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Modulation includes varying the fundamental properties of the basic signal by superimposing it with a carrier signal. This is done so that the basic signal can be carried from one location to another. Modulation is essential for many tasks like video chatting and talking to people anywhere on the planet. For example: Consider two radio stations on the FM Scale. They have different addresses because they travel from the radio station in different forms than they actually have.
Also read: Modulation and Demodulation
| Table of Content |
Key Terms: Frequency, Wavelength, Frequency modulation, Transmission of information, Messages, Signals, Phase modulation, Waves, Communication system
What is Modulation?
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Modern technology makes the transmission of information, messages, and signals possible within seconds. Communication systems rely on modulation to enhance the range of signals. Most signals that are generated in daily life are sinusoidal waves.
Modulation
Sinusoidal waves are waves that describe smooth repetitive oscillations. Communication of signals involves transferring information in the forms of sinusoidal waves. Modulation plays a crucial role in quickly transmitting signals from sender to receiver.
During the process of modulation, the carrier signal is superimposed over the base signal to transmit from the sender to the receiver. At the receiver, the carrier signal is filtered out to remove any unwanted noise. The process is called demodulation.
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Signals Used in Modulation
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Modulation is a crucial branch of electronic science. It includes using the different fundamental properties of signals to transmit them from one location to another.
Following are the different types of signals used in modulation.
Modulated Signal
After modulation, the resulting signal is called the modulated signal. It is a mixture of the carrier signal and the modulating signal.
Modulating Signal
This signal contains the message to be transmitted and is also called the message signal. Message signals are often in the band of low or high frequencies and are called baseband signals. The frequency of message signals to be sent is generally low and hence, they need to undergo modulation to be correctly sent.
Carrier Signal
Carrier signals are high-frequency sinusoidal waves. They can travel much quicker compared to baseband signals. They have a specific frequency, amplitude, and phase but they have no information. After modulation, they are used to transmit information from sender to receiver.
Signals Used in Modulation
Types of Modulation
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In general, there are three types of modulation:
Amplitude Modulation
If the amplitude of the basic signal modifies or modulates when superimposed with the carrier signal of the same frequency but different amplitude, it is called amplitude modulation.
Amplitude Modulation
Phase Modulation
If the phase of the base signal changes when superimposed with a carrier signal, it is called phase modulation.
Phase Modulation
Frequency Modulation
If the frequency of the base signal modifies or modulates when superimposed by a carrier signal of the same amplitude but different frequency, it is called frequency modulation.
Frequency Modulation
Read More: Terms used electronic communication systems
Why is Modulation Needed?
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In a digitally advanced era, wires are no longer a requirement to stay in touch. Messages, information, and signals can travel all over the world in seconds. Modulation plays an essential role in communication systems. Below are some of the reasons why modulation is a crucial requirement in communication systems:
- To increase the signal strength: The baseband signals transmitted are often incapable of direct transmission. Its strength needs to be increased to travel long distances. That is where modulation comes in. The most crucial need for modulation is to enhance the signal strength.
- To prevent the message signal from mixing: Modulation prevents the interference of message signals from other signals. By using a carrier signal of high frequency, the mixing of signals can be prevented. In other words, modulation ensures that the signals received by the receiver are perfect.
- Size of the antenna: Signals within the frequency of 20 Hz to 20 kHz frequency cannot travel large distances. To send the message signal, the length of the antenna has to be one-fourth wavelength of the used frequency. Modulation is required to increase the message signal’s frequency and enhance its strength so that it properly reaches the receiver.
The length of the antenna can be calculated by the formula:
L = λ = u/v = (3×108)/v
where L is the length of the antenna, λ is the wavelength of the transmitted signal and v is the carrier wave frequency.
Read More: Frequency and Wavelength
Uses of Modulation
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- Different types of modulation are used for the inter-conversion of signals from one form to another.
- Transmissions of digital signals over analog baseband are done by digital modulation.
- Transfer of low bandwidth signals over higher bandwidth is done by analog modulation.
- Modern modulation is used for Frequency Division Multiplexing.
Things to Remember
- Modulation is a branch of science that includes varying the fundamental properties of the basic signal by superimposing it with a carrier signal.
- Communication systems rely on modulation to enhance the range of signals.
- Communication of signals involves transferring crucial information in the forms of sinusoidal waves.
- During the process of modulation, the carrier signal is superimposed over the base signal to transmit from the sender to the receiver. At the receiver, the carrier signal is filtered out to remove any unwanted noise. The process is called demodulation.
- If the amplitude of the basic signal modifies or modulates when superimposed with the carrier signal of the same frequency but different amplitude, it is called amplitude modulation.
- If the phase of the base signal changes when superimposed with a carrier signal, it is called phase modulation.
- If the frequency of the base signal modifies or modulates when superimposed by a carrier signal of the same amplitude but different frequency, it is called frequency modulation.
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Sample Questions
Ques. How does modulation reduce the size of the antenna? (3 marks)
Ans. When transmitting the radio signals, the height of the antenna must be λ/4, where λ is the wavelength. Hence modulation reduces the size of the antenna. Modulation is required to increase the message signal’s frequency and enhance its strength so that it properly reaches the receiver.
Ques. Why is modulation necessary for long-distance communication? (3 marks)
Ans. Modulation provides numerous benefits for communication. It allows us to transmit a signal across numerous frequencies. The modulated signals do not interfere with one another. The lower the frequency of a signal, the larger is the size of the antenna required for transmission.
Ques. How does modulation cause noise reduction? (3 marks)
Ans. The phase modulation technique is used to reduce the coherent noise that is caused by spurious interference. But choosing the appropriate driving signal, the technique can reduce the coherent function of coherent noise while keeping the coherent function of a coherent signal nearly unchanged.
Ques. Why is amplitude modulation used for video transmission? (3 marks)
Ans. AM is used because the video amplitude modulated signal can be easily coded and decoded since the change in amplitude of the carrier wave and the amplitude of the original video signal is proportional. But amplitude modulation is sensitive to noise and electromagnetic interference.
Ques. What is modulation? Give examples. (3 marks)
Ans. Modulation, in electronics and communication systems, is a branch of science that includes varying the fundamental properties of the basic signal by superimposing it with a carrier signal. This is done so that the basic signal can be carried from one location to another. Modulation is essential for many tasks like video chatting and talking to people anywhere on the planet.
Examples: Digital signals representing binary digits, audio signals representing sound from a microphone.
Ques. Does the modulation index remain less than one in frequency modulation? (2 Marks)
Ans. Frequency modulation index remains consistently over 1. It requires high bandwidth in the range of 200 kHz and operates in a very high-frequency range of 88 to 108 Megahertz. It has a complex circuit with an infinite number of sidebands and receives high-quality signals with high sound quality.
Ques. What is pulse modulation? (2 Marks)
Ans. In pulse modulation, signals are transmitted in the form of pulses. Continuous signals are transferred at regular intervals. It can be used to transfer analog information.
Ques. What is meant by 100% modulation? (3 marks)
Ans. The envelope will vary when a radio frequency signal is modulated by an audio signal. As it is the maximum amount that can be applied, it is called 100% modulation. Distortion will arise if the level of modulation is increased beyond the 100% level as the envelope cannot fall below zero.
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