What is the function of the "port impedance" for the voltage and current sources?
Altair EmployeeAnswers
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The 'port impedance' box on the voltage and current source is a post processing tool that allows for plotting the realised gain in POSTFEKO.
'Realised gain' as selected in POSTFEKO includes mismatch losses whereas 'Gain' does not. 'Gain' in FEKO is strictly according to the IEEE definition - all losses are included except mismatch losses.
When the user specifies an arbitrary impedance on the 'port impedance' box, POSTFEKO will use this value when it displays the 'realised gain' of the antenna. In addition, the ASCII OUT file will show, for models that contain only a single voltage or current source, the S11 for the antenna relative to this impedance.
Note that this is purely a post-processing tool and plotting the source data in POSTFEKO will give the same answer for e.g. reflection coefficient regardless of the 'port impedance' setting on the voltage/current sources.
[A further post-processing tool is provided in POSTFEKO when plotting source data namely the 'reference impedance' available on the result palette for source data. This allows plotting the reflection coefficient (or for the case of a single antenna, the S11 derived from the reflection coefficient) relative to an arbitrary impedance.]
The 'port impedance' setting on the voltage and current sources will not affect the 'gain' or the source power or the radiated power.
Note further that when multiport S-parameters are requested, a new S-parameter configuration is created in CADFEKO which does not allow for any voltage or current sources to be specified. FEKO will compute the S-parameters only and these parameters will be relative to the reference impedances specified in the S-parameter request in CADFEKO.
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