摘要： This paper proposed an X-band compact 3-dB waveguide coupler with high power capacity and compact structure designed for a SLED pulse compression device and conducted the researches on structure design, theoretical analysis and numerical simulation. The structure of the 3-dB coupler is very simple, which is mainly constructed by two standard rectangular waveguides with a coupling hole connects them. The numerical simulation results show that the reflection coefficient S11 and the transmission coefficient S21 are both smaller than -47dB at the center frequency of 9.3GHz, which means low reflection and high isolation between Port 1 and Port 2. The transmission coefficients S31 and S41 are - 2.99dB and -3.01dB, respectively, which implies good 3-dB coupling characteristic of the device. And the phase difference of the output signals of these two 3-dB coupling ports is exactly 90 degrees. The 3-dB coupler is with higher power capacity because there is no electric field enhancement in the coupling area. When two 45 MW microwave pulses with phase difference of 90 degrees are injected from Port 3 and Port 4, the microwave energy will be composited and output from Port 2. The maximum electric field of 300kV/cm appears in the center of the output waveguide. Under the vacuum condition, the power capacity of the 3-dB coupler is up to 250MW.