| 摘要 |
PROBLEM TO BE SOLVED: To provide an AM data multiplex modulated wave signal demodulation circuit that demodulates a base band digital signal from an AM data multiplex modulation signal based on a multiplexed digital modulation wave signal. SOLUTION: The demodulation circuit uses an Am modulator to amplitude- modulate a carrier whose frequency is fc with an analog signal wave and demodulates a base band digital signal from an AM data multiplex modulated wave signal in which a digital modulated wave signal is multiplexed at a position of a frequency (fc+fα) and at a position of a frequency (fc-fα) in axial symmetry on a frequency base. In this case, the AM data multiplex modulated wave signal is sampled at a position at which a level of the carrier is zero, the sampled signal is A/D-converted by an A/D converter 4 and the A/D converted discrete output signal is orthogonally detected at a orthogonal detector 6 by using two carrier wave signals orthogonal to each other whose frequency is fα, a high frequency component of an orthogonal detection output is eliminated by a low-pass filter 7 to demodulate a base band digital signal. |
