- It is the process of changing the characteristic properties of carrier signal like amplitude, frequency, and phase.
- The message signal is also known as modulating signal or base-band signal.
- The resultant signal after modulation is known as modulated or band-pass signal.
Types of Modulation:
1. Analog Modulation:
- Analog signal is used as a carrier signal that modulates the message signal or data signal.
There are 3 types of analog modulation.
- Amplitude Modulation (AM)
- Frequency Modulation (FM)
- Phase Modulation (PM)
Amplitude Modulation:
- In this modulation the amplitude of carrier signal varies in accordance with the message signal and phase and frequency remains constant.
Frequency Modulation:
- In this the frequency of carrier signal varies in accordance with the message signal and amplitude, phase are remains constant.
Phase Modulation:
- In this the phase of the carrier signal varies in accordance with the message signal.
- When the phase of the signal is changed then it affects the frequency, so for this reason this modulation comes under the frequency modulation.
- It is an essential part of many digital transmission coding schemes like GSM, WiFi, and satellite television.
2. Digital Modulation:
- For better quality and efficient communication digital modulation technique is used.
- The main advantages of the digital modulation is it include bandwidth, high noise immunity and permissible power.
- In this a message is converted from analog to digital message and then modulated by using a carrier wave.
Ex: ASK, FSK, PSK, DPSK, QPSK....etc.
Advantages:
- Reduction in the height of antenna.
- Avoids mixing of signals.
- Increase the rang of communication.
- Multiplexing is possible.
- Improve quality of reception.
Disadvantages:
- FM requires a larger bandwidth.
- PM is more complex receiving hardware.
- ASK have low power efficiency.
Examples:
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