Elements of Electronic Communications System
Basic Elements of Electronic Communications System
Electronic communications is the transmission, reception, and processing of information between two or more locations with the use of electronic circuits. The basic components of electronic communications system are the transmitter, communications channel or medium, receiver, and noise. Analog signals (such human voice) or digital signals (binary data) are inputted to the system, processed in the electronic circuits for transmission, and then decoded by the receiver. The system is said to be reliable and effective only when errors are minimized in the process.
Let’s discuss each component of the system and we’ll take note of their important functions.
Transmitter is defined as a collection of one or more electronic devices or circuits that converts the original source information - also called as baseband signal - to a form suitable for transmission. It is a part of the system where the sender inputs or encodes the information. Examples of transmitters are our mobile phones and AM radio transmitters.
Functions of a Radio Transmitter
A radio transmitter is an electronic unit that accepts the information signal to be transmitted and converts it into a radio frequency (RF) signal capable of being transmitted over long distances.
A transmitter must:
- generate a signal of desired frequency
- provide some form of modulation that allows the information signal to modify a signal of higher frequency, also known as the carrier signal. Amplitude Modulation (AM) and Frequency Modulation are commonly used in broadcasting.
- provide power amplification in order to ensure that the signal level is high, in such a way that it will carry over the desired distance for which the signal is to be sent
The channel is the medium by which the electronic signal is sent or propagated from one place to another. It provides a means of transporting signals between a transmitter and a receiver. The channel can be as simple as copper wire or as complex as the optical fiber and satellite systems. Signals can also be propagated through radio waves or free space depending upon the type of modulation and frequency being used.
Although channel provides a way for communication, it also attenuates the signal that carries the message. All types of media are capable of degrading the signals, resulting to weaker signals, and appear to have smaller amplitudes. Amplifiers are included both in the transmitter and receiver to compensate this problem.
The receiver is a collection of electronic devices and circuits that accepts the transmitted signals from the transmission medium and then converts those signals back to their original form which is understandable by humans. One good example of a receiver is the television.
Primary requirements for any communications receiver:
- The ability of a receiver to select a signal of a desired frequency while rejecting those on closely adjacent frequencies. With good selectivity, the receiver can select the desired signal and eliminate all other RF signals. Tuned circuits or LC circuits are used to obtain selectivity.
- It is the ability of a receiver to pick up weak signals. Sensitivity is directly related to receiver's gain. By the way, gain is the factor by which an input signal is multiplied to produce the output. This can be increased by having a series of amplification. Better sensitivity is attained with higher gain.
This is how noise degrades the quality of a signal
- Noise is any unwanted electrical signals that interfere with the information signal. It is a random electrical energy that enters the system via the medium. However, noise can also be generated in the receiver which causes some errors in demodulation process. Noise may come from different sources such as the atmosphere, particularly lightning and thunderstorms. It may also come from the outer space where the sun and billions of stars emit radiation which interferes with the signal.
- Noise is inevitable, it is always present in a system. It can never be avoided, but can always be minimized with the use of sophisticated techniques and electronic circuits.
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