Analysis of Multiconductor Transmission Lines, 2nd Edition

5

THE PER-UNIT-LENGTH PARAMETERS FOR MULTICONDUCTOR LINES

In this chapter, we will extend the notions developed for two-conductor lines in the previous chapter to multiconductor lines. In general, the concepts are identical but the details are more involved. We will find that numerical approximate methods must generally be employed to compute the entries in the per-unit-length parameter matrices L, C, and G. The entries in the per-unit-length resistance matrix R are grouped as shown in Chapter 3, Eqs. (3.12) and (3.13), and are computed, as an approximation, for the isolated conductors. Hence, the entries in R are the same as were obtained for two-conductor lines in the previous chapter; that is, we disregard proximity effect in the resistance calculation.

In the case of multiconductor transmission lines (MTLs), the situation is somewhat similar except that the details become more involved. In the case of a MTL where the conductors have circular, cylindrical cross sections such as wires and the surrounding medium is homogeneous, we can obtain approximate closed-form solutions for the entries in the per-unit-length parameter matrices L, C, and G under the assumption that the conductors are widely separated from each other. This condition of being widely separated is not very restrictive for typical dimensions of wire-type lines such as ribbon cables. However, dielectric insulations are usually present around the conductors of wire-type lines such as ribbon cables, and therefore ...