Negative Real part Of input impedance

[mirok]

Hi

I simulate an inverted patch microstrip antennac using FDTD. the feed structure that I used, was a Gussian Pulse input J-current. Everything is ok. and I almost get good result but the problem is that the real part of input impedance is negative. Can anybody have any comment about that?

tanx

 

[JRAMA]

the negative real part of the input impedance is due to the lack of energy absorbing layers.
so you need to incorporate some kind of energy absorbing mechanism(like dielectric loading) in your design.

i had the similar problem when i was simulating my antenna using FDTD based Zeland Software.When i increased the number of perfectly matched layers(PML),i could able to get the real part of the impedance in positive.

all the best.

 

[jbartos]

Suggestion: Have you tried to increase the antenna thickness?