I. Introduction
Pulse-modulation power measurement is a crucial technology in research on large power microwave, which is of great significance for judging power capacity and radiation efficiency of pulse power source. As pulse power enhances to megawatt level or more, it puts higher demands on the measurement and calibration methods of large power pulse microwave[1]. Radiation field integral technologies[2–4] has been used for pulse-modulation power measurement. In this letter, we try to deduce formula of power based on radiation field integral algorithm, and analyze factors which affected the measurement results, and it would improve accuracy of radiation field integral algorithm.