Amultiple-inputmultiple-output(MIMO)sonarcansynthesizealarge-aperturevirtualuniformlineararray(ULA)fromasmallnumberofphysicalelements.However,thelargeapertureisobtainedatthecostofagreatnumberofmatchedfilterswithmuchheavycomputationload.Toreducethecomputationload,aMIMOsonarimagingmethodusingavirtualsparselineararray(SLA)isproposed,whichcontainstheofflineandonlineprocessing.Intheofflineprocessing,thevirtualULAoftheMIMOsonaristhinnedtoavirtualSLAbythesimulatedannealingalgorithm,andmatchedfilterscorrespondingtoinactivevirtualelementsareremoved.Intheonlineprocessing,outputsofmatchedfilterscorrespondingtoactiveelementsarecollectedforfurthermultibeamprocessingandhence,thenumberofmatchedfiltersintheechoprocessingprocedureiseffectivelyreduced.Numericalsimulationsshowthattheproposedmethodcanreducethecomputationloadeffectivelywhileobtainingasimilarimagingperformanceasthetraditionalmethod.
