JPH0758789A - Center frequency carrier reproduction circuit and frequency modulated data demodulator - Google Patents

Abstract

PURPOSE:To provide a center frequency carrier reproduction circuit capable of highly accurately reproducing center frequency carrier signals relating to the center frequency carrier reproduction circuit for reproducing the center frequency carrier signals of two frequencies from frequency modulated signals for which '1' and '0' of digital data are allocated to the two frequencies. CONSTITUTION:This circuit is provided with a first carrier reproduction means 11 for demodulating the carrier signals of one of the two frequencies from the frequency modulated signals, a second carrier reproduction means 12 for demodulating the other carrier signals from the frequency modulated signals, an integration means 13 for integrating both carrier signals, a filter means 14 for eliminating at least low frequency components equivalent to the difference of the two frequencies from the output signals of the integration means 13 and a 1/2 frequency dividing means 15 for dropping the frequency of the output signals of the filter means 14 to 1/2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a center frequency carrier reproducing circuit for reproducing center frequency carrier signals of two frequencies from an FM modulated signal in which digital data 1 and 0 are assigned to two frequencies, and an FM. The present invention relates to an FM modulation data demodulation device that reproduces original digital data from a modulation signal.

[0002]

2. Description of the Related Art Digital data of 1 and 0 at two frequencies
Wireless communication and commercial broadcasting using FM-modulated signals to which is assigned have been put into practical use. If the FM modulated signal is used, the transmission data can be reproduced by a relatively simple receiver, and relatively high quality data can be received even by a low power transmitter.

A demodulation operation for reproducing original digital data from an FM modulated signal in which digital data 1 and 0 are assigned to two frequencies is, for example, a detection operation for synchronously detecting the FM modulated signal to remove a carrier signal component. , A data reproducing operation for reading the amplitude of a baseband signal formed through synchronous detection at a predetermined phase position and reproducing digital data.

In synchronous detection of an FM modulated signal, (1) a carrier signal corresponding to the center of two frequencies (center frequency carrier signal) is reproduced from the FM modulated signal, and the FM signal is orthogonally demodulated by this carrier signal. Although the demodulation method detection is adopted, (2) a carrier signal corresponding to one of two frequencies (shift frequency) is reproduced from the FM modulation signal, and the FM modulation signal is demodulated using this shift frequency carrier signal. The shift frequency lock type detection may be adopted.

FIG. 8 is an explanatory diagram of quadrature demodulation type detection, and FIG. 9 is an explanatory diagram of shift frequency lock type detection. They are,
A conventional method for reproducing original digital data from an FM-modulated signal that has been FM-modulated by the MSK method has been described.

In the MSK-based FM modulation, the main bands of the two frequencies are mutually overlapped, and the ordinary FM detection method used in FM radio receivers and analog radios cannot be used.

In FIG. 8, an FM modulation signal y (t), which is FM-modulated by the MSK method, is branched into two, and an integrator 8
Input to 3A and 83B. In the center frequency carrier reproduction circuit 81, the center frequency carrier signal c (t) is reproduced from the FM modulation signal y (t), the center frequency carrier signal c (t) is unchanged in the integrator 83A and π / in the integrator 83B.
It is integrated with the two phases shifted.

A low-pass filter 84A removes a high-frequency component including a term of a carrier signal from the output of the integrator 83A, and a baseband signal sin [Φ (t)] is taken out. A low-pass filter 84B removes a high-frequency component from the output of the integrator 83B, and a baseband signal cos [Φ (t)] is taken out. The data reproduction circuit 88 reads the amplitudes of the two baseband signals at a predetermined phase position and restores the original digital data from the combination of the amplitudes.

In FIG. 9, the shift frequency carrier reproduction circuit 91 reproduces the shift frequency carrier signal d (t) from the FM modulation signal y (t), and the integrator 93 converts it into the FM modulation signal y (t). The shift frequency carrier signal d (t) is integrated.

The output of the integrator 93 has the high-frequency component removed by the low-pass filter 94, and the detected signal g (t)
Is taken out. The detection signal g (t) includes an unnecessary component related to 2πΔf, but is not affected by the unnecessary component at a specific phase position where t = nT. Data reproduction circuit 98
Then, the detected signal g (t) is read at the phase position of t = nT to restore the original digital data.

An example of commercial broadcasting using an FM modulated signal in which digital data 1 and 0 are assigned to two frequencies is F
It is FM multiplex broadcasting in which digital data broadcasting such as traffic information is transmitted from a broadcasting station by being multiplexed with M radio broadcasting. FM
In the multiplex broadcasting, character information or simple image information is substantially 20 kbps by utilizing a portion not used for FM radio broadcasting in one channel band (100 kHz) of commercial FM radio broadcasting of 76 to 90 MHz band. Broadcast as the following digital data.

In FM multiplex broadcasting, road information, traffic congestion information, latest accident information, regulation information, etc.
Continuously broadcast weather information, parking lot availability information, required transit time for specific sections, warnings, warnings, etc., regardless of the broadcasting program. Therefore, the driver does not need to wait for the traffic information inserted at the intervals of the broadcasting program or miss the traffic information of the necessary place, and the information of the desired type at the desired place can be displayed at any time. Can be acquired in the form of display and image display.

[0013]

When performing synchronous detection of the FM modulation signal, it is necessary to completely synchronize the phase of the integrated carrier with the FM modulation signal, but 1 and 0 of digital data at two frequencies are used. In the FM modulated signal to which is assigned, there is a problem that the center frequency carrier is not easily reproduced and the phase accuracy is poor.

That is, the center frequency components of the two frequencies are relatively weak and are easily affected by noise and phase distortion contained in the received radio wave. In addition, the low frequency components in the selected band may affect (multipath distortion or the like), and the phase of the reproduced center frequency carrier may shift.

For example, in the FM multiplex broadcasting described above, data broadcasting is performed from the received signal in the selected 100 kHz band (see FIG. 3).
Reference, MSK system FM modulation component) is reproduced, but since the center frequency of data broadcasting is set to 76 kHz, 19
Phase distortion occurs in the reproduced center frequency carrier signal due to 76 kHz noise generated due to the pilot signal (4 times) of kHz and the L-R component (2 times). Then, the phase distortion of the center frequency carrier signal deteriorates the accuracy of quadrature detection and increases the error rate of reproduced digital data.

The present invention is a center frequency carrier reproduction circuit capable of reproducing a center frequency carrier signal with high accuracy, and
An object of the present invention is to provide an FM-modulated data demodulation device having a low error rate of reproduced digital data.

[0017]

FIG. 1 is an explanatory view of the basic constitution of the invention of claim 1. In FIG. In FIG. 1, the center frequency carrier recovery circuit according to claim 1 uses an FM modulated signal in which digital data 1 and 0 are assigned to two frequencies,
In a center frequency carrier reproduction circuit for reproducing center frequency carrier signals of the two frequencies, first carrier reproduction means 11 for demodulating the carrier signal of one of the two frequencies from the FM modulation signal, and the FM modulation signal From at least the two carrier reproducing means 12 for demodulating the other carrier signal of the two frequencies, the accumulating means 13 for accumulating both reproduced carrier signals, and the accumulating signal of the both carrier signals, It has a filter means 14 for removing a low frequency component corresponding to a frequency difference, and a ½ frequency divider for reducing the frequency of the integrated signal band-selected by the filter means 14 to ½. .

The FM-modulated data demodulating device according to the second aspect is 2
FM with digital data 1 and 0 assigned to one frequency
In an FM modulated data demodulating device for reproducing original digital data from a modulated signal, first carrier reproducing means for reproducing a carrier signal corresponding to one of the two frequencies from the FM modulated signal, and the FM modulated signal , A second carrier reproducing means for reproducing a carrier signal corresponding to the other of the two frequencies, and both reproduced carrier signals are integrated to generate a low frequency component of a frequency corresponding to at least the difference between the two frequencies. Center frequency carrier reproducing means for removing and dividing by 1/2 to form a center frequency carrier signal, quadrature detecting means for quadrature demodulating the FM modulated signal using the formed center frequency carrier signal, and quadrature demodulation First reproducing means for detecting the amplitudes of the two generated signals at a predetermined phase position and reproducing the original digital data. That.

An FM-modulated data demodulating device according to a third aspect is the FM-modulated data demodulating device according to the second aspect, wherein a carrier signal corresponding to one of the reproduced two frequencies is integrated with the FM-modulated signal, Second reproducing means for reproducing the digital data by removing high frequency components from the integrated signal, and a carrier signal corresponding to the other of the two reproduced frequencies are integrated into the FM modulated signal, Third reproducing means for reproducing high-frequency components to reproduce the digital data, and first, second, and third reproducing means
A majority decision means for performing majority decision processing on one output data to determine 1 and 0 of the output data.

[0020]

In FIG. 1, the center frequency carrier reproducing circuit of claim 1 does not directly reproduce the center frequency carrier signal from the center frequency component included in the band, but allocates 1 and 0 of digital data to the FM. The center frequency carrier signal is indirectly formed from the two frequency components that are substantially used in the modulated signal.

The first carrier reproducing means 11 reproduces the carrier signal c ₁ (t) corresponding to one of two frequencies from the FM modulated signal y (t), and the second carrier reproducing means 12 reproduces the F signal.
A carrier signal c ₂ (t) corresponding to the other of the two frequencies is reproduced from the M modulation signal y (t).

In the integrating means 13, two carrier signals c
₁ (t) and c ₂ (t) are integrated to obtain a frequency component twice the center frequency f _C and two carrier signals c ₁ (t) and c ₂ (t)
A signal is formed by adding a frequency component corresponding to the difference 2Δf.

The filter means 14 is preferably composed of a bandpass filter for selectively passing a narrow band including a frequency twice the center frequency f _C , and together with other unnecessary noise components, the two carrier signals c ₁ ( t), c ₂ (t)
The frequency component corresponding to the difference 2Δf of 2 is removed. As a result, the center frequency f completely synchronized with the FM modulation signal f (t)
A frequency component twice as large as _C is extracted, and the 1/2 frequency dividing means 15 is extracted.
Then, the frequency is divided in half to form the center frequency carrier signal c (t).

The carrier reproduction method in the first carrier reproduction means 11 and the second carrier reproduction means 12 is (1) 4
The multiplication method, (2) Costas loop method, (3) inverse modulation tank limiter method, etc. can be used.

Further, the configuration from the first carrier reproducing means 11, the second carrier reproducing means 12 to the 1/2 frequency dividing means 15 may be formed by a dedicated electric circuit using a capacitor or a resistor. Some or all of them may be replaced with a digital signal processing circuit.

For example, the FM modulated signal y (t) is sampled and input in the form of digital data, and the entire circuit is composed of one arithmetic element. The first carrier reproducing means 11 and the second carrier Each unit from the reproducing unit 12 to the 1/2 frequency dividing unit 15 can be replaced with the steps of the arithmetic program.

In the FM-modulated data demodulating device of claim 2,
The center frequency carrier signal reproduced by the center frequency carrier reproducing circuit according to claim 1 is used to orthogonally demodulate the FM modulated signal.

That is, the center frequency carrier signal is directly added to the FM modulated signal to remove the high frequency component, and the center frequency carrier signal whose phase is delayed by π / 2 is added to the FM modulated signal to obtain the high frequency component. The original digital data is reproduced using the removed signal and the signal.

In the FM-modulated data demodulating device of claim 3,
By utilizing the configuration of the FM modulation data demodulation device according to claim 2,
Forming three independent FM modulation data demodulators,
The majority decision of the output data of the FM modulation data demodulation device of the system is adopted. As a result, even if one of the three FM-modulated data demodulation devices erroneously demodulates data, the digital data that is output does not include an error as long as the other two accurately demodulate the data.

[0030]

FIG. 2 is an explanatory diagram of a circuit configuration of an FM multiplex broadcasting receiver of an embodiment, and FIG. 3 is an explanatory diagram of an FM multiplex broadcasting standard. Here, an FM multiplex broadcast receiver is built in a normal FM receiver, and while receiving a normal music broadcast, etc.
Data can be received and accumulated by multiplex broadcasting, and the operator can visually recognize necessary information at any place at any time in the form of characters or images.

In FIG. 2, the FM multiplex broadcast receiver of the embodiment stores an FM radio broadcast receiver 21 which reproduces a normal stereo broadcast by voice and data through the FM multiplex broadcast, and responds to an operator's search operation. F to output information data
The M multiplex broadcast receiving section 22 and the interface section 23 for displaying the information data stored in the FM multiplex broadcast receiving section 22. The radio waves received through the antenna 25 are received by the FM radio broadcast receiving unit 21 and the FM multiplex broadcast receiving unit 2.
2 through branch 24.

The FM multiplex broadcast receiver 22 has two memories. One memory stores and updates the received data. The other memory stores the reception frequency of a specific channel that can receive FM multiplex broadcasting.

In the FM multiplex broadcast receiver 22, the FM modulated signal is reproduced by selecting the 100 kHz band assigned to one channel of FM broadcast. Next, from the FM modulated signal, a center frequency f _C = 60 to 90 kHz centered at 76 kHz
Select the Hz band and select MSK (Minimumm Shift Keying
) Method, FM-modulated signal components are extracted, and two baseband signals are reproduced through a quadrature demodulation operation.
Then, the original digital data is reproduced by reading the amplitudes of the two baseband signals.

The reproduced digital data is subjected to predetermined error detection and code correction, then classified into information categories, and stored in a memory. The operator selects the necessary information through the operation unit of the interface unit 23, and the microcomputer of the FM multiplex broadcast receiving unit 22 reads out the necessary data from the memory according to this selection operation and sends it to the interface unit 23.

In FIG. 3, in the 100 kHz band assigned to one channel of FM broadcasting, the L + R component of 0 to 15 kHz, the pilot signal of 19 kHz, and the range of 23 to 53 kHz.
The L-R component of Hz is included. Then, in the channel in which the FM multiplex broadcast is multiplexed, MSK (Minimumm) is set in the band of 60 to 92 kHz centered on the center frequency f _C = 76 kHz.
FM multiplex broadcast components FM-modulated by the Shift Keying method are arranged.

Therefore, the quadruple frequency component of the 19 kHz pilot signal and the doubling frequency component of the 38 kHz L-R component are likely to overlap at 76 kHz, and the phase of the center frequency carrier signal shifts due to these noise components, and synchronous detection is performed. There is a problem that makes it difficult. The FM multiplex broadcast component constitutes digital data by replacing 1 with a mark frequency (f _C + Δf: 80 kHz) and 0 with a space frequency (f _C −Δf: 72 kHz), and is transmitted at a data rate of 16 kbps.

FIG. 4 is an explanatory diagram of the configuration of the demodulation circuit of the FM multiplex broadcasting receiver of the embodiment, FIG. 5 is an explanatory diagram of the shift frequency carrier recovery circuit of the demodulation circuit of FIG. 4, and FIG. 6 is the demodulation circuit of FIG. FIG. 7 is an explanatory diagram of the data reproducing circuit of FIG. 7, and FIG. 7 is an explanatory diagram of a majority circuit of the demodulating circuit of FIG. In FIG. 6, (a) shows the case of the shift frequency lock system, and (b) shows the case of the orthogonal demodulation system. Figure 7
Inside, (a) shows the circuit configuration and (b) shows the truth table.

In FIG. 4, the FM modulated signal y (t) is distributed to the branches 40A, 40B and 40C, and independent detection processing and data reproduction processing are executed in the respective branches 40A, 40B and 40C. And branches 40A, 4
At 0B, the shift frequency lock type detection is performed, and at the branch 40C, the quadrature demodulation type detection using the center frequency carrier signal is performed.

The mark carrier reproducing circuit 41 has a frequency of 80 k which represents 1 of bit data of the FM modulated signal y (t).
The mark carrier signal c ₁ (t) of Hz is reproduced. Branch 40
In A, a shift frequency lock type detection process using the mark carrier signal c ₁ (t) is performed. The integrator 46A integrates the mark carrier signal with the FM modulated signal y (t), and the low pass filter 47A removes a high frequency component from the integrated signal. The data reproducing circuit 48A reads the amplitude of the output signal of the low-pass filter 47A at a predetermined phase position, and reproduces the original digital data X.

Similarly, the space carrier reproducing circuit 4
2 reproduces the space carrier signal c ₂ (t) having a frequency of 72 kHz, which represents 0 of the bit data of the FM modulated signal y (t). In the branch 40B, the space carrier signal c
A shift frequency lock detection process using ₂ (t) is performed. The integrator 46B integrates the FM carrier signal y (t) with the space carrier signal c ₂ (t), and the low-pass filter 47B removes high-frequency components from the integrated signal. The data reproducing circuit 48B reads the amplitude of the output signal of the low pass filter 47B at a predetermined phase position,
The original digital data Y is reproduced.

On the other hand, the center frequency carrier signal c (t) of 76 kHz used in the branch 40C is the mark carrier signal c ₁ (t) reproduced in the mark carrier reproducing circuit 41 and the mark carrier reproducing circuit 42 in the branch 40B. After the reproduced space carrier signal c ₂ (t) is integrated by the integrator 43, the bandpass filter 44 lowers the frequency corresponding to the frequency difference between the two carrier signals c ₁ (t) and c ₂ (t). It is formed by removing the frequency component and further reducing the frequency to 1/2 by the 1/2 frequency divider 45.

In the integrator 46C, the center frequency carrier signal c (t) is integrated with the FM modulated signal y (t), and in the low pass filter 47C, high frequency components are removed from the integrated signal. On the other hand, in the integrator 46D, the center frequency carrier signal c (t) whose phase is delayed by π / 2 is integrated into the FM modulation signal y (t), and the high-frequency component is removed by the low-pass filter 47D. Then, the data reproduction circuit 4
At 8C, the amplitudes of the output signals of the low-pass filters 47C and 47D are read, and the original digital data Z is reproduced.

The majority circuit 49 includes branches 40A, 40B,
The majority processing of the three bit data X, Y, Z reproduced independently at 40C is performed to obtain the bit data X, Y,
Bit data R in which at least two of Z match is output.

In FIG. 5, the mark carrier reproducing circuit 41 shown in FIG. 4 reproduces the mark carrier signal by the inverse modulation tank limiter system. In the inverse modulation tank limiter system,
Since the oscillation state is kept stable even during the period when the space signal continues in the FM modulation signal y (t), the cycle slip ratio can be minimized as compared with the quadruple multiplication method and the Costas loop method.

The FM modulated signal y (t) is divided into branches 50A and 50A.
It is distributed to B and input to the integrators 52A and 52B. The branch 50A includes an integrator 52A and a low pass filter 53.
A and an integrator 54A to reach an adder 55. Branch 50B
Goes to the adder 55 through the integrator 52B, the low-pass filter 53B and the integrator 54B.

The feed-forward components obtained by correcting the delay times of the low-pass filters 53A and 53B by the delay element 51 are input to the integrators 54A and 54B. However, the signal is input to the integrator 54A with a phase delayed by π / 2 from that to the integrator 54B.

The integrators 52A and 52B include tanks 57,
The feedback component of the output of the adder 55 is input through the limiter 56. The tank 57 has a mark frequency of 8
It is composed of a resonator tuned to 0 kHz. Integrator 52A
On the other hand, this input is
It is input with the phase delayed by π / 2.

In the mark carrier reproducing circuit 41 thus constructed, the mark carrier signal c ₁ (t) is separated and extracted from the FM modulated signal y (t). The space carrier reproducing circuit 42 of FIG. 4 employs a similar circuit configuration in which the tank 57 of FIG. 5 is tuned to the space frequency of 72 kHz.

In FIG. 6A, the data reproducing circuit 48A
Then, the clock recovery circuit 62 is the low-pass filter 47.
The clock is regenerated from the output of A. The limiter 61 limits the amplitude of the output of the low pass filter 47A at the phase position of the clock. In the detection processing of the shift frequency lock method, since the data subjected to the sum logical conversion is output, the difference logical conversion is performed in consideration of this and the original information is taken out. Therefore, the data X is transmitted through the bit delay 63 and the adder 64.
Is restored. The data reproducing circuit 48B shown in FIG.
The configuration is similar to that of the data reproducing circuit 48A shown in FIG.

Here, the adder 64 performs a mod 2 operation. mod2 means to take the remainder of dividing the result by 2, and is specifically configured by an EXOR gate.

In FIG. 4B, the data reproducing circuit 48C
Then, the clock recovery circuit 66 is the low-pass filter 47.
The clock is reproduced from the outputs of C and 47D. Limiter 6
5A and 65B limit the amplitude of the outputs of the low pass filters 47C and 47D based on the clock. The adder 67 adds the outputs of the limiters 65A and 65B, and the adder 68 adds the clock to the output of the adder 67. The restored data Z is output from the adder 68. Like the adder 64, the adders 67 and 68 perform a mod 2 operation, and are replaced by EXOR gates.

In FIG. 7A, the majority circuit 49 of FIG.
Is an AND gate 71, 74, 75, an OR gate 72,
76 and an inverter 73. Majority circuit 49
Of the X, Y, and Z bit data input at every 16 kbps, select the bit data in which at least two match, and determine it as the data output R. FIG. 7B shows a truth table of the majority decision process in the majority decision circuit 49.

[0053]

According to the center frequency carrier reproducing circuit of the first aspect, since the center frequency carrier signal can be formed without depending on the center frequency component included in the FM modulation signal, unnecessary noise components are included in the center frequency component. When they easily overlap (for example, MSK type F with a center frequency of 76 kHz)
Even in M-multiplex broadcasting, the center frequency carrier signal can be reproduced without being affected by noise components.

As a result, it is possible to carry out various accurate synchronous detections using the center frequency carrier signal having no phase shift due to the influence of noise components.

According to the FM-modulated-data demodulation device of the second aspect, even when the unnecessary noise component is likely to overlap with the central frequency component, the center frequency carrier signal having no phase shift due to the influence of the noise component is used to accurately perform the correction. Quadrature demodulation processing can be executed.

Therefore, the reading error of the data due to the error of the orthogonal demodulation is eliminated, and the reliability of the reproduced data is improved.

According to the FM-modulated data demodulating device of the third aspect, the output is determined by the majority decision of the data reproduced by the plurality of independent systems, so that it is caused by the noise component contained in the FM-modulated signal or the noise component due to the circuit noise. Error in the data to be read is corrected, and the reliability of the output data is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the invention of claim 1.

FIG. 2 is an explanatory diagram of a configuration of an FM multiplex broadcast receiver according to an embodiment.

FIG. 3 is an explanatory diagram of an FM multiplex broadcasting standard.

FIG. 4 is an explanatory diagram of a configuration of a demodulation circuit.

FIG. 5 is an explanatory diagram of a shift frequency carrier recovery circuit.

FIG. 6 is an explanatory diagram of a data reproducing circuit.

FIG. 7 is an explanatory diagram of a majority decision circuit.

FIG. 8 is an explanatory diagram of a quadrature detection method.

FIG. 9 is an explanatory diagram of a shift frequency locking method.

[Explanation of symbols]

 11 First Carrier Regenerating Means 12 Second Carrier Regenerating Means 13 Accumulating Means 14 Filter Means 15 1/2 Dividing Means

Claims (3)

[Claims] 1. Digital data 1s and 0s at two frequencies.
In a center frequency carrier reproducing circuit for reproducing the center frequency carrier signals of the two frequencies from the FM modulated signal to which is assigned, first carrier reproducing means for demodulating the carrier signal of one of the two frequencies from the FM modulated signal. (11), a second carrier reproducing means (12) for demodulating the other carrier signal of the two frequencies from the FM modulated signal, and an accumulating means (1 for accumulating both reproduced carrier signals.
3), a filter means (14) for removing at least a low-frequency component corresponding to the difference between the two frequencies from the integrated signal of both carrier signals, and the integrated means band-selected by the filter means (14). A center frequency carrier regenerating circuit having a 1/2 frequency dividing means for reducing the frequency of a signal to 1/2. 2. Digital data of 1 and 0 at two frequencies.
In an FM-modulated data demodulating device for reproducing original digital data from an FM-modulated signal assigned with, first carrier reproducing means for reproducing a carrier signal corresponding to one of the two frequencies from the FM-modulated signal, A second carrier reproducing means for reproducing a carrier signal corresponding to the other of the two frequencies from the FM modulated signal, and both reproduced carrier signals are integrated, and at least a frequency corresponding to the difference between the two frequencies. A center frequency carrier reproducing means for removing a low frequency component and dividing the frequency by 1/2 to form a center frequency carrier signal; and the F using the formed center frequency carrier signal.
It has a quadrature detection means for quadrature demodulating the M-modulated signal, and a first reproduction means for reproducing the original digital data by detecting the amplitudes of the two quadrature-demodulated signals at a predetermined phase position. FM modulation data demodulation device. 3. The FM-modulated data demodulation device according to claim 2, wherein a carrier signal corresponding to one of the reproduced two frequencies is integrated into the FM-modulated signal, and high frequency components are removed from the integrated signal. Second reproducing means for reproducing the digital data and a carrier signal corresponding to the other of the reproduced two frequencies are integrated into the FM modulated signal, and a high frequency component is removed from the integrated signal to remove the digital signal. It has a third reproducing means for reproducing data, and a majority determining means for performing majority processing on three output data of the first, second and third reproducing means to determine 1 and 0 of the output data. FM modulation data demodulation device.