| 摘要 |
PURPOSE:To demodulate quickly a digital signal with a simple constitution of circuit by dividing the time series data converted into a series data with every 8 bits and converting adversely the five modulation rules of an FEM-4 in the order of the 3rd, 4th, 5th, 2nd and 1st rules. CONSTITUTION:The signal recorded to a recording medium 1 is reproduced through a magnetic head 2 and a reproduction amplifier 3 and converted into a digital signal. At this time point, the NRZI modulation is maintained. Then a synchronizing clock is extracted as soon as the digital signal is demodulated by an NRZI demodulating circuit 4. For demodulation of an FEM-4, the five modulation rules undergo the adverse conversion in the order of the 3rd, 4th, 5th, 2nd and 1st rules. First, the 3rd modulation rule (III) is applied to the continuous two data when the former 8th bit and the latter 3rd bit are ''1'' at a time. Then both bits are set at ''O'' at one time. The flow of the above-mentioned adverse convertion is shown here in the logical symbols. |
