| 摘要 |
PURPOSE:To vary an attenuation variation curve from logarithmic linear characteristics by varying the attenuation step speed of a variable attenuator under digital control according to the position of an attenuation step. CONSTITUTION:Frequency division signals (a)-(e) are selected by a data selector 24 for output ranges A-E of an up/down counter 12 which supplies data on the attenuation step. Frequency division outputs of higher order than a frequency division output selected by the data selector 24 [e.g. (a) and (b) when (c) is selected] are regarded as one set to make the initial state of the frequency division output constant in case of transition of ranges. Thus, even when the variable attenuator under digital control performs attenuation at a specific ratio per step, its variation characteristics are expressed by a natural curve as well as a conventional variable resistor. Further, the frequency division outputs of higher order than the selected frequency division output are set or reset to exclude uncertainties of the variation characteristics. |
