The Low Loss Saw Filter For Mobile Communication Design

Surface acoustic wave(SAW) is a technology based on elastic wave propagating on the surface of an object. It is a new technology developed since the late 1960 th.Semiconductor fabrication methods including photolithography can be employed to fabricate high quality SAW devices.Therefore, SAW devices were quikly used in areas such as: radar/telecommunication/navigation target identification and electronic warfares.The fast developing telecommunication industry has provided a much greater market for SAW filters leading to an increase of demand and production quantity. In mobile communication systems, SAW filters must be used in their transimter and receiver end to filter out the undesired signals. This requires filters to exhibits low insertion loss, high band rejection, high power,low cost and small size. Becasue SAW filters’ unique advantages of small size and low cost, it has played a major role in mobile communication application.China electronics technology corporation(CETC 26) No. 26 is the only institue focusing on surface and ball acoustic technologies research. Currently, surface acoustic devices have been successfully commercialized and entered into mass production.Recently, the fast development of 3rd and 4th generation telecommunication technologies require further reductions in filter’s insertion loss and much higher working frequency.The main focus of this paper is to optimize the design methods and fabrication techniques of high frequency and low loss SAW filters for 3G and 4G applications. In this work, both SAW filter’s design and fabrication methods have been modified.In filter design aspect, the design parameters are optimized to allow higher simulation efficiency. The filter’s power sustainability is also optimized by choosing the right filter structure.In fabrication aspect, new process has been developed. Based on current SAW fabrication process, electron beam expossure and other techniques are used to fabricate submicron level metal pattern.In addition, SAW device’s power sustainability has also been improved by employing multilayerfilm technique. At last, the required filter parameters for mobile communicationhave been achieved.In the present work, the design methodology and fabrication process have already been used as a guidance to the design and manufacturing of SAW filters.