Modulation

         

   

Short questions and answers about modulation

1. What Is Modulation?

Ans: Modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.

2. What is modulator ?

Ans: A modulator is a device that performs modulation.

3. What is Need Of Modulation?

Ans: Modulation is required to send the information over long distances as low frequency signals are not able to cover large area.

4. In which modulation is done?

Ans: Transmitter .

5. What is Analog Modulation ?

Ans: The modulating technique is applied to the analog information signal.

6. What is the type of  Analog Modulation?

Ans: There are following types of analog modulation

Amplitude modulation(AM), Frequency modulation(FM), Phase modulation(PM)

7. What is Amplitude modulation(AM):

 In amplitude modulation, the amplitude of the carrier wave is varied in proportion to the message signal, and the other factors like frequency and phase remain constant.

8. What is Frequency modulation(FM):

In Frequency modulation (FM) varies the frequency of the carrier in proportion to the message or data signal while maintaining other parameters constant.

9. What is Phase modulation(PM):

In phase modulation, the carrier phase is varied in accordance with the data signal. In this type of modulation, when the phase is changed it also affects the frequency, so this modulation also comes under frequency modulation.

10. Why Frequency Modulation is Better Than Amplitude Modulation?

Ans: Frequency Modulation is better as it provide more resistance to noise as compared to Amplitude modulation.

11. What is digital modulation?

And:  In digital modulation, a message signal is converted from analog to digital message, and then modulated by using a carrier wave.

The main advantages of the digital modulation over analog modulation include permissible power, available bandwidth and high noise immunity.

12. What are the types of digital modulation:

Ans: There are following types of digital modulation.

PSK- Phase shift keying

ASK- Amplitude shift keying

FSK- Frequency shift keying

QAM- Quadrature amplitude modulation

13. What is the  Depth Of Modulation or modulation Index?

Ans : It refers to the ratio of the unmodulated carrier amplitude to the amplitude deviation for which the modulated carrier wave reaches its minimum value.

14. What are the advantages of Analog Communication Over Digital Communication ?

Ans: Due to analog to digital conversion, the data rate becomes high in digital communication. So the transmission bandwidth is also increased. Digital transmission also needs synchronization in certain applications which is not needed in case of analog communication systems.

15. What is cross talk ?

Ans: Cross talk is the disturbance caused in the nearby channel or circuit due to transmitted signal. Cross talk is usually caused by undesired coupling of capacitors or inductors from one channel to another. Electromagnetic interference (EMI) causes cross talk in the circuits or the channels. In crosstalk, the signals traveling closer to each other interfere with each other and cause disturbance in the signal.

16. What is high level Amplitude Modulation?

Ans : In High level Amplitude Modulation system, Modulation is done at high power of carrier and modulating signals so Power amplifiers are used to boost the carrier and modulating signals before modulation. Collector modulation method is the example of High level Amplitude Modulation.

17. What is ring Modulator ?

Ans: Ring modulator is a product modulator used for DSB SC generation. It consists of four diodes connected in the form of ring. In AM , the ring modulator acts as a product modulator for a square wave carrier and modulating signal and generated a Double Side Band-Suppressed Carrier signal.

18. What is Pilot Carrier?

Ans: Pilot carrier is a small carrier transmitted with modulated signal from the transmitter. It is separated at the receiver and used to phase lock the locally generated carrier signal generated at the receiver. It provides synchronization at the receiver.

19. What happen when Modulation Index is greater than 1?

Ans : Modulation index is the measure of extent to which the parameter of the carrier is varied in accordance with the modulating signal. If modulation index is greater than 1, or the modulation percentage is more than 100%, it is called over modulation.

The baseband signal is not preserved in the envelope of the AM signal and therefore, the recovered signal is distorted at the output of the receiver.

20. What is the results of over modulation?

Ans. Distortion.

21. If modulation power is increased what happen the carrier power?

Ans: Remains the same.