As　a　rapid　and　efficient　nondestructive　testing　method,　Lamb　wave　technology　possesses　great　application　potentials　in　structural　health　monitoring　fields　and　has　been　paid　considerable　attention.　In　this　paper,　the　wide-band　linear　chirp　signal　is　chosen　as　the　excitation　signal　to　replace　traditional　narrow　band　tone　burst　signal.　Through　post-processing,　the　response　signal　of　the　chirp　signal　can　be　demodulated,　and　the　equivalent　tone　burst　response　signals　with　any　center　frequencies　in　the　bandwidth　range　of　the　chirp　signal　can　be　extracted.　A　kind　of　piezoelectric　transducer　is　designed　optimally,　which　can　excite　and　receive　the　pure　A0　mode　signal　in　low　frequency　range.　The　A0　mode　signal　is　very　sensitive　to　the　defects　in　plates,　which　makes　the　signal　to　be　analyzed　more　conveniently.　These　developed　piezoelectric　transducers　were　arranged　on　a　quasi-isotropic　composite　plate　sparsely,　and　the　simulated　faults　were　detected.　The　detection　data　of　the　chirp　signal　obtained　in　the　experiment　were　demodulated,　and　the　response　signals　with　multiple　center　frequencies　were　achieved.　The　elliptic　imaging　technique　and　data　fusion　method　were　combined　to　perform　defect　imaging,　and　the　defect　location　in　the　composite　plate　was　realized.　The　imaging　results　from　the　signal　fusion　of　the　response　signals　with　multiple　frequencies　have　higher　resolution,　contrast　and　location　accuracy.　©,　2015,　Science　Press.　All　right　reserved.