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ECE Objective Questions { Digital Communication System }



99. Frequency division multiplexing (FDM) allows
A. several subsystems to use same transmitter facilities
B. different frequency ranges to beused by different communicators
C. several communicators communicate simultaneously using same transmitter
D. all of above

100. The process in which the signal is first compressed before modulation and expanded after demodulation so as to allow the use of a uniform quantising rate is known as
A. companding
B. pre-emphasis
C. de-emphasis
D. quantization

101. The value of a resistor is doubled. The thermal noise power generated by this resistor is
A. doubled too
B. halved
C. unchanged
D. none of these

102. One of the following parameters is not useful for comparing the noise performance of receivers
A. Equivalent noise resistance
B. Noise figure
C. Equivalent noise temperature
D. Input noise voltage

103. One of the following types of noise assumes importance at high frequencies
A. Thermal noise
B. Shot noise
C. Transit-time noise
D. Flicker noise

104. One of the following statements is wrong regarding modulation.
A. Modulation is used to ensure that intelligence can be transmitted over long distances
B. Modulation is used to ensure that different transmissions can be separated from one another
C. Modulation is used to allow the use of practicable antennas
D. Modulation is used to reduce the signal bandwidth

105. Optical communication uses the frequency range of
A. 109 to 1010 Hz
B. 105 to 106 Hz
C. 1014 to 1015 Hz
D. 1016 to 1017 Hz

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