Transmission Lines and Wave Behavior

Transmission Lines

• A metallic conductor system used to transfer electrical energy from one point to another.
• Can be thought of as a material medium or structure that forms a path for directing the transmission of energy from one place to another.
• Impedance matching circuits are used to optimize energy transfer.

Behavior of Transmission Lines

• At low frequencies, behavior can be considered resistive, ideal, with no loss and no reactance.
• At high frequencies, behavior becomes complex and factors like resistance, inductance, capacitance, and conductance (RLCG) come into play.

Basic Kinds of Waves

• Incident Waves travel from the source to the load.
• Reflected Waves travel from the load back to the source.
• Longitudinal waves have a displacement of the medium that is parallel to the wave's propagation.
• Transverse waves have a displacement of the medium that is perpendicular to the wave's propagation.

Losses in Transmission Lines

Conductor heating loss

• Also known as I²R loss or power loss.
• Increases with frequency due to the skin effect.

Solutions to Skin Effect

• Increase the diameter of the conductor.
• Plate the conductor with silver.
• Use multi-stranded wire.

Dielectric heating loss

• Increases with frequency due to gradually worsening properties of the dielectric material at higher frequencies.
• More pronounced in solid dielectric but negligible in air dielectric.

Radiation loss

• Occurs because transmission lines can act as antennas when the separation between conductors is a significant fraction of a wavelength.
• Loss increases with frequency.
• Can be reduced by proper shielding.

Coupling loss

• Occurs when separate lines are connected or reconnected.
• Mechanical connections can cause discontinuities, leading to heat generation, radiation, and energy dissipation.
• UTP (Unshielded Twisted Pair) is an example of a transmission line that is susceptible to coupling loss.