Introduction

The method of modifying the carrier signal in response to the message signal is known as modulation. In the process of modulation, the high-frequency sin wave signal is referred to as the carrier signal. The modulating signal is the name given to the output signal. Modulation is a signal processing technique that involves shifting the signal’s frequency range. Modulation is used to enhance the range of the signals and also for fast transmission. A sinusoidal wave is a generally used curve that ensures smooth repetitive oscillations. The modulation uses sinusoidal waves. Modulation is a branch of science in electronics and communication systems. One example of modulation is seen in radio signals.

Types of Signals in modulation are:-

• Modulating Signal: A message signal is a signal that contains the message that will be transferred from the sender to the receiver. Message signals are often in the low or high-frequency region and are referred to as baseband signals. The sender’s message signals are the signals that will be sent to the recipient. The message signals to be conveyed are normally sent infrequently. As a result, these signals are modulated to be transferred accurately from one site to another.
• Carrier Signal: The carrier signal, which has high-frequency sinusoidal waves, is the other signal used in the modulation process. In comparison to the baseband signal, the high-frequency carrier wave can travel much faster. There is no information in these signals, which have a defined frequency, amplitude, and phase. Carrier signals are used to transmit the signal to the receiver after it has been modulated.
• Modulated Signal: The resultant signal refers to the modulated signal after it has been modulated. This signal is the result of combining the carrier and message signals.

Types of modulation are:-

• Amplitude Modulation: In this type of modulation, a carrier signal with a different amplitude is superimposed with a base signal to change the amplitude of the base signal or modulate that, but the frequency of both signals remains the same.
• Frequency Modulation: In this type of modulation, the carrier signal with a different frequency is superimposed with the base signal so that the frequency of the base signal could be changed or modulated. The amplitude of both of the signals remains the same.
• Phase Modulation: In this type of modulation, the phase of the base signal changes or modifies after it is superimposed with the carrier signal.

Why modulation is needed in communication systems?

We live in a digitally evolved era were using wires to stay connected to everyone is no longer necessary. Within minutes, messages, information, and signals are sent from one part of the planet to another. To transmit messages quickly, the modulation procedure is crucial. 

Some of the reasons why we need modulation are as follows:

• It is not possible to build an antenna to radiate the base signal provides, to be in the order of the magnitude of the wavelength of the transmitted signal. For example, if there is a signal of wavelength λ the length of the antennae should be λ/4 at least so that smooth transmission could be possible.
• If we directly transmit the signal the ratio of highest to lowest frequency becomes very high. Hence, transmission is very difficult. But with the modulation of transmission with the carrier signal, the ratio of highest to lowest frequency becomes low and hence transmission becomes possible.
• Wireless communication is possible due to modulation. Modulation helps in long-distance transmission of signals hence this technology is used in mobile phones nowadays so that effective mobile communication could be possible. 
• Modulation is also important to differentiate between two different message signals. After carrier signal modulation every signal is given with specific amplitude, frequency, and wavelength so that it could be transmitted and could be received only by those for whom the message is supposed to be.
• Before transmission, the original low-frequency baseband message or information signal must be translated into a high-frequency wave so that the translated signal retains the information included in the original signal. To do so, we use a high-frequency signal called the carrier wave and a procedure called modulation to attach information to it. The carrier wave can be either continuous (sinusoidal) or pulsed. 
• The power radiated increases with decreasing, i.e., the increasing frequency for the same antenna length. As a result, the effective power emitted by a baseband signal with a long wavelength would be below. We require high powers for good transmission, hence this also speaks to the need for a high-frequency transmission. 

Modulation Stages

Consider the scenario of a person utilizing his or her phone to call a friend for a talk.

1. The words they say cause a vibration in the microphones, resulting in a sinusoidal wave when the string or surface vibrates due to the pressure difference as they talk. This is the initial stage of signal interconversion. 
2. The analog signal is then converted to digital by string motion, which generates current flow on a switch that is turned on and off. This is the second stage of the process. 
3. The phone modulates this signal with the use of a carrier signal to give it a bandwidth for transmission and then sends it to a nearby tower for transmission over longer distances. The signal is received again by the receiver, which must be demodulated and filtered before it can be regenerated with its original information. 

Modulation Uses

• The inter-conversion of signals from one form to another is one of the most common applications of various types of modulation.
• The digital signals are transmitted over analog baseband using digital modulation.
• Analog Modulation is a technique for transferring low-bandwidth transmissions, such as TV or radio, to a higher-bandwidth signal.
• Another notable application of current modulation techniques is Frequency Division Multiplexing, or FDM, which allows for the simultaneous transmission of several signals in opposite directions utilizing modulation with various frequencies across the same channel.  
• Another application of modulation in modern times is in music. Synthesizers are commonly used in modern musical instruments to generate and manipulate signals over various frequencies, superimpose them, or demodulate (differentiate) them to create strange effects that many people love. 

Conclusion

In this article, we read about Modulation and its necessity. Also, we gained knowledge of various topics related to modulation like types of signal in modulation, types of modulation, why modulation is needed, modulation stages, and modulation uses.