Title :
Development of ladder type SAW RF filter with high shape factor
Author :
Hashimoto, K. ; Ueda, M. ; Kawachi, O. ; Ohmori, H. ; Ikata, O. ; Uchishiba, H. ; Nishihara, T. ; Satoh, Y.
Author_Institution :
Fujitsu Labs. Ltd., Kawasaki, Japan
Abstract :
The paper presents ion implantation technology to improve the shape factor of a ladder-type SAW RF filters for mobile communication systems. The improvement of the shape factor was confirmed experimentally. However we found that the SAW phase velocity is decreased by ion implantation. To stabilize and recover the SAW phase velocity, several annealing conditions were investigated. At the annealing condition of over 450°C×1 hour, SAW phase velocity was recovered to almost the same as the initial velocity. In the past, the shape factor values of ladder-type SAW filters using a LiTaO3 substrate have been almost 1.7. The ion implantation technology has been applied to a PDC (personal digital cellular) -1.5 GHz SAW band pass filter using a LiTaO3 substrate. We have obtained the shape factor value of 1.4 under the following conditions; ion: double charge Ar++, dose: 5×1013/cm2, acceleration voltage: 180 keV
Keywords :
UHF filters; annealing; band-pass filters; cellular radio; interdigital transducers; ion implantation; ladder filters; surface acoustic wave resonator filters; 1 hour; 1.5 GHz; 450 C; Ar; LiTaO3; LiTaO3 substrate; SAW RF filter; SAW phase velocity; annealing conditions; bandpass filter; high shape factor; ion implantation technology; ladder type; mobile communication systems; personal digital cellular communication; Annealing; Argon; Band pass filters; Ion implantation; Mobile communication; Paper technology; Radio frequency; SAW filters; Shape; Surface acoustic waves;
Conference_Titel :
Ultrasonics Symposium, 1995. Proceedings., 1995 IEEE
Conference_Location :
Seattle, WA
Print_ISBN :
0-7803-2940-6
DOI :
10.1109/ULTSYM.1995.495552
