Modulator-demodulator for obtaining and demodulating frequency-modulated signal

Claim 2

A modulator-demodulator for obtaining and demodulating a frequency-modulated signal and for performing a modulating operation and a demodulating operation time-sequentially, said modulating and demodulating operations using a circuit part in said modulator-demodulator in common, said modulator-demodulator comprising: a voltage-controlled oscillator, the oscillation frequency of said oscillator varying in accordance with a signal applied to a control terminal of said oscillator; a phase detector, one input terminal of said phase detector being applied with a frequency-modulated signal, the other input terminal of said phase detector being applied with the output signal of said voltge-controlled oscillator; a switching circuit, one input terminal of said switching circuit being applied with a modulating signal, the other input terminal of said switching circuit being applied with the output signal of said phase detector, said switching circuit being operated in such a manner that said modulating signal applied to said one input terminal is selectively applied to said control terminal of said voltage-controlled oscillator in said modulating operation and said output signal of said phase detector applied to said other input terminal is selectively applied to said control terminal of said voltage-controlled oscillator in said demodulating operation; means for taking out a frequency-modulated signal from an output terminal of said voltage-controlled oscillator; and means for taking out a demodulated signal from the control terminal of said voltage-controlled oscillator.

Claim 3

A modulator-demodulator for obtaining and demodulating a frequency-modulated signal according to claim 1, wherein said voltage-controlled oscillator is provided with automatic frequency control means for suppressing variations in the oscillation frequency of said voltage-controlled oscillator by utilizing a frequency lower than the frequency of said modulating signal.

Claim 4

A modulator-demodulator for obtaining and demodulating a frequency-modulated signal to be used in a recording/reproducing device for recording a signal in a recording medium in the form of a frequency-modulated signal and for obtaining a reproduced signal by demodulating a signal read out of said recording medium, said modulator-demodulator comprising: means for inputting a signal to be recorded; a voltage-controlled oscillator, the oscillation frequency of said oscillator varying in accordance with a signal applied to a control terminal of said oscillator; a phase detector, one input terminal of said phase detector being applied with a frequency-modulated signal, said frequency-modulated signal being read out of said recording medium, the other input terminal of said phase detector being applied with the output signal of said voltage-controlled oscillator, said phase detector outputting an error signal corresponding to a difference in phase between said frequency-modulated signal and said output signal of said voltage-controlled oscillator applied respectively to said one and other input terminals of said phase detector; a loop filter for removing a ripple component from the output signal of said phase detector; a switching circuit operated in such a manner that said to-be-recorded signal inputted through said input means is applied to said control terminal of said voltage-controlled oscillator in a recording operation, and said error signal outputted from said phase detector and having passed through said loop filter is applied to said control terminal of said voltage-controlled oscillator in a reproducing operation; means for outputting, as a signal recorded in said recording medium, a frequency-modulated signal from an output terminal of said voltage-controlled oscillator, in said recording operation; and output means for outputting, as a reproduced signal, a signal which is obtained by demodulating said frequency-modulated signal applied to said phase detector, from the control terminal of said voltage-controlled oscillator in said reproducing operation, and for outputting, as a monitor signal in said recording operation, said to-be-recorded signal which is supplied from said input means to said control terminal of said voltage-controlled oscillator, in said recording operation.

Claim 5

A modulator-demodulator for obtaining and demodulating a frequency-modulated signal to be used in a recording/reproducing device for recording a signal in a recording medium in the form of a frequency-modulated signal and for obtaining a reproduced signal by demodulating a signal read out of said recording medium, said modulator-demodulator comprising: means for inputting a signal to be recorded; a voltage-controlled oscillator, the oscillation frequency of said oscillator varying in accordance with a signal applied to a control terminal of said oscillator; a phase detector, one input terminal of said phase detector being applied with a frequency-modulated signal, said frequency-modulated signal being read out of said recording medium, the other input terminal of said phase detector being applied with the output signal of said voltage-controlled oscillator, said phase detector outputting an error signal corresponding to a difference in phase between said frequency-modulated signal and said output signal of said voltage-controlled oscillator applied respectively to said one and other input terminals of said phase detector; a loop filter for removing a ripple component from the output signal of said phase detector; a switching circuit operated in such a manner that said to-be-recorded signal inputted through said input means is applied to said control terminal of said voltage-controlled oscillator in a recording operation, and said error signal outputted from said phase detector and having passed through said loop filter is applied to said control terminal of said voltage-controlled oscillator in a reproducing operation; means for outputting, as a signal recorded in said recording medium, a frequency-modulated signal from an output terminal of said voltage-controlled oscillator, in said recording operation; and output means for outputting, as a reproduced signal, a signal which is obtained by demodulating said frequency-modulated signal applied to said phase detector, from the control terminal of said voltage-controlled oscillator in said reproducing operation, and for outputting, as a monitor signal in said recording operation, said to-be-recorded signal which is supplied from said input means to said control terminal of said voltage-controlled oscillator, in said recording operation.

Claim 6

A modulator-demodulator for obtaining and demodulating a frequency-modulated signal according to claim 3, wherein said voltage-controlled oscillator is provided with automatic frequency control means for suppressing variations in the oscillation frequency of said voltage-controlled oscillator by utilizing a frequency lower than the frequency of said to-be-recorded signal.

Claim 7

A modulator-demodulator for obtaining and demodulating a frequency-modulated signal to be used in a recording/reproducing device for recording a signal in a recording medium in the form of a frequency-modulated signal and for obtaining a reproduced signal by demodulating a signal read out from said recording medium, said modulator-demodulator comprising: means for inputting a signal to be recorded; a voltage-controlled oscillator, the oscillation frequency of said oscillator varying in accordance with a signal applied to a control terminal of said oscillator; automatic frequency control means including a reference signal source for delivering a reference signal, a frequency divider for dividing the frequency of the output signal of said voltage-controlled oscillator, and a first phase detector for comparing the phase of the output signal of the frequency divider with the phase of said reference signal to output an error signal corresponding to a difference in phase between said output signal of said frequency divider and said reference signal, said reference signal having a frequency lower than the frequency of said to-be-recorded signal applied through said input means, said error signal being applied to said control terminal of said voltage-controlled oscillator; a second phase detector, one inut terminal of said second phase detector being applied with a frequency-modulated signal, said frequency-modulated signal being read out of said recording medium, the other input terminal of said second phase detector being applied with the output signal of said voltage-controlled oscillator, said second phase detector outputting an error signal corresponding to a difference in phase between said frequency-modulatpd signal and said output signal of said voltage-controlled oscillator applied respectively to said one and other input terminals of said second phase detector; a loop filter for removing a ripple component from the output signal of said second phase detector; a switching circuit operated in such a manner that said to-be-recorded signal inputted through said input means is applied to said control terminal of said voltage-controlled oscillator in a recording operation, and said error signal outputted from said second phase detector and having passed through said loop filter is applied to said control terminal of said voltage-controlled oscillator in a reproducing operation; means for outputting, as a signal recorded in said recording medium, a frequency-modulated signal from an output terminal of said voltage-controlled oscillator, in said recording operation; and output means for outputting, as a reproduced signal, a signal which is obtained by demodulating said frequency-modulated signal applied to said second phase detector, from the control terminal of said voltage-controlled oscillator in said reproducing operation, and for outputting, as a monitor signal in said recording operation, said to-be-recorded signal which is supplied from said input means to said control terminal of said voltage-controlled oscillator, in said recording operation.

Claim 8

A modulator-demodulator for obtaining and demodulating a frequency-modulated signal to be used in a recording/reproducing device for recording a signal in a recording medium in the form of a frequency-modulated signal and for obtaining a reproduced signal by demodulating a signal read out from said recording medium, said modulator-demodulator comprising: means for inputting a signal to be recorded; a voltage-controlled oscillator, the oscillation frequency of said oscillator varying in accordance with a signal applied to a control terminal of said oscillator; automatic frequency control means including a reference signal source for delivering a reference signal, a frequency divider for dividing the frequency of the output signal of said voltage-controlled oscillator, and a first phase detector for comparing the phase of the output signal of the frequency divider with the phase of said reference signal to output an error signal corresponding to a difference in phase between said output signal of said frequency divider and said reference signal, said reference signal having a frequency lower than the frequency of said to-be-recorded signal applied through said input means, said error signal being applied to said control terminal of said voltage-controlled oscillator; a second phase detector, one inut terminal of said second phase detector being applied with a frequency-modulated signal, said frequency-modulated signal being read out of said recording medium, the other input terminal of said second phase detector being applied with the output signal of said voltage-controlled oscillator, said second phase detector outputting an error signal corresponding to a difference in phase between said frequency-modulatpd signal and said output signal of said voltage-controlled oscillator applied respectively to said one and other input terminals of said second phase detector; a loop filter for removing a ripple component from the output signal of said second phase detector; a switching circuit operated in such a manner that said to-be-recorded signal inputted through said input means is applied to said control terminal of said voltage-controlled oscillator in a recording operation, and said error signal outputted from said second phase detector and having passed through said loop filter is applied to said control terminal of said voltage-controlled oscillator in a reproducing operation; means for outputting, as a signal recorded in said recording medium, a frequency-modulated signal from an output terminal of said voltage-controlled oscillator, in said recording operation; and output means for outputting, as a reproduced signal, a signal which is obtained by demodulating said frequency-modulated signal applied to said second phase detector, from the control terminal of said voltage-controlled oscillator in said reproducing operation, and for outputting, as a monitor signal in said recording operation, said to-be-recorded signal which is supplied from said input means to said control terminal of said voltage-controlled oscillator, in said recording operation.

Claim 9

A modulator-demodulator for obtaining and demodulating a frequency-modulated signal according to claim 5, wherein means for operating said second phase detector only for a reproducing period is added to said second phase detector.

Claim 10

A modulator-demodulator for obtaining and demodulating an audio frequency-modulated signal to be used in a magnetic recording/reproducing device in which a signal obtained by frequency-modulating a carrier with a video signal and a signal obtained by frequency-modulating another carrier different in frequency band from said carrier with an audio signal are mixed with each other to be recorded in a magnetic recording medium, said modulator-demodulator comprising: a voltage-controlled oscillator, the oscillation frequency of said oscillator varying in accordance with a signal applied to a control signal input terminal of said oscillator; a phase detector, one input terminal of said phase detector being applied with an audio frequency-modulated signal, said audio frequency-modulated signal being read out of said magnetic recording medium, the other input terminal of said phase detector being applied with the output signal of said voltage-controlled oscillator, said phase detector outputting an error signal corresponding to a difference in phase between said audio frequency-modulated signal and the output signal of said voltage-controlled oscillator applied respectively to said one and other input terminals of said phase detector; a switching circuit for performing such a switching operation that said voltage-controlled oscillator is operated as a modulator for carrying out frequency modulation, in a recording operation, by supplying a to-be-recorded audio signal to said control signal input terminal of said voltage-controlled oscillator, and said voltage-controlled oscillator and said phase detector are operated as a demodulator having a phase locked loop configuration for demodulating a frequency-modulated signal, in a reproducing operation, by supplying said error signal outputted from said phase detector to said control signal input terminal of said voltage-controlled oscillator; means for outputting, as an audio frequency-modulated signal recorded in said magnetic recording medium, the output signal of said voltage-controlled oscillator in said recording operation; and means for outputting a demodulated audio signal from between an output terminal of said switching circuit and said control signal input terminal of said voltage-controlled oscillator in said reproducing operation.

Claim 11

A modulator-demodulator for obtaining and demodulating an audio frequency-modulated signal to be used in a magnetic recording/reproducing device in which a signal obtained by frequency-modulating a carrier with a video signal and a signal obtained by frequency-modulating another carrier different in frequency band from said carrier with an audio signal are mixed with each other to be recorded in a magnetic recording medium, said modulator-demodulator comprising: a voltage-controlled oscillator, the oscillation frequency of said oscillator varying in accordance with a signal applied to a control signal input terminal of said oscillator; a phase detector, one input terminal of said phase detector being applied with an audio frequency-modulated signal, said audio frequency-modulated signal being read out of said magnetic recording medium, the other input terminal of said phase detector being applied with the output signal of said voltage-controlled oscillator, said phase detector outputting an error signal corresponding to a difference in phase between said audio frequency-modulated signal and the output signal of said voltage-controlled oscillator applied respectively to said one and other input terminals of said phase detector; a switching circuit for performing such a switching operation that said voltage-controlled oscillator is operated as a modulator for carrying out frequency modulation, in a recording operation, by supplying a to-be-recorded audio signal to said control signal input terminal of said voltage-controlled oscillator, and said voltage-controlled oscillator and said phase detector are operated as a demodulator having a phase locked loop configuration for demodulating a frequency-modulated signal, in a reproducing operation, by supplying said error signal outputted from said phase detector to said control signal input terminal of said voltage-controlled oscillator; means for outputting, as an audio frequency-modulated signal recorded in said magnetic recording medium, the output signal of said voltage-controlled oscillator in said recording operation; and means for outputting a demodulated audio signal from between an output terminal of said switching circuit and said control signal input terminal of said voltage-controlled oscillator in said reproducing operation.

Claim 12

A modulator-demodulator according to claim 7, wherein said voltage-controlled oscillator is provided with an automatic frequency control loop which includes another phase detector for detecting a difference in phase between a signal obtained by frequency-dividing the output signal of said voltage-controlled oscillator and a reference signal having a frequency lower than the frequency of said to-be-recorded audio signal to output an error signal, and means for supplying the output signal of said another phase detector to said control signal input terminal of said voltage-controlled oscillator.