Last Week's Question
The ratio of the electric field strength to the magnetic field strength for a wave propagating in RG58 coaxial cable (Z0 = 50 Ω, εr =2.3) is,
- 50 Ω
- 250 Ω
- 377 Ω
- > 10 MΩ
The correct answer is "b". The ratio of the electric field strength to the magnetic field strength for a wave propagating in a transmission line is equal to the intrinsic impedance of the dielectric. In this example, the dielectric has a relative permittivity equal to 2.3. Therefore, the intrinsic impedance is
Note that the "intrinsic impedance" of the dielectric is not the same thing as the "characteristic impedance" of the transmission line. Characteristic impedance is the ration of the voltage to the current in a wave propagating on the transmission line (in this example, 50 Ω).