What is Modulation and Demodulation: Difference, Working, Types, and Mechanism

Modulation and Demodulation Overview

Modulation and demodulation are two crucial procedures used in data communication. A communication is successful when data and information are transferred with the least amount of distortion, loss, and inefficient use of spectrum. The term "modem" refers to the electronic device used for modulation and demodulation. During transmission, it modifies and demodulates the information.

What is Modulation?

Modulation is the process of overlaying a message signal on a carrier signal to enable long-distance message transmission. The high frequency signal used to carry the message signal in this case is known as the carrier signal. A modulator circuit (a component of a modem) is used to perform the signal modulation in the communication system at the transmitting end. In the process of modulation, the carrier signal's amplitude, frequency, or phase are changed in accordance with the modulating signal or message signal. A transmitter transmits the modulated signal over the communication channel after modulation.

Amplitude modulation, frequency modulation, phase modulation, polarization modulation, pulse code modulation, quadrature amplitude modulation, and others are common types of modulation that are widely used in data communication.

What is Demodulation?

Demodulation is the process of extracting the original message from a modulated signal. Demodulation is the process of separating a message signal from a carrier signal, to put it simply.

The demodulator, a component of the modem, is the electronic circuit used to carry out the demodulation process. At the receiver end of a communication system, demodulation is carried out.

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Difference between Modulation and Demodulation

The fundamental steps in data communication are modulation and demodulation. The following table highlights numerous distinctions between modulation and demodulation.

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Need For Modulation and Demodulation

A baseband signal's fundamental system allows for either mixed or lower frequency ranges because it has not been modulated or demodulated. Interruptions in communication may result from this. Therefore, here are the basic needs for the modulations.

1. These problems were resolved by modulation, which offered distinct and long-distance frequencies.
2. Additionally, modulation offers signal parameters that are unaffected.
3. Modulation can also make the entire communication process less complex.

Information can be extracted from modulated carrier waves with the aid of demodulation. Wireless signals are waves of radio frequencies that carry modulated audio frequencies.

1. When a high frequency is present, the diaphragm of a telephone receiver cannot vibrate.
2. The human ear is also incapable of hearing this frequency. A demodulator must be used to separate the audio frequencies from the radio waves.

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How Modulation works

By changing the carrier's amplitude, frequency, phase, polarization -- for optical signals -- and even quantum-level phenomena like spin, information can be added to it.

Radio waves, lasers/optics, and computer networks are examples of electromagnetic signals that are typically modulated. As in Morse code telegraphy or a digital current loop interface, modulation can even be applied to direct current, which can be thought of as a degenerate carrier wave with a fixed amplitude and frequency of 0 Hz. Baseband modulation refers to the special case of no carrier, which is a response message indicating an attached device is no longer connected to a remote system.  As with powerline networking, modulation can also be used with low-frequency alternating current (50–60 Hz).

What are the types of modulation?

There are numerous typical modulation techniques, and the following is only a partial list of them:

1. Amplitude modulation (AM):To represent the data being added to the signal, the height (i.e., the strength or intensity) of the signal carrier is changed.
2. FM: Frequency modulation is the process of changing the carrier waveform's frequency to match the frequency of the data.
3. Phase modulation (PM): To reflect changes in the frequency of the data, the carrier waveform's phase is altered. While the phase with respect to the base carrier frequency is altered in PM, the frequency remains constant. It is similar to FM.
4. Polarization modulation: To reflect transmitted data, a carrier optical signal's angle of rotation is changed.
5. Pulse-code modulation: A digital carrier signal is modulated by using a data stream created by sampling an analog signal.
6. Quadrature amplitude modulation (QAM): Encodes two or more bits in a single transmission using two AM carriers.

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Why use modulation?

Radio frequency (RF) transmissions use a carrier wave, which carries very little information by itself. The carrier wave must be superimposed with another wave in order to carry speech or data, changing the carrier wave's shape. Modulation is the term used to describe this action. The audio signal must first be transformed into an electric signal using a transducer in order to transmit sound. After conversion, it is used to modulate a carrier signal.

Analog vs. Digital Modulation

Analog or digital modulation schemes are both possible. A sine wave-like continuous input wave characterizes an analog scheme. The voice is sampled at a certain rate, compressed, and transformed into a bit stream in a digital modulation scheme. This bit stream is then created into a specific type of wave, which is then superimposed on the carrier signal.

Modulation and Demodulation

Information is encoded in a transmitted signal through the process of modulation, and it is extracted from the signal through the process of demodulation. How accurately the extracted information replicates the original input information is influenced by a variety of factors. Signals can be weakened by electromagnetic interference, making it impossible to separate the original signal. To get rid of interference, demodulators frequently use multiple stages of amplification and filtering.

The first letters of MOdulator and DEModulator were combined to form the name "modem," which refers to a device that can both modulate and demodulate signals.

A computer audio modem uses the data signal to modulate an analog audio tone in order to connect a computer to another computer or to a data network over a regular analog phone line. A modem at the far end demodulates the audio signal to recover the data stream. A cable modem uses network data to modulate the cable service carrier signal.

A carrier signal may occasionally carry multiple modulating information streams. Time-division multiplexing (TDM) is the process of combining the streams onto a single carrier, for example by encoding a fixed-duration segment of one, then of the next, for example, cycling through all the channels before returning to the first. Frequency-division multiplexing (FDM) is another type in which numerous carriers with various frequencies are used on the same medium.

Another technique is wavelength-division multiplexing (WDM), which increases the total amount of bandwidth available by modulating several laser wavelengths/frequencies on long-distance fiber links.

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Why use modulation in communications?

It is frequently possible to transmit multiple carriers of various frequencies over a single medium while modulating each carrier with a separate signal. For instance, Wi-Fi uses distinct channels to send and receive data from various clients simultaneously.

For effective transmission and reception, the wavelength is reduced using a carrier signal. A 25-kilometer antenna would be required for an audio frequency of 3000 Hz because the ideal antenna size is half or a quarter of a wavelength. The antenna would only need to be 80 cm long if it used an FM carrier with a wavelength of 3 meters and a frequency of 100 MHz.

Things to Remember

1. One of the most crucial parts of the communication system is modulation and demodulation.
2. The process of modifying the message source into a format suitable for transmission is known as modulation.
3. Decoding the modulated signal back to its original form is called demodulation.
4. Amplitude, frequency, and phase modulation are the three different types of modulation.
5. Analog, digital, pulse, and spread spectrum modulation are the four different types of modulation mechanisms.

Conclusion

In data communication, modulation and demodulation are crucial procedures. A device known as a modem (modulator-demodulator) is capable of performing both modulation and demodulation. The table above lists a number of distinctions between modulation and demodulation. The most important distinction is that, while the message signal and carrier signal are combined during modulation, they are separated during demodulation.

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