In summer 2008 I had an idea of directional Wlan antenna and I started to simulate it in 4nec2. The basic idea was to design an antenna which can be made on same PCB as the rest of Wlan router and the antenna shouldn't lose power to the surrounding walls when mountedÂ on the wall (or corner of the room).
I used a smd-balun and capacitive matching to match the antenna for 50 ohm feed.
Here is the antenna draft simulated in 4nec2.
Final design in Eagle PCB CAD.
It works! Diameters are 5.5 cm x 4.3 cm