Before Starting Modulation we have to know what is Carrier Wave and Input(Message) Signal.
Carrier Wave:
- Wave with the high frequency.
- These waves are combined with the input wave for conveying the information or transferring the message signal.
Input(Message) Signal:
- These are wave which are given as input with certain information,
- As these signals are weak, they cannot carry message for long distance.
- In order to carry for long distance, we use carrier signal.
Modulation:
- Imposing the Message signal on carrier signal is called Modulation.
- Modulation helps to increase the strength of Message Signal to carry large distance.
- There are some types in Modulation
- Frequency Modulation
- Amplitude Modulation
- Pulse Modulation
Frequency Modulation:
- Varying the frequency of the carrier wave is called frequency modulation.
- Carrier Wave Frequency changing depends on the input signal.
| Input Signal Negative | Carrier Wave Frequency Increases |
| Input Signal Positive | Carrier Wave Frequency remains same |
- Frequency Range is 87.5 MHz to 108 MHz.
Advantages:
- Large decrease in noise.
- Noise may reduce by increasing deviaton.
- Operates in very high frequency.
Disadvantages:
- FM wave cannot cover large area.
- Transmitting and Receiving equipment for FM are costly.
Applications:
- Television Sound
- Satellite TV
- Radio
Amplitude Modulation:
- Varying the amplitude of the carrier wave
- Carrier Wave Amplitude changes according to the amplitude of the signal.
- Frequency Range is 535 to 1705 KHz.
Advantages:
- It is simple to implement.
- It can be demodulated using a circuit consisting of very few components.
- AM receivers are very cheap as no specialized components are needed.
Disadvantages:
- It is not efficient in terms of its power usage.
- It is not efficient in terms of the bandwidth.
Applications:
- Computer Modems
- Aircraft
- Television Video
Phase Modulation:
- Changes the Phase of the carrier signal.
- Carrier Wave changes the phase when input signal frequency is zero.