Interview Questions on DSP - Open Thread - Please Contribute

digital signal processing viva

choose true or false . if true/false explain how
FIR filters require fewer computation then IIR filter for the same frequency response.

what questions will they ask in a dsp interview

rramya said:

choose true or false . if true/false explain how
FIR filters require fewer computation then IIR filter for the same frequency response.

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False..... for same filter specs FIR requires filter coedds in 1000s

Re: interview questions dsp

aditya6355 said:

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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Hi,

Thanks very much for this comment. I was actually hired from another interview I had. I'm sure this thread will be useful for others though.

Rgs.

Re: dsp interview question and answers

amit_8561 said:

"what is use of windowing in digital filters"

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Buffering all the many hours signal in an array is difficult.
Buffering all real time data in an array is not only difficult but also impossible.
So we process it part by part, now to avoid discontinuities in frames we use non-rectangular windows. How we do it is a different question !!

nagacnu said:

what is the special about minimum phase filter ?

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smileysam said:

why we use DCT extensilvely in compression?

why after DCt we use a zig zag manner for run length coding?

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I general , in time domain

1hz= 1cycle per sec
2hz= 2cycle per sec
100hz= 100 cycle per sec ,
1000hz= 1000 cycles per sec , hard to count in this case

In time domain its very hard to count number of cycles per sec to we have gone for Frequency domain in which we will get exact peak at the respective frequency,

in frequency domain there are many errors such as

2 peaks in the same plot, and side lobes.

So here the DCT & DST originated , As Fourier transforms has (e^jw) i.e sine and cos terms. The DCT will Pic up informative samples in FFT. Due to this this memory is conserved.

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shameem said:

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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A1) The basic Difference is the Transfer function. hope you know it , Fir is Non-recursive (no feed back) IIr is Recursive.If we go on there are lot to say such as designing , ripples.

The condition for orthogonality is when the cross co-relation of two signal is equal to zero .

Why does an RC filter never reach it's destination and become the simplest Infinite Impulse Response filter?
How can we measure that? we can't. not enough resolution.

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Here were my favorite questions back in 1980 when I interviewed students for Test Engineers to test their analog skills on digital logic.

1. What is the DC gain of an unbuffered CMOS inverter at midrange on input? (which has not changed for 40 yrs AFAIK)

2. What precisely is the Threshold for TTL in words without numbers, where the output becomes a linear amplifier ( for any operating temperature)? THis is not VIL or VIH.

Place your bets/votes and/or your answers folks. There is a huge (sur)PRIZE for the right answers. really.

Embeded sysytems implimentation point of veiw, which is better and easier fft or dct.

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which algorithm need less processing time and why, fft or dct ?

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what are the advantages of DSP over Analoge Processing?