Design of mobile phone IIDT-type SAW filters with block-like distribution of transducers

Author

Fischerauer, Gerhard ; Bader, Bernhard ; Russer, Peter ; Weigel, Robert

Author_Institution

Corp. Res. & Dev., Siemens AG, Munich, Germany

Volume

42

Issue

7

fYear

1994

fDate

7/1/1994 12:00:00 AM

Firstpage

1380

Lastpage

1386

Abstract

Wide band low-loss SAW filters employing interdigitated interdigital transducers (IIDT´s) and suitable for cellular radio applications are presented. After an investigation of the many design parameters that have to be taken into account, a new block-like distribution of transducers within the IIDT structure is studied in detail. This distribution leads to almost identical impedances at the filter input and output. An automatic optimization algorithm is also described. In particular, the finger numbers and the withdrawal weighting functions employed to increase the stopband rejection have been optimized by this algorithm. Filters fabricated on 36° rot Y, X-LiTaO₃ exhibit fractional bandwidths of up to 5.2% with passband ripples smaller than 1 dB at a center frequency of 500 MHz. The minimum insertion loss and the stopband rejection obtained were 1.8 and 23 dB, respectively

Keywords

band-pass filters; cellular radio; radiofrequency filters; surface acoustic wave devices; surface acoustic wave filters; 1.8 dB; 500 MHz; LiTaO₃; block-like distribution; cellular radio applications; center frequency; filter input; filter output; finger numbers; fractional bandwidths; insertion loss; interdigitated interdigital transducers; mobile phone IIDT-type SAW filters; passband ripples; stopband rejection; withdrawal weighting functions; Band pass filters; Bandwidth; Fingers; Impedance; Land mobile radio cellular systems; Mobile handsets; Passband; SAW filters; Transducers; Wideband;

fLanguage

English

Journal_Title

Microwave Theory and Techniques, IEEE Transactions on

Publisher

ieee

ISSN

0018-9480

Type

jour

DOI

10.1109/22.299732

Filename

299732