A quasi-stationary method in conjunction with geometrical theory of diffraction (GTD) techniques is used for calculating the backscattered field from a large rotating conducting cylinder with an arbitrary cross section. Using this method, the scattered field at each time

is obtained as if the cylinder were stationary. The power density spectrum is then obtained using a Fourier transform. The backscattcr power density spectrum of a large rotating cylinder consists of discrete spectral lines. For an orthogonal polygon-cylinder rotating about its geometrical center axis, the backscatter power density spectrum is symmetric about the incident frequency.