| 摘要 |
PURPOSE:To obtain a demodulator not susceptible to fluctuation such as temperature or power supply voltage fluctuation by forming a received FSK signal into a rectangular wave, differentiating it so as to leave only a positive pulse, counting the pulse by an n-bit counter and outputting the pulse at every (n)- period for each time interval shifted in the direction of time base from a decoder. CONSTITUTION:The received FSK signal is shaped into a rectangular form by a comparator 1, the obtained sampling value is differentiated so as to divide it finely to be the positive pulse. Then the pulse is counted by a 2-bit counter 3, a leading signal of the pulse is generated one by one time at every half period, the pulse interval time of the measurement object is selected as the length by 2 periods, decoded by a decoder 4 to be shared to each pulse interval measurement device 5. Then the time interval of pulse leading edge is counted for each signal and when the interval is shorter than a prescribed pulse interval, it is taken as a high level and when longer, it is taken as a low level, outputted from the selector 6 to demodulate the transmission data. |
