Title :
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
fDate :
7/1/1994 12:00:00 AM
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;
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
