Transmission Media

1. Transmission Media
Dr. Atiqur Rahman
ড. আতিক
ু র রহমান
PhD(CQUPT, China), MS.Engg.(CU), B.Sc.(CU)
Associate Professor
Department of Computer Science and Engineering
University of Chittagong

2. Unguided Media
• Unguided medium
transport waves without
using a physical
conductor
• Often referred to
wireless communication
• Signals are normally
broadcast through free
space and thus are
available to anyone who
has a device capable of
receiving them

3. Electromagnetic spectrum for Transmission Media

4. Electromagnetic Spectrum

5. Wireless Propagation
• Signal travels along three routes
-Ground wave
Follows contour of earth
Up to 2MHz
AM radio
-Sky wave
Amateur radio, BBC world service, Voice of America
Signal reflected from ionosphere layer of upper atmosphere
-Line of sight
Above 30Mhz
May be further than optical line of sight due to refraction

6. Ground Wave Propagation

7. Sky Wave Propagation

8. Line of Sight Propagation

9. Propagation Methods

10. Bands

11. Radio Waves
• Electromagnetic waves
ranging in frequencies
between 3 kHz and 1
GHz are normally called
radio waves
• Electromagnetic waves
ranging in frequencies
between 1 and 300 GHz
are called microwaves

12. Radio Waves

13. Omnidirectional Antenna

14. Electromagnetic Spectrum

15. Microwaves
• Electromagnetic waves
having frequencies
between 1 and 300 GHz
are called microwaves
• Microwaves are
unidirectional
• When an antenna
transmits microwaves,
they can be narrowly
focused

16. Electromagnetic Spectrum

17. Electromagnetic Spectrum

18. Terrestrial Microwave
• Parabolic dish
• Focused beam
• Line of sight
• Long haul telecommunications
• Higher frequencies give higher data rates

19. Terrestrial Microwave

20. Satellite Microwave
• Satellite is relay station
• Satellite receives on one frequency, amplifies or repeats signal and transmits
on another frequency
• Requires geo-stationary orbit
-Height of 35,784km
• Television
• Long distance telephone
• Private business networks

21. Satellite Microwave

22. Satellite Microwave

23. Satellite Microwave

24. Satellite Point to Point Link

25. Satellite Broadcast Link

26. Unidirectional Antennas

27. Satellite Microwave

28. Infrared
• Infrared waves, with
frequencies from 300
GHz to 400 THz
(wavelengths from 1 mm
to 770 nm), can be used
for short-range
communication
• Infrared waves, having
high frequencies, cannot
penetrate walls
• Prevents interference
between one system and
another

29. Infrared