Phase diagram of s11 positive and always >0 deg
please , when i simulate patch antenna , i find s11 for desirable frequency (fr) <-10dB (good adaptation) , but i find phase diagram of s11 positive and always >0 deg!
what that means please (physically) and is there an error §?
Can you post an S11 plot (on a Smith Chart with some frequency markers)?
phase of S11 always >0 means that your antenna appears to be (somewhat) inductive over the simulated frequency range. This can be a combination of certain transmission line length and non-optimum match.
yes thanks
../imgqa/eboard/EM/EM-55cqnhj2wm3.jpg
and look please , i have good adaptation in s11 magnitude coefficient (s11<-10dB)!
Nothing wrong with this!
If you change the match a bit, the S11 graph (on Smith chart) may encircle the center of the graph, and then you will see negative phase also.
If you would add a quarter wave transmission line between the actual feedpoint and the source, the S11 curve will be in the negative half of the Smith Chart. You may know that adding a 90 degrees long transmission line (50 Ohms, assuming 50 Ohms reference impedance), will rotate the curve on the Smith chart over -180 degrees.
De-embedding the port along the length of the transmission line will also counteract it's effect - essentially, giving you the phase response at the edge of the patch antenna.