Estimation of multibeam phase difference using variable bandwidth filter

This paper deals with an improved processing for differential phase estimation of multibeam echosounder. In order to decreases noise and increase phase difference measurement precision the low pass filter is often used. In traditional method the filter bandwidth is fixed which often selected by experience. The main drawback of this fix bandwidth filter is that it does not concern the change of seabed backscattered signals, when the seabed circumstance changes, this filter become unsuitable. Moreover the signal to noise ratio of interferometric signals in different beams of one swath is largely different, using same filter on each beam of entire swath is obviously incorrect. Here we propose to use variable bandwidth filter on different beam signals, the parameter of filter is determined by sea depth, beam angle and noise level. The performance of this new method is illustrated by data from a 300-kHz multibeam echosounder.