Research And Implementation Of CAD System For SAW Devices

Recently, surface acoustic wave (SAW) devices as a new type of electric devices have attracted considerable attention. In the field of scientific research,the significant progress has been made on the research of SAW device materials,production, technology,performance and application,but the research and development of CAD technique and system about SAW devices is still lacking.A CAD system for SAW devices which can realize the automatic design and the simulation of SAW devices, not only can improve the efficiency of actual production,but also can guide the development of new products.So this paper studys on the CAD technique and system about SAW devices (SAW filters and SAW delay line).In this paper, by studying the design process of the SAW band pass filter and the SAW delay line,the key technologies required for CAD system are analysed and studied, including:the establishment of a database of piezoelectric material, the computer-aided solving SAW coupled wave equations, IDT computer-aided design and simulation.After designing its function structure and architecture,the CAD system for SAW devices is developed with Visual Basic language and the method of modularization,which can realize the data management of piezoelectric material,the automatic design of IDT and the frequency response and impulse response simulation of SAW filters. In the process of programming code, the hybrid programming of Visual Basic and Matlab is used, which not only realizes a large number of complex calculations and the function of drawing simulation curves in the system, but also greatly improves the system's operational efficiency and stability.The results of last example show that the SAW bandpass filter with a center frequency of 70 MHz and a-3dB bandwidth of 4.1 MHz designed by the software has an in-of-band fluctuation of less than 1 dB and an out-of-band rejection of more than 60 dB and satisfies all industrial requirements.