| 摘要 |
PURPOSE:To obtain a deviation convertor of high resolving capacity and prompt response, by using a linear phase filter as a filter for removing higher hormonics involved in an input from an image sensor. CONSTITUTION:An output signal of an image sensor 4 is removed of its higher hormonics in a linear phase filter 61. Namely, in the filter 61, as group delay time becomes constant (A phase changes linearly against a frequency) in a constant frequency range, a phase error does not occur in a filter output, if the group delay time is assumed constant within a range: fsig=F0+ or -DELTAf, where DELTAf is defined as a fluctuation range of output frequency fsig. The output signal of the filter 61 is calculated on its phase shift quantity by the reference clock fC in a phase measuring circuit 7.
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