Abstract:  The radar cross section(RCS)is an important parameter of the scattering ability of incident wave, this pa-
per choose it as the research object，using the finite difference time domain method(FDTD)to simulate the progress
of terahertz Gaussian pulse scattering by particles making of copper and melamine formaldehyde resin(MF).The in-
cident plane wave is set as Gaussian pulse,the band width of which coverage for a range of frequencies to be calculat-
ed and the frequency response to scattering spheres can be get from Fouricr transform. In this paper, numerical cal-
culation of RCS has the following characteristic;the size of scattering target range from 300? m to 3? m，and tcra-
hertz wavelength range from 3 mm to 30? m，they are broadly overlapping. As a result of terahertz bandwidth, the
size range of the scattering particles is in the transition zone from Raylcigh scattering to Mie scattering, the use of
analytical solution is limited by the range of application, In this situation, numerical computational method FDTD is
selected to classify and compare scattering targets in different sizes(range from 300 ?m to 3? m)，matcrials(copper
and MF)and gcometrics(solid sphere, hollow sphere,two layers sphere). With the increase of diameters,electromag-
netic scattering intensity of metal and MF spheres radius of which are from 3? m to 300? m increase. At the same
time,the distribution of scattering intensity gradually focus to back. For the symmetry of forward and backward
scattering,MF spheres radius of which arc from 3 ?m to 30 ?m arc better than that of the metal spheres. Forward
and backward RCS of MF sphere radius of which is 3 um consistently increase with the frequency increase. On the
other hand，with the increase of particles size, oscillation of frequency response curves exacerbate，especially for the
backward scattering. When the particle size is increased by one order of ma}nitudc，the forward scattering intensity
of electric field is increased by 2 to 3 orders of magnitude.The numerical size difference of electric field scattering in-
tensity between forward scattering and backward scattering of MF spheres radius of which arc from 3 ? m to 300? m
gradually increase from the almost identical to 3 orders of magnitude. At last，for the hollow MF sphere radius of
which is 30 ?m,duc to the formation of a resonant cavity and small volume which takes part in forced vibration,
merge a number of distinct minima,and at the same time its RCS is significantly smaller than that of the solid MF
sphere.
The broadband characteristics of target contains a lot of information,thc low frequency region contains volume
information of the target，the resonant region contains contour information of the target.The research of RCS pro-
vides the basis for target detection and materials selection of terahertz band shielding.