Apparatus for demodulating AM data multiplexed modulated wave signal
First Claim
1. An apparatus for demodulating an AM data multiplexed modulated wave signal to derive therefrom a baseband digital signal, the AM data multiplexed modulated wave signal being obtained by amplitude modulating a carrier having a frequency fc with an analog signal by an AM type modulator to multiplex digital modulated signals at frequency positions of (fc+fα
- ) and (fc-fα
) line symmetrical to the carrier having the frequency fc on the frequency axis, the apparatus comprising;
an AM type modulated wave signal eliminating circuit for removing an AM type modulated wave signal from an input AM data multiplexed modulated wave signal; and
a data demodulation circuit for receiving an output of said AM type modulated wave signal eliminating circuit and deriving therefrom a baseband digital signal.
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Abstract
An apparatus for demodulating an AM data multiplexed modulated wave signal in which an analog modulated signal and digital modulated signals are multiplexed, in order to derive therefrom a baseband digital signal. The demodulation apparatus aims to derive the digital baseband signal from the AM data multiplexed modulated wave signal in which the analog modulated signal obtained by amplitude modulating a carrier having a frequency fc with an analog signal and the digital modulated signals at frequency position of (fc+fα) and (fc-fα) line-symmetrical with respect to a frequency axis of the frequency fc are multiplexed. A demodulation apparatus includes an AM type modulated wave signal eliminating circuit for removing an AM modulated wave signal from an input AM data multiplexed modulated wave signal, and a data demodulation circuit for receiving an output of the AM type modulated wave signal eliminating circuit and for deriving therefrom a baseband digital signal.
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Citations
9 Claims
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1. An apparatus for demodulating an AM data multiplexed modulated wave signal to derive therefrom a baseband digital signal, the AM data multiplexed modulated wave signal being obtained by amplitude modulating a carrier having a frequency fc with an analog signal by an AM type modulator to multiplex digital modulated signals at frequency positions of (fc+fα
- ) and (fc-fα
) line symmetrical to the carrier having the frequency fc on the frequency axis, the apparatus comprising;an AM type modulated wave signal eliminating circuit for removing an AM type modulated wave signal from an input AM data multiplexed modulated wave signal; and a data demodulation circuit for receiving an output of said AM type modulated wave signal eliminating circuit and deriving therefrom a baseband digital signal. - View Dependent Claims (2, 3, 4, 5, 6)
- ) and (fc-fα
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7. An apparatus for demodulating an AM data multiplexed modulated wave signal to derive therefrom a baseband digital signal, the AM data multiplexed modulated wave signal being obtained by amplitude modulating a carrier having a frequency fc with an analog signal by an AM type modulator to multiplex digital modulated signals at frequency positions of (fc+fα
- ) and (fc-fα
) line symmetrical to the carrier having the frequency fc on the frequency axis, the apparatus comprising;a first orthogonal detector for orthogonally detecting the AM data multiplexed modulated wave signal with a signal having a frequency (fc+fα
);a second orthogonal detector for orthogonally detecting the AM data multiplexed modulated wave signal with a signal having a frequency (fc-fα
);first calculation means for calculating a difference between I components output from said first orthogonal detector and I components output from said second orthogonal detector; and second calculation means for calculating a sum of Q components output from said first orthogonal detector and Q components output from said second orthogonal detector.
- ) and (fc-fα
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8. An apparatus for demodulating an AM data multiplexed modulated wave signal to derive therefrom a baseband digital signal, the AM data multiplexed modulated wave signal being obtained by amplitude modulating a carrier having a frequency fc with an analog signal by an AM modulator to multiplex digital modulated signals at frequency positions of (fc+fα
- ) and (fc-fα
) line symmetrical to the carrier having the frequency fc on the frequency axis, the apparatus comprising;A/D converting means for sampling the AM data multiplexed modulated wave signal when a level of the carrier becomes 0 and A/D converting the sampled signal; orthogonal detection means for orthogonally detecting an A/D converted and dispersed output signal with two orthogonal carrier signals having a frequency fα
; anda low-pass filter for removing high frequency components of an orthogonally detected output.
- ) and (fc-fα
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9. An apparatus for demodulating an AM data multiplexed modulated wave signal to derive therefrom a baseband digital signal, the AM data multiplexed modulated wave signal being obtained by amplitude modulating a carrier having a frequency fc with an analog signal by an AM type modulator to multiplex digital modulated signals at frequency positions of (fc+fα
- ) and (fc-fα
) line symmetrical to the carrier having the frequency fc on the frequency axis, the apparatus comprising;carrier reproduction means for reproducing the carrier from the AM data multiplexed modulated wave signal and shifting the phase of the reproduced carrier by π
/2;multiplying means for multiplying an output from said carrier reproduction means by the AM data multiplexed modulated wave signal; orthogonal detection means for orthogonally detecting the multiplication output signal by two orthogonal carrier signals having a frequency fα
; anda low-pass filter for removing high frequency components of an orthogonally detected output.
- ) and (fc-fα
Specification