Mobile electronic devices have become both more numerous and more compact while at the same time integrating more and more radio frequency (RF) functionality. Multiple transmit and receive systems with different communications protocols and with different antennas are routinely being used for personal communications: voice, data, location services, etc. High speed clock and data lines in devices can radiate and couple to antennas. Modern automobiles can have 10 to 30 antennas at different frequencies and locations for functions ranging from collision avoidance to tire pressure. To make introduction of new products in this environment faster, it is important that the possible couplings between the various systems on one platform can be determined before fabrication and field testing. We will discuss the use of CST STUDIO SUITE® to perform EM analysis of a cell phone with multiple antennas and high speed data lines, and of an automobile containing an LTE cell phone, commercial FM, GPS, and commercial VHF & UHF antennas.