The Study Of SAW Filter Design And Diffraction Compensation

Surface acoustic wave (SAW) filter is a kind of frequency selection component which makes use of SAW effect and harmonic oscillating characteristic. It can be designed flexibly and it has good frequency selection characteristic and high reliability. So SAW filter is widely used in television, radio terminals and some other fields. One most important application has been developed in television. With the development of stereo TV and high-definition television (HDTV), an improvement in filter performance becomes necessary. Some second order effects like diffraction must be compensated strictly.In this thesis, the design of SAW-TV-IF filter is discussed. The diffraction effect is analyzed and compensated in order to increase the stop band attenuation and suppress signals of adjacent frequency channels.The basic principles of SAW, inter-digital transducer (IDT), and SAW filter are introduced at first in the thesis. Then the design method of SAW filter is discussed, and a SAW-TV-IF filter is designed, the center frequency of which is 37.4MHz. The Remez exchange algorithm is used in the design. The ideal frequency response is analyzed and simulated. The diffraction effect in SAW filter is described and the frequency response with diffraction is simulated. Then the diffraction compensation methods are discussed. The SAW-TV-IF filter is compensated and the frequency response after compensation is simulated. The frequency response after compensation accords with design request.