This paper discusses the spectrum function of InSAR baseline decorrelation coefficient

and analyzes the effect of weighting function to InSAR baseline decorrelation coefficient in the procedure of range compression.And the equivalent bandwidth of interferogram spectrum in range direction is defined.Based on the estimated value of the equivalent bandwidth of interferogram spectrum in range direction

the relation between the equivalent bandwidth of interferogram spectrum in range direction and InSAR baseline decorrelation coefficient can be deduced.So the effect of fixed bandwidth filtering upon the coherence of the InSAR images could be quantitatively analyzed.At last of this paper

the experimental results using X-SAR data illustrate the validity of the analysis.