Wireless Communication Methods
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Questions and Answers

What type of wireless signal propagation allows signals to reach beyond the visible horizon?

Ground wave propagation

What causes electromagnetic waves to slow down near the Earth's surface, enabling ground wave propagation?

Induction of tiny currents in the Earth

What atmospheric layer plays a crucial role in sky wave propagation?

Ionosphere

What is the frequency range typically used for radio beacons and AM radio?

<p>Frequencies below 2 MHz</p> Signup and view all the answers

What phenomenon allows ground waves to bend around obstacles like hills, extending their reach?

<p>Diffraction</p> Signup and view all the answers

What type of wireless communication allows signals to travel long distances beyond the horizon?

<p>Sky wave propagation</p> Signup and view all the answers

What is the benefit of using coaxial cables over twisted pair in long-distance telephone transmission?

<p>Shielding and layered design, allowing it to carry more than 10,000 phone calls.</p> Signup and view all the answers

What is the most common type of connector used in coaxial cables?

<p>BNC connector</p> Signup and view all the answers

What is the main advantage of using optical fiber cables?

<p>Immunity to electromagnetic interference (EMI) and high bandwidth.</p> Signup and view all the answers

What is the purpose of the cladding material in an optical fiber core?

<p>The cladding material is less dense than the core material, allowing for refraction and total internal reflection.</p> Signup and view all the answers

What is the bending of waves, such as light, as they pass from one medium to another with different densities?

<p>Refraction</p> Signup and view all the answers

What is the angle of incidence at which light, traveling from a denser medium to a less dense one, refracts at an angle of 90 degrees?

<p>Critical angle</p> Signup and view all the answers

What occurs when the angle of incidence is greater than the critical angle?

<p>Total internal reflection</p> Signup and view all the answers

What is Snell's Law used for?

<p>To find the relative refractive index and the critical angle.</p> Signup and view all the answers

What is the main advantage of twisted-pair cables over parallel lines?

<p>Reduced electromagnetic interference (EMI) and crosstalk between adjacent pairs</p> Signup and view all the answers

What type of material is used in fiber-optic cables?

<p>Glass or plastic</p> Signup and view all the answers

What is the purpose of the outer metallic mesh in coaxial cables?

<p>It serves as a shield against noise and as the second conductor to complete the circuit</p> Signup and view all the answers

What is the difference between RJ-11 and RJ-45 connectors?

<p>RJ-11 is used for telephone cables, while RJ-45 is used for computer networks and Ethernet</p> Signup and view all the answers

What is the benefit of using shielded twisted pair (STP) cables over unshielded twisted pair (UTP) cables?

<p>STP cables improve the quality of the signal by preventing noise and crosstalk penetration</p> Signup and view all the answers

What type of signals can coaxial cables transmit?

<p>Both analog and digital signals</p> Signup and view all the answers

Why are fiber-optic cables less susceptible to interference and crosstalk?

<p>Because they use light signals, which are not affected by electromagnetic interference</p> Signup and view all the answers

What is the main advantage of coaxial cables over twisted pair cables?

<p>Coaxial cables can carry signals of higher frequency ranges</p> Signup and view all the answers

Study Notes

Wireless Signals

  • Signals are broadcast through free space
  • Examples: Radio waves, Microwaves, Infrared

Radio Frequency Band

  • Propagation types:
    • Ground Wave Propagation
      • Travel along the surface of the Earth, following the curvature of the Earth
      • Can reach beyond the visible horizon
      • Frequencies below 2 MHz
      • Examples: Radio beacons, AM radio
    • Sky wave
      • Radio waves reflect off the ionosphere, the ionized upper layer of the atmosphere
      • Travel back down to Earth, allowing communication over long distances beyond the horizon

Transmission Media

  • Guided Media
    • Provide a physical path between devices, containing and directing signals within this pathway
    • Types:
      • Twisted-Pair cables
      • Coaxial Cables
      • Fiber-Optic cables
    • Unguided Media

Twisted-Pair Cables

  • Least expensive and most widely used guided media
  • Twisted to reduce electromagnetic interference (EMI) and crosstalk between adjacent pairs
  • Types:
    • Unshielded Twisted Pair (UTP)
      • Less expensive and most widely used
      • Connectors: RJ-11 (telephone cables), RJ-45 (computer networks, Ethernet)
    • Shielded Twisted Pair (STP)
      • Improves quality of cable by preventing noise or crosstalk
      • Bulkier and more expensive than UTP

Coaxial Cables

  • Carries signals of higher frequency ranges than twisted pair cables
  • Outer metallic mesh serves as a shield against noise and as the second conductor to complete the circuit
  • Transmit both analog and digital signals
  • Uses: Television, Cable TV, long-distance telephone transmission, LANs
  • Connectors: BNC connector is the most common

Optical Fiber Cables

  • Uses light signals
  • Immune to electromagnetic interference (EMI)
  • High bandwidth
  • Low Attenuation
  • Expensive
  • Core sizes: 50µm, 62.5µm, 9µm, etc.
  • Cladding diameter: 125µm
  • Core material is denser than the Cladding material

Refraction of Light

  • Refraction is the bending of waves, such as light, as they pass from one medium to another with different densities
  • Snell’s Law
    • Relative refractive index = Refractive index of the second medium / Refractive index of the first medium
  • Critical Angle
    • The angle of incidence at which light, traveling from a denser medium to a less dense one, refracts at an angle of 90 degrees
    • Making the light beam bend along the interface
  • Total Internal Reflection
    • If the angle of incidence is greater than the critical angle, then the light ray would undergo total internal reflection at the interface of the two mediums and reflect back into medium it originated

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Description

This quiz covers the basics of wireless communication, including signal propagation methods and types of waves used in wireless communication.

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