Interview Questions.

Q1. Distinguish Between Linear Convolution And Circular Convolution Of Two Sequences?

Linear convolution:

If x(n) is a sequence of L variety of samples and h(n) with M quantity of samples, after convolution y(n) can have N=L+M-1 samples.

It can be used to locate the reaction of a linear filter out.

Zero padding isn't necessary to find the reaction of a linear clear out.

Circular convolution:

If x(n) is a chain of L variety of samples and h(n) with M samples, after convolution y(n) may have N=max(L,M) samples.

It can't be used to find the reaction of a filter out.

Zero padding is necessary to find the reaction of a clear out.

Q2. What Are The Different Types Of Arithmetic In Digital Systems.?

There are 3 styles of arithmetic used in digital systems. They are fixed point mathematics, floating factor ,block floating point arithmetic.

Q3. How One Can Design Digital Filters From Analog Filters?

Map the desired virtual clear out specifications into the ones for an equal analog filter out.

Derive the analog trfer characteristic for the analog prototype.

Trform the trfer function of the analog prototype into an equivalent virtual filter out trfer characteristic.

Q4. What Is Rounding?

Rounding a variety of to b bits is achieved via selecting a rounded result because the b bit range closest number being unrounded.

Q5. Define Periodic And Aperiodic Signal?

A sign x (n) is periodic in length N, if x (n+N) =x (n) for all n. If a sign does not fulfill this equation, the sign is referred to as aperiodic sign.

Q6. What Are The Elementary Discrete Time Signals?

Unit sample sequence (unit impulse)

δ (n)= 1 n=0

0 Otherwise

Unit step sign

U (n) = 1 n>=zero

zero Otherwise

Unit ramp signal

Ur(n)=n for n>=0

0 Otherwise

Exponential sign

x (n)=an where a is real

x(n)-Real signal

Q7. What Are The Different Quantization Methods?

Truncation and Rounding

Q8. How Many Multiplications And Additions Are Required To Compute N Point Dft Using Radix-2 Fft?

The range of multiplications and additions required to compute N factor DFT using radix-2 FFT are N log2 N and N/2 log2 N respectively,.

Q9. State The Structure Of Iir Filter?

IIR filters are of recursive type whereby the prevailing o/p pattern depends on gift i/p, beyond i/p samples and o/p samples. The design of IIR filter is realizable and stable.

The impulse response h(n) for a realizable filter is

h(n)=0 for n≤zero

Q10. What Is Bilinear Trformation?

The bilinear trformation is a mapping that trforms the left 1/2 of S-aircraft into the unit circle inside the Z-aircraft handiest once, thus keeping off aliasing of frequency components.

The mapping from the S-aircraft to the Z-aircraft is in bilinear trformation is

S=2/T(1-Z-1/1+Z-1)

Q11. What Are The Advantages & Disadvantages Of Bilinear Trformation?

Advantages:

The bilinear trformation affords one-to-one mapping.

Stable continuous structures can be mapped into realizable, stable virtual structures.

There is not any aliasing.

Disadvantage:

The mapping is enormously non-linear generating frequency, compression at excessive frequencies.

Neither the impulse response nor the section reaction of the analog filter is preserved in a virtual filter out obtained by means of bilinear trformation.

Q12. Mention The Procedures For Digitizing The Trfer Function Of An Analog Filter.?

The two important techniques for digitizing the trfer characteristic of an analog filter out are:

Impulse invariance technique. 

Bilinear trformation approach.

Q13. Define Time Variant And Time Invariant System?

A system is called time invariant if its output , input traits dos now not exchange with time.

E.G.Y(n)=x(n)+x(n-1)

A machine is known as time variant if its enter, output characteristics adjustments with time.

E.G.Y(n)=x(-n).

Q14. What Is Truncation?

Truncation is a method of discarding all bits much less big than LSB that is retained

Q15. Define Dynamic And Static System?

A discrete time gadget is known as static or reminiscence less if its output at any immediate n depends almost at the enter pattern on the identical time however no longer on beyond and future samples of the input.

E.G. Y(n) =a x (n)

In anyother case the gadget is said to be dynamic and to have memory. 

E.G. (n) =x (n)+3 x(n-1)

Q16. Why The Computations In Fft Algorithm Is Said To Be In Place?

Once the butterfly operation is completed on a pair of complex numbers (a,b) to supply (A,B), there's no need to store the enter pair. We can keep the result (A,B) within the identical locations as (a,b). Since the identical storage places are used troughout the computation we say that the computations are executed in place.

Q17. State The Methods For Evaluating Inverse Z-trform.?

Direct valuation by way of contour integration.

Expion into collection of phrases in the variable Z and Z-@

Partial fraction expion and look up desk.

Q18. What Is Product Quantization Error?

The product quantization errors stand up on the out placed of the multiplier. Multiplication of a b bit statistics with a b bit coefficient effects a product having 2b bits. Since a b bit register is used the multiplier output will be rounded or truncated to b bits which produces the mistake.

Q19. Define Stable And Unable System?

A device is said to be strong if we get bounded output for bounded input.

Q20. What Is Meant By Fixed Point Number?

In constant point number the location of a binary point is fixed. The bit to the proper constitute the fractional part and people to the left is integer component.

Q21. State Properties Of Roc.?

The ROC does no longer include any poles.

When x(n) is of finite length then ROC is complete Z-aircraft except Z=0 or Z=∞.

If X(Z) is causal,then ROC includes Z=∞.

If X(Z) is anticasual,then ROC consists of Z=@

Q22. What Are The Methods To Prevent Overflow?

Saturation arithmetic and

Scaling

Q23. What Are The Quantization Errors Due To Finite Word Length Registers In Digital Filters?

Input quantization mistakes

Coefficient quantization mistakes

Product quantization mistakes

Q24. What Is The Principle Of Designing Fir Filter Using Frequency Sampling Method?

In frequency sampling approach the favored importance response is sampled and a linear segment response is targeted .The samples of preferred frequency response are recognized as DFT coefficients. The clear out coefficients are then decided because the IDFT of this set of samples.

Q25. What Are The Design Techniques Of Designing Fir Filters?

There are three well known methods for designing FIR filters with linear section .They are (1.)Window technique (2.)Frequency sampling technique (3.)Optimal or minimax design.

Q26. What Is Fft?

The Fast Fourier Trform is an set of rules used to compute the DFT. It makes use of the symmetry and periodicity homes of twiddle issue to efficaciously reduce the DFT computation time.It is based on the essential precept of decomposing the computation of DFT of a series of length N into successively smaller DFTs.

Q27. What Are The Advantages Of Floating Point Representation?

Large dynamic variety

Overflow is not likely.

Q28. What Are The Different Types Of Fixed Point Arithmetic?

Depending on the negative numbers are represented there are three varieties of fixed factor arithmetic. They are signal significance,1’s supplement,2’s supplement

Q29. State The Properties Of Dft?

Periodicity

Linearity and symmetry

Multiplication of  DFTs

Circular convolution

Time reversal

Circular time shift and frequency shift

Complex conjugate

Circular correlation

Q30. What Is Overlap-store Method?

In this technique the information sequence is split into N point sections xi(n).Each section includes the ultimate M-1 records points of the previous segment accompanied by L new data points to shape a records series of length N=L+M-1.In round convolution of xi(n) with h(n) the first M-1 factors will not consider the linear convolution of xi(n) and h(n) due to aliasing, the remaining factors will trust linear convolution. Hence we discard the first (M-1) points of filtered section xi(n) N h(n). This manner is repeated for all sections and the filtered sections are abutted together.

Q31. Write A Short Note On Pre-warping.

The impact of the non-linear compression at excessive frequencies may be compensated. When the preferred magnitude reaction is piece-clever consistent over frequency, this compression may be compensated by means of introducing a appropriate pre-scaling, or pre-warping the important frequencies by means of the use of the formulation.

Q32. What Dif Algorithm?

It is a popular shape of the FFT algorithm. In this the output collection X(okay) is split into smaller and smaller sub-sequences , that is why the name Decimation In Frequency.

Q33. Distinguish Between Fir Filters And Iir Filters?

FIR filter:

IR filter out

These filters may be without difficulty designed to have perfectly linear segment.

FIR filters may be found out recursively and non-recursively.

Greater flexibility to control the shape of their significance response.

Errors due to round off noise are much less extreme in FIR filters, especially because comments isn't always used.

IIR clear out:

These filters do now not have linear segment.

IIR filters are without difficulty found out recursively.

Less flexibility, usually restrained to particular sort of filters.

The round off noise in IIR filters is more.

Q34. What Are The Advantages Of Kaiser Window?

It provides flexibility for the dressmaker to pick the facet lobe degree and N

It has the attractive belongings that the facet lobe stage can be varied continuously from the low price in the Blackman window to the excessive fee within the rectangular window

Q35. What Are The Different Types Of Filters Based On Impulse Response?

Based on impulse response the filters are of two sorts:

IIR filter out

FIR filter out

The IIR filters are of recursive type, whereby the present output pattern relies upon on the existing enter, beyond enter samples and output samples.

The FIR filters are of non recursive kind, whereby the prevailing output pattern depends on the existing enter sample and previous input samples.

Q36. What Is Zero Padding?What Are Its Uses?

Let the sequence x(n) has a duration L. If we need to locate the N-point DFT(N>L) of the collection x(n), we must upload (N-L) zeros to the sequence x(n). This is known as zero padding.

The makes use of of zero padding are:

We can get better display of the frequency spectrum.

With 0 padding the DFT may be used in linear filtering.

Q37. What Is Dit Algorithm?

Decimation-In-Time algorithm is used to calculate the DFT of a N factor series. The idea is to interrupt the N factor collection into two sequences, the DFTs of which can be mixed to offer the DFt of the

authentic N factor series.This algorithm is known as DIT because the sequence x(n) is often splitted into smaller sub- sequences.

Q38. What Are Differences Between Overlap-store And Overlap-upload Methods?

Overlap-store technique:

In this approach the dimensions of the enter data block is N=L+M-1

Each statistics block includes the final M-1 records points of the preceding records block observed with the aid of L new records points

In every output block M-1 points are corrupted because of aliasing as round convolution is employed

To form the output series the first

M-1 records points are discarded in every output block and the closing records are equipped collectively

Overlap-upload approach:

In this method the size of the input records block is L

Each facts block is L points and we append M-1 zeros to compute N factor DFT

In this no corruption due to aliasing as linear convolution is executed using circular convolution

To form the output collection the closing

M-1 points from each output block is brought to the primary M-1 points of the succeeding block

Q39. What Is Overlap-add Method?

In this method the size of the input facts block xi(n) is L. To each records block we append M-1 zeros and carry out N point circular convolution of xi(n) and h(n). Since every records block is terminated with M-1 zeros the remaining M-1 factors from every output block have to be overlapped and brought to first M-1 points of the succeeding blocks.This technique is referred to as overlap-upload method.

Q40. Define Discrete Time System?

A discrete or an algorithm that performs a few prescribed operation on a discrete time sign is called discrete time device.

Q41. Define Symmetric And Antisymmetric Signal?

A real value signal x (n) is called symmetric (even) if x (-n) =x (n). On the other hand the sign is referred to as antisymmetric (atypical) if x (-n) =x (n).

Q42. What Is Input Quantization Error?

The filter coefficients are computed to infinite precision in principle. But in virtual computation the clear out coefficients are represented in binary and are stored in registers. If a b bit sign up is used the clear out coefficients must be rounded or truncated to b bits ,which produces an errors.

Q43. When Cascade Form Realization Is Preferred In Fir Filters?

The cascade form attention is desired while complex zeros with absolute importance is less than one.

Q44. What Is Trposition Theorem & Trposed Structure?

The trpose of a structure is defined by the subsequent operations:

Reverse the directions of all branches inside the sign drift graph

Interchange the enter and outputs.

Reverse the roles of all nodes within the waft graph.

Summing points turn out to be branching points.

Branching factors become summing factors.

According to trposition theorem if we reverse the guidelines of all department trmittance and interchange the input and output inside the flowgraph, the system feature remains unchanged.

Q45. Define Sectional Convolution?

If the statistics sequence x(n) is of lengthy length it's far very difficult to gain the output series y(n) because of constrained reminiscence of a virtual computer. Therefore, the information series is divided up into smaller sections. These sections are processed separately separately and managed later to get the output.

Q46. What Is Meant By Radix-2 Fft?

The FFT set of rules is maximum green in calculating N factor DFT. If the quantity of output points N may be expressed as a electricity of 2 this is N=2M, in which M is an integer, then this set of rules is known as radix-2 algorithm.

Q47. State Some Applications Of Dsp?

Speech processing ,Image processing, Radar signal processing.

Q48. Define Discrete Time Signal?

A discrete time signal x (n) is a feature of an independent variable that is an integer. A discrete time signal isn't always described at instant among  successive samples.

Q49. What Are The Applications Of Fft Algorithm?

The programs of FFT algorithm consists of:

Linear filtering

Correlation

Spectrum analysis

Q50. What Is Meant By Floating Pint Representation?

In floating point shape the fantastic wide variety is represented as F =2CM,wherein is mantissa, is a fragment such that1/2<M<1and C the exponent may be either positive or terrible.