The purpose of this research was to design a dual feed, dual frequency (i.e., L1L5) patch antenna for the Global Navigation Satellite System (GNSS). First, two commercially available patch antennas were simulated using Ansoft High Frequency Structure Simulator (HFSS) and measured in the Ohio University, School of Electrical Engineering and Computer Science, Antenna Anechoic Chamber. One was a low-cost GPS L1 single frequency patch antenna and other was a GPS L1L2 dual frequency patch antenna. The results from the simulation and measurement for these two antennas are presented, compared, and used as part of the validation process for the dual frequency right hand circularly polarized patch antenna designed for GNSS L1L5 operation. This prototype antenna design was targeted at dual frequency high accuracy civil applications for future GNSS applications. The antenna was designed based on the simulations from HFSS, through which the radiation patterns and other antenna parameters were generated. The predicted performance of this prototype antenna from HFSS simulation generally matches the performance specification for a GNSS dual frequency patch style antenna.