Transmission Lines

TRANSMISSION LINES
Introductory Lecture Engr. Duwi E. Iscala SoE/APC

What are transmission lines?
• Transmission lines are pieces of wire or cable used to carry telephone signals, computer data in LANs, TV signals in cable TV systems, and signals from a transmitter to an antenna, or vice versa.

Transmission Line
• Definition:
– Any means of conveying signal or power from one point to another

What are the different types of transmission lines?
• Parallel-wire lines

What are the different types of transmission lines?
• Coaxial cable

What are the different types of transmission lines?
• Twisted-pair cable

What are the different types of transmission lines?
• Fiber optic cable

Why are transmission lines important?
• Because they are MORE than pieces of wire or cables. They are CIRCUITS.
• They act as RESONANT CIRCUITS and REACTIVE COMPONENTS at very high frequencies

REACTIVE COMPONENTS

TUNED CIRCUITS

Electrical Characteristics
• They act as tuned circuits and filters. Their ELECTRICAL CHARACTERISTICS are critical in any communication system

Filters

MATCHING CIRCUIT
• Equipment and transmission lines must be MATCHED to each other for successful communication to take place. Transmission lines perform such matching.

Matching Circuit

General Classifications of Transmission Lines
• Balanced lines – used when balanced properties are considered
• Unbalanced lines – used when unbalanced properties are considered

Balanced Line
• Transmission line connection in which neither wire is connected to ground. Signal in each wire is referenced to ground.

Balanced Lines

Unbalanced Lines
• Transmission line connection in which one conductor is connected to ground.

Unbalanced Lines

Conversion
• To convert from balanced to unbalanced operation, or vice versa, uses BALUN (balanced-unbalanced)

Balun

Common-mode Rejection
• Balanced lines protection from noise pick up or cross talk from