Need explanation of high-order mode in hfss

[si_green]

high-order mode in hfss?

I don't undstand the high-order mode in hfss?
what is high-order mode?
I want to ask when should we conside the effect the high-order mode.
by the way, should the impedence of waveport be set??

Regards!

 

[svarun]

Re: high-order mode in hfss?

si_green,

As an example take a rectangular waveguide. It is known from basic EM theory that there are several modes of propagation (infinite to be exact ). Modes meaning the way the fields are distributed in space. When you start from very low frequencies no mode will propagate. As you go up only one mode wil be propagating (TE10) while all others will be cut-off. As you increase the frequency further after another cut-off two modes might propagate , the first one plus the new one which can propagate only when the driving frequency is above its cut-off and so on. HFSS asks you as to whether you want to take into account only the dominant mode ( lowest cut - off ) or more than one mode which may propagate at the given frequency. Normally for antenna and microstrip based applications for which I use HFSS, I consider only one mode. You may want to use more modes if the application type requires that. May be our other friends may throw light on this.

You don't need to set the impedance of a wave port. You may wish to define an integration line with respect to which HFSS calculates the voltage and current to determine the port impedance using the relation Z=V/I. This is optional.If you want to however , normalize the network parameters to some reference impedance you may use that value. Hope this helps.

-svarun