The applet applies the complex combination theory of Section 1.3.3 and calculates the VSWR and load power for a cascaded component chain. The chain comprises two variable electrical length transmission line components separated by a resistive attenuator; each are specified by VSWR and resistive insertion loss. The source and load are also specified by VSWR.
All the 32 possible impedance combinations of the five defining VSWRs are evaluated. The common linear combination approximation is also evaluated for comparison.
Two plots options are available from the drop-down menu, Plot 1 shows the VSWR for two combinations of components. Plot 2 shows the resulting power delivered to the load.
Shown and tagged in black are the results of using simple linear combination.
Only two (shown in red and blue) of the 32 impedance combinations are displayed at any one time for clarity. The Z combination drop-down menu allows examination of all 16 pair sets of impedance combinations. Entered at the bottom of the display are the component impedance values, based on a system characteristic impedance of 100Ω, for the currently displayed pair. The component impedances are sent to the data console when data is saved.
The frequency range is adjustable and the default chosen to exhibit frequency dependent variation. Components 1 and 2 are characterised by different propagation time delays, defined by their electrical length.
Moving the mouse in VSWR/Frequency space displays the plotted values referred to the mouse x-axis position. The display automatically scales to the data input.
Components are normally specified by VSWR. Actual impedances may be above or below the system characteristic impedance. Alternating high and low impedance values produce the worst-case mismatches. On the other hand, if all impedances were identical regardless of the system characteristic impedance design value, the chain would not produce a standing wave and so appear matched.