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US 5,293,408 AGranted
FSK data receiving system
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsKazuaki Takahashi, Makoto Hasegawa, Katsushi Yokozaki, Yasumi Imagawa, Hiroyuki Harada, Masahiro Mimura, Yasuaki Namura
Life of this patent
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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.
Claims49
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.degree. or 90.degree. 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.
5 more elements
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.degree. or 90.degree. 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.
5 more elements
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 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.degree. or 90.degree. 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.degree. and 90.degree. phase-shifts.
4 more elements
A data receiving system comprising:
- 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.
3 more elements
A data receiving system comprising:
- 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.
3 more elements
A data receiving system comprising:
- 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.
5 more elements
A data receiving system comprising:
- 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.
2 more elements
Dependencies are inferred from the claim text.