| 摘要 |
PURPOSE:To attain good demodulation characteristics even in case of frequency drift by using an average of output maximum and minimum values, which are obtained by allowing the detection output of a digital frequency modulated signal to pass an integral discharging filter, as a discriminating threshold of data transition points. CONSTITUTION:The input digital frequency modulated signal is detected by a detecting circuit 2, and the detection output is inputted to an integral discharging filter 3. In the filter 3, integration of a detection output 10 is started at a transition point of a data, and the next integrating process is started simultaneously with discharging after integration over a data repeat period is terminated, and this operation is repeated. An integral output 11 of the filter 3 is inputted to a maximum value detecting circuit 4, a minimum value detecting circuit 5, and a discriminating circuit 7. Circuits 4 and 5 detects maximum value 12 and a minimum value 13 of integral values at the integration end time of the integral output 11 and input them to a threshold control circuit 6. The circuit 6 obtains an arithmetic average value of the maximum value 12 and the minimum value 13 and the inputs a threshold control signal 14 to the circuit 7. The circuit 7 usesthe signal 14 as the discriminating threshold to discriminate marks and spaces of the integral output 11, thus obtaining a discrimination reproduced output 15. |
