The Research Of Wavelet-based Inter Digital Transducer (IDT) Structure Algorithm

With the rapid development of surface acoustic wave(SAW) technology, SAW devices have been increasingly wide applications in electronic information fields, at the same time,SAW devices have become increasingly demand: higher response frequency, wider bandwidth and lower insertion loss and smaller size, etc. Since inter digital transducer(IDT) is an important part of SAW devices, in order to meet the requirements of the above-mentioned range, the improvement of the structure of IDT, which describes optimization algorithm is particularly important, in order to improve the characteristics of SAW devices, to improve its performance, it is necessary to proceed from IDT’s description model, the first establish mathematical model, then analog simulation, compared to the simulation results of traditional model, the model parameters are improved to optimize the IDT modeling and analysis algorithms and to meet IDT structure optimization purpose.Improved the structure of IDT not only can get a better side lobe suppression and high frequency response, also can get a lower insertion loss. Therefore, to improve study of its structure is one of the key to improve performance of SAW devices. IDT’s structure is changed, the use of IDT’s traditional mathematical description methods would be meaningless,therefore, it’s necessary to find a new structure description method. This article is proceeded in Guizhou Province Natural Science Fund Project, conducting extension research on the base of “Compensation method of surface SAW filter insertion loss”, the main research is modeling method of IDT of SAW devices. This paper firstly introduces the working principle and piezoelectric effect and original algorithms models of IDT, then elaborates what selects wavelet function to describe the basis of IDT structure, finally, on the basis of improved ?function and impulse response function select Morlet wavelet function to build IDT mathematical model, IDT’s structure parameters(such as that the strip width a, fingers spacing b, w coupling length, etc.) introduce into a new mathematical model(refer to IDT’s Morlet wavelet function model), then simulation and verification. Then, the traditional mathematicalmodel compare with new model in the same IDT structure, the results show IDT’s Morlet wavelet function model is more accurate than traditional? function model.Innovation of this paper is to use Morlet wavelet function to establish the mathematical model of IDT, because of the Morlet wavelet function can transform, so that it can be concluded multiple description the Morlet wavelet function model of IDT structure and make description mathematical model of IDT structure is fleible variability, there are Morlet mother wavelet function model and funcion model after Morlet wavelet transformation, and after the frequency response of Morlet mother wavelet function model of IDT is adjusted that will get more precise structure model. Therefore, the Morlet wavelet function model solves the restriction of original basic ? function model, which is only suitable for IDT structure of rules, at the same time, the simulation results show the structure parameters of IDT respectively influence its insertion loss and frequency response, the Morlet morther wavelet function model relatives to the IDT structure of rules that its sidelobe level is better suppress and insertion loss is smaller.