JP5327960B2 - Modulator, demodulator, communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a modulator for reducing distortion caused by a radio communication path, a demodulator, and a radio communication system. <P>SOLUTION: The modulator for executing modulation for radio communication includes: a conversion part for obtaining data to be converted to symbol values; a first signal generation part for subjecting a carrier to phase modulation by the symbol values converted by the conversion part to generate a first signal; a second signal generation part for generating a second signal having a frequency different from that of the carrier; and an output part for setting a first period of a predetermined time length and a second period based on a time length of impulse response of a radio communication system for each symbol value converted by the conversion part, outputting a first signal generated by the first signal generation part in the first period, and outputting a second signal generated by the second signal generation part in the second period. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a modulation device, a demodulation device, and a wireless communication system for wireless communication using phase modulation.

  As digital modulation / demodulation techniques, amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), quadrature amplitude modulation (QAM), and quadrature amplitude modulation (QAM) Etc. are known (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

  The above-described digital modulation / demodulation technique modulates a binary data sequence composed of “0” and “1” by changing any one of amplitude, frequency, and phase in a reference signal (carrier wave) to obtain a modulated signal. . PSK has been confirmed to have superior performance compared to ASK and FSK.

  In general wireless communication, an electrical signal converted from a wireless signal by a receiving device is described in the form of a convolution of a modulated signal and an impulse response of a wireless communication path. The wireless communication path here includes a transmission element that converts an electric signal into a radio signal in the transmission apparatus, a propagation path, and a reception element that converts the radio signal into an electric signal in the reception apparatus.

  Among wireless communication, acoustic communication uses vibrators (mass electro-mechanical energy conversion element and machine-electric energy conversion element, respectively) having mass in a transmitting element and a receiving element. Therefore, when the time length of the impulse response of the wireless communication path is compared between the acoustic communication and the radio communication, the value of the acoustic communication is larger than the value of the radio communication.

S. Haykin: Communication Systems (Wiley, New York, 2001) p. 417. A. Burr: Modulation and Coding for Wireless Communications (Prentice-Hall, New York, 2001) p. 36.

  When using PSK and QAM that rapidly change the phase of a carrier wave, a wireless communication path using an element having a long impulse response time (for example, a vibrator such as a piezoelectric ceramic having a large mechanical Q value, a vibrator whose weight cannot be ignored) is used. There is a problem that the passed electric signal is greatly distorted.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a modulation device, a demodulation device, and a wireless communication system that reduce distortion caused by a wireless communication path.

  In order to solve the above-described problem, one embodiment of the present invention is a modulation device that performs modulation for wireless communication, a conversion unit that acquires data and converts the data into a symbol value, and a symbol converted by the conversion unit For each symbol value converted by the conversion unit, a first signal generation unit that generates a first signal by phase-modulating the carrier wave with a value, a second signal generation unit that generates a second signal having a frequency different from that of the carrier wave, The first period having a predetermined time length and the second period based on the time length of the impulse response of the wireless communication system are set, and the first signal generated by the first signal generation unit is output during the first period. And an output unit that outputs the second signal generated by the second signal generation unit during the second period.

  Another embodiment of the present invention is a demodulation device that demodulates a signal that is modulated by a modulation device and received via wireless communication. The modulation device acquires data, converts the data into a symbol value, and the symbol value The carrier wave is phase-modulated to generate a first signal, a second signal having a frequency different from that of the carrier wave is generated, and for each symbol value, the first period of a predetermined time length and the time of the impulse response of the wireless communication system A second period of time length based on the length is set, the first signal is output during the first period and the second signal is output during the second period, and each symbol period corresponds to the first period. A reference signal generation unit that outputs a carrier wave and outputs a third signal having a frequency different from that of the carrier wave corresponding to the second period, and a multiplication unit that multiplies the output of the modulation device and the output of the reference signal generation unit .

  One embodiment of the present invention is a wireless communication system that transmits data using phase modulation, and includes a conversion unit that acquires data and converts the data into symbol values at predetermined symbol periods, and the conversion unit converts the data. A first signal generation unit that generates a first signal by phase-modulating a carrier wave with the determined symbol value, a second signal generation unit that generates a second signal different from the first signal, and shorter than the symbol period for each symbol period The first signal generated by the first signal generator in the first period is output, and the second signal generated by the second signal generator in the second period, which is the remaining period obtained by removing the first period from the symbol period. An output unit that outputs the output of the output unit as a radio signal, a reception unit that receives the radio signal transmitted by the transmission unit, and outputs a carrier wave in the first period for each symbol period, It has a carrier generating unit which outputs a third signal that is different from the carrier in the two periods, a multiplying unit for multiplying the outputs of the carrier wave generating unit of the modulator.

  According to the present invention, it is possible to reduce distortion caused by a wireless communication path.

2 is a block diagram illustrating an example of a configuration of an acoustic communication system according to Embodiment 1. FIG. 3 is a block diagram illustrating an example of a configuration of a modulation device in Embodiment 1. FIG. It is a block diagram which shows an example of a structure of a demodulation apparatus. It is a block diagram which shows an example of a structure of the modulation apparatus in a comparative example. It is a block diagram which shows an example of a structure of the demodulation apparatus in a comparative example. It is a wave form diagram which shows the waveform of a transmission baseband signal. It is a wave form diagram which shows the waveform of the signal in a comparative example. FIG. 3 is a waveform diagram illustrating a waveform of a signal in the first embodiment. 6 is a block diagram illustrating an example of a configuration of an acoustic communication system according to Embodiment 2. FIG. 6 is a block diagram illustrating an example of a configuration of a modulation device according to Embodiment 2. FIG. FIG. 6 is a waveform diagram showing a signal waveform in the second embodiment. It is a block diagram which shows an example of a structure of an experimental system. It is a wave form diagram which shows the measurement result of the impulse response of the radio | wireless communication path in an experimental system. It is a wave form diagram which shows the modulation signal waveform in an experimental system. It is a figure which shows the measurement result of BER vs. SNR by an experimental system.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, an example of an acoustic communication system to which the present invention is applied will be described. The acoustic communication system here uses BPSK (Bi-Phase Shift Keying) to transmit 1-bit information with one symbol.

<Embodiment 1>
The configuration of the acoustic communication system according to Embodiment 1 will be described below.

  FIG. 1 is a block diagram illustrating an example of a configuration of an acoustic communication system according to the first embodiment. This acoustic communication system includes a modulation device 1a, a vibrator 21, a vibrator 41, a demodulation device 2a, and information processing devices 4a and 4b. The binary bit sequence output from the information processing device 4a is modulated by the modulation device 1a, converted into a sound wave signal by the vibrator 21, and output to the propagation path 3 in the medium. Next, the sound wave signal propagated from the vibrator 21 to the vibrator 41 via the propagation path 3 is converted into an electric signal by the vibrator 41, demodulated by the demodulator 2a, and output to the information processing device 4b as a binary bit sequence. Is done. The modulation device 1a and the vibrator 21 constitute a transmission device. The vibrator 41 and the demodulating device 2a constitute a receiving device.

  FIG. 2 is a block diagram illustrating an example of the configuration of the modulation device 1a according to the first embodiment. The modulation device 1a includes a bipolar comparator 11 (Bipolar Comparator), a carrier frequency generator 12 (Carrier Frequency Oscillator), a mixer 13 (Mixer), a buffer signal frequency generator 14, and a multiplexer 15 (Multiplexer).

  FIG. 3 is a block diagram showing an example of the configuration of the demodulation device 2a. The demodulator 2a includes a carrier frequency generator 42 (Carrier Frequency Oscillator), a mixer 43, a reference voltage source 44 (Reference Potential), a multiplexer 45 (Multiplexer), an LPF 46 (Low-Pass Filter), and a data determination unit 48 (Data Decision). Have

  The operation of the modulation device 1a will be described below.

  The bipolar comparator 11 converts “0” and “1” of the binary bit sequence input from the information processing device 4a into “−1” and “1”, respectively, and generates a transmission baseband signal.

  Here, a synchronization signal generation unit that generates a signal for synchronization between the modulation device 1a and the demodulation device 2a may be provided. For example, the synchronization signal generation unit performs a process of adding a reference signal for synchronization between the data output from the bipolar comparator 11. Alternatively, the modulation device 1a may have a function of performing DPSK (Differential Phase Shift Keying) modulation instead of the synchronization signal generation unit.

Carrier frequency generator 12, as the carrier wave to produce a sine wave of amplitude A, frequency f _c. The mixer 13 multiplies the output of the bipolar comparator 11 and the output of the carrier frequency generator 12 to generate a BPSK signal.

The buffer signal frequency generator 14 compares the current symbol value with the immediately preceding symbol value, and determines the frequency f _b based on the comparison result. For example, the buffer signal frequency generator 14 sets f _b to 1 / ΔT when the current symbol value is equal to the previous symbol value, and sets f _b to 2 when the current symbol value is different from the previous symbol value. Set to / ΔT.

The buffer signal frequency generator 14 generates a sine wave having an amplitude B and a frequency f _b as a BS (Buffer Signal). Here, the symbol time is T, the guard time is ΔT, and the impulse response duration of the wireless communication path is I. By using I and a predetermined coefficient K, ΔT = K · I. K is assumed to be in the vicinity of 1. That is, ΔT is in the vicinity of I. The impulse response duration I is a time from the peak level of the impulse response to −60 dB.

  The multiplexer 15 switches between the two inputs according to the symbol timing and outputs a modulation signal. Here, the multiplexer 15 first selects and outputs the mixer 13 output during the first period of time length T, and then selects the buffer signal frequency generator 14 output during the second period of time length ΔT. And repeat this operation.

  The transducer 21 converts the modulation signal output from the multiplexer 15 into a sound wave signal (wireless signal) and outputs the sound wave signal to the propagation path 3.

  Here, the time is t, the symbol value is m (t), the signal amplitude is A and B, the guard time length is ΔT, and the modulation signal is s (t). The wireless communication path here includes the vibrator 21, the propagation path 3, and the vibrator 41. The modulation signal s (t) in the first embodiment is expressed by the following equation (1).

  The operation of the demodulator 2a will be described below.

  The transducer 41 receives the sound wave signal transmitted from the transducer 21 and propagated through the propagation path 3 and converts it into an electrical signal.

Carrier frequency generator 42, like the carrier frequency generator 12, as the carrier wave to produce a sine wave of amplitude A, frequency f _c. The reference voltage source 44 outputs a voltage equal to the DC level of the carrier frequency generator 42 output.

  A synchronization unit may be provided for synchronization between the modulation device 1a and the demodulation device 2a. For example, the synchronization unit detects a reference signal from the output of the vibrator 41 and generates a symbol timing. Alternatively, when the modulation device 1b uses the above-described DPSK modulation, the synchronization unit performs DPSK demodulation.

  The multiplexer 45 switches between the two inputs according to the symbol timing. Here, the multiplexer 45 first selects and outputs the output of the carrier frequency generator 42 during the period of time length T corresponding to the first period, and then during the period of time length ΔT corresponding to the second period. The reference voltage source 44 output is selected and output, and this operation is repeated.

  The mixer 43 multiplies the output of the vibrator 41 and the output of the multiplexer 45. The LPF 46 removes the high frequency component of the output of the mixer 43 and passes the baseband component of the output of the mixer 43 to obtain a demodulated signal. The data determination unit 48 determines data from the demodulated signal in accordance with the symbol timing to obtain demodulated data, and outputs the demodulated data to the information processing device 4b.

  The mixers 13 and 43 are realized by a double balanced mixer.

  Hereinafter, the modulation / demodulation method of the first embodiment is referred to as a BS method.

  Waveforms in the acoustic communication system according to Embodiment 1 will be described in comparison with the acoustic communication system of the comparative example.

  The acoustic communication system of the comparative example includes a modulation device 1x and a demodulation device 2x.

  FIG. 4 is a block diagram illustrating an example of the configuration of the modulation device 1x in the comparative example. In this figure, the same reference numerals as those in the configuration of the modulation device 1a indicate the same or equivalent objects shown in the configuration of the modulation device 1a, and the description thereof is omitted here. Compared with the modulation device 1a, the modulation device 1x does not have the buffer signal frequency generator 14 and the multiplexer 15.

  FIG. 5 is a block diagram illustrating an example of the configuration of the demodulation device 2x in the comparative example. In this figure, the same reference numerals as those in the configuration of the demodulating device 2x indicate the same or equivalent parts as those shown in the configuration of the demodulating device 2a, and the description thereof is omitted here. Compared with the demodulator 2 a, the demodulator 2 x does not have the reference voltage source 44 and the multiplexer 45.

  In the following waveform diagrams, the horizontal axis represents time, and the vertical axis represents relative amplitude with the maximum absolute value being 1. FIG. 6 is a waveform diagram showing the waveform of the transmission baseband signal. This transmission baseband signal a0 corresponds to the output of the bipolar comparator 11. The bipolar comparator 11 outputs symbol values “1” and “−1” corresponding to the input data values “0” and “1”, respectively.

  FIG. 7 is a waveform diagram showing signal waveforms in the comparative example. This figure shows waveforms b1, c1, d1, and e1 in order from the top. A waveform b1 represents a modulation signal in the BPSK of the comparative example. A waveform b1 shows an ideal received signal (modulated signal) in the BPSK of the comparative example. A waveform c1 represents an actual received signal (a signal obtained by superimposing an impulse response of a wireless communication system on a modulated signal) in BPSK of the comparative example. A waveform d1 represents an ideal demodulated signal (a signal obtained by demodulating an ideal received signal) in the BPSK of the comparative example. A waveform e1 shows an actual demodulated signal (a signal obtained by demodulating an actual received signal) in the BPSK of the comparative example. Compared with the ideal waveform d1, the actual waveform e1 has a large fluctuation in amplitude.

  FIG. 8 is a waveform diagram showing signal waveforms in the first embodiment. This figure shows waveforms b2, c2, d2, e2 in order from the top. A waveform b2 shows an ideal received signal in the BS system of the first embodiment. A waveform c2 shows an actual received signal in the BS system of the first embodiment. A waveform d2 represents an ideal demodulated signal in the BS system of the first embodiment. A waveform e2 represents a baseband signal obtained by demodulating the received signal in the BS system of the first embodiment. Compared with the waveform e1 of the actual demodulated signal in the comparative example, the waveform e2 of the actual demodulated signal in the first embodiment has a small amplitude variation.

<Embodiment 2>
The configuration of the acoustic communication system according to the second embodiment will be described below.

  FIG. 9 is a block diagram illustrating an example of a configuration of an acoustic communication system according to the second embodiment. In this figure, the same reference numerals as those in the configuration of FIG. 1 denote the same or corresponding parts as those shown in the configuration of FIG. 1, and description thereof will be omitted here. Compared to the acoustic communication system according to the first embodiment, the acoustic communication system according to the second embodiment includes a modulation device 1b instead of the modulation device 1a.

  The configuration of the modulation device 1b will be described below.

  FIG. 10 is a block diagram illustrating an example of the configuration of the modulation device 1b according to the second embodiment. In this figure, the same reference numerals as those in the configuration of the modulation device 1a indicate the same or equivalent objects shown in the configuration of the modulation device 1a, and the description thereof is omitted here. Compared to the modulation device 1 a, the modulation device 1 b has a reference voltage source 17 instead of the buffer signal frequency generator 14. Compared with the buffer signal frequency generator 14, the reference voltage source 17 outputs a DC voltage of 0 level.

  The multiplexer 15 switches between the two inputs according to the symbol timing and outputs a modulation signal. Here, the multiplexer 15 first selects and outputs the output of the mixer 13 during the first period of the time length T, and then selects and outputs the output of the reference voltage source 17 during the second period of the time length ΔT. Then, this operation is repeated. A signal in a period during which the output of the reference voltage source 17 is selected in the multiplexer 15 is defined as GT (Guard Time).

  The modulation signal s (t) in the second embodiment is expressed by the following equation (2).

  This equation is obtained by setting B = 0 in the equation (1).

  The demodulator 2a demodulates the signal received from the modulator 1b as in the first embodiment.

  Hereinafter, the modulation / demodulation method of the second embodiment is referred to as a GT method.

  The waveform in the acoustic communication system will be described in comparison with a comparative example.

  FIG. 11 is a waveform diagram showing a waveform of a signal in the second embodiment. This figure shows waveforms b3, c3, d3, e3 in order from the top. A waveform b3 shows an ideal received signal in the GT system of the second embodiment. A waveform c3 shows an actual received signal in the GT system of the second embodiment. A waveform d3 shows an ideal demodulated signal in the GT system of the second embodiment. A waveform e3 shows an actual demodulated signal in the GT system of the second embodiment. Compared with the waveform e1 of the actual demodulated signal in the comparative example, the waveform e3 of the actual demodulated signal in the second embodiment has a small amplitude variation.

  Experimental examples of the BS method and the GT method will be described.

  FIG. 12 is a block diagram illustrating an example of the configuration of the experimental system. This evaluation system includes a PC 61, a DAC (Digital Analog Converter) 62, an amplifier 63, a speaker 64 (SP), a microphone 66 (MIC), an amplifier 67, and an ADC (Analog Digital Converter) 68.

  The speaker 64 corresponds to the vibrator 21. The microphone 66 corresponds to the vibrator 41. The PC 61 has a CPU and a storage device, and executes the measurement control software stored in the storage device, whereby the information processing device 4a, the modulation devices 1a, 1b, and 1x, the demodulation devices 2a and 2x, and the information processing device 4b. Realize the function.

  In the evaluation of BPSK to which the present invention is not applied, the PC 61 realizes the functions of the modulation device 1x and the demodulation device 2x. In the evaluation of BPSK to which the BS method is applied, the PC 61 realizes the functions of the modulation device 1a and the demodulation device 2a. In the evaluation of BPSK to which the GT method is applied, the PC 61 realizes the functions of the modulation device 1b and the demodulation device 2a.

  Further, the PC 61 realizes an AWGN (Additive White Gaussian Noise) channel by adding WGN (White Gaussian Noise) to the output of the amplifier 67, and measures BER (Bit Error Rate) vs. SNR (Signal to Noise Ratio). Do.

Here, the carrier frequency f _c = 200 Hz, the symbol time T = 5 ms, and the distance L between the speaker 64 and the microphone 66 is 1.8 m.

  The wireless communication path of this experimental system has a speaker 64, a space 65, and a microphone 66. FIG. 13 is a waveform diagram showing the measurement result of the impulse response of the wireless communication path in the experimental system. In this figure, the horizontal axis represents time, and the vertical axis represents relative amplitude with a peak level of 1. Here, the impulse response duration I = 1 ms. If K = 1.25 to prevent the impulse response from affecting the communication performance, the guard time ΔT = 1.25 ms.

  FIG. 14 is a waveform diagram showing a modulation signal waveform in the experimental system. In this figure, (g1) represents a BPSK modulated signal to which the present invention is not applied, (g2) represents a BPSK modulated signal to which the GT scheme is applied, and (g3) represents a BPSK to which the BS scheme is applied. The modulation signal is shown. In (g1), (g2), and (g3) of this figure, the horizontal axis indicates time, and the vertical axis indicates relative amplitude with the maximum absolute value being 1. As described above, the symbol time T = 5 ms and the guard time ΔT = 1.25 ms. As shown in (g2) and (g3), in the GT method and BS method, a guard time is inserted between each symbol time. As shown in (g2), the modulation signal at the guard time of the GT system is a 0-level DC signal. As shown in (g3), the modulation signal at the BS guard time is a sine wave (buffer signal) having a frequency different from the carrier frequency at the symbol time and a frequency based on the immediately preceding and current symbol values.

  Since this experimental system has functions of a modulator and a demodulator in the PC 61, it can be completely synchronized.

  FIG. 15 is a diagram showing a measurement result of BER vs. SNR by the experimental system. In this figure, the horizontal axis represents SNR [dB], and the vertical axis represents BER. This figure also shows a calculated value BER of BER vs. SNR and measured values f2, f3, and f4 of BER vs. SNR. Here, f1 represents the calculated value of the ideal BPSK BER vs. SNR. f2 represents the measured value of BER vs. SNR of the experimental system using BPSK to which the present invention is not applied. f3 represents a measurement value of BER vs. SNR of the experimental system using BPSK to which the GT method is applied. f4 shows the measured value of BER versus SNR of the experimental system using BPSK to which the BS method is applied. Compared with the measurement value f2 to which the modulation / demodulation method of the present invention is not applied, the measurement values f3 and f4 to which the modulation / demodulation method of the present invention is applied approach the ideal calculated value f1.

  In a conventional wireless communication system to which the present invention is not applied, if the symbol time is increased in order to reduce the influence of the impulse response of the wireless communication path, the communication speed decreases. On the other hand, according to the wireless communication system to which the present invention is applied, it is possible to reduce the influence of the impulse response without significantly reducing the communication speed.

  According to the wireless communication system of each of the embodiments described above, the distortion performance of the signal output from the wireless communication path is reduced, so that the anti-noise performance against disturbances such as external noise is improved.

  The performance of a conventional wireless communication system using PSK is greatly inferior to that of ideal PSK. The performance is, for example, BER vs. SNR. By applying the modulation / demodulation method of the above-described embodiment to a wireless communication system, the performance of the wireless communication system can be improved.

  The acoustic communication system in the above-described embodiment can use PSK and QAM instead of BPSK.

In the above embodiment, the carrier frequency f _c is not limited to the audible frequency band.

  The present invention can be applied not only to sound waves but also to wireless communication systems using radio waves, light, and the like.

  The conversion unit corresponds to the bipolar comparator 11 in the embodiment. The first signal generation unit corresponds to the carrier frequency generator 12 and the mixer 13 in the embodiment. The second signal generation unit corresponds to the buffer signal frequency generator 14 or the reference voltage source 17 in the embodiment. The output unit corresponds to the multiplexer 15 in the embodiment. The reference signal generation unit corresponds to the reference voltage source 44 in the embodiment. The multiplication unit corresponds to the mixer 43 in the embodiment.

  The wireless transmission unit corresponds to the vibrator 21 in the embodiment. The wireless reception unit corresponds to the vibrator 41 in the embodiment.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is shown by the scope of claims, and is not restricted by the text of the specification. Moreover, all modifications, various improvements, substitutions and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention.

1a, 1b Modulator 2a Demodulator 3 Propagation paths 4a, 4b Information processor 11 Bipolar comparator 12 Carrier frequency generator 13 Mixer 14 Buffer signal frequency generator 15 Multiplexer 17 Reference voltage source 21, 41 Vibrator 42 Carrier frequency generator 43 Mixer 44 Reference voltage source 45 Multiplexer 46 LPF
48 Data judgment part

Claims (8)

A modulating device which performs modulation for signals passing,
A conversion unit that acquires data and converts it into a symbol value;
A first signal generation unit that generates a first signal by phase-modulating a carrier wave with the symbol value converted by the conversion unit;
A second signal generator for generating a second signal having a frequency different from that of the carrier wave;
For each of the symbol value which is converted by the conversion unit sets the second period based on the time length of the impulse response of the first period and the previous SL communications systems of a predetermined length of time, during said first time period An output device that outputs the first signal generated by the first signal generation unit and outputs the second signal generated by the second signal generation unit during the second period. The second signal is a DC signal;
The modulation device according to claim 1. The second signal generation unit determines a frequency of the second signal based on the symbol value.
The modulation device according to claim 1. The second signal generation unit is configured such that the frequency of the second signal when the current symbol value is equal to the previous symbol value is smaller than the frequency of the second signal when the current symbol value is different from the previous symbol value. Determining the frequency of the second signal,
The modulation device according to claim 3. Furthermore,
Includes a transmit portion you wirelessly transmitting an output of said output section,
Before Symbol communications of the system, including pre Kioku trust unit,
The modulation device according to claim 1. A demodulator that receives a signal output from a modulator via a communication path and demodulates the signal,
The modulation device acquires the data is converted into symbol values, a carrier wave to generate a first signal to the phase modulation by the symbol value, and generating a second signal having a frequency different from the carrier, the symbol value Each time, a first period having a predetermined time length and a second period having a time length based on the time length of the impulse response of the communication path are set, and the first signal is used as the signal during the first period. and outputs the road, and during the second period to output the result to the communication path the second signal as a signal,
The demodulator outputs a carrier wave corresponding to the first period and outputs a third signal having a frequency different from that of the carrier wave corresponding to the second period for each symbol period. When,
A demodulation device comprising: a multiplication unit that multiplies the output signal of the modulation device received via the communication path by the output of the reference signal generation unit. The demodulator further includes a wireless receiver that receives the output signal of the modulator via the communication path ,
The communication path includes the wireless reception unit,
The demodulation device according to claim 6. A communication system that transmits data using phase modulation,
A conversion unit that acquires data and converts it into a symbol value every predetermined symbol period;
A first signal generation unit that generates a first signal by phase-modulating a carrier wave with the symbol value converted by the conversion unit;
A second signal generator for generating a second signal different from the first signal;
For each symbol period, the first signal generated by the first signal generation unit is output in a first period shorter than the symbol period, and the second period is a remaining period obtained by removing the first period from the symbol period. An output unit that outputs the second signal generated by the second signal generation unit in a period;
A transmission unit for transmitting an output of the output section as a signal,
A receiver for receiving a signal transmitted by the transmitting unit,
For each symbol period, a carrier wave generation unit that outputs the carrier wave in the first period and outputs a third signal different from the carrier wave in the second period;
Communication system Ru and a multiplying unit for multiplying the outputs of said carrier wave generating portion of the modulator.

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