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A class-S power amplifier architecture theoretically offers high efficiency operation and seems to be an attractive alternative for classical PAs architecture. Switching mode PA principle assumes operation on digital, single-bit Delta-Sigma (Â¿Â¿) modulated signals which contain significant level of out-of-band noise. As a result, switching concept requires very narrowband, low loss filter solution which can handle with high power signals. Complexity of class-S idea and operation on different types of signals require definitions of new analyze and test procedures which are valid for switching mode PAs. Presented work describes spectral measurement tests for Â¿Â¿ modulated signals and output reconstruction filter. Moreover work defines filter requirements for output of the 3 types of modulation based on Â¿Â¿ scheme which can be engaged in class-S PA. Analyses and measurements were performed at the carrier frequency of 450 MHz.