Antenna design required ?

Hi,

I am working on a design of RHCP antenna having a minimum gain of 18dBi with a beamwidth of 40-50 degrees. The maximum I can achieve is 12 dBi with 60 degrees beamwith using conical ridged septum polarizer. Can somebody tell me that is there any way to come close to my requirement. Any new antenna or a new configuration would be appreciated. Waiting an early reply

You can make a phased array of four of these elements and get about 5 dB more gain. This will about halve your beam width.