This paper investigates the feasibility of using a commercial electromagnetic solver - WIPL-D Microwave - to completely model frequency reconfigurable patch antennas based on packaged RF MEMS switches. The objective is to combine a 3D analysis of the antenna with a microwave circuit analysis in order to properly account the MEMS switch RF characteristic, the influence of MEMS encapsulation and the effects of the DC actuation circuit on the overall antenna performance. The results from the proposed simulation procedure are validated experimentally using a manufactured printed antenna prototype designed to switch between two frequencies in the 2 to 3 GHz range.