Sector Antenna for 5GHz Wifi

It is a centre-fed broadside array antenna, based on the Franklin Antenna
It has high gain but a very narrow focus beam
You will often find these antennas on mobile phone masts in an array setup of 6 or more.

¼ wave 12.93mm
½ wave 25.86mm
Back Reflector 35mm by 240mm

http://en.wikipedia.org/wiki/Sector_antenna