Consider the definition of the admittance Y=G−iB of a two-terminal linear passive network in terms of field quantities by means of the complex Poynting theorem of Section 6.9.
(a) By considering the complex conjugate of (6.134) obtain general expressions for the conductance G and susceptance B for the general case including radiation loss.
(b) Show that at low frequencies the expressions equivalent to (6.139) and (6.140) are
G≈∣Vi∣21∫Vσ∣E∣2d3xB≈−∣Vi∣24ω∫V(wm−we)d3x