| 摘要 |
PURPOSE:To obtain a desired frequency characteristic with less insertion losses and excellent shoulder characteristics without any external circuit by changing the length of an oblique electrode finger to apply weighting in a surface acoustic wave filter having respectively the oblique electrode finger at the transmission side or reception side or at both sides. CONSTITUTION:Transducers 4, 5 and common electrodes 41, 51 are provided on piezoelectric substrate 1. Captions 42, 52 are the oblique electrode fingers applied with weighting. As clearly shown in the figure, the weighting is applied by providing a change to the length of the electrode fingers prolonged from the common electrodes 41B, 51B of the lower part. Through the weighting above, the characteristics of the surface acoustic wave filter are improved and excellent band pass characteristics are obtained. Thus, the number of pairs at the high frequency side when the oblique electrode fingers are split by a channel in parallel with the direction of propagation T is increased, the input admittance of the transducers is controlled and the pass band characteristic is made flat. |
