The transmission of information by communication systems over large distances is quite a feat of human ingenuity. We can talk, video chat, and text anyone on this planet! Communication systems have used a very clever technique called modulation to increase the reach of the signals. In this article, we will briefly talk about what modulation is and its need.
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What is Modulation?
Two signals are involved in the modulation process. Message signals are also known as baseband signals. Baseband signals are the band of frequencies representing the original signal. This is the signal to be transmitted to the receiver. The frequency of such a signal is usually low. The other signal involved in this is a high-frequency sinusoidal wave. This signal is called the carrier signal. The frequency of the carrier signals is almost always higher than that of the baseband signal. The amplitude of the baseband signal is transferred to the high-frequency carrier. Therefore, modulation can be defined as
, The process of superimposing a low-frequency signal on a high-frequency carrier signal.
The process of varying the RF carrier wave in accordance with the information in a low-frequency signal
Such a higher frequency carrier wave can travel farther than the baseband signal. But that’s not the only advantage of modulation. In the next section, we will discuss the various advantages of modulation.
There are three types of modulation:
- Amplitude Modulation
- Frequency Modulation
- Phase Modulation
What is the need for modulation?
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Size of the Antennae
When the transmission occurs over free space, the antennae radiate the signal, and the receiver receives it. To operate efficiently, antennae need to be in the order of the magnitude of the wavelength of the transmitted signal.
\(\begin{array}{l}L = \lambda = \frac{u}{\vartheta } = \frac{(3*10^{8})}{\vartheta }{Hz}\end{array} \)Speech frequencies range from 20 Hz to 20 kHz. So supposing this is a frequency of 20 kHz and radiated out to a receiver through a channel of free space.
\(\begin{array}{l}Length \;of \;Antennae = \frac{3*10^{8}}{20*10^{3}} = 15000 m = 15 km\end{array} \)It is impossible to build an antenna this big. Instead, we use the concept of using a high-frequency carrier wave for the transfer of the signal and, thus, use a 1000 kHz carrier wave to carry the signal. The length of the antennae now would be;
\(\begin{array}{l}Length\; of\; Antennae = \frac{3*10^{8}}{1000*10^{3}} = 300 m\end{array} \)This antenna length can be built easily; this example clearly shows how hugely the modulation process enables communication systems.
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Wireless Communication
By using modulation to transmit the signals through space to long distances, we have removed the need for wires in the communication systems. The modulation technique helped humans to use the wireless equipment in a big way in their lives. Telephones no longer had to remain plugged into a wall. All these benefits of modulation have raised our standards of living considerably.
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Interference from other signals
This is a point from the practical side of things. Suppose you are transmitting the baseband signal as it is to a receiver, say your friend’s phone. Just like you, there will be thousands of people in the city using their mobile phones. There is no way to tell such signals apart, and they will interfere with each other leading to a lot of noise in the system and a very bad output. By using a carrier wave of high frequencies and allotting a band of frequencies to each message, there is no mixing up of signals, and the received signals are absolutely perfect.
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Frequently Asked Questions – FAQs
Q1What is modulation?
Modulation is the technique of superimposing a low-frequency signal over a high-frequency carrier signalQ2What are the types of modulation?
There are three types of modulation:- Amplitude Modulation
- Frequency Modulation
- Phase Modulation
Q3What is demodulation?
The process of recovering the original information-carrying signal from a modified carrier wave is known as demodulation. A demodulator is a type of electrical circuit that is used to retrieve information from a modulated carrier wave.Q4What is a measuring wave?
Measuring waves is also known as the modulating wave. The wave is superimposed on a carrier wave with high frequency.Q5What is the effect of distortion in modulation?
Distortion occurs when the modulating signal’s amplitude is greater than the amplitude of the carrier. This results in the transmission of incorrect information.Test your Knowledge on Modulation Need Modulation
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