Worked example 7.2.1: An EMC stripline for immunity testing

$Z_0=\frac{377\times 0.15}{0.8}=70.7\Omega$. Fringing changes this somewhat. Real cells are built for $50$ to $90\Omega$.

$f_{co,1}=\frac{c}{2b}=\frac{3\times 10^8}{0.3}=1\mathrm{GHz}$. The finite width adds further modes, so such cells are used only to a few hundred MHz ($b\le 0.2\lambda$ at $400\mathrm{MHz}$).

$100V/m$: $V=100\times 0.15=15\mathrm{V}$ and $P=\frac{15^2}{2\times 70.7}=1.59\mathrm{W}$. $200V/m$: $V=30\mathrm{V}$ and $P=6.37\mathrm{W}$, four times as much since $P\propto E^2$.

$H=E/{\eta }_0=100/377=0.265A/m$ and $S=\frac{E^2}{2{\eta }_0}=13.3W/{\mathrm{m}}^2$.

The Poynting flux over the cross-section, $Sbw=13.3\times 0.15\times 0.8=1.59\mathrm{W}$, equals the circuit power of part (c).