hi yuanboshybshyb
yeah in lower frequencies the antenna gain is about -2 to -3 dBi while for higher frequencies it is increased to 5 dBi.
Added after 5 minutes:
dear Aya2002
i desigend and implemented this antenna two years ago. are you implemented it? if yes, what did you do for feeding network and 180 hybrid?
oh ok! so are you simulated the feeding network. i saw your thesis, in your thesis you only presented the Duhamel approach for hybrid and couplers. are you could find any other approach for it?