Applications of Amplitude Modulation

In this physical world the electronic communication is made possible because of a technique known as modulation by which any message, signal or data is converted into electrical or digital signals for transferring that signal, message, or data over a medium. There are three types of modulation Amplitude modulation, Frequency modulation, and Phase modulation.

In this article we are going to understand about what this Amplitude modulation is and how it is used for transmitting information or any message signals via a radio carrier wave, carrying the signal over large distances. After the signal transmission is happened the next process is that the modulated signal is converted back into the original signal to retrieve or extract the original information by the help of Demodulation process. This article has also included various applications of amplitude modulation, highlighting its importance in modern communication systems.

What is Amplitude Modulation?

Amplitude modulation can be defined as a process in which the changing of the amplitude of a high-frequency carrier wave is directly proportion to the amplitude of the input signal, which contains the information or any message to be transmitted. The amplitude of the carrier wave is varying with respect to the modulating signal that signal is known as amplitude modulated signal.

Alternately, we can also define that amplitude modulation is the process of changing the amplitude of a carrier signal with respect to the instantaneous value of a message signal while keeping the carrier signal's frequency and phase constant.

Mathematically the equation of Amplitude Modulated wave can be written as,

\begin{array}{l}s(t)=\left \lfloor A_{c}+A_{m}cos(2\pi f_{m}t) \right \rfloor cos(2\pi f_{c}t)\end{array}

Where:

• m(t) is the message signal which contains the information it is also known as baseband signal
• c(t) is the carrier signal which is a high frequency signal used to carry the message to the receiver
• s(t) is the final modulating signal wave.

The Process of Amplitude Modulation

1. In the first step the carrier wave c(t) is generated which is a high-frequency sine wave. This wave is like the foundation for carrying the information or message to be transmitted. Mathematically, the representation of carrier wave is as follows:

c(t) = A_c \cos(2 \pi f_c t)

2. Second step include the generation of Message Signal m(t)- The next step in the process of amplitude modulation is generating the message signal m(t). This signal wave contains the information or message and data to be transmitted. The frequency of this signal is generally lower as compared to carrier signal and mathematically it is represented as:

m(t) = A_m \cos(2 \pi f_m t)

3. Third step is Modulation of the Carrier Wave- After the generation of above two waves, In amplitude modulation, the amplitude of the carrier wave is changed with proportional to the instantaneous amplitude of the message signal. Mathematically the resulting AM signal can be expressed as:

s(t) = \left[ A_c + m(t) \right] \cos(2 \pi f_c t)

After expanding the AM signal:

s(t) = A_c \cos(2 \pi f_c t) + A_m \cos(2 \pi f_m t) \cos(2 \pi f_c t)

By using trigonometric identities, the modulated signal finally expressed as:

s(t) = A_c \cos(2 \pi f_c t) + \frac{A_m}{2} \left[ \cos \left( 2 \pi (f_c + f_m) t \right) + \cos \left( 2 \pi (f_c - f_m) t \right) \right]

4. Transmission of message along with carrier signal - Transmission is very important step after modulation of carrier wave as, in this step the modulated signal is then transmitted over the air by help of an antenna the better the modulation is the lesser the size of antenna is required. The carrier wave, which is modulated with the message signal, can now travel long distances and the message is sent from the sender's end to the receiver.

5. Finally, Reception or receiving of the sender's message by the receiver- As the message is already sent in the above processes now at the receiving end, an receiver antenna is used to pick up or collect the transmitted AM signal. Then the receivers such as TRF or SHR is used to demodulate the signal and receive the original message.

Applications of Amplitude Modulation

1. AM Radio Broadcasting: AM radio broadcasting is the most and well know application of AM modulation. As its common usability of AM radio remains a popular medium for news, music, and emergency broadcasts. Even the new advancements of FM and digital broadcasting, AM radio is still used due to its ability to cover large geographical areas and its lower susceptibility to geographical obstacles we know as noise or disruptions.
2. Aviation Communication: Amplitude modulation is used very much in aviation communication. The VHF (Very High Frequency) aviation band, which have a operating range of 118 MHz to 137 MHz, depended on AM for voice communication between pilots and air traffic control (ATCs). The strength of AM in the presence of interference of obstacles and its simplicity makes it a reliable choice in this particular application.
3. Maritime Communication: The application of AM in Maritime Industry is used for short-range ship-to-ship and ship-to-shore communication purposes. As we know that the AM signals can travel long distances over water, making them ideal and suitable for maritime usability. This is crucial for navigation, safety, and operational communication.
4. Two-Way Radios: Two-way radios like the Motorola devices(walkie talkie), commonly used by police, firefighters, and other emergency services to quickly communicate with each other, also employ amplitude modulation. The simplicity and effectiveness of AM make it suitable for ensuring clear communication in critical situations where reliability is paramount.
5. Remote Sensing and Control: Amplitude modulation is used in various remote sensing and control applications. For instance, AM signals are used in remote-controlled toys, garage door openers, and wireless sensors. The straightforward nature of AM simplifies the design and operation of these devices.
6. Signal Processing and Testing: In signal processing and electronic testing, amplitude modulation is used to test the performance of circuits and systems. Modulated signals help engineers analyze how devices respond to different types of input, facilitating the development and optimization of electronic equipment.

Conclusion

In this article, we have studied about the Amplitude modulation and got basic understanding of it. There are various techniques involved during the Amplitude modulation. Amplitude modulation will remain a unique and important technique in the field of communication, We have studied the workings of the various systems. From past time AM radio broadcasting to the modern day advancements such as aviation and maritime communication, AM continues to serve as a reliable method for transmitting information over long distances. This perform the vital performance by its applications and usability in emergency services it is also very important in remote sensing etc.