PIFA Antenna ground plane size reduction

[Rengalakshmi]

hi frnd,
I need to design PIFA antenna for Gsm 900 band.. In which i want to know about how to reduce ground plane Size without affecting Resonate freq...And If any one know about Ansoft HFSS antenna design kit....and where we can download this design kit..

 

[pragash]

there few method of PIFA antenna size reduction. one i can remember is capacitive loading. add capacitance to the PIFA antenna, between the feed point and the open edge. however the trade off is efficiency and bandwidth reduction.

 

[AndreyG]

You can tune PIFA with small ground plane by increasing length of horizontal arm, meandering it, adding capacitance in different places as Pragash suggested, adding inductor in the middle of horizontal arm, playing with the short (changing it's position, adding components into it) but two things will always happen: bandwidth becomes narrow and you lose overall efficiency. The reduction of efficiency is fundamental: efficiency is function of antenna aperture. To understand better about efficiency and aperture relationships look at Chu - Wheeler criteria/limit, some recent publications by Steve Best. Ever since 1950's there are publications claiming to overcome Chu limit which would be revolutionary. Yet to my knowledge none of them resulted in practical designs.