FSK data receiving system
First Claim
Patent Images
1. A data receiving system comprising:
- a carrier wave signal being modulated with a frequency deviation;
a local oscillator means generating a local oscillator signal having substantially the same frequency as said carrier wave signal;
a mixer means for producing a base-band signal by mixing said local oscillator signal and said carrier wave signal;
a standard voltage detecting means which detects a standard voltage of said base-band signal so as to change its output signal at the timing the standard voltage is detected;
a phase control means which is provided between said local oscillator means and said mixer means for shifting a phase of the local oscillator signal by an amount of 0°
or 90°
in response to the output signal from the standard voltage detecting means;
a first base-band mixer means for mixing said base-band signal and said output signal from said standard voltage detecting means; and
a first demodulation means for executing a demodulation on the basis of said base-band signal and an output signal from said first base-band mixer.
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Abstract
A data receiving system comprising an I base-band signal and a Q base-band signal which are used in a quadrature demodulation operation. Zero-crossing points of respective base-band signals are detected and a control signal is generated in response to each zero-crossing point. A phase-shift switching circuit alternately selects either the I base-band signal or the Q base-band signal in response to the control signal to generate an I/Q base-band signal. And, a demodulation operation is executed on the basis of the I/Q signal.
57 Citations
49 Claims
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1. A data receiving system comprising:
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a carrier wave signal being modulated with a frequency deviation; a local oscillator means generating a local oscillator signal having substantially the same frequency as said carrier wave signal; a mixer means for producing a base-band signal by mixing said local oscillator signal and said carrier wave signal; a standard voltage detecting means which detects a standard voltage of said base-band signal so as to change its output signal at the timing the standard voltage is detected; a phase control means which is provided between said local oscillator means and said mixer means for shifting a phase of the local oscillator signal by an amount of 0°
or 90°
in response to the output signal from the standard voltage detecting means;a first base-band mixer means for mixing said base-band signal and said output signal from said standard voltage detecting means; and a first demodulation means for executing a demodulation on the basis of said base-band signal and an output signal from said first base-band mixer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 16)
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11. A data receiving system comprising:
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a carrier wave signal being modulated with a frequency deviation; a local oscillator means generating a local oscillator signal having substantially the same frequency as said carrier wave signal; a mixer means for producing a base-band signal by mixing said local oscillator signal and said carrier wave signal; a standard voltage detecting means which detects a standard voltage of said base-band signal so as to change its output signal at the timing the standard voltage is detected; a phase control means which is provided between said local oscillator means and said mixer means for shifting a phase of the local oscillator signal by an amount of 0°
or 90°
in response to the output signal from the standard voltage detecting means;a limiter amplifier means for limiting an amplitude of said base-band signal; a first base-band mixer means for mixing an output signal from said limiter amplifier means and the output signal from the standard voltage detecting means; a first demodulation means for executing a demodulation on the basis of said base-band signal, an output signal from said first base-band mixer, and the output signal from the standard voltage detecting means. - View Dependent Claims (12, 13, 14, 15, 47)
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17. A data receiving system comprising:
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a carrier wave signal being modulated with a frequency deviation; a local oscillator means generating a local oscillator signal having substantially the same frequency as said carrier wave signal; a mixer means for producing a base-band signal by mixing said local oscillator signal and said carrier wave signal; a standard voltage detecting means for detecting a standard voltage of said base-band signal; a pulse generating means for generating a pulse having a width corresponding to a predetermined period of time; a phase control means which is provided between said local oscillator means and said mixer means for shifting a phase of the local oscillator signal by an amount of 0°
or 90°
in response to an output signal from the pulse generating means;a fourth demodulation means for executing a demodulation operation on the basis of a sign change of the base-band signal with respect to the standard voltage in any one or both of the changing points of said 0° and
90°
phase-shifts. - View Dependent Claims (18, 19, 20, 21, 22)
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23. A data receiving system comprising:
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a first and a second base-band signals which have quadrature phases with each other and whose phase relationship is relatively inverted in accordance with a positive and a negative frequency deviations of a carrier wave signal; a signal selecting means for inputting said first and second base-band signals and alternately selecting either of them to generate a third base-band signal; a standard voltage detecting means for comparing the third base-band signal with a standard voltage to generate a control signal when the third base-band signal crosses the standard voltage; a sign change judging means for inputting said control signal and said third base-band signal to make a judgement of whether or not a sign of the third base-band signal is changed before and after a changing point of the control signal; and a mixer means for mixing a judging signal outputted from said sign change judging means and said control signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 48, 49)
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32. A data receiving system comprising:
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a first and a second base-band signals which have quadrature phases with each other and whose phase relationship is relatively inverted in accordance with a positive and a negative frequency deviations of a carrier wave signal; a signal selecting means for inputting said first and second base-band signals and alternately selecting either of them to generate a third base-band signal; a standard voltage detecting means for comparing the third base-band signal with a standard voltage to generate a control signal when the third base-band signal crosses the standard voltage; a mixer means for mixing said third base-band signal and said control signal; and a quadrature demodulation means for inputting said third base-band signal and an output signal from said mixer means. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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40. A data receiving system comprising:
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a carrier wave signal being modulated with a frequency deviation; a control signal generating means wherein, a standard voltage detecting means which detects a standard voltage of said first base-band signal and outputs the control signal to said phase-shift switching means; a phase-shift switching means for switching a phase of the carrier wave signal; a local oscillator means for generating a local oscillator signal having substantially the same frequency as the carrier wave signal; a mixer means for mixing said local oscillator signal and an output signal from said phase-shift switching means; a low-pass filter means for generating a first base-band signal from the output of the mixer means; and a demodulation means for executing a demodulation operation based on said first base-band signal. - View Dependent Claims (41, 42, 43, 44)
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45. A data receiving system comprising:
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an I base-band signal and a Q base-band signal which are used in a quadrature demodulation operation; a means for detecting a standard voltage of respective base-band signals and generating a control signal in response to this detection; a means for alternately selecting either said I base-band signal or said Q base-band signal in response to said control signal to generate an I/Q base-band signal; and a means for executing a demodulation operation on the basis of said I/Q signal. - View Dependent Claims (46)
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Specification