| 摘要 |
PURPOSE:To expand a dynamic range of an A/D converter circuit and to improve the conversion accuracy by applying nonlinear processing before and after the A/D converter circuit converts an analog signal into a digital signal. CONSTITUTION:A received analog signal is amplified by an amplifier means 57a having a logarithmic characteristic, the level is limited to a level and an A/D converter circuit 52 converts the analog signal into a digital signal. The vicinity of the center level of the digital value in the eye pattern ts expanded to draw a magnified eye pattern. Then the signal converted into a digital signal by the A/D converter 52 is restored to a digital signal before amplification with a logarithmic characteristic in a storage means 58a having a table of the opposite characteristic and the compressed signal is also restored to a level before the compression. Since the nonlinear processing of the logarithmic characteristic is applied before and after the A/D conversion of the basic band analog signal into the digital signal, the dynamic range of the A/D converter 52 is expanded and the conversion accuracy is improved. |
