antenna efficiency

I've tried HFSS ver.10 and it's efficiency simulation is way off the measurement from chamber...
any other candidates?

Take a look at the Antenna Modeling Design System

http://eesof.tm.agilent.com/products/amds_main.html

hi electro, that has to depend on what type of antenna you are simulating. HFSS is a full wave simulator using FEM, this should give you a much accurate result. But that has to depend on how you model you antenna in the simulator. But then, with any simulator, you can only get a rough idea of the actually efficiency so its best to build one and measure to find the actual efficiency of the antenna you have designed. Good luck