TECHNICAL QUIZ-I

EC6501 DIGITAL COMMUNICATION

YEAR-III SEM-V

1. What is the first Communication system used?

A) TelephonyB) Telegraphy C) Analog Transmission system D) None of the above

2) Which does not belong to analog pulse modulation?

A) Pulse Amplitude modulation B) Pulse Position modulationC)Pulse Width modulation D)Pulse Code modulation

3) Which of the given communication medium offers very high speed?

A) Microwave B) Optical C) WLAN D) Coaxial

4) What is the interval between frequencies at which spectrum, Gx(f) dropped 3dB below the peak value is called as?

A) Null-null bandwidth B) Fractional power containment bandwidthC) Half power bandwidth D) Absolute bandwidth

5) What is the width of the main spectral lobe, where most of the signal power contained is called as?

A) Null-null bandwidth B) Fractional power containment bandwidthC) Half power bandwidth D)Absolute bandwidth

6) Which Bandwidth is infinite for all the realizable waveforms?

A) Null-null bandwidth B) Fractional power containment bandwidthC) Half power bandwidth D)Absolute bandwidth

7) What is Symbol or Baud rate?

A) Bits per second B) Bytes per secondC) Symbols per secondD) none of the above

8) What is the Bandwidth of the digital signal , (given Rs , the symbol rate)?

A) B = RS / 2

B) B = 2RS

C) B = RS * T0

D) B = RS / T0

9) What is the carrier and message signal in an analog Pulse Communication system?

A) Carrier = Pulse, Message = PulseB) Carrier = analog, Message = PulseC) Carrier =analog, Message = PulseD)Carrier = Pulse, Message = analog

10) Which modulation varies the amplitude of the carrier wave in accordance with that of the message signal?

A) Pulse modulation B) Amplitude modulationC) Frequency modulation D)Angle modulation

11) What is the Unit of Bit error rate?

A) bit / sec B) B) byte/sec C) symbols/sec D) no unit

12) What is the property to which the Additive noise channel is related with?

A) Gaussian probability distribution B) additive noiseC) Uniform Spectral density D) all the above

13) What is the other name for AWGN Noise channel model ?

A) Linear filter channel B) Linear time variant channelC)Additive noise channel D)None of the above

14) Which is called the figure of merit of the digital communication?

A) Spectral densityB) Power efficiency C) Spectral efficiencyD) BER

15) What is GSOP?

A) Gram Schmidt Orthogonalisation Principle B) General Schmidt Orthogonalisation PrincipleC) Gram Schmidt Orthogonalisation ProcedureD) Gram Schmidt Orthogonalisation Problem

16) What is obtained from GSOP?

A) Basis set B) Dimension of the signal spaceC) Basis functionsD) signal space

17) Which channel requires Repeater?

A) Free Space broadcastB) Wireless LANC) Coaxial Cable D) None

18) Which modulation is affected by the Aperture effect?

A) PAMB) PPMC) PWMD) PCM

19) What is the value of the inner product for orthonormal basis functions?

a)oneB) zero C)twice their valueD)square of the value

20) Which block coverts analog signal into digital signal?

A) FormatterB) EncoderC) Sampler D) Quantiser

21. Which is the first process performed in analog to digital conversion?

A)oneB) zero C)twice their valueD)square of the value

22. What is the Nyquist interval ?

A)2W samples per sec B) 1/2W samples per secC)1/2W secondsD)2W seconds

23. Which Sampling is used for reconstructing a waveform on real time basis?

A)Flat top samplingB)Impulse samplingC) Natural sampling D)None of the above

25) What is the condition to avoid anti-aliasing, given Fs and Fm are sampling & modulating frequency?

A) Fs < 2Fm B) Fs > 2Fm C) Fs = 2Fm D)Fm > 2Fs

26) What is the discrete representation of the message signal is called as?

A)Sampling B)Quantization C)Encoding D)Formatting

27. What is the spacing between two adjacent representation levels ?

A)Step size B)Quantum size C)Reconstruction level D)Both A & B

28) Which Quantizer has maximum quantization error ?

A) Midtread B) Midriser C) Biased D) None of the above

29) What is the Crest factor?

A)Rms Value / Peak Value B)Rms Value * Peak Value C) Peak value / Rms Value D)2* peak value

30) What is the process of Compression and expansion in PCM is called as?

A) Uniform Quantisation B) Non-uniform quantizationC) Companding D) Tappered quantizing levels

31. Which is not a temporal waveform coding?

A)DM B) DPCM C)LPC D)PCM

31) Which Noise affects a PCM system?

A) Aliasing noise B)Channel noise C) Quantisation noise D)All

33) Which of them does not belong to source coding?

A)DPCMB)DMC)ADMD) PCM

34) What is the sampling rate value for Delta Modulation?

A) 2 * Nyquist rate B) 3 * Nyquist rate C)4 * Nyquist rate D) none of the above

35) What is the Reason for Slope overload distortion ?

A) Step size is too large B)Step size is too smallC)BothD)None

36) Which coding performs a spectral channelization by a bank of narrow filters?

A) Sub band coding B) Adaptive Sub band codingC)Adaptive Transform coding D)Model based coding

37) Which coding is a powerful speech analysis technique to estimate the basic speech parameters?

A) Sub band codingB) Adaptive Sub band codingC)Linear Predictive coding D)Model based coding

38) What is the difference between the input signal m(t) and the output quantized signal mq(t) is called as?

A) quantisation B)quantization noise C)quantization error D)both B & C

39) What is the SNR of a PCM system with L representation levels?

A) L2

B) 2L2

C) 3L2 D) 4L2

39) What is meant by binary frequency shift keying (BFSK)?

a)  Shifting two frequencies to key a microphone b)  Using two distinctly different frequencies to represent digital 0s and 1s c)  Shifting digital information at a binary frequencyd)  Half of quadrature shift keying

40) Which of the following item affects the bit error rate (BER) of a received signal?a)  Oscillator phase noise b)  Baseband filteringc)  Carrier suppression d)  All the above

41) What frequency is allowed by the Federal Communications Commission (FCC) for each FM station?

A) 20 KHz B) 100 KHz C) 200 KHz D) 300Khz

42)Which modulation allows the amplitude of the carrier signal to be varied to represent data, with both frequency and phase remaining constant?

A) ASK B) PSK C) FSK D) QAM

43)What frequency is allowed by the Federal Communications Commission for each AM station?

A) 5 KHzB) 10 KHzC) 20 KHzD) 200KHz

44) How many carrier frequencies are used in BFSK?

A) 2B) 1C) 0D) 3

45) How many carrier frequencies are used in BASK?

A) 2 B) 1 C) 0 D) 3

46) What Conversion happens in AM and FM?A) digital-to-digital B) digital-to-analog C) analog-to-analog D) analog-to-digital

47) What Conversion happens in ASK, PSK, FSK, and QAM ?

A) digital-to-digital B) digital-to-analog C) analog-to-analog D) analog-to-digital

48) Which transmission allows the carrier signal to be modulated so that its amplitude varies with the changing amplitudes of the modulating signal?

A) AM B) PM C) FM D) DM

49) Which transmission allows the phase of the carrier signal to be modulated to follow the

changing voltage level (amplitude) of themodulating signal?

A) AM B) PM C) FM D) DM

50) Which modulation allows the frequency of the carrier signal to be varied to represent data, with both peak amplitude and phase remaining constant?

A) ASK B) PSK C) FSK D) QAM