A wire antenna illuminated by plane wave or using port

[moshel]

Hi all,

I ran a simulation of a wire antenna (PEC) and wanted to see the RCS polar plot using a far field monitor.

I did it in two ways:
1. Used a port as my excitation source.
2. Used a plane wave as my excitation source.

Now,
When I set the antenna's lengths above one wavelength the results became different between the two cases.

Can someone tell me why is that?

 

[e_m_c]

Which software do you use? Could you attache corresponding projects?

 

[moshel]

I'm using CST. I will try to upload the files later on.

My question is basicly this:
Are the two cases I stated in 1,2 similar in any way?
Or should I expect to see totaly different results?

Thanks.