JP2009021678A - Power line communication system, and noise component removal control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove a noise component superimposed on a power line, in relation to a power line communication system and a noise component removal control method. <P>SOLUTION: In this power line communication system transmitting/receiving data between PLC modems through a power line by modulating the data by an OFDM method, and this noise component removal control method, the PLC modem detects a noise component superimposed on a reception signal transmitted through the power line and received by an auxiliary operational amplifier 14, an A/D converter 15 and a fast Fourier transformation part 16, generates a cancel signal having the same frequency as and a phase reverse to those of the noise component in a transmission pause period in a certain cycle by a configuration comprising a carrier spectrum detection circuit 17, a continuously signaling circuit 18, a fast inverse Fourier transformation part 19 and a D/A converter 20, and adds the cancel signal to the reception signal input to an operational amplifier 10 to cancel the noise component. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power line communication system that controls transmission / reception of data via a power line and a noise component removal control method that removes a noise component that interferes with data transmitted / received via a power line.

  An indoor power line supplies power to home appliances or the like with a single-phase 100 V or single-phase or three-phase 200 V AC voltage of 50 Hz or 60 Hz, and a PLC (Power) that transmits and receives various types of data via this power line. A Line Communication (power line communication) system is known, and as a transmission method, for example, an OFDMA (Orthogonal Frequency Multiple Access) method, a CDMA (Code Division Multiple Access) method, or the like is applied. The data transmission is performed at a transmission rate of about 200 Mbps at the maximum.

  Also, noise of various frequency components generated from home appliances is superimposed on the power line, and in the vicinity of antennas such as broadcasting stations and amateur radio stations, the radio frequency components radiated from the antenna are the power lines. And is superimposed on the transmission / reception data in the PLC system, causing a reception data error due to saturation of the reception amplifier. For example, FIG. 10 shows an outline of a PLC system. A plurality of outlets 103 to 105 are provided on a power line 100 drawn indoors from the outside and wired, and a household electrical appliance 102 is connected to the outlet 104. PLC modems 106 and 107 are connected to each other, and data is transmitted and received between the PLC modems 106 and 107. In such a PLC system, a noise component generated from the home appliance 102 propagates to the power line 100 and interferes with transmission / reception data. When there is a wireless device 110 such as a broadcast station or an amateur radio station, the power line 100 of the indoor wiring is several meters to several tens of meters long. Therefore, even if the antenna gain is small, the signal of the radio frequency is 100 may be induced as a noise component.

  The OFDM (Orthogonal Frequency Division Multiple) method applied to the PLC system divides the band of 2 to 30 MHz into several hundred subcarriers and transmits / receives data by each subcarrier. Can be transmitted in parallel, avoiding the frequency band where data is generated, enabling high-speed data transmission, and data transmission in a wide frequency band with multiple subcarriers, and transmission per subcarrier. Since the power can be lowered, it is advantageous in terms of EMI (Electro-Magnetic Interference), and the specific frequency band is not used at all for the band that interferes with wireless communication by a notch filter or the like. Unisuru it is also possible.

  For example, as shown in the conceptual diagram of FIG. 11, the relationship between OFDM subcarriers and noise includes noise generated from household appliances or the like having a high level in a frequency band lower than 2 MHz to 30 MHz of the OFDM system. In many cases, these can be filtered out. The subcarrier band includes a frequency used for amateur radio and the like, and may have a relatively large noise level. The noise component in this case corresponds to the radio frequency to be used, and is generally not a single frequency component but a plurality of frequency components, and thus cannot be removed by a simple filter. Therefore, the amplifier on the receiving side of the PLC system may be saturated with a noise component having a large level.

  FIG. 12 is an explanatory diagram of a conventional PLC modem, 111 is an OFDM signal processing unit, 112 is a fast inverse Fourier transform unit (OFDM IFFT), 113 is a D / A converter, 114 is a low-pass filter (LPF), 115, 116 is a high-speed high-current operational amplifier, 117 is a coupling transformer, 118 is a coupling capacitor, 119 is an attenuator (ATT), 120 is a reception operational amplifier, 121 is an A / D converter, and 122 is a fast Fourier transform unit (OFDMFT). The power line is connected via a coupling transformer 117 and a coupling capacitor 118.

  The received OFDM signal via the power line is attenuated to a predetermined level by an attenuator 119 via a coupling capacitor 118 and a coupling transformer 117 and input to the reception operational amplifier 120, and the output signal is converted into a digital signal by the A / D converter 121. The received data is restored by the fast Fourier transform unit 122 and the OFDM signal processing unit 111. The OFDM signal processing unit 111 and the high-speed inverse Fourier transform unit 112 convert the transmission data to an OFDM signal, the D / A converter 113 converts the transmission data into an analog signal, and the low-pass filter 114 removes quantization noise and the like, thereby increasing the speed. A current operational amplifier 115 performs non-inverting amplification, an operational amplifier 116 performs inverting amplification, and sends it to a power line through a coupling transformer 117 and a coupling capacitor 118 as shown as PLC signal transmission. Since the characteristic impedance of the power line is often 100Ω or less, operational amplifiers 115 and 116 having high-speed and high-current output characteristics and operating in a complementary manner are used for transmission. Further, a noise component in the PLC signal band as shown as AM radio noise is superimposed on the power line.

  FIG. 13 is an explanatory diagram of an OFDM signal generation concept outlining the functions of the OFDM signal processing unit 111 and the fast inverse Fourier transform unit 112 in FIG. 12, and the serial / parallel conversion unit uses transmission data as a serial spectrum data string. The signal is input to 131 and converted into parallel corresponding to the subcarrier, the product of the sine wave corresponding to the subcarrier is obtained in the modulator 132, added by the adder, and converted into serial by the parallel-serial converter 133. And an OFDM signal. Therefore, this OFDM signal generation process corresponds to an inverse Fourier transform process. The fast Fourier transform unit 122 in FIG. 12 can restore the data by performing the reverse process of the fast inverse Fourier transform unit 112.

Since various noise components are included in the power line communication system as described above, for example, signal processing is performed on the transmission side so as to include a zero point between modulation points of transmission data, and the timing of the zero point is received on the reception side. The noise component on the reception modulation point is removed by subtracting the noise component superimposed on the reception modulation point using the extracted noise component. Thus, a means for receiving processing has been proposed (see, for example, Patent Document 1).
JP 2003-8521 A

  When a radio communication wave of any frequency in the 2 MHz to 30 MHz band is induced in the OFDM signal transmitted through the power line, if the induction signal level is large, for example, the reception operational amplifier 120 in FIG. The setting of the attenuator 119 may be saturated. Due to the saturation of the reception operational amplifier 120, there are many errors in the reception data, and practical data communication cannot be performed. Although it is possible to attenuate the reception level by increasing the attenuation amount of the attenuator 119 and prevent the reception operational amplifier 120 from being saturated, the induction signal level is not always large, Since the actual received signal level is also attenuated, errors increase. That is, since the amount of information that can be transmitted is proportional to the frequency band and the S / N ratio, a decrease in the signal level causes a problem that the amount of information that can be transmitted decreases and the advantage of the OFDM scheme cannot be utilized.

  An object of the present invention is to solve the conventional problems by extracting a noise component induced in a power line, forming a cancellation signal having an antiphase with respect to the noise component, and removing the noise component. The amplifier that amplifies the received signal is reliably prevented from being saturated.

  The power line communication system of the present invention is a power line communication system that transmits and receives data by modulating data between PLC modems via the power line in accordance with the OFDM method, wherein the PLC modem is superimposed on the received signal transmitted through the power line. Detecting means for detecting the generated noise component in a transmission suspension period of a fixed period, and the amplitude and frequency of the noise component detected by the detecting means are the same or close to each other and vice versa. It has a configuration including a generation unit that generates a cancellation signal that is a continuous wave of phase, and a noise cancellation unit that adds the cancellation signal generated by the generation unit to the reception signal.

  The PLC modem includes an operational amplifier for amplifying the received signal, processing means for converting the received signal amplified by the operational amplifier into a digital signal, separating the signal into signals corresponding to subcarriers by fast Fourier transform, and receiving processing; The reception signal is amplified by the sub-operational amplifier in parallel with the operational amplifier, and the detection means for detecting the noise component of the transmission pause period in accordance with the information of the transmission pause period of the fixed period from the processing means, and the detection means detects A generation unit that Fourier-transforms the noise component to generate a cancel signal having the same or close amplitude and opposite phase with respect to the amplitude and frequency of the noise component, and generated by the generation unit And a noise canceling means for inputting a cancel signal to the operational amplifier together with the received signal.

  The PLC modem selects an operational amplifier and a sub operational amplifier for amplifying the received signal, and selects the amplified output signal of the operational amplifier during a fixed period of transmission suspension, and outputs the amplified output signal of the operational amplifier during other periods. And processing means for selecting each frequency component and amplitude value including subcarriers by fast Fourier transform, receiving processing, and receiving the transmission pause period by fast Fourier transform of the processing means. Generating means for generating a cancel signal as a continuous wave having the same or close frequency and amplitude as the frequency and amplitude determined based on the signal, and a reverse phase; and the received signal generated by the cancel signal generated by the generating means to the operational amplifier And noise canceling means for input.

  The noise component removal control method of the present invention is a noise component removal control method in which data is modulated and transmitted / received between PLC modems via a power line using the OFDM method, and the noise component superimposed on the power line is removed. A noise component superimposed on the received signal received via the signal is detected in a transmission suspension period of a fixed period, and a continuous wave having the same frequency as that of the carrier of the noise component and having an opposite phase is generated as a cancel signal. This includes a control process in which the cancel signal is added to the reception signal to perform data reception processing.

  The reception signal transmitted through the power line is amplified in parallel by an operational amplifier and a sub-operation amplifier, and the reception signal amplified by the sub-operation amplifier is processed in a transmission suspension period of a predetermined period, and the reception A noise component superimposed on the signal is detected, a cancellation signal of a continuous wave having the same frequency as that of the noise component and having an opposite phase is generated, and the cancellation signal is added to the operational amplifier and input to the operational amplifier. This includes a process of converting the received signal amplified by the operational amplifier into a digital signal, separating it into a signal corresponding to the subcarrier by fast Fourier transform, and performing a data reception process.

  Also, the received signal transmitted through the power line is amplified in parallel by the operational amplifier and the sub operational amplifier, and the amplified output signal of the sub operational amplifier is selected during the transmission suspension period of a certain period, and the computation is performed during the other periods. Select the amplified output signal of the amplifier, convert it to a digital signal, obtain the frequency components and amplitude values including subcarriers by fast Fourier transform, receive them, and find them by fast Fourier transform in the transmission pause period. A cancel signal is generated as a continuous wave having the same or close frequency and amplitude as the frequency and amplitude of the received signal, and this cancel signal is input to the operational amplifier together with the received signal to receive data. Including processes.

The noise component in the transmission band induced in the power line when data is transmitted / received between PLC modems by modulating with the OFDM system through the power line is detected in the transmission pause period of the fixed period, and the same frequency An anti-phase cancellation signal is generated and added to the received signal to remove noise components. Even when the signal level of the radio frequency induced on the power line is relatively high, it is removed by the anti-phase cancellation signal. Therefore, the problem that the operational amplifier that amplifies the received signal is saturated can be solved.
Within the use band of PLC signal

  Referring to FIG. 1, the power line communication system according to the present invention is a power line communication system that transmits and receives data by modulating data between PLC modems via the power line using the OFDM method. The PLC modem transmits and receives power lines. The noise component superimposed on the received signal is detected by the detection means including the sub operational amplifier 14, the A / D converter 15 and the fast Fourier transform unit 16 for detecting the transmission pause period of a fixed period, and the detection means. Carrier spectrum detection circuit 17, continuous signal generation circuit 18, and high-speed inverse Fourier transform unit for generating a cancel signal having the same or close amplitude with respect to the amplitude and frequency of the noise component and an antiphase continuous wave 19, D / A converter 20, low-pass filter 21, generating means including operational amplifiers 22 and 23, and generated by this generating means The Yanseru signal has a structure that includes a noise cancel means for adding to the received signal.

  The noise component removal control method of the present invention is a noise component removal control method for removing and transmitting noise components superimposed on a power line by modulating and transmitting / receiving data between PLC modems via a power line using an OFDM method. The noise component superimposed on the received signal received via the signal is detected in a transmission suspension period of a fixed period, and a continuous wave having the same frequency and opposite phase as the carrier of the noise component is detected by the carrier spectrum detection circuit 17, The signal is generated as a cancel signal by the configuration including the continuous signal conversion circuit 18, the fast inverse Fourier transform unit 19, the D / A converter 20, and the low-pass filter 21, and this cancel signal is added to the reception signal input to the operational amplifier 10. And a control process for performing data reception processing.

  FIG. 1 is an explanatory diagram of Embodiment 1 of the present invention, in which 1 is an OFDM signal processing unit, 2 is a fast inverse Fourier transform unit (OFDM IFFT), 3 is a D / A converter, 4 is a low-pass filter (LPF), 5 , 6 is a high-speed high-current operational amplifier, 7 is a coupling transformer, 8 is a coupling capacitor, 9 is an attenuator (ATT), 10 is an operational amplifier, 11 is an A / D converter, 12 is a fast Fourier transform unit (OFDMFT), 13 Is a sub-attenuator (ATT), 14 is a sub-operational amplifier, 15 is an A / D converter, 16 is a fast Fourier transform unit (FFT), 17 is a carrier spectrum detection circuit, 18 is a continuous signal converting circuit, and 19 is a fast inverse Fourier transform. A conversion unit (IFFT), 20 is a D / A converter, 21 is a low-pass filter (LPF), and 22 and 23 are operational amplifiers.

  As a PLC signal transmission from the OFDM signal processing unit 1 to the power line through the high-speed inverse Fourier transform unit 2, the D / A converter 3, the low-pass filter 4, the high-speed high-current operational amplifiers 5 and 6, the coupling transformer 7 and the coupling capacitor 8. Send as shown. The PLC signal received through the power line is received by the OFDM signal processing unit 1 through the coupling capacitor 8, the coupling transformer 7, the attenuator 9, the operational amplifier 10, the A / D converter 11, and the fast Fourier transform unit 12. The main configuration of this reception processing is the same as the configuration shown in FIG. 12, for example, and the function of each unit is also the same, and redundant description is omitted. In the first embodiment, a received signal shown as PLC signal reception via the coupling transformer 7 is also input to the sub-attenuator 13 connected in parallel with the attenuator 9 and attenuated by the sub-attenuator 13. The received PLC signal is amplified by the sub operational amplifier 14 and input to the A / D converter 15.

  The A / D converter 15 performs A / D conversion processing in accordance with a signal from the OFDM signal processing unit 1 that designates a transmission suspension period of an OFDM signal having a fixed period. That is, in the OFDM system, a plurality of subcarriers are used to transmit data in parallel, and in order to absorb the difference in transmission delay time between the subcarriers, a fixed transmission suspension period is set. Information on the transmission pause period is notified from the OFDM signal processing unit 1 to the A / D converter 15, and only the noise component is transmitted during the transmission pause period, so that it is converted into a digital signal by the A / D converter 15, and a fast Fourier transform unit 16, the frequency component and the amplitude component are obtained by Fourier transform, and the carrier spectrum detection circuit 17 detects the phase including the phase of the noise component. The Fourier transform unit 19 converts the signal into a continuous wave signal, the D / A converter 20 converts the signal into an analog signal, and the quantization noise at the time of the D / A conversion. Is removed by the low-pass filter 21, and a cancel signal having a phase opposite to that of the noise component and a value equal to or close to the amplitude of the noise component is obtained via the operational amplifiers 22 and 23 as shown in FIG. The signal is input to the operational amplifier 10 together with the input signal. That is, the received signal from which the noise component has been removed is amplified by the operational amplifier 10 by adding a cancel signal having the same frequency and amplitude as the noise component superimposed on the input signal to the input signal and having the opposite phase. Then, reception processing can be performed.

  As described above, since the signals input from the operational amplifiers 22 and 23 to the operational amplifier 10 are signals having a phase opposite to that of the noise component included in the received PLC signal, the noise component superimposed on the received PLC signal is canceled. can do. In this case, it is the best state if the noise component can be canceled by 100%, but if it can be canceled by about 80%, saturation of the operational amplifier 10 can be prevented, and a sufficient error reduction effect can be obtained. In this case, the attenuation amount of the attenuator 9 can be set to a sufficient value as long as the operational amplifier 10 and the A / D converter 11 can be reduced to a level that does not saturate. Since cancellation signal generation can be performed almost digitally, noise components that can cause the reception operational amplifier of the PLC signal to become saturated can be easily obtained by adding a slight configuration and an arithmetic processing function to an existing PLC modem. Can be canceled.

  FIG. 2 is a conceptual explanatory diagram of a noise component and a cancel waveform, where (a) shows an AM signal waveform in which a radio frequency signal is amplitude-modulated by an audio signal or the like, and (b) shows a carrier wave. (C) shows a case where demodulation is performed by multiplying an AM wave signal and a carrier wave, and (d) shows a case where a cancel signal is added to the AM signal to perform cancellation processing. (E) shows the spectrum of the AM waveform, (f) shows the spectrum when the demodulated waveform is obtained by multiplying the AM wave and the carrier wave, and (g) shows the spectrum after adding the cancel waveform. When the cancel waveform level is increased successively, the spectrum level shown in (g) gradually decreases, and when it is the same as the spectrum level of the AM waveform in (e), it becomes the minimum zero.

  FIG. 3 is a conceptual explanatory diagram of a PLC signal and a cancel signal, where (a) is a PLC signal according to the OFDM system, (b) is a radio frequency AM signal that interferes, (c) is a cancel signal, and (D). Indicates a signal after cancellation. The PLC signal transmits data by a plurality of subcarriers, and as shown in (a), provides a transmission suspension period of a fixed period every predetermined period. Since the signal in the transmission suspension period indicates a noise component induced in the power line, a state in which the signal extracted in the transmission suspension period is a continuous signal is shown in FIG. By adding this cancel signal as an opposite phase to the carrier wave of the AM signal of (b), the signal shown in (d) is obtained. Although this is an audio signal component, since the audio level is continuous and hardly high, the amplitude modulation level is low as shown in (d), and saturation of the operational amplifier 10 is ensured. Can be prevented.

  FIG. 4 is a conceptual explanatory diagram of noise component extraction, where (a) is a PLC signal based on OFDM, (b) is a noise component extracted during a transmission suspension period of a certain period, and (c) is intermittent extracted noise component. (D) shows the signal after cancellation, respectively. As described above, the intermittent noise component shown in (b) extracted during the transmission suspension period of the fixed period of the PLC signal is a continuous wave signal as shown in (c), and this phase is set as the noise component carrier. By adding to the received PLC signal as an opposite phase, the noise component is canceled out, and the signal becomes a low level signal similar to (d) of FIG.

  FIG. 5 shows an outline of an example of subcarriers having orthogonality, and shows outline waveforms of F2 = 122 kHz, F3 = 183 kHz,... F512 = 31.25 MHz in one cycle of F1 = 61 kHz. As described above, the actual PLC signal uses a plurality of subcarriers in the frequency range of 2 MHz to 30 MHz.

  FIG. 6 is a diagram illustrating the principle of a radio frequency noise component superimposed on the received PLC signal and its cancel signal, FIG. 7 is a diagram illustrating the cancel signal generation principle, and FIG. 8 is a diagram illustrating real axis Re and imaginary axis Xe. It is vector explanatory drawing on a complex plane by. FIG. 6A shows an example of a signal Acos (ωt + θ) of an amplitude value A of a frequency that is superimposed on a received PLC signal as a noise component signal and detected in a transmission pause period of a certain period. If it shows on a complex plane, it will become what is shown to (a) of FIG. This signal is multiplied by sin ωt and cos ωt shown in FIG. 6B of the same frequency. This multiplication configuration is shown in FIG. The multiplication results are the signals shown in (c) and (d) of FIG. 6, and −A / 2 {sin θ} and A / 2 {cos θ} can be obtained by integration. On this complex plane, As shown in FIG. As described above, the phase θ and the amplitude A / 2 of the AM wave signal that becomes a noise component are shown. Therefore, when the multiplication unit and the addition unit shown in FIG. 7B multiply sin ωt by −A / 2 {sin θ} and cos ωt by A / 2 {cos θ}, and add, Acos (ωt + θ) can be obtained, and on the complex plane, as shown in FIG. 8C, the phase component of the detection noise in FIG. In the preceding stage, the noise component superimposed as the AM signal can be canceled by adding the cancel signal to the received PLC signal, and the level of the noise component is greatly reduced even if it is not completely canceled. be able to.

As described above, the AM component signal of the noise component superimposed on the received PLC signal and the cancel signal having the opposite phase can be expressed by the following equations (1) to (6). That is, with respect to the detected AM wave signal F (ω) shown in the equation (1), a cancel signal −F (ω) shown in the equation (6) having an opposite phase can be obtained, and this cancel signal −F (ω ), The noise component superimposed on the received PLC signal can be canceled.

  FIG. 9 is an explanatory diagram of Embodiment 2 of the present invention. The same reference numerals as those in FIG. 1 denote the same parts, 31 is an attenuator (ATT), 32 is a sub-operational amplifier, 33 is a carrier spectrum detection circuit, 34 Is a continuous signal converting circuit, 35 is a fast inverse Fourier transform unit (IFFT), 36 is a D / A converter, 37 is a low-pass filter (LPF), and 38 and 39 are operational amplifiers. From the OFDM signal processing unit 1 to the operational amplifier 10, an amplification operation is performed during a period other than the transmission pause period of the fixed period of the received PLC signal, and the transmission pause of the received PLC signal is fixed to the sub-operational amplifier 32. Amplifying operation is performed only for a period, and each amplified output signal is converted into a digital signal by the A / D converter 11, Fourier-transformed by the fast Fourier transform unit 12, and sent to the OFDM signal processing unit 1 and the carrier spectrum detection circuit 33. input. That is, with respect to the noise component as well, the A / D converter 11 and the fast Fourier transform unit 12 are shared, and the sub-operation amplifier 32 and the carrier spectrum detection are performed according to a signal indicating a fixed transmission period from the OFDM signal processing unit 1. The circuit 33 is operated to detect a noise component.

  Similarly to the carrier spectrum detection circuit 17 shown in FIG. 1, the carrier spectrum detection circuit 33 detects a noise component including a phase component of a transmission pause period of a certain period of the received PLC signal, and the continuous signal conversion circuit 34 generates a continuous wave. The signal is generated as a signal, a continuous wave cancel signal including a carrier phase component of a noise component is generated by the fast inverse Fourier transform unit 35, converted to an analog signal by the D / A converter 36, and quantum at the time of D / A conversion by the low-pass filter 37. The noise is removed, amplified by the operational amplifiers 38 and 39, and a cancel signal having an opposite phase to the noise component is input to the operational amplifier 10 to cancel the noise component. The second embodiment has an advantage that the configuration is simplified as compared with the first embodiment shown in FIG. 1 by sharing the control means for the received signal processing and the noise signal detection processing.

It is explanatory drawing of Example 1 of this invention. It is a conceptual explanatory drawing of a noise component and a cancellation waveform. It is a conceptual explanatory drawing of a PLC signal and a cancellation signal. It is a conceptual explanatory view of noise component extraction. It is outline | summary explanatory drawing of an example of the subcarrier which has orthogonality. It is principle explanatory drawing of the signal of a noise component, and its cancellation signal. It is a cancellation signal generation principle explanatory drawing. It is vector explanatory drawing on the complex plane by the real number axis | shaft Re and the imaginary number axis | shaft Xe. It is explanatory drawing of Example 2 of this invention. It is an outline explanatory view of a PLC system. It is explanatory drawing of the subcarrier and noise of an OFDM system. It is explanatory drawing of the PLC modem of a prior art example. It is a conceptual explanatory view of OFDM signal generation.

Explanation of symbols

1 OFDM signal processing unit 2 Fast inverse Fourier transform unit (OFDM IFFT)
3 D / A converter 4 Low-pass filter (LPF)
5,6 High-speed high-current operational amplifier 7 Coupling transformer 8 Coupling capacitor 9 Attenuator (ATT)
10 operational amplifier 11 A / D converter (A / D)
12 Fast Fourier Transform (OFDMFT)
13 Sub-attenuator (ATT)
14 Sub operational amplifier 15 A / D converter (A / D)
16 Fast Fourier transform unit {FFT)
17 Carrier Spectrum Detection Circuit 18 Continuous Signal Conversion Circuit 19 Fast Inverse Fourier Transform (IFFT)
20 D / A converter {D / A)
21 Low-pass filter (LPF)
22, 23 operational amplifier

Claims (6)

In a power line communication system for transmitting and receiving data modulated by an OFDM method between PLC modems via a power line,
The PLC modem has a detecting means for detecting a noise component superimposed on a received signal transmitted through the power line in a transmission suspension period of a fixed period;
Generating means for generating a cancellation signal that is the same or close to the amplitude and frequency of the noise component detected by the detecting means and a continuous wave of opposite phase;
Noise cancellation means for adding the cancellation signal generated by the generation means to the received signal;
A power line communication system having a configuration including:   The PLC modem includes an operational amplifier for amplifying a received signal, processing means for converting the received signal amplified by the operational amplifier into a digital signal, separating the signal into a signal corresponding to a subcarrier by fast Fourier transform, In parallel with the operational amplifier, the received signal is amplified by a sub-operational amplifier, and in accordance with information on the transmission pause period of a fixed period from the processing means, a detection means for detecting a noise component in the transmission pause period, and the detection means Generation means for generating a cancel signal having a Fourier transform of the detected noise component and having an amplitude that is the same as or close to the amplitude and frequency of the noise component and a continuous wave having an opposite phase; and Noise cancellation means for inputting the generated cancellation signal to the operational amplifier together with the received signal. Power line communication system according to claim 1, wherein a.   The PLC modem selects an operational amplifier and a sub operational amplifier for amplifying the received signal, and selects an amplified output signal of the sub operational amplifier during a transmission suspension period of a fixed period, and an amplified output signal of the operational amplifier during other periods. And processing means for obtaining each frequency component and amplitude value including subcarriers by fast Fourier transform and receiving processing, and the transmission pause period by the fast Fourier transform of the processing means Generating means for generating a cancellation signal as a continuous wave having the same or close to the frequency and amplitude as the frequency and amplitude obtained from the received signal, and the opposite phase, and the operational amplifier for generating the cancellation signal generated by the generating means The power line communication system according to claim 1, further comprising noise canceling means for inputting the received signal together with the received signal. In a noise component removal control method for removing and transmitting noise components superimposed on the power line by modulating and transmitting data between PLC modems via a power line in accordance with the OFDM method,
A noise component superimposed on a received signal received via the power line is detected during a transmission suspension period of a fixed period, and a continuous wave having the same frequency as that of the carrier of the noise component and an opposite phase is generated as a cancel signal. And a control process of adding the cancel signal to the received signal and performing the data receiving process.   A reception signal transmitted through a power line is amplified in parallel by an operational amplifier and a sub-operational amplifier, and the reception signal amplified by the sub-operational amplifier is processed in a transmission suspension period of a predetermined period, and the reception Detecting a noise component superimposed on the signal, generating a cancellation signal of a continuous wave having the same frequency and opposite phase as the noise component, and adding the cancellation signal to the operational amplifier in addition to the received signal; 5. The noise component according to claim 4, further comprising a step of converting the received signal amplified by the operational amplifier into a digital signal, separating the signal into a signal corresponding to a subcarrier by fast Fourier transform, and performing a data reception process. Removal control method.   The reception signal transmitted through the power line is amplified in parallel by the operational amplifier and the sub operational amplifier, the transmission suspension period of a certain period is selected from the amplified output signal of the sub operational amplifier, and the other period is the above The amplified output signal of the operational amplifier is selected, converted into a digital signal, and each frequency component including the subcarrier and the amplitude value are obtained by fast Fourier transform and received, and the fast Fourier is transmitted during the transmission pause period. A cancel signal is generated as a continuous wave having the same or close to the frequency and amplitude of the signal obtained by the conversion and having an opposite phase, and the cancel signal is input to the operational amplifier together with the received signal. 5. The noise component removal control method according to claim 4, further comprising a step of performing reception processing.

Images