Chapter 13, Problem 13.6P

Consider an air-filled coaxial transmission line having inner and outer radii a and b. (a) Show that skin effect loss in the line is minimized when b/a = 3.6, yielding characteristic impedance $Z_0=77\Omega$. (b) Show that the maximum power the line can carry before air breakdown occurs is achieved when b/a = 1.65., yielding characteristic impedance Z₀ = 30 ohms. Assume low loss, such that the attenuation coefficient is given by Eq. (54a) in Chapter 10.