microstrip antenna feed position

i m new to design microstrip antenna...If anybody can help me to find whats the feed position to get 50ohms in microstrip antenna for 1.645GHz and whats the equation for input impedance of microstrip antenna...

Take a look at chapter 14: Microstrip antennas in Balanis book "Antenna theory". Example 14.2 in that chapter gives an example what you are looking for.

Regards,
Shameem