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ECE :: Communication Systems

  1. In a 4-ary FSK, the frequencies are separated by fs. Then they are

  2. A.
    in phase
    B.
    in phase opposition
    C.
    orthogonal
    D.
    none of the above

  3. In cell communication, cell stands for

  4. A.
    Geographical Area
    B.
    Battery
    C.
    Location
    D.
    No meaning

  5. In which of the following frequency bands are the standard AM radio broadcast stations?

  6. A.
    MF
    B.
    HF
    C.
    VHF
    D.
    UHF

  7. The frequency tolerance for the RF carrier in the standard AM radio broadcast band is

  8. A.
    zero
    B.
    +20 Hz
    C.
    +1000 Hz
    D.
    +25 Hz

  9. If carrier is modulated by a digital bit stream having one of the possible phases of 0°, 90°, 180°, and 270°, then modulation is called

  10. A.
    BPSK
    B.
    QPSK
    C.
    QAM
    D.
    MSK

  11. In FM, the frequency deviation is

  12. A.
    always constant
    B.
    directly proportional to modulating frequency
    C.
    inversely proportional to modulating frequency
    D.
    proportional to amplitude of modulating signal

  13. If fh(t) is the Hilbert transform of f(t), and f(t) is a real valued signal, the pre-envelope of f(t) is

  14. A.
    f(t) - jfh(t)
    B.
    f(t) + jfh(t)
    C.
    fh(t) + jf(t)
    D.
    fh(t) - jf(t)

  15. Speech amplifiers are usually operated as

  16. A.
    class A
    B.
    classes AB
    C.
    class B
    D.
    class C

  17. In which frequency range is the noise figure in a transistor independent of frequency

  18. A.
    intermediate frequencies
    B.
    high frequency
    C.
    low frequencies
    D.
    both low and high frequencies

  19. Which of the following is likely to be associated with FM radio broadcasting?

  20. A.
    90 Hz
    B.
    90 kHz
    C.
    900 kHz
    D.
    90 MHz