| 摘要 |
PURPOSE:To demodulate digitally AM, PM and FM signals by providing the 1st and 2nd multiplier means multiplying orthogonal sinusoidal signals to a signal to be modulated and the 1st and 2nd separating means separating the output signal from the means into low and high frequency components respectively. CONSTITUTION:An orthogonal sinusoidal wave generator 3, multipliers 4, 5 filters 6, 7, an adder 10 and a root circuit 11 are provided, the orthogonal sinusoidal wave signals generated from the generators 3 are multiplied with an input modulation signal, the result is separated into low or high frequency components, each component is squared and added and then the root operation is applied. Thus, the amplitude of all modulation signals having a frequency band below 1/2 of the sampling frequency is obtained. Further, since the amplitude is used and the modulation signal with constant amplitude is obtained, an inverse triangle function operating device 14 obtains a phase of the said modulation signal and a difference circuit 15 obtains an angular frequency and then the AM, PM, FM demodulation signals are obtained.
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