Broadband Low-loss Saw Filter Development,

With the rapid improvement of mobile communication, the system of the communication is required to be more advanced especially on the requirement of signal-to-noise ratio and signal bandwidth. The requrements of the filters which are the key devices in the signal process system become higher since the wideband communication system became the mainstream. And that makes a bigger market for wideband low-loss filter. However, there's no domastic manufactor which can seize the technique of wideband low-loss surface acoustic wave filter (SAWF) maturely. In order to shake off the dependence of devices imported, we have to research the techinque and make it suitable for mass production. The target of the research here is to achieve the performance of the device of LB070DS26 from SAWTEK. Through designing and techical process, we can achieve the goal and set a foundation for the improvement of wideband low-loss SAWF.In the design of the SAWF, SPUDT reflective structures are adopted which includes the structure of DART, EWC and HANMA. In this paper, in order to achieve a wider wideband and lower loss with the same configuration, slanted interdigital transducer and SPUDT technical are adopted. The design combines different weighting technique and SPUDT technique, and realized a high performance wideband low-loss SAWF.To get thinner lines, insure the steepness of the figure,reduce the number of connected figures and improve the consistency and repeatability of the technique, stripping technique was chosen. And in order to realize a high resolution ratio during the graphics transfer printing, a method of step and repeat exposure is adopted. To achieve the high request of film accuracy and obtained the discontiguous metal film on the substrate with photoresist graphic which is required by stripping technique, electron beam was utilized to coat. Meanwhile, the loss and the passband ripple were reduced through optimizing the distribution of the spot welding wires. In the paper, the process conditions like the photoresist and the exposure time are confirmed to realize the required small graphic. The problem of Bulk Wave is solved through notching. Meanwhile, the parameters of notching were confirmed and the wifer which is less affected by the stress was chosen to reduce the hidden defect of reliability from notching.Other hidden defects caused by braking of the spot welding wires and the substrate and the excrescent objects are controled through technical process.The research mainly solved the following problem. The wide-band low-loss filter was designed; the parameters of thick film denudation technique were confirmed; the equipments and the technique flow of notch for restraining bulk wave were also confirmed. The design and the technique flow satisfied the requirements of restraining bulk wave and performance, and ensured the reliability of the products also.At the end of the paper, the experimental results are given. The parameter of the realized device ultilized the slanted interdigital transducer is as well as the device from SAWTEK.