Communication System
Habish Ribin Haneef
Communication is a very imperative process in our everyday life. As you know, today we are living in a generation of great technological advancement. But, without the process of communication, all these advancements are difficult to process. Mobile phones, televisions, the Internet, etc., everything works through the process of communication. Such important is the process of communication. But, have you ever imagined what is actually happening in a communication system? How does it work? Ok, let’s see.
The process of transmission of information from one end to the other is called communication and the system through which this process occur is called communication system. A communication system mainly consists of a transmitter, a receiver, and a channel.
Depending on the signal specification or technology, the communication system is classified into two- analog communication and digital communication. In analog communication, the information is passed from the source to the destination in the form of analog signal. The analog signal is a continuous time-varying signal. A sound wave is an example of analog signal. Some of the common modes of analog communication are broadcast and telephone transmission. On the other hand, the transfer of data or information using digital signals is called digital communication. Here, the data are generated and processed in two states- a high state, represented as “1” and a low state, represented as “0”. In digital communication, data are stored and transmitted in the form of 1s and 0s, i.e., bits.
Now, depending on the communication channel, the communication system is again classified into two- wired communication and wireless communication. The transmission of data over a wire-based communication technology is called wired communication. Wired communication is also called wireline communication. Parallel wire communication, twisted wire communication, coaxial cable communication, and optical fibre communication are the common types of wired communication. Wireless communication is the transfer of data or information between two points without a continuous guided medium for the transfer process. Ground wave communication, skywave communication, space wave communication, and satellite communication are the common types of wireless communication.
Block Diagram of Communication System:
The block diagram of a communication system mainly consists of a transmitter, a receiver, and a channel in between them. The transmitter section consists of an information source, input transducer, amplifier, modulator and transmitting antenna. The receiver section consists of a receiving antenna, demodulator, detector, amplifier, output transducer, and information source.
The process of communication starts with the information source. The information source is the entity to be transmitted. It could be audio, video, pressure, temperature, picture, etc. The information signal or message signal is passed to the input transducer. The transducer is a device that converts one form of energy to the other. The process of converting energy from one form to another is called transduction. Actually, it is very difficult to find out the exact magnitude of physical forces like pressure and temperature. But if these physical forces are converted into electrical signals, then their values can be easily determined using a meter and it is for this purpose, transducers are used. A transducer converts physical force into an electrical signal and hence the values can be easily determined. Some examples of transducers are microphones and photodetectors. A microphone converts audio signals into electrical signals and a photodetector converts light signals into electrical signals.
From the input transducer, the signal is then fed to an amplifier. The amplifier is used to boost the power of a signal. In case of the signal strength becoming less than the required value, amplification can be done anywhere between the transmitter and receiver. For amplification process, a DC power source is installed.
After getting amplified, the signal is then passed to the modulator.The input information signal cannot be transmitted over a large distance due to its low frequency and amplitude. So, the information source is superimposed with carrier wave, a wave with high frequency and amplitude. The process of superimposing the information source with the carrier wave is called modulation. Modulation is of three types- amplitude modulation(AM), frequency modulation(FM), and phase modulation(PM). In amplitude modulation, the amplitude of the signal is varied by superimposing it with the high frequency carrier wave. In frequency modulation, the frequency of the signal is varied by superimposing it with the high frequency carrier wave. Frequency modulation is better than amplitude modulation as it removes noise from various sources. In phase modulation, the phase of the signal is varied by modulating the signal with the carrier wave. This type of modulation is also resistive to noise to a good extent.
After the modulation process, the modulated information signal is passed to the transmitting antenna. An antenna is a metallic object, often a collection of wires. The transmitting antenna supplies an electric current to the antenna’s terminals and the antenna radiates the energy from the current as electromagnetic waves.
The signal is then passed to the receiver section via a channel. A channel is a physical medium(wires, cables) through which the signal is transmitted from the transmitter to the receiver. Noise, attenuation, and distortion are some factors affecting the performance of the channel. These factors are a challenge for communication engineers. Noise is caused by some external and internal sources. Some examples for external sources are interference from nearby transmitted signals, interference generated by a natural source like lightning, solar or cosmic radiation, automobile generated radiation, etc. External noise can be reduced by the appropriate design of the channel, shielding of cables, and digital transmission. Some examples of internal noise are noise due to random motion and collision of electrons in the conductors, and thermal noise due to diffusion and recombination of charge carriers in other electronic devices. Internal noise can be reduced by cooling and digital transmission.
Attenuation is an issue caused by the medium. When the signal propogates through a medium for longer distance, the initial power decreases depending on the length of the medium. This is called attenuation. Attenuation can be minimized by boosting the power of the signal using amplifiers.
Distortion is another factor affecting the performance of the channel. When the signal gets distorted, the distorted signal’s frequency and bandwidth may be different from the transmitted signal.
In the receiver section, the signal first reaches the receiving antenna. The receiving antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified.
The signal is then fed to a demodulator. In demodulation, the reverse process of modulation occurs. Here, the separation of message signal from the carrier wave takes place. The information is retrieved from the modulated wave.
This is the working of a communication system in brief.
Applications of Communication System:
Some of the important applications of communication system are listed below,
- It is used in digital signal processing
- It is used in video compression
- It is used in speech processing
- It is used in data compression
- It is used in digital audio transmission
- It is used in space communication
- It is used in military for secure communication and missile guidance
- It is used in image processing
Read more:Integrated Circuits
Check your knowledge
Answer. The process of transmission of information from one end to the other is called communication.
Answer. The amplifier is used to boost the power of a signal. In case of the signal strength becoming less than the required value, amplification can be done anywhere between the transmitter and receiver
Answers. Noise, attenuation, and distortion
Answers. The process of superimposing the information source with the carrier wave is called modulation.