6.2.3   Frequency dependent propagation constant

QuickWave enables the calculation of the frequency dependent complex propagation constant in the transmission lines. The propagation constant is calculated at each transmission line port. It is given as a magnitude and phase curves (in Extended Results mode), which can be easily transformed into real and imaginary parts using the built in calculator functions.

The value of propagation constant calculated at each port can serve in the following ways:

• Since we usually know what kind of propagation constant dependence versus frequency we can expect, it can serve, as a supplementary verification if the mode we are using is the correct one.

• Ripples on this characteristic can indicate the frequency bands with lower accuracy of analysis of the particular port (for example, in the case of a very small signal appearing at this port).

• It can be used in calculation of S-parameters with changed reference plane position.

Frequency dependent propagation constant is calculated when S-Parameters post-processing is active. The magnitude is available in a standard Results window display and the phase becomes available when the results are displayed in the Extended Results regime.

A discussion concerning the propagation constant in the exemplary waveguide to coaxial line transition is presented in User Guide 3D: Advanced S-parameter problems for waveguide-to-coax example.