We present the performance of an RF amplifier and digital modulation techniques in the presence of high-power electromagnetic interference (EMI) to provide existing and next generation communication systems with critical information. An advanced measurement setup comprised of a large-signal network analyzer is used to characterize the adverse effects of EMI on the device characteristics of an RF power amplifier and the performance of digital modulation schemes. Furthermore, our analysis incorporated hybrid numerical tools, such as the hybrid S-parameter method to carry out an extensive EMI analysis of digital modulation schemes in the presence of complex structures, such as cylindrical cavities. Our studies yield critical information for the communication systems. For instance, our analysis suggests that digital modulation schemes are more susceptible to EMI than the RF power amplifier that processes the modulated signals. Power levels of the order of megawatts are required to have a notable impact on the device characteristics of an RF amplifier in the presence of a missile-like body, whereas, much lower power levels are sufficient to degrade the performance of a digital modulation scheme as long as it is within the bandwidth of the modulated signal. Our analysis further indicates that nonconstant envelope digital modulation schemes are more susceptible to EMI.