JP2011166458A - Digital signal transmitting method, digital signal receiving method, digital signal transmitting apparatus, and digital signal receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital signal transmitting method by which two different digital signals can be simultaneously transmitted and power consumption during transmission can be suppressed. <P>SOLUTION: In a first modulation step, in accordance with a data value of a binary or more multi-level first digital signal to be varied at a first transmission rate, a frequency or a phase of a carrier wave is varied at the first transmission rate. In a second modulation step, in accordance with a data value of a binary or more multi-level second digital signal to be varied at a second transmission rate lower than the first transmission rate, an amplitude of the signal obtained in the first modulation step is varied at the second transmission rate. The signal obtained in the second modulation step is transmitted. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a digital signal transmission method, a digital signal reception method, a digital signal transmission device, and a digital signal reception device that are suitable for application to transmission and reception of digital signals in, for example, a wireless LAN.

  For example, in the case of transmitting a digital signal in wireless communication such as a wireless LAN, a digital modulation method is used. As examples of this digital modulation system, for example, FSK (Frequency Shift Keying), PSK (Phase Shift Keying), ASK (Amplitude Shift Keying) and the like are known. Yes.

  FSK is a method of changing the frequency of a carrier wave according to the data value of a digital signal. PSK is a method of changing the phase of a carrier wave according to a digital data value. ASK is a method of changing the amplitude of a carrier wave according to the data value of a digital signal.

  Further, QAM (Quadrature Amplitude Modulation) combining ASK and PSK is also known. This QAM is a modulation method with high transmission efficiency that can obtain a multi-level symbol by simultaneously changing the phase and amplitude of a carrier wave according to the data value of a digital signal to increase the communication speed.

  An example of this QAM will be described with reference to FIGS. FIG. 5 shows an example of a multi-value symbol assigned to a (phase, amplitude) coordinate in a phase-amplitude coordinate space in which the phase and amplitude are coordinate axes orthogonal to each other. The example of FIG. 5 is an example in the case of 16QAM in which 16 symbols are assigned to 16 combinations of 16 phases and amplitudes, that is, 16 (phase, amplitude) coordinates.

That is, in the phase-amplitude coordinates of FIG. 5, the positions surrounded by circles are the coordinate positions of 16 symbols in the 16QAM of this example, and the numbers 0 to 15 surrounded by circles are the symbols in the 16QAM of this example. The data value of the digital signal transmitted corresponding to is shown. In the example of FIG.
(Phase, amplitude) = (1,1) = 0
= (-1,1) = 1
= (-1, -1) = 2
= (1, -1) = 3
= (2,1) = 4
= (2,2) = 5
= (1,2) = 6
= (− 1,2) = 7
= (-2,2) = 8
= (-2,1) = 9
= (-2, -1) = 10
= (-2, -2) = 11
= (-1, -2) = 12
= (1, -2) = 13
= (2, -2) = 14
= (2, -1) = 15
Thus, a data value is assigned to each symbol.

  Therefore, when the multi-value data of the digital signal “530128” is transmitted by 16QAM in this example, as shown in FIG. 6, the data values of the digital signal are allocated as shown in FIG. The phase and amplitude of the carrier wave are changed so that the phase and amplitude correspond to the received symbols.

  In FIG. 5, the symbols used for the data value “530128” to be transmitted in this case are shaded, and the symbols are selected in the order indicated by the arrows according to the transmission data value. It shows that the phase and amplitude of the carrier wave are changed.

JP 2004-056734 A JP 2002-290417 A

  By the way, although QAM is a digital modulation method with good transmission efficiency, the data value of a digital signal to be transmitted is one in spite of using phase and amplitude as modulation elements, and two digital signals are transmitted. The signal data values cannot be transmitted simultaneously.

  Therefore, in order to increase the confidentiality of communication data, it is necessary to perform encryption and use passwords and authentication information. However, since QAM can send only transmission data, an encryption key, password, and authentication information are required. Etc. had to be sent separately from the transmission data.

  Further, in QAM, it is necessary to simultaneously change the phase and the amplitude at the same clock rate at the same time. In this case, the transient response of the transmission amplifier is particularly important with respect to the amplitude. For this reason, with an emphasis on response speed, an amplifier having a large back-off (margin) is generally used as a transmission amplifier. For this reason, there existed a problem that power consumption will become large.

  In view of the above points, an object of the present invention is to provide a digital signal transmission method capable of simultaneously transmitting two different digital signals and suppressing power consumption during transmission.

In order to solve the above problems, the present invention provides:
A first modulation step of changing a frequency or phase of a carrier wave at the first transmission rate in accordance with a data value of a first digital signal having two or more values changing at a first transmission rate;
The amplitude of the signal obtained in the first modulation step depends on the data value of the second digital signal having a multi-value that is two or more that changes at a second transmission rate that is slower than the first transmission rate. A second modulation step of changing at the second transmission rate;
A transmission step of transmitting the signal obtained in the second modulation step;
A digital signal transmission method is provided.

  In the present invention configured as described above, first, in the first modulation step, the frequency or phase of the carrier wave is changed at the first transmission rate in accordance with the data value of the first digital signal. This modulation processing corresponds to FSK or PSK.

  Next, in the second modulation step, the amplitude of the signal after modulation in the first modulation step is a second transmission rate that is slower than the first transmission rate, depending on the data value of the second digital signal. Can be changed. The processing in the second modulation step corresponds to ASK modulation processing. In the transmission step, the signal obtained in the second modulation step is transmitted.

  Thus, according to the present invention, one of the two digital signals is transmitted by a change in the frequency or phase of the carrier wave, and the other is transmitted by a change in the amplitude. That is, two digital signals are transmitted simultaneously.

  In the case of the present invention, the transmission rate of the second digital signal transmitted by the change in the amplitude of the carrier wave is the same as the transmission rate of the first digital signal transmitted by the change in the frequency or phase of the carrier wave. There is no need to do so, and it is possible to reduce the transmission power consumption because the response speed of the transmission amplifier does not need to be emphasized.

  According to the present invention, as in claim 2, for example, as the second digital signal, information for obtaining desired information from the first digital signal, such as a password or identification information, or a recognition code, It can be transmitted simultaneously with the first digital signal. For example, as in claim 3, the second digital signal can be information on an encryption key for decrypting the encrypted first digital signal.

  Therefore, according to the second and third aspects of the present invention, not only the first digital signal but also the second digital signal cannot be demodulated. Therefore, other than the reception method corresponding to the digital signal transmission method of the present invention, desired information cannot be obtained, and the confidentiality of the transmission information can be ensured.

  According to the present invention, it is possible to provide a digital signal transmission method capable of simultaneously transmitting two different digital signals and suppressing power consumption during transmission. Moreover, according to this invention, the transmission method of the digital signal which ensured the confidentiality of transmission information can be provided.

It is a block diagram which shows embodiment of the digital signal transmitter by this invention. It is a figure used in order to demonstrate the processing operation of embodiment of the digital signal transmitter by this invention. It is a block diagram which shows embodiment of the digital signal receiver by this invention. FIG. 4 is a diagram illustrating a configuration example of a part of FIG. 3. It is a figure for demonstrating QAM. It is a figure for demonstrating QAM.

[Embodiment of Digital Signal Transmission Method]
FIG. 1 is a block diagram of an example of a digital signal transmission apparatus to which an embodiment of a digital signal transmission method according to the present invention is applied. FIG. 2 is a diagram for explaining a transmission signal in the example of the digital signal transmission apparatus. Hereinafter, an embodiment of a digital signal transmission method will be described with reference to FIGS. 1 and 2.

  In the embodiment described below, FSK (frequency shift keying) is performed in the first modulation step. In this embodiment, the first digital signal to be transmitted is obtained by encrypting data to be transmitted using an encryption key, and the second digital signal to be transmitted is It is information on the encryption key used for this encryption. In this embodiment, the first and second digital signals to be transmitted are binary data “0” and “1”.

  The digital signal transmission apparatus in the example of FIG. 1 includes a transmission digital signal generation unit 10. In this example, the transmission digital signal generation unit 10 includes a transmission data generation unit 101, an encryption unit 102, an encryption key generation unit 103, and a frequency divider 104. In this example, the transmission digital signal generation unit 10 is configured by a microcomputer including a memory, and each unit is configured as a software function unit executed by a software program. The digital signal generator 10 for transmission can, of course, be configured by hardware for each part shown in the figure and other necessary parts.

  The transmission data generation unit 101 includes a memory, in which data to be transmitted is held in advance. Then, in response to a transmission start instruction from the control unit (not shown), the transmission data generation unit 101 reads the data to be transmitted that has been held and supplies the data to the encryption unit 102.

  The encryption unit 102 performs encryption processing on the data to be transmitted from the transmission data generation unit 101 by using the encryption key from the encryption key generation unit 103, and transmits the encrypted data to the transmission Is output as the first digital signal Sf.

  In this embodiment, the transmission data generation unit 101 and the encryption unit 102 are supplied with a clock signal CLK having a predetermined clock rate, and the data after the encryption processing is a signal having a clock rate of the clock signal CLK. It is said. That is, in this embodiment, the transmission rate Rf of the first digital signal Sf to be transmitted is equal to the clock rate of the clock signal CLK. In this example, the encryption unit 102 constitutes a first digital signal generating means.

  The encryption key generation unit 103 includes a memory, and the encryption key data used when encrypting data to be transmitted is held in advance in the encryption key generation unit 103. In response to a transmission start instruction from a control unit (not shown), the encryption unit 102 requests the encryption key generation unit 103 to acquire the stored encryption key data, and performs encryption processing. Use.

  Further, the clock signal CLK is divided by the frequency divider 104 and the clock signal CLKa having a frequency lower than that of the clock signal CLK is supplied to the encryption key generation unit 103. The encryption key generation unit 103 outputs the encryption key data as a second digital signal Sa to be transmitted at the clock rate Ra of the clock signal CLKa in response to a transmission start instruction from a control unit (not shown). To do. The clock signal CLKa is obtained by dividing the clock signal CLK, and the transmission rate Ra of the second digital signal Sa is slower than the transmission rate Rf of the first digital signal Sf. However, since the clock signal CLKa is obtained by dividing the clock signal CLK, the clock signal CLKa is in a synchronous relationship with the clock signal CLK. In this example, the encryption key generator 103 constitutes a second digital signal generator.

  As described above, in this embodiment, the transmission digital signal generator 10 encrypts data to be transmitted from the encryption unit 102 in response to the transmission start instruction. The digital signal Sf is output from the encryption key generation unit 103 as a second digital signal Sa composed of encryption key data for the encryption.

  However, from the encryption unit 102 and the encryption key generation unit 103 of the transmission digital signal generation unit 10, at the beginning of the transmission signal, as described later, the encrypted data and the encryption key of the data to be transmitted Prior to the data, a preamble signal is transmitted as the first digital signal Sf and the second digital signal Sa. This preamble signal repeats, for example, “0” and “1” alternately at the respective transmission rates as the first digital signal Sf and the second digital signal Sa, for example, the first digital signal Sf and the second digital signal Sa. The signal Sf is transmitted for a period of 3 to 20 bytes.

  As will be described later, on the receiving side, the received signal strength (RSSI (Received Signal Strength Indication)) in the preamble signal is determined, and the demodulation threshold of the ASK modulated signal is determined. In signal transmission using ASK, the electric field strength level of the transmission RF signal varies depending on the condition of the transmission path. Thus, the reception side discriminates the received signal strength in the received preamble signal on the receiving side, and the ASK modulated signal. By determining the demodulation threshold value, it is possible to cope with fluctuations in the electric field strength level of the transmission RF signal due to the condition of the transmission path. The preamble signal is also used to regenerate the data clock on the receiving side.

  The first digital signal Sf output from the encryption unit 102 of the transmission digital signal generation unit 10 is supplied to the FSK modulator 11. When the data value of the first digital signal Sf input to the FSK modulator 11 is “0”, the FSK modulator 11 outputs the carrier signal of the low frequency f1, and the data value of the first digital signal Sf is “1”. ", A carrier wave signal having a high frequency f2 (> f1) is output.

  The signal from the FSK modulator 11 is supplied to the mixer circuit 13 after unnecessary band components are removed through the filter 12. Further, a local oscillation frequency signal from a local oscillator 14 made of, for example, a variable frequency oscillator is supplied to the mixer circuit 13. In the mixer circuit 13, the signal from the FSK modulator 11 that has passed through the filter 12 is frequency-converted by the local oscillation frequency signal from the local oscillator 14 to be a transmission frequency signal.

  The transmission frequency signal from the mixer circuit 13 is supplied to a variable gain amplifier (transmission amplifier) 15. The variable gain amplifier 15 is supplied with the second digital signal Sa from the transmission digital signal generator 10 as a gain control signal.

  This variable gain amplifier 15 constitutes an ASK modulator. That is, when the data value of the second digital signal Sa from the transmission digital signal generator 10 is “0”, the variable gain amplifier 15 sets the amplitude of the transmission frequency signal from the mixer 13 to a relatively small amplitude A1. When the data value of the second digital signal Sa from the transmission digital signal generator 10 is “1”, the amplitude of the transmission frequency signal from the mixer 13 is set to a relatively large amplitude A2 ( > A1) is controlled.

  As described above, the transmission frequency signal obtained by FSK modulation using the first digital signal Sf and ASK modulation using the second digital signal Sa is band-limited through the filter 16 from the variable gain amplifier 15. Radio transmission is performed through the transmission antenna 17.

  Next, with reference to FIG. 2, a signal transmitted from the digital signal transmission apparatus of this embodiment will be described.

  FIG. 2C is a schematic diagram for explaining modulation of a signal transmitted from the digital signal transmission apparatus of this embodiment shown in FIG. 2A shows a clock signal CLKa for outputting the second digital signal Sa from the transmission digital signal generator 10, and FIG. 2B shows the second digital signal Sa. An example of the signal Sa is shown. Further, FIG. 2 (E) shows a clock signal CLK for outputting the first digital signal Sf from the transmission digital signal generator 10, and FIG. 2 (D) shows the first digital signal. An example of the signal Sf is shown.

  As shown in FIGS. 2A and 2E, in this example, the clock signal CLK is a signal having a frequency four times that of the clock signal CLKa. That is, in the frequency divider 104, the clock signal CLK is divided by a quarter to obtain the clock signal CLKa.

  As described above, the transmission data generation unit 10 transmits a preamble signal as each of the first digital signal Sf and the second digital signal Sa prior to the transmission data to be transmitted. In this example, since the digital signal is binary data in this example, both the first digital signal Sf and the second digital signal Sa have a data value of “0” and a data value of “1”. Are generated in an interval of 20 bytes of the first digital signal Sf (for example, 5 bytes for the second digital signal Sa).

  In FIG. 2C, FSK_Lo shown on the left frequency axis indicates that the first digital signal Sf is at a low level, that is, the data value is “0” and the frequency of the carrier wave is f1. In addition, FSK_Hi indicates that the first digital signal Sf is at a high level, that is, the data value is “1” and the frequency of the carrier wave is f2.

  In FIG. 2C, ASK_Lo shown on the right amplitude axis indicates that the second digital signal Sa is at a low level, that is, the data value is “0” and the amplitude is A1. ASK_Hi indicates that the first digital signal Sa is at a high level, that is, the data value is “1” and the amplitude is A2.

  In the example of FIG. 2, in the data section after the preamble section, data “01001011001100101101” is transmitted as the first digital signal Sf, and an encryption key “01001” is transmitted as the second digital signal Sa. Is sent out.

  As shown in the schematic diagram of FIG. 2C, the first digital signal is transmitted by changing the frequency of the carrier wave according to the data value of the first digital signal Sf. That is, the first digital signal is transmitted as an FSK modulated signal.

  Further, as shown in the schematic diagram of FIG. 2C, the amplitude (transmission power) of the signal whose carrier frequency is changed by the data value of the first digital signal Sf is the second digital signal. The second digital signal is transmitted by being changed according to the data value. That is, the second digital signal is transmitted as an ASK modulated signal. Thus, according to the digital signal transmission method of this embodiment, the first digital signal Sf and the second digital signal Sa are multiplexed and transmitted simultaneously.

  In this embodiment, the first digital signal Sf sent by FSK and the second digital signal Sa sent by ASK do not need to have the same clock rate, and in this embodiment, they are sent by ASK. The transmission rate of the second digital signal Sa to be transmitted is slower than the transmission rate of the first digital signal Sf.

  Therefore, since the transient response of the transmission amplifier (variable gain amplifier 15) only needs to be able to adapt to the second digital signal Sa having a low transmission rate, the transmission amplifier does not require a large back-off and suppresses transmission power consumption. There is an advantage that can be.

[Embodiment of Digital Signal Receiving Method]
FIG. 3 is a block diagram of an example of a digital signal receiving apparatus to which an embodiment of the digital signal receiving method according to the present invention is applied. FIG. 4 is a block diagram showing a detailed configuration example of a part of the blocks in FIG.

  The digital signal receiving apparatus of the example of FIGS. 3 and 4 receives a transmission signal wirelessly transmitted from the digital signal transmitting apparatus of FIG. 1 of the above-described embodiment, and receives the first digital signal and the second digital signal. The signal is demodulated and the encryption of the first digital signal is decrypted.

  As shown in FIG. 3, the transmission signal received by the reception antenna 21 is supplied to the filter 23 through the reception amplifier 22 and is supplied to the mixer circuit 24 after removing unnecessary band components. The mixer circuit 24 is also supplied with a local oscillation frequency signal from a local oscillator 25 made of, for example, a variable frequency oscillator.

  In the mixer circuit 24, the received signal is frequency-converted by the local oscillation frequency signal from the local oscillator 25 to be a signal in the original frequency band on the transmission side. The signal from the mixer circuit 24 is supplied to the filter 27 through the amplifier 26 to remove unnecessary band components, and then supplied to the FSK demodulator 28 and the A / D converter 29.

  Then, the FSK demodulator 28 converts the frequency f1 into the data value “0” and the frequency f2 into the data value “1”, respectively, to generate the binarized data for the signal from the filter 27, and the data restoration unit 30.

  The A / D converter 29 converts the amplitude of the signal from the filter 27 into a digital value and supplies the digital value to the data restoration unit 30. The digital value from the A / D converter 29 indicates the received signal strength (RSSI).

  In this example, the data restoration unit 30 is configured as shown in FIG. In this example, the data restoration unit 30 is configured by a microcomputer including a memory, and each unit in FIG. 4 is configured as a software function unit that is executed by a software program. The data restoring unit 30 can of course be configured by configuring the illustrated units and other necessary units by hardware.

  As shown in FIG. 4, the data restoration unit 30 includes a clock reproduction unit 301, a data reproduction unit 302, a decryption unit 303, a binarization unit 304, an amplitude threshold setting unit 305, and an encryption key reproduction unit. 306.

  The digital value from the A / D converter 29 is supplied to the binarization unit 304 of the data restoration unit 30 and also to the amplitude threshold setting unit 305. The amplitude threshold setting unit 305 sets an amplitude threshold for ASK demodulation from the digital value (RSSI) from the A / D converter 29 of the preamble signal portion, and supplies the set amplitude threshold to the binarization unit 304. .

  The binarization unit 304 compares the digital value from the A / D converter 29 with the amplitude threshold value, and sets the data value “0” when the digital value from the A / D converter 29 is smaller than the amplitude threshold value. When the value is larger than the amplitude threshold, the data value is converted to “1” to generate binary data. Then, the binarization unit 304 supplies the binarized data to the clock reproduction unit 301 and also to the encryption key reproduction unit 306.

  The binarized data from the FSK demodulator 28 is supplied to the clock recovery unit 301 and also to the data recovery unit 302.

  The clock reproduction unit 301 reproduces the clock signal CLK and the clock CLKa from the binarized data supplied thereto, the reproduced clock signal CLK to the data reproduction unit 302, and the reproduced clock signal CLKa is the encryption key reproduction unit. 306, respectively.

  In the data reproduction unit 302, the binarized data from the FSK demodulator 28 is sampled by the clock signal CLK from the clock reproduction unit 301, so that the transmitted first digital signal is restored. Since the first digital signal has been encrypted, it is supplied from the data reproduction unit 302 to the decryption unit 303.

  Although not shown, the data reproducing unit 302 also detects a preamble signal section, and supplies the detection signal of the preamble signal section to the threshold setting unit 305.

  In addition, the encryption key reproduction unit 306 samples the binary data from the binarization unit 304 by the clock signal CLKa from the clock reproduction unit 301, thereby encrypting the second digital signal transmitted. The key data is restored. The restored encryption key data from the encryption key reproduction unit 306 is supplied to the decryption unit 303.

  Using the encryption key data from the encryption key reproduction unit 306, the decryption unit 303 decrypts the encryption of the first digital signal from the data reproduction unit 302 and outputs the decrypted data. The decrypted data is processed such as being stored in a memory.

  As described above, in the digital signal receiving apparatus according to this embodiment, the two data of the first digital signal and the second digital signal are demodulated independently from one received signal. In this embodiment, the first digital signal is encrypted by using the second digital signal as an encryption key, and the first digital signal is demodulated so that the first digital signal is demodulated. It becomes possible to decrypt the encryption of the signal.

[Other Embodiments and Modifications]
In the above description, FIG. 1 shows an embodiment of a digital signal transmission device, and FIGS. 3 and 4 show embodiments of a digital signal reception device. However, in the case of a digital signal communication device having a transmission / reception function, FIG. 1 is provided in the transmission system, and the digital signal receiving apparatus in FIGS. 3 and 4 is provided in the reception system.

  In the above-described embodiment, the first digital signal is transmitted by FSK. However, the present invention can also be applied to the case where the first digital signal is transmitted by PSK.

  Further, in the description of the above-described embodiment, for the sake of simplicity, the two digital signals to be transmitted are both binary data. It goes without saying that the invention is applicable.

  Moreover, although the above-mentioned embodiment is a case of radio | wireless communication, of course, this invention is not limited only to the case of radio | wireless communication.

  DESCRIPTION OF SYMBOLS 10 ... Transmission data generation part, 11 ... FSK modulator, 15 ... Variable gain amplifier, 28 ... FSK demodulator, 30 ... Data restoration part

Claims (7)

A first modulation step of changing a frequency or phase of a carrier wave at the first transmission rate in accordance with a data value of a first digital signal having two or more values changing at a first transmission rate;
The amplitude of the signal obtained in the first modulation step depends on the data value of the second digital signal having a multi-value that is two or more that changes at a second transmission rate that is slower than the first transmission rate. A second modulation step of changing at the second transmission rate;
A transmission step of transmitting the signal obtained in the second modulation step;
A digital signal transmission method comprising: The digital signal transmission method according to claim 1,
The digital signal transmission method, wherein the second digital signal is information for obtaining desired information from the first digital signal on the receiving side. The digital signal transmission method according to claim 2,
The digital signal transmission method, wherein the second digital signal is encryption key information for decrypting the encrypted first digital signal. In the digital signal transmission method according to any one of claims 1 to 3,
Before transmitting the first digital signal and the second digital signal, a step of transmitting a reference digital signal as a preamble through the first modulation step and the second modulation step is provided. Digital signal transmission method. The amplitude of the signal obtained by changing the frequency or phase of the carrier wave at the first transmission rate according to the data value of the first or second multi-valued digital signal that changes at the first transmission rate. Receives a transmission signal that is transmitted by being changed in accordance with a data value of a second digital signal having a multi-value of 2 or more that changes at a second transmission rate that is slower than the first transmission rate. A digital signal receiving method for demodulating the first digital signal and the second digital,
A first demodulation step of detecting a change in frequency or phase of a carrier wave of the received signal and demodulating the first digital signal;
A second demodulation step obtained by demodulating the second digital signal from the signal level of the received signal;
A digital signal receiving method comprising: First digital signal generating means for generating a first digital signal having a multi-value of 2 or more at a first transmission rate;
Second digital signal generating means for generating a second digital signal having a multi-value of 2 or more at a second transmission rate slower than the first transmission rate;
First modulation means for changing the frequency or phase of a carrier wave in accordance with the data value of the first digital signal from the first digital signal generating means;
Second modulation means for changing the amplitude of the signal obtained by the first modulation means in accordance with the data value of the second digital signal from the second digital signal generation means;
Transmitting means for transmitting the signal obtained by the second modulating means;
A digital signal transmission device comprising: The amplitude of the signal obtained by changing the frequency or phase of the carrier wave at the first transmission rate according to the data value of the first or second multi-valued digital signal that changes at the first transmission rate. Receives a transmission signal that is transmitted by being changed in accordance with a data value of a second digital signal having a multi-value of 2 or more that changes at a second transmission rate that is slower than the first transmission rate. A digital signal receiving apparatus for demodulating the first digital signal and the second digital,
First demodulation means for detecting a change in frequency or phase of a carrier wave of the received signal and demodulating the first digital signal;
Second demodulating means obtained by demodulating the second digital signal from the signal level of the received signal;
A digital signal receiving apparatus comprising:

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