The wavenumber domain (WD) algorithm has the ability to handle the range-azimuth coupling correctly

which is suitable for processing the wide-beam low frequency ultra-wideband synthetic aperture radar (UWB SAR) data.But the traditional WD algorithm is difficult to integrate with motion compensation method

which limits its application.Especially

in the case of no navigational instrument data available

it is difficult to achieve high quality low frequency UWB SAR image.In this paper

a modified WD (MWD) algorithm is proposed.Based on the MWD algorithm

the parameters estimation from the raw data and the accurately motion compensation could be implemented.Moreover

some modifications were made on the traditional motion compensation method according to the characteristics of MWD

and the focusing performance of MWD algorithm on low frequency UWB SAR raw data is improved.At last

some simulation experiments and the raw data processing results demonstrated the effectiveness of the proposed algorithms.