Traveling Waves: Lossless Lines

The provided content explores the behavior of traveling waves on single-phase lossless transmission lines. It begins with a single-phase two-wire lossless transmission line of length Δx, characterized by a loop inductance LH/m and a line-to-line capacitance C F/m. These parameters result in a series inductance LΔx  and a shunt capacitance CΔx.

The voltage v(x,t) and current i(x,t) at any position x and time t on the line are expressed using Kirchhoff's Voltage Law (KVL) and Kirchhoff's Current Law (KCL).

As Δx approaches zero, partial differential equations emerge, capturing the relationships between voltage, current, and their rates of change with respect to both time and position. Laplace transforms are applied to convert these partial differential equations into ordinary differential equations, assuming zero initial conditions.

The solutions to these equations reveal that the velocity of the traveling waves depends on the inductance and capacitance per unit length of the transmission line.

These solutions describe forward and backward waves; forward waves travel in the positive x-direction, and backward waves move in the negative x-direction. The solution incorporates a time shift and results in functions that describe voltage and current as sums of forward and backward traveling waves. These waves move in opposite directions along the transmission line, influenced by the line's inductance and capacitance. These expressions lead to the line's characteristic impedance, a function of the inductance and capacitance per unit length.

This parameter is crucial for understanding how the waves propagate along the line and interact with the terminations at each end.