| 摘要 |
PURPOSE:To reduce the distortion of an FM demodulation output signal, by multiplying an FM signal, which is sampled at a certain period, and a signal obtained by delaying this FM signal by one sampling period, and performing the inverse sine operation after allowing the multiplication output of pass through a digital filter. CONSTITUTION:The FM signal which is sampled at a certain sampling period T is inputted to a terminal 1, and this FM signal is inputted to a delay circuit 3, which delays the signal by the period T, and a multiplying circuit 2. The FM signal delayed by one sampling period in the circuit 3 and the input FM signal delayed by one sampling period in the circuit 3 and the input FM signal are multiplied in the circuit 2, and the multiplication output is inputted to a digital filter 5. The filter 5 allows only a band including a modulation signal of the output of the circuit 2 to pass through, and the output is inputted to an inverse sine function operating circuit 6 constituted with an ROM table. In the circuit 6, the output signal of the filter 5 is subjected to the inverse sine operation to output a demodulation signal of the FM modulation signal to a terminal 7. The linear region of the detection characteristic of this FM demodulator is extended, and the distortion of the output signal is reduced. |
