A Ku-band rotating

range-gated

fanbeam spaceborne scatterometer and its main parameters are described in this paper.This scatterometer is designed for a polar-orbit satellite with an orbit height of 500km.By simulation

the wind retrieval qualities with different antenna types are compared;and then two important parameters of the antenna

the two-way antenna gain and the half power beam-width in the range direction

are optimized

for an expected swath width of more than 1000km.It is concluded that the two-way antenna gain should be no less than 51.5dB

and -3dB beam width along the range direction (the elevation direction) is about 25degree.The results show that this new kind of scatterometer has better performance in wind retrieval compared with the spaceborne pencil-beam radar scatterometer

such as SeaWinds.Especially

the quality of retrieved wind direction can be improved significantly by this new system

under high wind-speed conditions.