Although pulse combustion has been successfully utilized in various commercial applications, one potential application yet to reach the market is the pressure gain gas turbine (PGGT). A PGGT would incorporate a pulse combustor rather than the typical steady-flow combustor to increase system efficiency and decrease pollutant emissions. The distinctive advantage of pulse combustion is its ability to achieve a stagnation ＇＇pressure gain＇＇ from inlet to exit A primary concern with pressure gain combustion development, however, is the lack of understanding as to how a combustor should be designed to achieve a pressure gain. While significant progress has been made in understanding the fundamental controlling physics of pulse combustor operation, little research has been aimed at understanding and predicting whether a given system will produce pressure gain. The following paper proposes a simple framework which helps to explain how a pulse combustor achieves a stagnation pressure gain from inlet to exit. The premise behind the framework is that pressure gain can be achieved by closely approximating a constant volume combustion process, and a constant volume combustion process is closely approximated by matching the resonant and operating frequencies of the system. The framework is primarily based upon results from a one-dimensional method-of-characteristics model.