| 摘要 |
PURPOSE:To realize a crystal selecting method by which the yield of crystal is improved, by combining two crystals for a Jaumann type 2-stage crystal band- pass filter so that the sum of loss coefficients of these two crystals is constant regardless of a temperature change. CONSTITUTION:The Q and loss coefficient (r) of a crystal X' of the 1st stage are defined as Q1 and r1 respectively; and at the same time the Q and (r) of the crystal X' of the 2nd stage are defined as Q2 and r2 respectively. Therefore the loss of the center frequency of a pass band is defined as b=20log (1+r1+r2). Thus it is not always necessary to reduce the temperature changes of the coefficients r1 and r2. Then the temperature changes due to a loss of the center frequency of a pass band is eliminated by combining a fixed sum r1+r2 although the coefficients r1 and r2 have considerably large fluctuations. As a result, the yield of crystal is improved. |
