| 摘要 |
PURPOSE:To obtain the filter with excellent characteristics, by decreasing the variance of insertion loss due to temperature change, through the series connection of the ceramic capacitor having the dielectric constant with positive temperature constant and made of a material smaller in the temperature coefficient of tandelta to the piezoelectric ceramic oscillator. CONSTITUTION:The piezoelectric ceramic filter of ladder type or Jahmann type circuit is formed by using a thickness-sliding piezoelectric ceramic oscillator 21. The ceramic capacitor 22 made of nonpolarization is connected in series with the ladder type filter oscillator 21, and as the capacitor 22, that has about 10 times the capacitance value as the parallel capacitance of the oscillator 21 and in which the temperature coefficient of dielectric constant is positive and the temperature change of tandelta is smaller, is unsed. Further, the insertion loss of the filter element against the temperature change is reduced, allowig to form the piezoelectric filter with excellent characteristics. |
