HFSS accepted power puzzle in a lossless matched antenna array

[alberthyc]

Hi all,

i've designed an two port antenna array in HFSS. The antenna is CPW, and each antenna is fed by a 50 Ohm coaxial cable, which is excited by a wave port. The antenna is lossless, using pec and no dielectric loss. at operating frequency, S11 and S22 is around -25dB and S12 is around -14dB. Each wave port is renormalized to input impedance (Z11,Z22) at the port, which is not 50Ohm but something else.

Th puzzle is, in HFSS, i make only 1 port have input power, which is 1W, the other port has 0 input power. Then i compute the far field parameter over a sphere, i found the accepted power is only 0.7Watt,(input power is 1 watt) but since my s11,s22 and s12 are pretty small, the ports are matched, i should expect something close to 1W. I wonder where does the power go?

Any answer will be appreciated. Thanks!

 

[kspalla]

Please share the design for better understanding

 

[alberthyc]

HI, i figured it out. The port renormalization (wave port) doesn't do anything to the calculation of accepted power. The value is the same before and after the renormalization, quite weird.

 

[kae_jolie]

Hi alberthyc,
Could you share how you figured out where the remaining power went? I'm trying to impedance match a 5-element dipole array but with no luck. I tried to match it with Active Z re and im values, but I still get power accepted much less than power incident.

Thanks.