1. Transmission lines

2. Outline Types of transmission lines parallel conductors coaxial cables
transmission line wave propagation
Losses
characteristics impedance
incident and reflected wave and impedance matching

3. transmission media Guided Unguided
some form of conductor that provide conduit in which signals are contained
the conductor directs the signal
examples: copper wire, optical fiber
Unguided
wireless systems – without physical conductor
signals are radiated through air or vacuum
direction – depends on which direction the signal is emitted
examples: air, free space

4. transmission media Cable transmission media
guided transmission medium and can be any physical facility used to propagate EM signals between two locations
e.g.: metallic cables (open wire, twisted pair), optical cables (plastic, glass core)

5. incident and reflected wave
Incident voltage
voltage that propagates from sources toward the load
Reflected wave
Voltage that propagates from the load toward the sources

6. classifications of transmission lines
Balanced Transmission line
2 wire balanced line.
both conductors carry current. But only one conductor carry signals.

7. classifications of transmission lines

8. classifications of transmission lines
Unbalanced Transmission line
One wire is at ground potential
the other wire is at signal potential
advantages – only one wire for each signal
disadvantages –reduced immunity to noises

9. classifications of transmission lines

10. classifications of transmission lines
Baluns
Balanced transmission lines connected to unbalanced transmission lines
e.g.: coaxial cable to be connected to antenna

11. Metallic Transmission Lines types
Parallel conductors
Coaxial cable

12. parallel conductors
consists of two or more metallic conductors (copper)
separated by insulator – air, rubber etc.
Most common
Open Wire
Twin lead
Twisted Pair (UTP & STP)

13. parallel conductors Open Wire two-wire parallel conductors
Closely spaces by air
Non conductive spaces
support
constant distance between conductors (2-6 inches)
Pro – simple construction
Contra – no shielding, high radiation loss, crosstalk
application – standard voice grade telephone

14. parallel conductors Twin lead
spacers between the two conductor are replaced with continuous dielectric – uniform spacing
application – to connect TV to rooftop antennas
material used for dielectric – Teflon, polyethylene

15. parallel conductors Twisted pair
formed by twisting two insulated conductors around each other
Neighboring pairs is twisted each other to reduce EMI and RFI from external sources
reduce crosstalk between cable pairs

16. parallel conductors Unshielded Twisted Pair
two copper wire encapsulated in PVC
twisted to reduce crosstalk and interference
improve the bandwidth significantly
Used for telephone systems and local area network

17. parallel conductors UTP – Cable Type Level 1 (Category 1)
ordinary thin cables
for voice grade telephone and low speed data
Level 2 (Category 2)
Better than cat. 1
For token ring LAN at tx. rate of 4 Mbps
Category 3
more stringent requirement than level 1 and 2
more immunity than crosstalk
for token ring (16Mbps), 10Base T Ethernet (10Mbps)

18. parallel conductors UTP – Cable Type Category 4 Category 5 Category 5e
upgrade version of cat. 3
tighter constraints for attenuation and crosstalk
up to 100 Mbps
Category 5
better attenuation and crosstalk characteristics
used in modern LAN. Data up to 100Mbps
Category 5e
enhanced category 5
data speed up to 350 Mbps

19. parallel conductors UTP – Cable Type Category 6
data speed up to 550 Mbps
fabricated with closer tolerances and use more advance connectors

20. parallel conductors Shielded Twisted Pair (STP)
wires and dielectric are enclosed in a conductive metal sleeve called foil or mesh called braid
the sleeve connected to ground acts as shield – prevent the signal radiating beyond the boundaries

21. parallel conductors STP – Category Category 5e
Feature individually shielded pairs of twisted wire
Category 7
4 pairs
surrounded by common metallic foil shield and shielded foil twisted pair
1Gbps
Foil twisted pair
Four pairs of 24-AWG copper wires encapsulated in a common metallic-foil shield with a PVC outer sheath
to minimize EMI susceptibility while maximizing EMI immunity
> 1Gbps
shielded-foil twisted pair
Four pairs of 24-AWG copper wires surrounded by a common metallic-foil shield encapsulated in a braided metallic shield
offer superior EMI protection

22. Coaxial cable used for high data transmission
coaxial – reduce losses and isolate transmission path
basics
center conductor surrounded by insulation
shielded by foil or braid

23. Metallic transmission lines
Coaxial cable
Rigid air filled
solid flexible

24. Guided Media – Coaxial Cable
BNC Connectors
To connect coaxial cable to devices, it is necessary to use
coaxial connectors.
The most common type of connector is the Bayone-Neill-Concelman, or BNC, connectors.
Types: BNC connector, BNC barrel, BNC T, Type-N, Type-N barrel.
Applications include cable TV networks, and some traditional Ethernet LANs like 10Base-2, or 10-Base5.

25. Two-wire parallel transmission line electrical equivalent circuit

26. Characteristic Impedance of a Line
A terminated transmission line that is matched in its characteristic impedance is called a matched line
The characteristic impedance depends upon the electrical properties of the line, according to the formula:
The characteristic impedance can be calculated by using Ohm’s Law:
Zo = Eo / Io
where Eo is source voltage and Io is transmission line current

27. Characteristic Impedance
The characteristic impedance for any type of transmission line can be calculated by calculating the inductance and impedance per unit length
For a parallel line with an air the dielectric impedance is:
Zo = the characteristic impedance (ohms)
D = the distance between the centers
r = the radius of the conductor

28. Coaxial cable Z0 = the characteristic impedance (ohms)
D = the diameter of the outer conductor
d = the diameter of the inner conductor
= the permittivity of the material
r = the relative permittivity or dielectric constant of the medium
0 = the permeability of free space
For extremely high frequencies, characteristic impedance can be given by
Zo =

29. Wave propagation on Metallic transmission lines
Velocity factor
The ratio of the actual velocity of propagation of EM wave through a given medium to the velocity of propagation through vacuum
Vf = velocity factor
Vp = actual velocity of propagation
c = velocity of propagation in vacuum

30. transmission line wave propagation
rearranged equation
the velocity via tx. line depends on the dielectric constant of insulating material
ϵr = dielectric constant
The velocity along tx. line varies with inductance and capacitance of the cable

31. transmission line wave propagationas
velocity x time = distance
therefore
normalized distance to 1 meter
Vp = velocity of propagation
√LC = seconds
L = inductance
C = capacitance

32. transmission line wave propagation
Question
A coaxial cable with
distributed capacitance C = 96.6 pf/H
Distributed inductance L = nH/m
Relative dielectric constant. ϵr = 2.3
Determine the velocity of propagation and the velocity factor

33. Losses Conductor Losses conductor heating loss - I2R power loss
the loss varies depends on
the length of the tx. line
Dielectric Heating Losses
difference of potential
between two conductors of
a metallic tx lines
Negligible for air dielectric
increase with frequency for
solid core tx line
Radiation Losses
the energy of electrostatic
and EM field radiated from
the wire and transfer to the
nearby conductive material
Reduced by shielding the cable

34. Losses Coupling Losses Corona
whenever connection is made between two tx line
discontinuities due to mechanical connection where dissimilar material meets
tend to heat up, radiate energy and dissipate power
Corona
luminous discharge that occurs between two conductors of transmission line
when the difference of potential between lines exceeds the breakdown voltage of dielectric insulator