What Is Modulation And Demodulation

Basic Electrical E-books Electrical Components

MODULATION

Table of Contents

Modulation is the process of mixing a low-frequency signal with a very high-frequency signal. High-frequency radio waves are called carrier waves.
or
It is the process of a combination of an Audio frequency (AF) signal with a Radiofrequency carrier wave. The AF signal is also called a Modulating wave.
The resultant wave is called a Modulated-carrier wave and this job is done at the transmitting station.

DEMODULATION

It is just the opposite of Modulation and is performed at the receiving end. Demodulation is the process of recovering or separating the signal from the modulation carrier wave.

Demodulation is the process of extracting the original information signal from a modulated carrier signal. It is the reverse operation of modulation and is crucial in various communication systems to recover the transmitted data or information. Demodulation is necessary because the carrier signal, after modulation, may have changed in terms of amplitude, frequency, or phase, making it necessary to retrieve the original information.

Demodulation is a critical step in receiving and interpreting signals in communication systems. The choice of demodulation technique depends on the modulation scheme used in the transmitter and the specific requirements of the communication system. Once the original information signal is successfully extracted through demodulation, it can be further processed or decoded for various applications, such as voice communication, data transmission, or multimedia playback.

WHAT IS A CARRIER WAVE?

It is a high-frequency undamped radio wave produced by Radiofrequency oscillators. The result of these oscillators is first amplified and then passed on to an Antenna.

Frequency	Designation	Abbreviation
3-30 KHz	Very low frequency	VLF
30-300KHz	Low frequency	LF
300-3 MHz	Medium frequency	MF
3-30 MHz	High frequency	HF
30-300MHz	Very high frequency	VHF
300MHz-3GHz	Ultra high frequency	UHF
3GHz-30GHz	Super high frequency	SHF
30GHz-300GHz	Extra high frequency	EHF

Generally, the frequency above 300GHz is classified as a Radio wave
The positive half cycles of sound current are produced by the compression and the negative half cycle by rarefactions.

INTENSITY

It is the energy content of the wave. It depends on its amplitude. In fact intensity of a wave is directly proportional to the square of its Amplitude I∝ square of A

METHOD OF MODULATION

The mathematical expression for a sinusoidal carrier wave

e = Ɛcsin(ωct + Φ) = Ɛcsin(2πfct + Φ)

Obviously, the waveform can depend on any of the following three factors or parameters

Ɛc – The amplitude
fc – The frequency
Φ – The phase

There are several common types of modulation:

Amplitude Modulation (AM)
Frequency Modulation (FM)
Phase Modulation (PM

Amplitude Modulation (AM): In AM, the amplitude of the carrier signal is varied in proportion to the amplitude of the information signal. AM is commonly used in radio broadcasting.

Frequency Modulation (FM): In FM, the frequency of the carrier signal is varied in proportion to the amplitude of the information signal. FM is widely used in radio broadcasting for its high-quality audio transmission.

Phase Modulation (PM): In PM, the phase of the carrier signal is varied in response to the amplitude of the information signal. PM is used in various communication systems, including some digital modulation schemes.

Binary Phase Shift Keying (BPSK) and Quadrature Amplitude Modulation (QAM): These are digital modulation schemes used in data communication. BPSK uses two phase states to represent binary data (0 and 1), while QAM employs both amplitude and phase changes to transmit multiple bits of digital data simultaneously.

Orthogonal Frequency Division Multiplexing (OFDM): OFDM is a digital modulation technique widely used in modern wireless communication systems, such as Wi-Fi and 4G/5G cellular networks. It divides the available frequency spectrum into multiple subcarriers, each carrying a lower-rate data stream.

The main purposes of modulation are:

Transmission: Modulation allows information signals to be transmitted over long distances by changing the frequency, amplitude, or phase of the carrier signal. This process enables efficient use of the available bandwidth and minimizes signal interference.

Signal Multiplexing: Multiple signals can be transmitted simultaneously over the same communication channel through modulation. Each signal is allocated a different frequency band or time slot for transmission and can be demodulated at the receiver to recover the original information.

Noise Immunity: Modulating an information signal onto a carrier can improve the signal’s resistance to noise and interference during transmission. By spreading the signal across a wider frequency spectrum, it becomes less susceptible to distortion.