[Physics Class Notes] on Need for Modulation Pdf for Exam

Nowadays, information, messages, data, and signals are sent from one location to another within seconds. How is such fast transmission possible? The communication system uses modulation to enhance the range of the signals. Most of the signals generated in daily life are sinusoidal waveforms. Sinusoidal wave is a curve that describes smooth repetitive oscillations. The signals transferred during communication include crucial information in the form of a sinusoidal wave. Modulation and its types play a crucial role in the rapid transmission of the signals from the sender to the receiver. Modulation is the superimposition of the signal wave (carrying the message) with a high-frequency carrier signal to ensure faster transmission of the signal. 

What is Modulation And Its Types?

Modulation is one of the crucial branches of electronics science that is widely used in communication systems. It includes the different fundamental properties of the signal to transpose it from one location to another. 

Types of Signals used in the Modulation

• Modulating Signal: This is the signal that contains the message to be transmitted from the sender to the receiver and is called a message signal. Generally, the message signals are the band of low or high frequencies and are often called baseband signals. The message signals are the signals to be transmitted from the sender to the receiver. The frequency of the message signals to be sent is generally low. Thus, these signals undergo modulation to get correctly transmitted from one location to another.

• Carrier Signal: The other signal used in the process of modulation is the carrier signal that has high-frequency sinusoidal waves. The high-frequency carrier wave can travel much quicker as compared to the baseband signal. These signals have a specific frequency, amplitude, and phase, but no information. After modulation, carrier signals are used to transmit the signal to the receiver. 

• Modulated Signal: After the modulation is done, the resultant signal refers to the modulated signal. This signal is the mixture of the carrier signal and message signal. 

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The diagram shows three types of signals, namely, message signal, carrier signal, and modulated signal that is the mixture of the message and carrier signal.

What Are The Types Of Modulation?

There are generally three types of modulation:

• Amplitude Modulation: By superimposing the base signal with the carrier signal having a different amplitude, but the same frequency, if the amplitude of the base signal modifies or modulates, then it is said to be amplitude modulation.

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The diagram shows the amplified modulated wave after superimposing the message signal with the carrier signal.

• Phase Modulation: It is the type of modulation in which the phase of the base signal changes while superimposing it with a carrier signal. 

• Frequency Modulation: By superimposing the base signal with the carrier signal having a different frequency, but the same amplitude, if the frequency of the base signal modifies or modulates, then it is said to be frequency modulation.

What is the Need for Modulation?

The baseband signals transmitted by the sender are not capable of direct transmission. The strength of the message signal should be increased so that it can travel longer distances. This is where modulation is essential. The most vital need of modulation is to enhance the strength of the signal without affecting the parameters of the carrier signal.

Modulation has removed the necessity for using wires in the communication systems. It is because modulation is widely used in transmitting signals from one location to another with faster speed. Thus, the modulation technique has helped in enhancing wireless communication systems.

Modulation and its types prevent the interference of the message signal from other signals. It is because a person sending a message signal through the phone cannot tell such signals apart. As a result, they will interfere with each other. However, by using carrier signals having a high frequency, the mixing of the signals can be prevented. Thus, modulation ensures that the signals received by the receiver are entirely perfect.

The signals within 20 Hz to 20 kHz frequency range can travel only a few distances. To send the message signal, the length of the antenna should be a quarter wavelength of the used frequency. Thus, modulation is required to increase the frequency of the message signal and to enhance its strength to reach the receiver.

Length of the antenna can be easily calculated using this formula: 

L = λ = u/ν

= (3 x 108) / ν

Here, L = length of antenna 

        λ =  wavelength of the transmitted signal

        ν = carrier wave frequency

What are the Uses of Modulation?

• One of the most common uses of different types of modulation is the inter-conversion of signals from its existing to another form. 

• Digital Modulation is used for the transmissions of the digital signals over analog baseband. 

• Analog Modulation is used to transfer the low bandwidth signals such as TV or radio signals over a higher bandwidth. 

• Modern modulation techniques are widely used to carry out FDM, that is, Frequency Division Multiplexing