Voltage-current definition of impedance of double ridge waveguide using the finite element method

The impedance of a ridge waveguide may be calculated by recognising that its electric field distribution is the same at cut-off and at infinite frequency and that the ratio of the transverse fields is equal to the wave impedance at infinite frequency. This means that a knowledge of the electric field normal to the interior metalisation of the waveguide is sufficient for the evaluation of the voltage-current definition of characteristic impedance in ridge and other homogeneous waveguides. This paper provides one numerical solution based on the finite element method. It also includes some additional calculations on the power-voltage and power-current definitions of impedance. It therefore embodies descriptions of all three classic definitions of impedance in this sort of waveguide.