Analog Communications Questions and Answers – Need of Transducers

This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “Need of Transducers”.

1. What is the effect on the transmitted power, if the modulation index changes from 0.8 to 1?
a) 0.1364
b) 0.239
c) 0.5
d) 0.3333

Explanation: The total power in an AM is given by, PT = PC (1+m22). When modulation index, m = 0.8 PT = PC (1+0.822)=1.32Pc and when modulation index, m = 1 PT=PC (1+122)=1.5PC.
So increase in power =

2. Analog signal may be converted into digital signal by ________
a) Filtering
b) Mixing
c) Sampling
d) Transducing

Explanation: Conversion of an analog signal into digital signal converts a continuous time signal in the form of digits, by discretizing it. Thus, the conversion is done with the help of sampling technique.

3. Radio waves travel through ________
a) Coaxial Cable
b) Wires
c) Optical fiber cable
d) Electromagnetic waves

Explanation: Radio communication or wireless communication takes place through electromagnetic waves. The message is transmitted through open space via electromagnetic waves or radio waves.

4. USB (Upper Side Band) is the band of frequencies _________
a) below carrier frequency in AM spectrum
b) above the carrier frequency in AM spectrum
c) includes the carrier frequency in AM spectrum
d) is the center frequency

Explanation: Upper Side Band is the band of frequencies above the carrier frequency that lies in AM spectrum. It is a part of the shifted spectrum obtained after amplitude modulation.

5. Which of the following is AM demodulation techniques?
a) Square law demodulator and Envelope detector
b) Ratio detector and PLL detector
c) PLL detector and Coherent detector
d) PLL detector

Explanation: AM signals are detected or demodulated using Square law demodulator and Envelope detector. The demodulator extracts the information from the received AM signal.

6. Vestigial side band signals are detected by ________
a) PLL detector
b) Ratio detector
c) Square law demodulator
d) Synchronous Detection

Explanation: Vestigial side band signals are detected by Synchronous detection or coherent detection technique. The distortion in a VSB signal may be reduced by reducing the modulation index and increasing the width of VSB.

7. What is the function of frequency mixer in super heterodyne receiver?
a) Multiplication of incoming signal and the locally generated carrier
b) Addition of incoming signal and the locally generated carrier
c) Amplification
d) Filtering

Explanation: The function of a frequency mixer in a super heterodyne receiver is that it mixes or multiplies the incoming modulated signal with the locally generated carrier in order to bring the incoming RF signal to a band of frequencies which can be processed easily.

8. The amount of frequency deviation in FM signal depends on ________
a) Modulating frequency
b) Modulation Index
c) Amplitude of the modulating signal
d) Carrier frequency

Explanation: The amount of frequency deviation in the FM signal depends on amplitude of the modulating signal. So for any audio signal, as the loudness increases frequency deviation in carrier signal also increases. Frequency deviation helps in determining the bandwidth of FM signal.

Sanfoundry Global Education & Learning Series – Analog Communications.