G. Riha

High performance low-loss SAW filters for mobile radio with improved stopband rejection

A low-loss surface acoustic wave (SAWs) filter configuration is presented that uses a dual-track configuration with a transducer coupling between the tracks. This filter was developed to obtain a high stopband rejection, small passband ripple, and small size, which is needed in mobile communication systems. A partial finger-splitting and an optimized binary withdrawal weighting were also incorporated into the design together with a nonresonant unidirectional configuration. Filters at 450 MHz were fabricated on 36 degrees rotYX-LiTaO/sub 3/ using a simple single-layer technology. An insertion loss of 3 to 4 dB was achieved over a bandwidth of 6.5 MHz with a passband ripple of less than +or-0.5 dB. The stopband rejection is better than 50 dB.<<ETX>>

Rayleigh-Mode Saw-Filters on Quartz for Timing Recovery at Frequencies Above 1 GHz

Different types of SAW-fiLters on quartz for timing recovery at frequencies up to 2 GHz have been designed and fabricated. Because of the good compromise between Low insertion Loss and smaLL temperature coefficient the RayLeigh-wave has been used. The fiLters have been produced with a standard photoLithographic process with projection printing and Liftoff technique. To achieve center frequencies above 1 GHz the filters have to operate at higher harmonics. Methods for the synthesis and the anaLysis of these fiLters have been developed. The fabricated fiLters are characterized by periodic structures and good suppression of reflection at the center frequency. The reproducibiLity of the center frequencies is comparabLe to that of fiLters operating beLow 1 GHz.

SAW devices in cellular and cordless phones

Cordless and cellular phone systems are one of the most rapidly growing areas of telecommunication and have become part of modern life. In addition personal communication with global access and wireless data networks will emerge. Handheld phones provoked a continuously increasing demand on miniaturized high performance components and led to the establishment of SAW filters in their radio circuits. Inversely the specific performance of SAW components influences the architecture of the receiver circuit. Radio quality could be increased, weight, size and total circuit cost were reduced. The present paper reviews specific requirements of filtering tasks in cellular and cordless phones. It shows benefits of SAW devices and explains challenges SAW designers face today. A number of representative filter solutions are sketched giving a brief outline of todays state of the art.

SAW devices for communication systems

The author considers the possibilities of software engineering for the development, modeling, and design of full-custom, high-precision SAW (surface acoustic wave) filters for communication systems, e.g. GHz delay lines for clock recovery in light-wave transmission systems low-loss filters for mobile radios and cordless telephones, spectrum-shaping filters for multilevel digital radio relay systems, and elastic convolvers for correlation in spread-spectrum communication. The high performance of these SAW devices and their applications are discussed.<<ETX>>

New system applications of modern RF SAW filters

Modern mobile communication systems have a radio frequency between 800 MHz and 2.0 GHz. Wireless communication systems are one of the most rapidly growing areas of telecommunication. The cellular phone and the cordless phone are already established in todays life. Additional systems like personal communication systems with global access and wireless data networks will become part of tomorrows communication. The development of such systems is focused on both technological evolution and functional features. The continuously increasing demand for miniaturised components has led to an establishment of SAW components in the circuit of advanced radio devices especially. Furthermore, the specific performance of RF SAW components has an influence on the receiver circuit already. The radio quality is increased, weight, size and total circuit cost are reduced.