To overcome the bulk acoustic wave （BAW）, the triple transit signals and the discontinuous frequency band in the first generation surface acoustic wave＇s （FGSAW＇ s） wavelet device, the full transfer multistrip coupler （MSC） is applied to implement wavelet device, and a novel structure of the second generation surface acoustic wave＇s （SGSAW＇s） wavelet device is proposed. In the SGSAW＇ s wavelet device, the BAW is separated and eliminated in different acoustic propagating tracks, and the triple transit signal is suppressed. For arbitrary wavelet scale device, the center frequency is three times the radius of frequency band, which ensures that the frequency band of the SGSAW＇s wavelet device is continuous, and avoids losing signals caused by the discontinuation of frequency band. Experimental result confirms that the BAW suppression, ripples in band, receiving loss and insertion loss of the SGSAW＇ s wavelet device are remarkably improved compared with those of the FGSAW＇ s wavelet device.
Wen Changbao Zhu Changchun Lu Wenke Liu Qinghong Liu Junhua
This paper proposes to use substrate materials of small electromechanical coupling coefficient k2 (such as X-112YLiTaO3) to manufacture wavelet transform element of SAW type so as to reduce finger reflections, i.e. to reduce the error of wavelet transform element of SAW type. And it is concluded that the smaller the center frequency of the transmitting IDT of wavelet type, the smaller the error. We suggest to choose substrate material with electromechanica coupling coefficient smaller than that of X-112Y LiTaO3 in the manufacture of the transmitting IDTs of wavelet type and the receiving IDTs at center frequencies above 100MHZ, so as to reduce the errors of the transmitting IDTs of wavelet type and the receiving IDTs at center frequencies above 100MHZ.
