This paper establishes the received signal model of parallel bistatic spotlight SAR adopting frequency modulated continuous wave(FMCW)

and analyzes the affect of doppler frequency shift introduced by platform's continuous motion while radar transmitting and receiving signals.Then using the concept of instantaneous frequency and through introducing the parameters

i.e.the sum and difference of the closest slant range

and the half quasi bistatic angle

the received signal expression in two dimensional wave-number domain is deduced.Based on this

a two-step processing approach for parallel bistatic spotlight FMCW SAR focusing is presented

which uses azimuth pre-filtering step to overcome azimuth spectral folding phenomenon first.Following this operation

a second residual focusing step is applied to carry out doppler frequency shift compensation and the bistatic frequency scaling processing.Meanwhile

the time frequency relations changing from each stage of azimuth pre-filtering are analyzed in detail.Simulation data processing verifies the analysis and the proposed algorithm.