Title :
Design of longitudinally coupled SAW resonator filters with Chebyshev characteristics
Author :
Nakamura, Kiyoshi ; Amano, Hiroyuki
Author_Institution :
Fac. of Eng., Tohoku Univ., Sendai, Japan
Abstract :
This paper presents a design method for longitudinally coupled SAW resonator filters with Chebyshev characteristics. First, an equivalent circuit representation of the n-coupled-resonator filter is given by acoustically cascading the distributed-parameter equivalent circuits for IDT´s and grating reflectors, based on the coupling-of-mode (COM) theory. Then, this original circuit is converted to a more refined coupled-resonator type circuit by applying a sequence of equivalent transformations to the original circuit without using any approximations. Finally this circuit is approximated by a lumped-parameter circuit. This enables us to design bandpass filters with Chebyshev characteristics. Some 4-coupled resonator filters on 36°Y-X LiTaO3 substrates are designed. Filters with a specific bandwidth less than 0.2% can be successfully designed
Keywords :
Chebyshev filters; band-pass filters; coupled mode analysis; equivalent circuits; interdigital transducers; lithium compounds; surface acoustic wave resonator filters; Chebyshev characteristics; IDT; LiTaO3; bandpass filters; coupled-resonator type circuit; coupling-of-mode theory; distributed-parameter equivalent circuits; equivalent transformations; grating reflectors; longitudinally coupled SAW resonator filters; lumped-parameter circuit; n-coupled-resonator filter; Band pass filters; Bandwidth; Chebyshev approximation; Coupling circuits; Design methodology; Equivalent circuits; Filtering theory; Gratings; Resonator filters; Surface acoustic waves;
Conference_Titel :
Frequency Control Symposium, 1996. 50th., Proceedings of the 1996 IEEE International.
Conference_Location :
Honolulu, HI
Print_ISBN :
0-7803-3309-8
DOI :
10.1109/FREQ.1996.559866