The complex design and development of a planar multilayer phased array antenna in microstrip technology can be simplified using two commercially available design tools (1) Ansoft Ensemble and (2) HP-EEsof Touchstone. In the approach presented here, Touchstone is used to design RF switches and phase shifters whose scattering parameters are incorporated in Ensemble simulations using its black box tool. Using this approach, Ensemble is able to analyze fully the performance of the radiating and beamforming layers of a phased array prior to its manufacture. This strategy is demonstrated in a design example of a 12-element linearly-polarized circular phased array operating at L band. A comparison between theoretical and experimental results of the array is demonstrated.