Design And Fabrication Of The Intermediate Frequency SAWF For Communication

With the development of communication industry, many communication systems have been rapidly developed, for example, the satellite communication and optical communication in the microwave communication system field, special telephone in the mobile communication system, digital wireless telephone and special communication network system, and so on. The operation frequency of these wireless systems has been up to 1 GHz. As the key device of these communication systems, the surface acoustic wave filter (SAWF) is becoming more and more important; the goal of the development of SAWF is high center frequency, low insertion loss, small size, low cost. This paper describes the basic concept of SAW, and then introduces the work principle and design method of SAWF. The SAWFs can be divided into two categories according to their work principle: Transverse SAWF and Resonator-based SAWF. Here we focus on the former and design, manufacture a kind of intermediate frequency(IF) SAWF by the method of digital Fourier transform. In order to improve the quality of SAWF,we carefully discuss the following: The study of digital Fourier transform. To transverse SAWF, we focus on how to decrease the input loss (IL). We can decrease the IL by increasing the finger pairs of receiving interdigital transducers(IDT) and by the weighting of receiving IDT. We can also increase the aperture to decrease the IL to fulfill the requirement. In practice, we decrease the IL by increasing the duty cycle of IDT. The second is the study of manufacturing technique. In order to fulfill the requirement of mass production, we adjust the process of manufacturing technique. For example, in the process of clean, film growth, photolithography, etching, we improve the manufacturing technique to fulfill the requirement of mass production, which result in short design cycle, low cost, high efficiency of the whole manufacturing cycle. Based on the above study and analysis, a kind of IF SAWF for military usage is designed and manufactured, which performance fulfill the specification and satisfy the customer. Now this kind of SAWF is in great demand.