[Physics Class Notes] on Communication Systems Pdf for Exam

The communication system is a system model that describes a communication exchange between two stations, transmitter, and receiver. Signals or information passes from source to destination through a channel. It represents a way in which the signal uses it to move from a source toward its destination. To transmit signals in a communication system, it should first be processed by beginning from signal representation, to signal shaping until encoding and modulation. After the transmitted signal is prepared, it is passed to the transmission line of the channel. Due to signal crossing this media, it is faced with many impairments like noise, attenuation, and distortion.

The process of transferring the information between two points is called communication. The main elements needed to communicate are the transmitter to send the information, the medium to send the information and the receiver to receive the information on the other end. 

Types of Communication Systems

Based on physical infrastructure:

Based on physical infrastructure there are two types of communication systems:

• Line communication systems: Uses the existing infrastructure of power lines to transfer data from one point to another point.

• Radio Communication systems: uses the infrastructure of radio waves to transfer the information from one point to another point.

There is a physical link, called a hardwire channel between the transmitter and the receiver inline communication systems. 

Based on Signal specifications:

Signal specifications that are used to decide the type of communication system are:

• Nature of the baseband or information signal: Baseband signals is a technology which can access the signals with very low frequency and also near zero frequency and based on the nature of the transmitted signal, the baseband signal can either be transmitted as it is without modulation or through a carrier signal with modulation.

Further, communication systems are divided into:

• Analog communication systems: The Analog system conveys the information from the audio, video and pictures between two points using the analogue signals. A sinusoidal signal is an example of an analogue communication system.

• Digital communication systems: Digital communication has become very important in the age of the internet. It is a physical exchange of information between two points discreetly. The information exchange happens through digital signals. 

• Baseband communication system: Baseband communication is the transfer of signals that are not amplified to higher frequencies. They help in transferring signals with near-zero frequency.

• Carrier communication system: Carrier communication systems transfer the information especially voice messages and calls by improving the frequency much higher than the actual rate. 

Out of four, a minimum of two types is needed to specify any communication system. Thus, two groups are formed consisting of each of the two types such that at least one of the types from each group is necessarily required to specify a communication system. These groups can be formed as:

To completely define any communication system, four out of the eight types are required. If any type is missing, then the description of the communication system will be incomplete.

Wireless and Wired communication system

Wireless communication systems use radio waves, electromagnetic waves and infrared waves to communicate from one point to another point and the wire communication system uses wire, optical fibre which works on the phenomenon of total internal reflection to communicate from one point to another point. 

Wireless communication is further divided into satellite communication, ground wave communication, skywave and space wave communication. The satellite communication receives the signals from the earth and resends them back to another point on the earth with the help of a transponder. Wired communication is further divided into parallel wire, twisted wire, optical fibre and coaxial wired communication.

Terms Used in Communication Systems

1. Signal

A signal is that information that has been converted into a digital format. Analog signals (such as human voice) or digital signals (binary data) are inputted to the system, processed within the electronic circuits for transmission, then decoded by the receiver. The system is claimed to be reliable and effective; only errors are minimized within the process. 

2. Communication Channel

A communication channel is a medium by which a signal travels.

3. Transducer

The device used to convert one form of energy into another form is a transducer.

4. Receiver

A receiver is a device that receives the signals sent/ transmitted by the senders and decodes them into a form that is understandable by humans. 

5. Attenuation

Attenuation is the reduction in the strength of analog or digital signal as it is transmitted over a communication medium. 

6. Amplitude

An amplitude of the signal refers to the strength of the signal.

7. Amplification

Amplification is the process to strengthen the amplitude of the signals using an electronic circuit.

8. Bandwidth

Bandwidth explains the range of frequency over which a signal has been transmitted.

9. Modulation

As the original message signal can’t be transmitted over an outsized distance due to their low frequency and amplitude, they’re superimposed with high frequency and amplitude waves called carrier waves. This phenomenon of superimposing a message signal with a carrier wave is called modulation. And the resultant wave is a modulated wave which is to be transmitted.

Different Types of Modulation.

10. Demodulation

Demodulation takes a modulated signal and then extracts the original message from it.

11. Repeater

The repeater extends the range of communication systems by amplifying the signals.

12. Noise

Any electrical signal which interferes with an information signal is called noise.

Did You Know?

• Communication in Organization Flows in Various Patterns.

• Communication Is Media or Channel Based

• There are around 250 billion emails sent every day. Around 80% of these are spam.

• Around 20 hours of video are uploaded to YouT
  ube every minute. 

• Fiber optics are good because they use less energy and are better for the environment than electrical wires. They are also very resistant to weather. 

• The first telephone pole was built in 1876. 

• There are over 4 billion cell phones within the world and phones that are thrown away every year are over  100 million.

• The first cell phone was invented by a company called Motorola.

• Over 3.8 billion people use the internet, which is 40% of the world’s population.

• The first smiley appeared in 1979, it first looked like this -) then three years later a colon was added to it and it took the form of 🙂 this.