disadv.
I have a good HTML on this issue.It gives a good introduction to the topic.
cheers
srinivas
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rsrinivas
Joined: 10 Oct 2006
Posts: 419
Helped: 36
Location: bengalooru
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14 Oct 2006 9:05 interview questions + dsp |
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pls review this.
How toget a magnitude response of a quantized filter.
Any noise estimation has to be done??
cheers
srinivas
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lena
Joined: 01 Jul 2006
Posts: 18
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22 Feb 2007 7:05 dsp basic questions |
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What is the basic difference blw FIR and IIR filters?
basic difference is FIR has liner phase response,where has IIR filter has nonlinear phase response.
why we use DCT extensilvely in compression?
DCT has excellent energy compaction property, for highly correlated input it give excellent energy compaction similar to KL transform.
why after DCt we use a zig zag manner for run length coding?
to convert to 2d to 1d data for run lenth coding, zig-zag is prefered because it scan the 2d data from low frequency to high frequency coef.
what is the special about minimum phase filter ?
minimum phase system has both poles and zeors reside in side unit circle, these are basically used for
compensating channel impairments.
"differences b/w butterworth, chebyshev, elliptical filter and advantages/disadvantages of each"?
butter worth -monotonic response in pass band and stop band.
chebyshev-1 ripple in pass band, and monotonic in stop band.
chebyshev-2 monotonic in passband ripple in stop band.
elliptic- ripple response both in passband &stop band.
for given set of parameters we can achive minimum transistion band width with elliptic filter , other way
we can implement with fewer number of coef than other methods
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helios
Joined: 03 Jun 2005
Posts: 166
Helped: 12
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22 Feb 2007 12:55 dsp questions |
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how can you compute fourier transform form Z-transform ?
Why IIR filters doesnt have Linear phase?
Can IIR filters be Linear phase? how to make it linear Phase?
What is the advantage of a Direct form II FIR over fom I?
Tell some thing about Interpolation and decimation?
What is Interpolation and decimation filters and why we need it?
FFT is in complex domain, how to use it in real life signals optimally?
what is the simplest high pass filter ? write the equation?
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csaspp
Joined: 02 Feb 2007
Posts: 52
Helped: 22
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22 Feb 2007 20:20 interview questions signal processing |
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what is the difference between DFT and DTFT?
what do u mean by spectral resolution?
how do u reduce spectral leakage?
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lena
Joined: 01 Jul 2006
Posts: 18
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23 Feb 2007 14:27 basic dsp questions |
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how can you compute fourier transform form Z-transform ?
z =r*e(-iw) when r=1 Z-transform converges to discrete Fourier tranform.
Why IIR filters doesnt have Linear phase?.
Liner phase IIR filter cannot physically realizable , its unstable.
Can IIR filters be Linear phase? how to make it linear Phase?
Idealy Physically realizable doesnt have linear phase, but we can implement IIR filter with linear phase response in passband. (refer Bessel series Approx)
What is the advantage of a Direct form II FIR over fom I?
i think Direct form -2 take less memory (not sure)
Tell some thing about Interpolation and decimation?
Intepolation basically filling missing samples,
decimation basically reducing the sample rate.
What is Interpolation and decimation filters and why we need it?
interpolation for reconstruction and for sample rate up conversion.
deciamtion filter sample rate down conversion.
FFT is in complex domain, how to use it in real life signals optimally?
use two diiferent buffers for real & complex
what is the simplest high pass filter ? write the equation?
give me some precise more details
Hp= 1- Lp
Added after 5 minutes:
what is the difference between DFT and DTFT?
DFT = spectrum of DFT also discrete in nature,where as spectrum of DTFT is continuous.
what do u mean by spectral resolution?
i think its separetion of two signal in frequency domain.
how do u reduce spectral leakage?
By incresing the window lenth in time domain we can reduce spectral leakage.
Added after 12 minutes:
Why is FFT faster than DFT? what is the actual concept behind this?
FFT is an algorithm to implement DFT , FFT is not at all a tranform,
if u implement Directly it take (N^2) complex Multiplications and (N^2 -N) complex additions , where as FFT will Nlog2(N) complex Mul & additions
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lena
Joined: 01 Jul 2006
Posts: 18
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01 Mar 2007 5:56 dsp viva questions |
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whats basic difference b/w winer filter and kalman filter and lms filter
Added after 5 minutes:
pls give me some points
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gowthamn
Joined: 06 Apr 2006
Posts: 38
Helped: 1
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02 Mar 2007 6:44 signal processing based interview questions |
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What is the application fo Cross correlation and Auto Correlation?
What is Auto Regressive Model? How is the order of auto regressive model is decided?
What is the difference between equiripple filter and FIR filter?
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lena
Joined: 01 Jul 2006
Posts: 18
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02 Mar 2007 11:07 interview questions digital filters |
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What is the application fo Cross correlation and Auto Correlation?
Cross correlation is used to find the similarities of two signals if its +1 or -1 it means its highly correlated and 0 signifies signals are uncorrelated
What is the difference between equiripple filter and FIR filter?
Equiripple filter means it has eual number of ripples in pass band and stop band
and its one of methos to implement filter design.
FIR filter is finate impluse response filter
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aditya6355
Joined: 25 Sep 2006
Posts: 1
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29 Oct 2007 4:35 interview questions dsp |
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1. Under what conditions is the available bandwidth of a digital system
Fs Hz instead of Fs/2 Hz?
2. What's the difference between an FFT and a DFT?
3. What two PSK modulation orders differ exactly by a factor of two
in spectral efficiency?
4. How does polyphase filtering save computations in a decimation filter?
5. How does polyphase filtering save computations in an interpolation filter?
6. Suppose we have a system with transfer function
H(z) = 1 / ((z - 1.1)*(z - 0.9)).
Is the system stable or unstable?
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