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ECE :: Communication Systems

  1. A narrow band noise n(t) has symmetrical spectrum and has power density spectrum 0.2 x 10-6. The power density of quadrature component is

  2. A.
    0.2 x 10-6
    B.
    10-7
    C.
    4 x 10-7
    D.
    5 x 10-8

  3. The radio receivers mostly used now a days are

  4. A.
    TRF receivers
    B.
    super heterodyne receivers
    C.
    CW receivers
    D.
    pulsed receivers

  5. The reactance of coupling capacitors, for DC quantities, is

  6. A.
    zero
    B.
    low
    C.
    infinite
    D.
    zero or low

  7. An AM wave is given by s(t)AM = 20 (1 + 0.5 cos 103t + 0.3 cos 104 t cos 106 t) the modulation index of the envelope is

  8. A.
    0.5
    B.
    0.58
    C.
    0.3
    D.
    0.8

  9. The modulating frequency in frequency modulation is increased from 10 kHz to 30 kHz. The bandwidth is increased by

  10. A.
    6
    B.
    1/6 times
    C.
    increase by 30 kHz
    D.
    increase by 20 kHz

  11. A sinusoidal signal with peak to peak amplitude of 1.536 volt is quantized into 128 levels using a mid-rise uniform quantizer. The quantization noise power is

  12. A.
    0.768 V
    B.
    48 x 10-6 V
    C.
    12 x 10-6 V
    D.
    3.072 Volt

  13. An FM wave is made to pass through a frequency tripler. If original modulation index is mf, the output of tripler has a modulation index equal to

  14. A.
    mf
    B.
    mf
    C.
    3 mf
    D.
    mf

  15. A balun provides an impedance transformation of

  16. A.
    16 : 1
    B.
    8 : 1
    C.
    4 : 1
    D.
    2 : 1

  17. If γ = (S0/N0)/(Si/Nm) where S0 and S1 are signal power output and signal power input and N0 and Nm are noise power output and noise power input, the value of γ for SSB-SC and DSB-SC amplitude modulated system respectively are

  18. A.
    1 and 1
    B.
    1 and 2
    C.
    2 and 1
    D.
    0.5 and 0.5

  19. Consider the draw backs

    1. Slope overload
    2. Serration noise
    3. Granular noise
    Which of these draw backs does Delta modulation have?

  20. A.
    1 and 2 only
    B.
    2 and 3 only
    C.
    1 and 3 only
    D.
    1, 2, 3