s11 antenna -10 db

Lets say I have a monopole antenna and S11 for this monopole is -5dB (in free space) over a certain frequency range. If I improve S11 from -5dB to -20dB over the same frequency range, would this be considered as a good improvement? In addition to the improvement in the S11, if I obtain 12 degrees of half power beamwidths both in E-plane and H-plane, would this be a good contribution?

S11 of below -15 dB is very much acceptable. I am amazed at the increase in directivity. Typical monopole on a PEC ground plane has directivity of 3dB + 2.15 dB = 5.15 dB ( Dipole - 2.15 dB , radiating into half space ). Using an approximate formula for directivity ( 31200/product of beam widths in degrees in principal planes) it turns out to be approx 23 dB which is very very huge !!

-Arun

thank you very much

just a note... theoretically with the current system I am working on, it is possible to obtain 6 degrees of half power beamwidths in both planes.

I suspect it has to do with metamaterials !! Is it ? One thing , have you performed any experimental studies on this type of antenna

-Arun

yes