RF Wideband Low Insertion Loss Of Longitudinal DMS Development Of Surface Acoustic Wave Filter

In recent years, the rapid development of mobile communication systems, extensive use of the third generation communication system, the coming of the next rainy day communication systems, the advantages of SAW filters include high frequency selectivity, low loss, small size, cost effective, those make the SAW filters are widely used in mobile communication system.this gives SAW filter tremendous market, broadband, low loss SAW filter to become hot topics.This paper covers the study of basic theory, design methods, simulation methods, design processes, production processes and test methods of longitudinal coupling resonator-type SAW filters, and make a filter work in 460MHz .Resonant filter form the passband through the two difference resonant waves within the filter. taking into account the stronger capability of low-frequency stopband rejection and weak high-frequency stopband rejection of longitudinal coupling filter, two filters connected in the electrical port, constitute the cascade structure, thus ensuring the longitudinal coupling filter passband width, insertion loss, in-band ripple performance while improving filter in high frequency stopband rejection. When in the design of longitudinal coupling filter, because lot of number of Structural parameters that impact the performance of filter. The traditional method is based on the experience of the designer to adjust the filter by hand the structural parameters to meet the requirements of the filter design, this paper introduces multi-objective simultaneous optimization of genetic algorithm to receive the optimal structure of the filter parameters of cable to achieve the optimal structure parameters filter the search for intelligent.After the compare of conventional photolithography process, benzene deal lift-off process, reverse plastic lift-off process, this paper choice reverse plastic lift-off process,which can avoid drilling cavitation, for the 2μm line width accuracy of longitudinal coupling filter. During test the performance of the filters whose maked of different structural parameters and analysis of the model of acoustic wave transmission, pore size, electrode thickness, interdigital transducer cycle, parasitic and other structural parameters on device performance.