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What type of antenna used in the mobile?

Answer is Omni directional antenna used in the mobile. There are various types of antenna used in mobile like, PIFA (Polar Inverted F Antenna) FICA etc

Radar Equation

The power Pr returning to the receiving antenna is given by the radar equation:

P_r = {{P_t G_t A_r \sigma F^4}\over{{(4\pi)}^2 R_t^2R_r^2}}

where

  • Pt = transmitter power
  • Gt = gain of the transmitting antenna
  • Ar = effective aperture (area) of the receiving antenna
  • σ = radar cross section, or scattering coefficient, of the target
  • F = pattern propagation factor
  • Rt = distance from the transmitter to the target
  • Rr = distance from the target to the receiver.

In the common case where the transmitter and the receiver are at the same location, Rt = Rr and the term Rt² Rr² can be replaced by R4, where R is the range. This yields:

P_r = {{P_t G_t A_r \sigma F^4}\over{{(4\pi)}^2 R^4}}.

This shows that the received power declines as the fourth power of the range, which means that the reflected power from distant targets is very, very small.

The equation above with F = 1 is a simplification for vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects should also be considered.

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Optical Fibers

FIG-OPTICAL FIBER

 Advantages and Disadvantages of Optical Fibres 
 ADVANTAGES
  • Capacity
Optical fibres carry signals with much less energy loss than copper cable and with a much higher bandwidth . This means that fibres can carry more channels of information over longer distances and with fewer repeaters required.
  •   Size and Weight
Optical fibre cables are much lighter and thinner than copper cables with the same bandwidth. This means that much less space is required in underground cabling ducts. Also they are easier for installation engineers to handle.
  • Security
Optical fibres are much more difficult to tap information from undetected; a great advantage for banks and security installations. They are immune to Electromagnetic interference from radio signals, car ignition systems, lightning etc. They can be routed safely through explosive or flammable atmospheres, for example, in the petrochemical industries or munitions sites, without any risk of ignition.
  • Running Costs
The main consideration in choosing fibre when installing domestic cable TV networks is the electric bill. Although copper coaxial cable can handle the bandwidth requirement over the short distances of a housing scheme, a copper system consumes far more electrical power than fibre, simply to carry the signals.
DISADVANTAGES
  • Price
In spite of the fact that the raw material for making optical fibres, sand, is abundant and cheap, optical fibres are still more expensive per metre than copper. Having said this, one fibre can carry many more signals than a single copper cable and the large transmission distances mean that fewer expensive repeaters are required.
  • Special Skills
Optical fibres cannot be joined together (spliced) as a easily as copper cable and requires additional training of personnel and expensive precision splicing and measurement equipment.


Why do we use optical fiber when we have wireless/mobile communication?
Answer is Because of its ability and stability to deliver very large throughput and at magnanimous speed which wireless/mobile are not able to deliver.WAN is largely interconnected with optical fiber between countries or continents.


applications of optical fiber
  • The use and demand for optical fiber has grown tremendously and optical-fiber applications are numerous. Telecommunication applications are widespread, ranging from global networks to desktop computers. These involve the transmission of voice, data, or video over distances of less than a meter to hundreds of kilometers, using one of a few standard fiber designs in one of several cable designs.
  • Carriers use optical fiber to carry plain old telephone service (POTS) across their nationwide networks. Local exchange carriers (LECs) use fiber to carry this same service between central office switches at local levels, and sometimes as far as the neighborhood or individual home (fiber to the home [FTTH]).
  • Optical fiber is also used extensively for transmission of data. Multinational firms need secure, reliable systems to transfer data and financial information between buildings to the desktop terminals or computers and to transfer data around the world. Cable television companies also use fiber for delivery of digital video and data services. The high bandwidth provided by fiber makes it the perfect choice for transmitting broadband signals, such as high-definition television (HDTV) telecasts.
  • Intelligent transportation systems, such as smart highways with intelligent traffic lights, automated tollbooths, and changeable message signs, also use fiber-optic-based telemetry systems.
  • Another important application for optical fiber is the biomedical industry. Fiber-optic systems are used in most modern telemedicine devices for transmission of digital diagnostic images. Other applications for optical fiber include space, military, automotive, and the industrial sector.

  
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