integration line in HFSS

can anybody tell me wats the purpose of an integration line once defining the ports, bcause sometimes i dont bother for defining the integration lines as it does not show any effect especially once i define a wave port...but for lumped port i have to define the integration line otherwise it gives an error...so can any body elaborate it plz.? and if am working on the waveguides then wat should be the direction of my integration line.?

If you search the site, you will find many previous posts on this subject. Below is a response I posted at the time:

The integration line is used to extract the impedance for a given waveguide cross section. There are three methods to extract the impedance in HFSS: Zpi, Zpv, Zvi. The Zpi (default) uses the initial power, 1Watt, and the enclosed current, I, to determine the impedance. The enclosed current is determined by the line integral of H around the periphery of the wave port (as it is a PEC boundary) so no integration line is required. The Zpv uses the integration line that is defined to integrate E upon, and it is best to define this line in the path of expected highest potential. As the line integral of E is the voltage, Zpv uses the initial power, 1Watt, and the voltage, as determined from the integration of E along the path defined by the integration line. Zvi determines Z using the voltage and the enclosed current.

The integration line also serves to set the initial phase (polarization) of the modes.

IMO, it is best simply to use the Zpi representation and not assigning integration lines in nearly 99% of waveports.

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