A new low loss SAW filter structure with extremely wide bandwidth for mobile communication systems

The authors present a low-loss surface-acoustic-wave (SAW) filter with a dual-track configuration which is characterized by a novel arrangement of interdigital transducers (IDTs) and reflectors in each acoustic track as well as a special electrical connection of the IDTs. Broadband filter characteristics can easily be achieved by using chirped components. The inherently good stopband rejection of the new structure has been further improved by applying proper weighting techniques to the IDTs and reflectors. A filter with a relative bandwidth of 10% and a center frequency of 200 MHz has been designed by means of a novel synthesis method. The filter has been fabricated on 128 degrees Y-X LiNbO/sub 3/. A minimum insertion loss of 4 dB, a small passband ripple of about 1 dB, and a stopband rejection of better than 35 dB were measured. Excellent agreement between simulation and measurement has been found.<<ETX>>

[1]  G. Tobolka,et al.  Mixed Matrix Representation of SAW Transducers , 1979, IEEE Transactions on Sonics and Ultrasonics.

[2]  H. Engan.  Surface Acoustic Wave Multielectrode Transducers , 1975, IEEE Transactions on Sonics and Ultrasonics.

[3]  W. Ruile,et al.  Design and analysis of single phase unidirectional transducers , 1991, IEEE 1991 Ultrasonics Symposium,.

[4]  Gerhard Fischerauer,et al.  IF and RF filters for mobile telephone systems , 1991, IEEE 1991 Ultrasonics Symposium,.

[5]  R. Weigel,et al.  Efficient analysis tool for coupled-SAW-resonator filters , 1991, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[6]  P.M. Smith,et al.  A theoretical and experimental study of low-loss SAW filters with interdigitated interdigital transducers , 1989, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[7]  K. Yamanouchi,et al.  New Low-Loss Surface Acoustic Wave Transducers in the UHF Range , 1987, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  R. B. Brown,et al.  Low-Loss Device Using Multistrip Coupler Ring Configuration with Ripple Cancellation , 1986, IEEE 1986 Ultrasonics Symposium.

[9]  W. Ruile,et al.  High performance low-loss SAW filters for mobile radio with improved stopband rejection , 1988, IEEE 1988 Ultrasonics Symposium Proceedings..

[10]  Mitsutaka Hikita,et al.  New high-performance and low-loss SAW filters used in ultra-wideband cellular radio systems , 1991, IEEE 1991 Ultrasonics Symposium,.

[11]  E. N. Fowle.  The design of FM pulse compression signals , 1964, IEEE Trans. Inf. Theory.

[12]  Mitsutaka Hikita,et al.  High Performance SAW Filters with Several New Technologies for Cellular Radio , 1984 .