Introduction: Modulation is the process in which one of the parameters (amplitude, frequency, or phase) of the carrier will vary linearly with the instantaneous value of the message signal. We need modulation to perform or conduct communication efficiently, as it is an important part of communication.
Communication is the transfer of information from one place to another place. It needs three main elements, a transmitter to send the information in the form of signals, a medium to pass the information, and a receiver on the other end to receive the information.
So to perform communication we need to understand modulation properly. Let’s continue to learn more about MODULATION.
So before moving on to how to use modulation in communication, we will learn about the need and advantages of modulation-
NEED OF MODULATION: The original signals either in analog or digital form are incomplete for distance transmission over the medium. They can not travel longer distances in the air (free space) such as voice signals. Therefore, we have to use modulation techniques for the communication of the baseband signal.
ADVANTAGES OD MODULATION:
- Communication range increases.
- Antenna size gets reduced.
- No signal mixing occurs.
- Multiplexing of signals occurs.
- Adjustments in the bandwidth are allowed.
- Reception quality improves.
Now we know what Modulation is and what it can do to make the communication process easier and more efficient.
Let’s now move on to the type of Modulation-
TYPES OF MODULATION:
ANALOG MODULATION:
Analog modulation is a type of modulation in which the characteristics of an analog signal are varied in proportion to the information signal.
There are three main types of analog modulation: amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM).
Amplitude modulation (AM):
Amplitude modulation is a type of analog modulation in which the amplitude of a carrier signal is varied in proportion to the information signal. An example of AM is a radio broadcast, in which the amplitude of the carrier signal is varied in proportion to the audio signal.
Expression for amplitude-modulated wave:
Carrier wave will be generally a high frequency wave and similar to sine or cosine wave and can be represented as :
where,
->Ac is the amplitude of the carrier wave,
->sinωct is the phase of the carrier wave,
->fc is the frequency of carrier wave
->C(t) is our carrier wave.
The modulating signal is also analogous to a sine or cosine wave and represented as:
where
->Am is the amplitude of the modulating wave,
->sinωmt is phase of modulating wave,
->fm is frequency of modulating signal
->m(t) is our modulating or input signal.
We are now superimposing modulating signal into a carrier wave to interpret the data and speech information and thus also varying the amplitude of the carrier wave in accordance with the amplitude of the modulating signal, and hence the amplitude-modulated wave Cm(t) will be:
This is the general form of an amplitude-modulated wave.
The degree of modulation is given by index of modulation.
From equation (3), we have,
Cm(t) = (Ac + Am sin ωmt) sin ωct
Taking Ac common in (3), we get
where
Am/Ac= μ, which is known as modulation index also known as modulation factor, modulation coefficient or degree of modulation.
Thus modulation index is defined as the ratio of the amplitude of the modulating signal to the amplitude of the carrier wave.
Modulation Index: Modulation index (μ) is defined as the ratio of the amplitude of the modulating signal to the amplitude of the carrier wave. Its mathematical expression and detailed explanation is discussed later in the article.
Frequency modulation (FM):
Frequency modulation is a type of analog modulation in which the frequency of a carrier signal is varied in proportion to the information signal. An example of FM is an FM radio broadcast, in which the frequency of the carrier signal is varied in proportion to the audio signal.
Phase modulation (PM):
Phase modulation is a type of analog modulation in which the phase of a carrier signal is varied in proportion to the information signal. An example of PM is a single-sideband (SSB) radio transmission, in which the phase of the carrier signal is varied in proportion to the audio signal.
DIGITAL MODULATION:
Digital modulation is a type of modulation in which a digital signal is used to modulate a carrier signal.
There are three main types of digital modulation: amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK).
Amplitude shift keying (ASK):
Amplitude shift keying (ASK) is a type of digital modulation in which the amplitude of a carrier signal is varied in accordance with the data. An example of ASK is binary ASK (BASK), in which the carrier signal is switched on and off to represent the data bits 1 and 0.
Frequency Shift Keying(FSK):
Frequency shift keying (FSK) is a type of digital modulation in which the frequency of a carrier signal is varied in accordance with the data. An example of FSK is binary FSK (BFSK), in which the carrier signal is shifted between two different frequencies to represent the data bits 1 and 0.
Phase shift Keying (PSK):
Phase shift keying (PSK) is a type of digital modulation in which the phase of a carrier signal is varied in accordance with the data. An example of PSK is binary PSK (BPSK), in which the carrier signal is shifted by 180 degrees to represent the data bits 1 and 0.
CONCLUSION: So today we learned about-
Modulation, Its importance in communication, need of modulation in communication, advantages of modulation, and types of modulation.
In types, We learned in detail about Amplitude modulation.