How to determine the size of the microstrip antenna

i want to design a circular polarization microstrip antenna at 2.4G band,are there any free software to calculate the size of the patch and the feed position.can anyone help me?

thanks in advance

ask www.zeland.com about trial of IE3D
or take Sonnet Lite for free from www.sonnetusa.com

both of this two are perfect and IE3D has examples of patch antenas and patch arrays designing.

the size fo the antenna depends largely on the operating frequncy and to some extent on the type of substrate material used (dielectric constant) and also the hieght of substrate. there are quite expressions available for regular sheped antennas (rectangular,circular,triangular and so on). u can refer them in any good book on microstrip antennas (like broadband microstrip antennas by g kumar and k p ray) . regarding feed postion there are no exact formulas available, the exact postion has to be optimised iteratively. and regarding cirular polarisation additonal techniques have to be employed like using two feeds or square shaped patches so on.

for the simulation of antennas u can use commercially available softwares like ie3d, hfss, ansoft designer and so on. ie3d is known to be quite accurate for microstrip antennas and evaluaton version is available which cab be used effectively.

sincerely
mstripman