This paper describes the development of a microwave window for high power pulsed traveling-wave tubes for radar application. Given the operational frequency band, the window dielectric materials (beryllia or alumina), and the standard waveguide (WR-90), a tridimensional frequency domain solver was used to design the window geometry. We present here the effect of the window parameters and the experimental result of a preliminary built window. The agreement between simulated and experimental results was about 97% at the beginning of the band and 92% at the end.