In Radio Ultra High Frequency (UHF)300-3000 MHzTelevision,

In this lesson, you will learn the concepts of wireless transmission and its components. You will study the basics of antennas, frequency ranges, signal types and signal strength.

Wireless Transmission

Wireless communication technology has developed significantly over the past few decades and has become one of the most important types of media transmission from one device to another. Without the use of wires or electronic conductors, information can be transmitted by using electromagnetic waves. The various types of wireless communication include radio broadcast (RF), Infrared (IR), satellite, microwave, and Bluetooth. Mobile phones, GPS, Wi-Fi, and cordless telephones are devices that use wireless transmission to exchange data and information.

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Wireless Transmission

Frequency Ranges

Have you ever wondered how your television and mobile phone can work at the same time? Both receive signals via antenna in the form of electromagnetic waves but don’t interfere with each other. The reason is that all wireless devices operate in their own frequency bands within which they transmit and receive signals. For example, television broadcast operates between 54-216 MHz, FM radio operates between 87.

5-108 MHz and cell phones operate either between 824-894 MHz or 1850-1990 MHz.

Frequency Band Name Frequency Range Application
Extremely Low Frequency (ELF) 3-30 Hz Underwater Communication
Super Low Frequency (SLF) 30-300 Hz AC Power
Very Low Frequency (VLF) 3-30 kHz For Navigation Alarms
Low Frequency (LF) 30-300 kHz AM Radio
Medium Frequency (MF) 300-3000 kHz Aviation
High Frequency (HF) 3-30 MHz Shortwave Radio
Very High Frequency (VHF) 30-300 MHz FM Radio
Ultra High Frequency (UHF) 300-3000 MHz Television, mobile phones, GPS
Super High Frequency (SHF) 3-30 GHz Satellite, Wireless Communication
Extremely High Frequency (EHF) 30-300 GHz Remote Sensing, Astronomy

Components

The main components of wireless transmission are discussed below.

Antennas

An antenna is a group of metal conductors or elements which are connected to a transmitter or receiver. These are important components of wireless equipment that convert the electrical current moving in metal conductors to electromagnetic waves or radio waves. This radio equipment is mainly used for broadcasting television, cell phones, satellite communication, and radio broadcasting.At the transmitter end, the radio transmitter passes the electric current to the antenna’s terminals, and the antenna transmits radio waves. At the receiver end, the antenna converts radio waves into the electric current at its terminals where the electrical signal is amplified.

Signal Strength

The strength of a radio signal is defined as the transmitted power output received by an antenna receiver after transmitting from a wireless device. The signal strength for broadcast transmission is measured in dB-millivolts per meter. For low powered systems like mobile phones, it is measured in dB-microvolts per meter.The amount of power present in a received radio signal is often measured in receiver signal strength indicator (RSSI).

In wireless networking, IEEE 802.11 devices usually share this RSSI value with consumers due to variations in signal strength.

Signal Degradation

All types of signal data in wireless transmission have to deal with degradation. One form of degradation is called fading which results in weakened signal strength. A repeater or an amplifier is required to improve the strength of a signal over the transmission. The strength of a signal is also influenced by:

  • Shadowing
  • Reflection
  • Scattering
  • Diffraction

Signal Types

In wireless transmission, various types of signals are used by devices to communicate with each other.

Depending on their frequency and wavelength, following signals are used:

  • Radio Frequency: RF signals are electromagnetic signals that can travel long distances.
  • Infrared: These signals are used for short-range communications like TV remote control.
  • Microwave: They are mainly used for long-distance communication.
  • Lightwave: Lightwave radiations are optical signals that travel in a single direction.

Fixed vs Mobile Network

In a fixed network, the transmitter and the receiver are fixed in one place. The data transmission happens over fiber optics or copper cables using fixed links. The location of the subscriber is fixed and the network configurations are almost static.

A landline telephone is an example of a fixed network.In case of a mobile network, both the transmitter and the receiver are not always fixed and communication happens through electromagnetic radio waves. The network configurations are dynamic as the sender or receiver moves from one location to another. A cell phone is an example of a mobile network.

Lesson Summary

Wireless communication has become an important medium of transmission over the past few decades. The information is transmitted through wireless equipment which converts an electric current in metal conductors to electromagnetic waves (radio waves).Depending on the application of equipment, signals are transmitted over a wide range of frequencies. The main components of wireless transmission are the antenna, transmitter and receiver, signal types, signal strength and degradation, and fixed and mobile networks. The main application for wireless transmission is navigation, AM/FM radio, television, mobile phones, and GPS.

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