JP5708139B2 - Noise canceling device - Google Patents

Description

  The present invention relates to a noise cancellation device that synthesizes a noise signal having an antiphase with a received signal.

  Conventionally, various noise canceling apparatuses that synthesize a noise signal having an antiphase with a received signal are known (see, for example, Patent Document 1 and Non-Patent Document 1). For example, Patent Document 1 discloses an additional circuit including an A / D converter, a D / A converter, a fast Fourier transform unit, and a fast inverse Fourier transform unit as a digital noise canceling device. The additional circuit is attached in parallel with the power line communication device in order to remove a noise signal generated in the power line communication system.

  The additional circuit receives the noise signal generated in the transmission line during the communication pause time, digitizes the noise signal by the A / D converter, and converts it to the frequency domain by the fast Fourier transform unit. Then, a signal in which the phase of the noise signal for each carrier is inverted is generated by digital signal processing. After that, this generated signal is converted into the time domain by the fast inverse Fourier transform unit, converted to analog by the D / A converter, and then added to the reception circuit unit of the power line communication device. Thereby, only the noise signal generated in the transmission path is canceled.

  On the other hand, Non-Patent Document 1 discloses a configuration including a noise receiving antenna, a phase shifter, a signal amplifier, and a hybrid combiner as an analog noise cancellation device. In this case, the phase of the noise signal received by the noise receiving antenna is inverted by a phase shifter composed of a resistor and a capacitor, and then the amplitude is adjusted by a signal amplifier. And the noise signal of the antiphase which adjusted the amplitude was mixed with the signal received by the main antenna using the hybrid combiner.

JP 2009-21678 A

“ANC-4 ANTENNA NOISE CANCELLER for Reducing Locally-Generated Noise Instruction Manual Revision 2.1”, Timewave Technology Inc., March 12, 2003

  By the way, in the noise cancellation apparatus described in Patent Document 1, a transmission / reception circuit including an A / D converter, a D / A converter, a fast Fourier transform unit, and a fast inverse Fourier transform unit is used to perform noise processing. Since it is required separately from the apparatus, it becomes expensive. Further, since the noise signal is once digitized, in the case of a wideband signal, a high-speed A / D converter is required, resulting in an increase in power consumption and a manufacturing cost. Further, since a noise signal at the time of non-communication is used, there is a problem that it is impossible to cope with a sudden noise signal during communication.

  On the other hand, in the noise cancellation device described in Non-Patent Document 1, since the phase shifter is composed of a resistor and a capacitor, the frequency band in which noise cancellation is possible is very narrow due to its frequency characteristics. Further, since the range of the phase that can be continuously changed by the phase shifter is limited to 90 °, means for switching the phase in steps is necessary. Furthermore, since the phase shifter has a high gain on the low frequency side and a low gain on the high frequency side, when processing a broadband noise signal, the low frequency component of the noise signal is emphasized. There is also.

  The present invention has been made in view of the above-described problems, for example, and an object of the present invention is to provide a noise canceling device that can remove a broadband noise signal using a simple configuration.

In order to solve the above-mentioned problem, the invention according to claim 1 is a noise canceling device for synthesizing a noise signal having an opposite phase to a received signal, a noise signal detector for detecting the noise signal , and the noise signal A noise signal distribution means for distributing the noise signals detected by the detector with a phase difference from each other; and a phase shifter for adjusting the phase of the distribution noise signal distributed by the noise signal distribution means, the signal of the received signal A noise removing unit that removes a noise signal by synthesizing a distribution noise signal having an antiphase for each divided band obtained by dividing the band, and a noise removal signal of a plurality of divided bands obtained by removing the noise signal by the noise removing unit. The phase shifter is configured using an all-pass filter that shifts the phase with a constant amplitude .

In the invention of claim 2, wherein the noise signal distribution means has a structure to distribute with a phase difference before Symbol noise signal 180 ° from each other.

In the invention of claim 3, wherein the noise signal distribution means includes a first coil for distributing the distribution noise signal of the noise signal and the same phase, a second coil for distributing the distribution noise signal of the noise signal in opposite phase It is comprised by the transformer provided with.

According to a fourth aspect of the present invention, the received signal is constituted by a short-wave power line communication signal by an orthogonal frequency division multiplexing system.

According to the invention of claim 1, the noise signal distribution means distributes the noise signals with a phase difference from each other. For this reason, for example, even when the phase of the noise signal can be inverted only in a narrow band due to the frequency characteristics of the phase shifter, the phase of the distributed noise signal distributed in advance with a phase difference can be inverted in different bands. . The noise removal means can be canceled by adjusting the amplitude for each frequency manning size signal. For this reason, for example, when removing a noise signal on the high frequency side, even if the noise signal on the low frequency side is emphasized, the noise removal processing on the high frequency side and the noise removal processing on the low frequency side can be performed separately. it can. Furthermore, since the signal synthesizing means for synthesizing a noise cancellation signal of the plurality of sub-bands with noise signals removed can be synthesized noise cancellation signal in a state of omitting the signal band in which the noise signal is emphasized, a broadband A noise removal effect can be obtained.

  In addition, since the phase is substantially constant in the plurality of divided bands, for example, by inputting a single control voltage to the phase shifter having the same configuration, the phase can be shifted in the plurality of divided bands. For this reason, the phase shift can be easily controlled, and the structure can be simplified to reduce the manufacturing cost.

Furthermore , since the phase shifter of the noise removing means is configured by an all-pass filter, the phase can be shifted while keeping the amplitude constant in all bands. For this reason, the amplitude does not differ for each band with the phase shift, and the phase of the distributed noise signal can be adjusted in a wide band.

According to the second aspect of the present invention, since the noise signal distribution means distributes the noise signals with a phase difference of 180 ° from each other, the noise is distributed in accordance with the phase change width of 180 ° of the one-stage all-pass filter. For example, by using a two-stage all-pass filter, the phase of the distributed noise signal can be reliably inverted in two bands.

According to the invention of claim 3, since the noise signal distribution means is constituted by the transformer, by a simple structure using the first and second coils, distributed noise distribution noise signal a noise signal having the same phase and antiphase it is possible to easily distributed to the signal, the phase of each distributed noise signal can be kept constant over a wide band.

According to the fourth aspect of the present invention, since the received signal is composed of a short-wave band power line communication signal based on the orthogonal frequency division multiplexing method, the received signal is a multicarrier signal using adaptive modulation. Next-order modulation can be performed, and low-order modulation can be performed in a band having a low noise removal effect with overlapping processing bands. Accordingly, even when the characteristics of the noise removal in the overlapping portion of the treatment zone as between the two sub-bands adjacent to deteriorate, I'm in suppressing the advance bit loading, it can be efficiently perform noise removal Thus, it is possible to suppress signal distortion accompanying the synthesis process.

It is a block diagram which shows the noise cancellation apparatus by 1st Embodiment. It is a characteristic diagram which shows the relationship between the phase and gain by a variable phase shifter in FIG. 1, and a frequency. It is a characteristic diagram which shows the relationship between the phase and frequency of a distributed noise signal output from a variable phase shifter. It is a block diagram which shows the noise cancellation apparatus by 2nd Embodiment. It is a characteristic diagram which shows the relationship between the phase and gain by a phase shifter in FIG. 4, and a frequency. It is a characteristic diagram which shows the relationship between the phase and frequency of the distribution noise signal output from a phase shifter. It is a characteristic diagram which shows the relationship between the attenuation amount of a noise signal, and a frequency. It is a block diagram which shows the noise cancellation apparatus by 3rd Embodiment. It is explanatory drawing which shows the relationship between the frequency characteristic of the attenuation amount of a noise signal, and the modulation degree of a PLC signal.

The present invention belongs to a group of inventions including a plurality of inventions described below. Hereinafter, first to third embodiments will be described as embodiments of the invention group. The second and third embodiments correspond to the invention described in the scope of claims of the present applicant.
Hereinafter, a noise canceling device according to an embodiment of the present invention will be described with reference to the accompanying drawings, taking as an example a case where it is applied to a power line communication (hereinafter referred to as PLC) system in a car.

  A first embodiment of the present invention is shown in FIG. The PLC transmitter 1 includes an A / D converter and a fast Fourier transform unit (both not shown). For example, the PLC signal St by power line communication in a short wave band (2 to 30 MHz) by orthogonal frequency division multiplexing (OFDM) is used. Is modulated and output.

  The PLC receiver 2 includes a D / A converter and a fast inverse Fourier transform unit (both not shown), and is connected to the PLC transmitter 1 using a transmission line 3 formed of a power line. Then, the PLC receiver 2 receives the PLC signal S0 from which the noise signal N has been removed by the noise cancellation device 4 from the received signal Sr propagated through the transmission line 3, and demodulates the PLC signal S0.

  The noise canceling device 4 is connected between the PLC transmitter 1 and the PLC receiver 2, and includes a noise pickup 5, a hybrid divider 6, a noise removing circuit 7, a duplexer 11, and the like which will be described later.

  The noise pickup 5 constitutes a noise signal detector that detects the noise signal N. The noise pickup 5 is formed using various antennas, for example, and is attached in the vicinity of an inverter, an engine, or the like that becomes a noise source. The noise pickup 5 then outputs the detected noise signal N toward the hybrid divider 6.

  The hybrid divider 6 constitutes a noise signal distribution unit, and distributes the noise signals N with a phase difference Δφ. Specifically, when the signal band (2 to 30 MHz) of the received signal Sr is divided into, for example, four divided bands F1 to F4, the distributed noise signal N1 having different phases φ1 to φ4 according to the divided bands F1 to F4. ~ N4 is output. Here, when the adjacent phase differences Δφ are all 30 °, the phase φ1 of the distributed noise signal N1 is 0 °, the phase φ2 of the distributed noise signal N2 is 30 °, and the phase φ3 of the distributed noise signal N3 is 60 °. In addition, the phase φ4 of the distributed noise signal N4 is set to 90 °. Note that the phase differences Δφ between the adjacent distributed noise signals N1 to N4 need not all be the same, and may be set to different values.

  At this time, among the distributed noise signals N1 to N4, those having a small phase value correspond to the low frequency side divided band, and those having a large phase value correspond to the high frequency side divided band. For this reason, the distribution noise signals N1 to N4 correspond to the divided bands F1 to F4 from the low frequency side to the high frequency side in the order.

  Four noise removal circuits 7 are provided according to the distributed noise signals N1 to N4 output from the hybrid divider 6. The noise removing circuit 7 constitutes a noise removing unit, and removes the noise signal N by synthesizing the distribution noise signals N1 to N4 having the opposite phases to the reception signal Sr for each of the divided bands F1 to F4. The noise removal circuit 7 includes a variable gain amplifier 8, a variable phase shifter 9, and a signal adder 10.

  The variable gain amplifier 8 adjusts the gains of the distributed noise signals N1 to N4 according to a gain adjustment signal from the control circuit 12 described later. Specifically, the variable gain amplifier 8 distributes so that the amplitude of the noise signal N mixed in the received signal Sr and the amplitude of the distributed noise signals N1 to N4 are substantially the same for each of the divided bands F1 to F4. The noise signals N1 to N4 are amplified.

  The variable phase shifter 9 constitutes a phase shifter that adjusts the phases φ1 to φ4 of the distributed noise signals N1 to N4 according to a phase adjustment signal from the control circuit 12 described later. Specifically, the variable phase shifter 9 is configured by connecting a plurality of stages (for example, two stages) of low-pass filters including, for example, resistors and capacitors. Then, as shown in FIG. 2, the variable phase shifter 9 shifts the phase φ of the input signal (distributed noise signals N1 to N4) to the minus side as the frequency increases, and increases the phase φ to 180 ° at the maximum. Change. At this time, the gain G of the variable phase shifter 9 decreases as the frequency of the input signal increases. The variable phase shifter 9 adjusts the shift amount of the phase φ by variably adjusting the resistance value of the resistor and the capacitance of the capacitor by a phase adjustment signal from the control circuit 12.

  The signal adder 10 constitutes a noise signal canceling means for canceling the noise signal N by synthesizing the received noise Sr and the distributed noise signals N1 to N4 whose phases φ1 to φ4 are shifted. The signal adder 10 is configured using, for example, an operational amplifier, and adds the distribution noise signals N1 to N4 output from the variable phase shifter 9 to the reception signal Sr. At this time, the reception signal Sr is a signal in which the noise signal N is mixed with the PLC signal St while passing through the transmission line 3. On the other hand, the signal adder 10 adds the distributed noise signals N1 to N4 having the opposite phase to the noise signal N mixed in the received signal Sr, thereby removing the noise signal N in each of the divided bands F1 to F4. The removal signals S1 to S4 are output.

  The duplexer 11 constitutes a signal synthesizing unit, and outputs a PLC signal S0 from which the noise signal N is removed by synthesizing the noise removal signals S1 to S4 output from the four signal adders 10. At this time, the duplexer 11 includes a bandpass filter corresponding to the divided bands F1 to F4, cuts signals other than the divided bands F1 to F4 from the noise removal signals S1 to S4, and extracts signals of the divided bands F1 to F4. To synthesize.

  The control circuit 12 is configured by, for example, a microcomputer and is provided by being connected to the PLC receiver 2. The control circuit 12 operates based on a known algorithm such as a maximum signal-to-noise ratio (MSN) method, for example, and the gain of each variable gain amplifier 8 is optimized so as to optimize the SN ratio of the PLC signal S0. And a phase adjustment signal for adjusting the phase shift amounts of the four variable phase shifters 9 together.

  The noise canceling apparatus 4 according to the present embodiment has the above-described configuration, and the operation thereof will be described next.

  When the PLC transmitter 1 outputs the PLC signal St, the PLC signal St propagates through the transmission line 3 and reaches the PLC receiver 2 side as the reception signal Sr. At this time, the noise canceling device 4 detects the noise signal N from the noise source using the noise pickup 5 and converts the noise signal N into distributed noise signals N1 to N4 having different phases φ1 to φ4 by the hybrid divider 6. Distribute. These distributed noise signals N1 to N4 are adjusted by the variable gain amplifier 8 so that the amplitude thereof is substantially the same as the amplitude of the noise signal N mixed in the reception signal Sr in each of the divided bands F1 to F4. The phase φ1 to φ4 is shifted to the minus side by the variable phase shifter 9.

  Here, the phases φ1 to φ4 of the distributed noise signals N1 to N4 are different from each other. Therefore, when the phase φ1 to φ4 of the distribution noise signals N1 to N4 is shifted by the variable phase shifter 9, the frequency bands in which the phases φ1 to φ4 of the distribution noise signals N1 to N4 match each other as shown in FIG. Different. Thereby, phases φ1 to φ4 of distributed noise signals N1 to N4 can be set to substantially the same value in different divided bands F1 to F4.

  The distributed noise signals N1 to N4 whose phases φ1 to φ4 are shifted are combined with the received signal Sr by the signal adder 10. At this time, the phases φ1 to φ4 of the distribution noise signals N1 to N4 are adjusted by appropriately adjusting the phase shift amount by the variable phase shifter 9, thereby the noise signal N mixed in the reception signal Sr in each of the divided bands F1 to F4. The phase is set to be opposite to the phase. Thereby, the signal adder 10 outputs noise removal signals S1 to S4 obtained by removing the noise signal N mixed in the reception signal Sr in each of the divided bands F1 to F4.

  These noise removal signals S 1 to S 4 are synthesized by the duplexer 11. At this time, the duplexer 11 extracts the signals of the divided bands F1 to F4 from the noise removal signals S1 to S4 and synthesizes the PLC signal S0. As a result, the PLC signal S0 from which the noise signal N has been removed can be obtained in all signal bands obtained by adding the divided bands F1 to F4, and the PLC receiver 2 can receive and demodulate the PLC signal S0. it can.

  Thus, according to the first embodiment, since the hybrid divider 6 distributes the noise signals N with a phase difference Δφ between them, the variable phase shifter 9 can invert the phase of the noise signal N only in a narrow band. Even at times, the distributed noise signals N1 to N4 distributed in advance with the phase difference Δφ are in opposite phases to the noise signal N in the divided bands F1 to F4 having different phases φ1 to φ4.

  Since the variable gain amplifier 8 adjusts the amplitudes of the distribution noise signals N1 to N4 for each of the divided bands F1 to F4, the signal adder 10 converts the distribution noise signals N1 to N4 and the reception signal Sr whose phases φ1 to φ4 are shifted. Can be combined to output noise-removed signals S1 to S4 obtained by canceling the noise signals N of the divided bands F1 to F4.

  Further, when the noise removal signals S1 to S4 are synthesized by the duplexer 11, the duplexer 11 extracts and synthesizes the signals of the divided bands F1 to F4 from the noise removal signals S1 to S4. For this reason, as the noise signal N of each divided band F1 to F4 is removed, for example, even when the noise signal N is emphasized in a band other than each divided band F1 to F4, the band in which the noise signal N is enhanced. Can be deleted to synthesize the PLC signal S0. As a result, the noise removal effect can be obtained in a wide band obtained by adding the divided bands F1 to F4 while suppressing the enhancement of the noise signal N.

  Further, since the phases are substantially constant in the four divided bands F1 to F4, for example, by inputting a single control voltage as a phase adjustment signal to the variable phase shifter 9 having the same configuration, a plurality of divided bands F1 to F4. The phase φ1 to φ4 of the distribution noise signals N1 to N4 can be shifted by F4. For this reason, the phase shift can be easily controlled, and the structure can be simplified to reduce the manufacturing cost.

  Next, FIG. 4 shows a second embodiment of the present invention. The feature of the second embodiment is that the phase shifter of the noise removal circuit is configured by an all-pass filter. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The noise cancellation device 21 is connected between the PLC transmitter 1 and the PLC receiver 2 and includes a noise pickup 5, a transformer 22, a noise removal circuit 23, a diplexer 28, and the like.

  The transformer 22 constitutes noise signal distribution means, and distributes the noise signals N with a phase difference Δφ of 180 ° from each other. The transformer 22 includes a primary side coil 22A, a secondary side first coil 22B, and a secondary side second coil 22C. The primary side coil 22A is connected to the noise pickup 5, and the secondary side first coil. 22B and the second secondary coil 22C are connected to different noise removal circuits 23, respectively. When the transformer 22 divides the signal band (2 to 30 MHz) of the received signal Sr into two divided bands F1 and F2, the distributed noise signal N1 having different phases φ1 and φ2 depending on the divided bands F1 and F2. , N2 is output.

  Here, the secondary side first coil 22 </ b> B and the secondary side second coil 22 </ b> C are connected to the noise removal circuit 23 in a state of having opposite polarities. Therefore, the phase difference Δφ between the distributed noise signals N1 and N2 is 180 °, the phase φ1 of the distributed noise signal N1 is set to 0 °, and the phase φ2 of the distributed noise signal N2 is set to 180 °. At this time, the distributed noise signal N1 corresponds to the low frequency side divided band F1, and the distributed noise signal N2 corresponds to the high frequency side divided band F2.

  Two noise removal circuits 23 are provided according to the distributed noise signals N1 and N2 output from the transformer 22. This noise removing circuit 23 constitutes a noise removing means, and synthesizes the distribution noise signals N1 and N2 having opposite phases for each of the divided bands F1 and F2 with the received signal Sr to remove the noise signal N. The noise removal circuit 23 includes a variable gain amplifier 24, a phase shifter 25, and a differential amplifier 27.

  The variable gain amplifier 24 is configured in substantially the same manner as the variable gain amplifier 8 according to the first embodiment, and adjusts the gains of the distributed noise signals N1 and N2 according to a gain adjustment signal from a control circuit 29 described later. Specifically, the variable gain amplifier 24 distributes so that the amplitude of the noise signal N mixed in the received signal Sr in each of the divided bands F1 and F4 and the amplitude of the distributed noise signals N1 and N4 are substantially the same value. The noise signals N1 and N4 are amplified.

  The phase shifter 25 adjusts the phases φ1 and φ2 of the distributed noise signals N1 and N2 according to a phase adjustment signal from the control circuit 29 described later. The phase shifter 25 is configured by connecting, for example, an all-pass filter 26 (hereinafter referred to as APF 26) capable of shifting the phase by 180 ° in a two-stage cascade. For this reason, the phase shifter 25 can adjust the phases φ1 and φ2 of the distributed noise signals N1 and N2 within a range of 360 °.

  The APF 26 includes an operational amplifier OPA, a resistor R1 having one end connected to the inverting input terminal of the operational amplifier OPA, a resistor R2 and a capacitor C having one end connected to the non-inverting input terminal of the operational amplifier OPA, and an operational amplifier. The resistor R3 is connected between the inverting input terminal and the output terminal of the OPA. Here, the resistors R1 and R2 are connected to each other at the other end located on the opposite side of the operational amplifier OPA, and a common signal is input thereto. The other end of the capacitor C is connected to the ground. Further, the resistors R1 and R3 are set to the same resistance value.

  Then, as shown in FIG. 5, the phase shifter 25 shifts the phase φ of the input signal (distributed noise signals N1, N2) to the minus side as the frequency increases, and the phase φ is increased to 360 ° at the maximum. Change. At this time, the gain G of the phase shifter 25 becomes constant regardless of the frequency of the input signal. The phase shifter 25 adjusts the phase shift amount by variably adjusting the resistance value of the resistor R2 and the capacitance of the capacitor C by a phase adjustment signal from the control circuit 29.

  Here, phases φ1 and φ2 of distributed noise signals N1 and N4 are different from each other. Therefore, when the phases φ1 and φ2 of the distribution noise signals N1 and N2 are shifted by the phase shifter 25, as shown in FIG. 6, the frequency bands in which the phases φ1 and φ2 of the distribution noise signals N1 and N2 match each other. Different. As a result, the phases φ1 and φ2 of the distributed noise signals N1 and N2 can be set to substantially the same value in the different divided bands F1 and F2.

  The differential amplifier 27 constitutes a noise signal canceling means for canceling the noise signal N by synthesizing the distribution noise signals N1, N2 and the received signal Sr whose phases φ1, φ2 are shifted. The differential amplifier 27 is configured using, for example, an operational amplifier, and subtracts the distributed noise signals N1 and N2 output from the phase shifter 25 from the received signal Sr. At this time, the reception signal Sr is a signal in which the noise signal N is mixed with the PLC signal St while passing through the transmission line 3. On the other hand, the differential amplifier 27 subtracts the distribution noise signals N1 and N4 having the same phase as the noise signal N mixed in the reception signal Sr, thereby removing the noise signal N in each of the divided bands F1 and F2. The removal signals S1 and S2 are output. At this time, the distributed noise signals N1 and N2 are removed with the divided bands F1 and F2 as the center. Therefore, the attenuation amounts A1 and A2 of the noise signal N in the noise removal signals S1 and S2 are divided bands as shown in FIG. Increased with F1 and F2.

  The diplexer 28 constitutes a signal synthesizing unit and synthesizes the noise removal signals S1 and S2 output from the two differential amplifiers 27 and outputs a PLC signal S0 from which the noise signal N is removed. At this time, the diplexer 28 includes a band pass filter corresponding to the divided bands F1 and F2, and extracts and synthesizes the signals of the divided bands F1 and F2 from the noise removal signals S1 and S2.

  The control circuit 29 is provided in connection with the PLC receiver 2 and is configured in substantially the same manner as the control circuit 12 according to the first embodiment. Then, the control circuit 29 outputs a gain adjustment signal for individually adjusting the gain of each variable gain amplifier 24 so as to optimize the SN ratio of the PLC signal S0, and the phase shift amount of the two phase shifters 25. A phase adjustment signal that adjusts the two together is output.

  Thus, the second embodiment can provide the same effects as those of the first embodiment. In particular, in the second embodiment, since the phase shifter 25 is configured by the APF 26, the phases φ1 and φ2 of the distributed noise signals N1 and N2 can be shifted while keeping the amplitude constant in all bands. Therefore, for example, when the phase is shifted using a low-pass filter, the amplitude does not differ for each band with the phase shift, and the phases φ1 and φ2 of the distributed noise signals N1 and N2 are adjusted in a wide band. can do.

  In addition, since the noise signal N is distributed with a phase difference of 180 ° from each other, the noise signal N can be distributed in accordance with the phase change width of 180 ° of the one-stage APF 26. By using the APF 26, the phases φ1 and φ2 of the distributed noise signals N1 and N2 can be reliably inverted with respect to the phase of the noise signal N in the two divided bands F1 and F2.

  Furthermore, since the noise signal N is distributed using the transformer 22, the distributed noise signal N2 having the same phase as the noise signal N and the distributed noise signal N2 having the opposite phase to the noise signal N can be obtained with a simple configuration using the first coil 22B and the second coil 22C. Can be distributed easily. In addition, the phases φ1, φ2 of the distributed noise signals N1, N2 can be made constant over a wide band.

  Next, a third embodiment of the present invention is shown in FIG. A feature of the third embodiment is that when modulating a PLC signal composed of a multicarrier signal, high-order modulation is performed in a band where the attenuation amount of the noise signal is large, and low-order modulation is performed in a band where the attenuation amount is small It is in that. In the third embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The PLC transmitter 31 is configured in substantially the same manner as the PLC transmitter 1 according to the first embodiment, and modulates a PLC signal St by short-wave band power line communication by orthogonal frequency division multiplexing as a multicarrier signal using adaptive modulation. And output. However, as shown in FIG. 9, the PLC signal St is subjected to high-order modulation in a band (for example, 2 to 4 MHz and 10 to 30 MHz) in which the attenuation amounts A1 and A2 of the noise signal N by the noise canceling device 21 are large, and the attenuation amount. Low-order modulation is performed in a small band (eg, 4 to 10 MHz).

  The PLC receiver 32 is configured in substantially the same manner as the PLC receiver 2 according to the first embodiment, and is connected to the PLC transmitter 31 using the transmission line 3 formed of a power line. Then, the PLC receiver 32 receives the PLC signal S0 from which the noise signal N has been removed by the noise cancellation device 21 from the received signal Sr propagated through the transmission line 3, and demodulates the PLC signal S0.

  Thus, also in the third embodiment, it is possible to obtain the same operational effects as those in the first and second embodiments. In particular, in the third embodiment, high-order modulation is performed in a band (for example, 2 to 4 MHz and 10 to 30 MHz) in which the attenuation amounts A1 and A2 of the noise signal N are large, and a band in which the attenuation amount is small (for example, 4 to 10 MHz). Thus, the low-order modulation is performed. For this reason, the attenuation amount of the noise signal N becomes small in the band where the noise removal processing overlaps, such as between the divided bands F1 and F2, and even when the characteristic deterioration occurs, the bit loading is performed in advance on such a small attenuation band. Thus, the noise signal N can be efficiently canceled. As a result, it is possible to suppress signal distortion associated with the synthesis processing of the noise removal signals S1 and S2.

  In the first embodiment, the band of the received signal Sr is divided into four divided bands F1 to F4. In the second and third embodiments, the band is divided into two divided bands F1 and F2. It was supposed to be. However, the present invention is not limited to this, and the band of the received signal may be divided into three divided bands or may be divided into five or more divided bands.

  Further, in the first embodiment, the variable phase shifter 9 is configured to shift the phase in the range of 180 °, but may be configured to shift the phase in the range of 270 ° or 360 °, for example.

  In the first embodiment, the signal adder 10 for adding the distributed noise signals N1 to N4 to the received signal Sr is used as the noise signal canceling means, but the second and third embodiments are used. Similarly to the above, a configuration using a differential amplifier may be adopted. Similarly, in the second and third embodiments, a signal adder may be used as the noise signal canceling unit, as in the first embodiment.

  In the first embodiment, the noise removal circuit 7 is configured to adjust the phases φ1 to φ4 after adjusting the amplitudes of the distributed noise signals N1 to N4, but after adjusting the phases φ1 to φ4. The amplitude may be adjusted. This also applies to the noise removal circuit 23 according to the second and third embodiments.

  In each of the above embodiments, the noise signal distribution means including the hybrid divider 6 and the transformer 22 is configured to distribute the noise signal and generate the phase difference together. It is good also as a structure which produces a phase difference after adjusting.

  Furthermore, in each of the above embodiments, the case where the present invention is applied to a power line communication system in an automobile has been described as an example. However, the present invention may be applied to a power line communication system such as an indoor wiring, and is not limited to wired or wireless. The present invention can be widely applied to various communication systems and reception systems using the above signals.

DESCRIPTION OF SYMBOLS 1,31 PLC transmitter 2,32 PLC receiver 4,21 Noise cancellation apparatus 5 Noise pickup (noise signal detector)
6 Hybrid divider (noise signal distribution means)
7,23 Noise removal circuit (noise removal means)
8,24 Variable gain amplifier 9 Variable phase shifter (phase shifter)
10 signal adder 11 duplexer (signal synthesis means)
22 transformer (noise signal distribution means)
22A Primary side coil 22B Secondary side first coil 22C Secondary side second coil 25 Phase shifter 26 All-pass filter (APF)

Claims (4)

A noise canceling device that synthesizes a noise signal having an antiphase with a received signal,
And a noise signal detector for detecting a noise signal,
A noise signal distribution means for distributing with a phase difference from each other noise signals detected by the noise signal detector,
Comprising a phase shifter, synthesized and the distribution noise signal in opposite phase to each divided band obtained by dividing the signal band of the received signal to a receiver signal noise for adjusting the phase of the distributed distributed noise signal by the noise signal distribution means Noise removal means for removing the signal;
And a signal synthesizing means for synthesizing a noise cancellation signal of the plurality of sub-bands with noise signals removed by the noise removal means,
The phase shifter is a noise canceling device configured by using an all-pass filter that shifts a phase with a constant amplitude . It said noise signal distribution means, the noise canceling device of claim 1 comprising a pre-Symbol noise signal as a structure for distributing with a phase difference of 180 ° from each other. It said noise signal distribution means, constituting a first coil for distributing the distribution noise signal of the noise signal and the same phase, the transformer and a second coil for distributing the distribution noise signal of the noise signal in opposite phase The noise cancellation apparatus according to claim 1 or 2 . The noise cancellation apparatus according to any one of claims 1 to 3 , wherein the received signal is a signal for short-wave power line communication using an orthogonal frequency division multiplexing system.

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