Communication circuit, communication module, communication system, and communication method

Abstract

This communication circuit includes an output equalization processing unit, a reference equalization processing unit, and a coefficient setting unit, and transmits and receives communication signals to and from another device through a cable during a steady operation period. The output equalization processing unit performs equalization processing on the communication signal transmitted by the other device on the basis of an equalization coefficient that has been set. The reference equalization processing unit equalizes the communication signal transmitted by the other device. The coefficient setting unit calculates an equalization coefficient on the basis of the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit, and updates the equalization coefficient set in the output equalization processing unit to the calculated equalization coefficient.

Description

Communication Circuit, Communication Module, Communication System, and Communication Method

[0001] The present invention relates to a communication circuit, a communication module, a communication system, and a communication method for transmitting signals.

[0002] In a communication system, a control device and a drive device are connected by a cable. Various signals indicating arbitrary information are transmitted between the control device and the drive device through the cable. However, the signals transmitted through the cable may be distorted due to the influence of the transmission path characteristics of the cable. Therefore, equalization processing is known as a technique for correcting the distorted signals to return them to the original signals or minimizing the signal distortion.

[0003] For example, in the data transmission system described in Patent Document 1, a plurality of data transmission devices are connected so as to form a ring topology. Each data transmission device is provided with an adaptive equalizer constituted by a FIR (Finite Impulse Response) filter. The adaptive equalizer equalizes the signal by filtering the received signal using the filter coefficients determined so that the error between the received signal and the ideal signal that should be originally received becomes small.

[0004] Japanese Patent Application Laid-Open No. 2006-222884

[0005] In the data transmission system of Patent Document 1, it is necessary to transmit predetermined data as the ideal signal to be received. Therefore, the latency increases.

[0006] An object of the present invention is to provide a communication circuit, a communication module, a communication system, and a communication method capable of performing equalization processing on signals while preventing an increase in latency.

[0007] A communication circuit according to the first aspect of the present invention is a communication circuit that transmits and receives communication signals to and from another device via a cable during a steady-state operation period, comprising: an output equalization processing unit that equalizes the communication signal transmitted by the other device based on a set equalization coefficient; a reference equalization processing unit that equalizes the communication signal transmitted by the other device; and a coefficient setting unit that calculates an equalization coefficient based on the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit, and updates the equalization coefficient set in the output equalization processing unit to the calculated equalization coefficient.

[0008] A communication module according to the second aspect of the present invention includes the above-described communication circuit.

[0009] A communication system according to a third aspect of the present invention comprises a cable, a first device provided with the above-mentioned communication module, and a second device provided with a second communication module that transmits and receives communication signals between the first device and the communication module via the cable.

[0010] A communication method according to a fourth aspect of the present invention is a communication method performed by a communication circuit that transmits and receives communication signals to and from another device via a cable during a steady-state operation period, and includes: equalizing a communication signal transmitted by the other device using an output equalization processing unit based on a set equalization coefficient; equalizing a communication signal transmitted by the other device using a reference equalization processing unit; calculating an equalization coefficient based on the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit; and updating the equalization coefficient set in the output equalization processing unit to the calculated equalization coefficient.

[0011] According to the present invention, signal equalization processing can be performed while preventing an increase in latency.

[0012] Figure 1 is a diagram showing the configuration of a communication system according to one embodiment of the present invention. Figure 2 is a block diagram showing the configuration of a communication circuit. Figure 3 is a block diagram showing a detailed configuration of the receiving section of the communication circuit. Figure 4 is a diagram illustrating an example of EVM value calculation. Figure 5 is a flowchart showing the calibration of filter coefficients performed by the communication circuit. Figure 6 is a flowchart showing an example of the initial calibration in Figure 5. Figure 7 is a flowchart showing an example of the initial calibration in Figure 5. Figure 8 is a flowchart showing an example of the initial calibration related to the primary device. Figure 9 is a flowchart showing an example of the initial calibration related to the secondary device. Figure 10 is a flowchart showing an example of the periodic calibration in Figure 5.

[0013] 1. Configuration of the Communication System Below, the communication circuit, communication module, communication system, and communication method according to embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a diagram showing the configuration of a communication system according to one embodiment of the present invention. As shown in Figure 1, the communication system 300 includes a control device 100, a drive device 200, and a cable 310. The communication system 300 is, for example, a servo motor system and is connected to a command device 400. In this case, the control device 100 is a servo amplifier, and the drive device 200 is a servo motor. Therefore, since the cable 310 is connected to the servo motor, it is expected that the shape of the cable 310 may change as the cable 310 itself moves, or that the surrounding environment of the cable 310 may change. It is necessary to correct the distortion of the signal being communicated in order to follow the changes in transmission path characteristics due to these changes in conditions.

[0014] The control device 100 includes a control unit 110 and a communication module 120. The control unit 110 includes, for example, a CPU (Central Processing Unit) and generates drive signals to control the operation of the drive unit 210 via the communication module 120 based on commands given from the command device 400 or the operating state of the drive unit 210 of the drive device 200 (described later). The control unit 110 also controls the operation of the power supply unit 121 of the communication module 120 (described later). The command device 400 is, for example, a PLC (Programmable Logic Controller) and mainly provides commands to the control device 100 to start the operation of the drive device 200.

[0015] The communication module 120 includes a communication circuit 10A, a power supply unit 121, and a filter unit 122. Each of the communication circuit 10A, the power supply unit 121, and the filter unit 122 is composed of, for example, an LSI (large-scale integrated circuit) chip. The communication circuit 10A, the power supply unit 121, and the filter unit 122 are modularized by being mounted on a circuit board.

[0016] The communication circuit 10A transmits the drive signal generated by the control unit 110 to the drive device 200 through the filter unit 122. The communication circuit 10A also receives a status signal indicating the operating status of the drive unit 210 from the drive device 200 through the filter unit 122 and provides it to the control unit 110. The power supply unit 121 transmits power to the drive device 200 through the filter unit 122 according to the PWM (pulse width modulation) control by the control unit 110. The filter unit 122 includes various filter elements for separating the drive signal, status signal, and power from each other.

[0017] The drive unit 200 includes a drive unit 210 and a communication module 220. The drive unit 210 includes a motor body connected to the gears of a machine (a device to be driven) (not shown), and various sensors for detecting the operating state of the motor body. The motor body is driven when a drive signal is applied. The various sensors, upon receiving power, detect the position of the device to be driven, the rotational speed or rotational angle of the motor body, etc., as the operating state of the drive unit 210, and generate a status signal indicating the operating state of the drive unit 210.

[0018] The communication module 220 includes a communication circuit 10B, a power supply unit 221, and a filter unit 222. Each of the communication circuit 10B, the power supply unit 221, and the filter unit 222 is, for example, composed of an LSI chip. The communication circuit 10B, the power supply unit 221, and the filter unit 222 are modularized by being mounted on a circuit board. Note that the communication circuit 10B has the same configuration as the communication circuit 10A of the communication module 120. Therefore, in the following description, when it is not necessary to distinguish between communication circuits 10A and 10B, they will be referred to as communication circuit 10.

[0019] The communication circuit 10B transmits a status signal generated by the drive unit 210 to the control device 100 through the filter unit 222. The communication circuit 10B also receives a drive signal from the control device 100 through the filter unit 222 and supplies it to the drive unit 210. The power supply unit 221 receives power from the control device 100 through the filter unit 222 and supplies the received power to the drive unit 210. The filter unit 222 has the same configuration as the filter unit 122 of the communication module 120.

[0020] The filter unit 122 of the communication module 120 and the filter unit 222 of the communication module 220 are connected by a cable 310. The cable 310 transmits drive signals, status signals, and power between the control device 100 and the drive device 200. In this example, the cable 310 is a PLC (Power Line Communication) cable capable of simultaneously transmitting drive signals, status signals, and power. In the following description, drive signals and status signals will be collectively referred to as communication signals. Note that the communication system to which the present invention can be applied is not limited to the communication system 300 using a PLC cable. Therefore, the power transmission function is not essential for the cable 310, and the cable 310 may be a cable that transmits only various types of signals.

[0021] 2. Communication circuit diagram 2 is a block diagram showing the configuration of the communication circuit 10. As shown in Figure 2, the communication circuit 10 includes a transmitting unit 20 and a receiving unit 30. In the following description, when distinguishing between communication circuit 10A and communication circuit 10B, components corresponding to communication circuit 10A will be indicated by adding "A" to the reference numeral of the component, and components corresponding to communication circuit 10B will be indicated by adding "B" to the reference numeral of the component. For example, the transmitting unit 20 and the receiving unit 30 corresponding to communication circuit 10A will be indicated as transmitting unit 20A and receiving unit 30A, respectively, and the transmitting unit 20 and the receiving unit 30 corresponding to communication circuit 10B will be indicated as transmitting unit 20B and receiving unit 30B, respectively.

[0022] The transmitting unit 20 includes an input interface (I / F) 21, a teacher signal generation unit 22, an encoding unit 23, a modulation unit 24, a frame generation unit 25, and a digital-to-analog (D / A) converter 26. A communication signal is input to the input interface 21. Specifically, when the communication circuit 10 is communication circuit 10A, the input interface 21A is connected to the control unit 110 in Figure 1, and a drive signal is input to the input interface 21A as a communication signal. When the communication circuit 10 is communication circuit 10B, the input interface 21B is connected to the drive unit 210 in Figure 1, and a status signal is input to the input interface 21B as a communication signal.

[0023] The teacher signal generation unit 22 generates a known data sequence as a teacher signal, in which multiple data points of value "0" or value "1" are arranged in any order in a time series. The encoding unit 23 acquires the communication signal input to the input I / F 21 during the periodic calibration of the equalization coefficient, which will be described later. The encoding unit 23 also acquires the teacher signal generated by the teacher signal generation unit 22 during the initial calibration of the equalization coefficient, which will be described later. Furthermore, the encoding unit 23 encodes the acquired signal (communication signal or teacher signal).

[0024] The modulation unit 24 modulates the signal encoded by the encoding unit 23. In this example, the signal is modulated using the QPSK (Quadrature Phase Shift Keying) method. The frame generation unit 25 frames the signal, using the signal modulated by the modulation unit 24 as the main data sequence. Specifically, a frame containing the main data sequence is generated by adding a preamble data sequence and a synchronization data sequence before the main data sequence in the time series. The D / A converter 26 converts the signal framed by the frame generation unit 25 from a digital state to an analog state.

[0025] When communication circuit 10 is communication circuit 10A, the signal converted to analog by the D / A converter 26A is transmitted to the drive unit 200 via the filter unit 122 and cable 310 shown in Figure 1. In this case, the transmitted signal is received by the A / D (analog / digital) converter 31B of the receiving unit 30B, which will be described later. On the other hand, when communication circuit 10 is communication circuit 10B, the signal converted to analog by the D / A converter 26B is transmitted to the control device 100 via the filter unit 222 and cable 310 shown in Figure 1. In this case, the transmitted signal is received by the A / D converter 31A of the receiving unit 30A.

[0026] The receiving unit 30 includes an A / D converter 31, a signal adjustment unit 32, a signal identification unit 33, a demodulation unit 34, a decoding unit 35, an output interface 36, an output equalization processing unit 40, a reference equalization processing unit 50, a communication signal regeneration unit 60, and a coefficient setting unit 70. As described above, the A / D converter 31 receives the transmitted signal. The A / D converter 31 also converts the received signal from an analog state to a digital state.

[0027] The signal adjustment unit 32 determines gain parameters and frequency parameters for adjusting the gain and frequency of the signal, respectively. In this example, during initial calibration, the gain parameters and frequency parameters are determined so that the symbol corresponding to the training signal is located at predetermined coordinates on a signal space diagram consisting of the real and imaginary axes. The signal adjustment unit 32 then adjusts the gain and frequency of the signal converted to a digital state by the A / D converter 31, respectively, according to the determined gain parameters and frequency parameters. The signal adjusted by the signal adjustment unit 32 is then supplied to the output equalization processing unit 40 and the reference equalization processing unit 50.

[0028] The signal identification unit 33 is supplied with a signal that has been equalized by the output equalization processing unit 40. During periodic calibration, the signal identification unit 33 identifies the portion of the communication signal, including the main data sequence, by identifying the preamble data sequence and the synchronization data sequence of the communication signal and performing synchronization processing. The demodulation unit 34 demodulates the communication signal identified by the signal identification unit 33. The decoding unit 35 decodes the communication signal demodulated by the demodulation unit 34. The communication signal demodulated by the demodulation unit 34 is then supplied to the communication signal regeneration unit 60.

[0029] The output interface 36 outputs the communication signal decoded by the decoding unit 35. Specifically, when the communication circuit 10 is communication circuit 10A, the output interface 36A is connected to the control unit 110 in Figure 1 and outputs a status signal as a communication signal to the control unit 110. When the communication circuit 10 is communication circuit 10B, the output interface 36B is connected to the drive unit 210 in Figure 1 and outputs a drive signal as a communication signal to the drive unit 210.

[0030] The output equalization processing unit 40 includes, for example, a Finite Impulse Response (FIR) filter. The output equalization processing unit 40 equalizes the signal by filtering the signal adjusted by the signal adjustment unit 32 using the filter coefficients set by the coefficient setting unit 70. The filter coefficients (equalization coefficients) set in the output equalization processing unit 40 are dynamically updated by calibration, which will be described later. The calibration of the filter coefficients includes initial calibration and periodic calibration.

[0031] The reference equalization processing unit 50 has the same configuration as the output equalization processing unit 40, except that it includes a buffer circuit 51, which will be described later. In this example, the signal equalized by the reference equalization processing unit 50 is not output outside the communication circuit 10. The communication signal regeneration unit 60 holds the communication signal demodulated by the demodulation unit 34 for several frames (one frame in this example), and then performs predetermined processing on the held communication signal to regenerate the communication signal equalized by the output equalization processing unit 40.

[0032] The coefficient setting unit 70 sets the filter coefficients of the output equalization processing unit 40. In addition, during initial calibration, the coefficient setting unit 70 dynamically updates the filter coefficients set in the output equalization processing unit 40 based on the teacher signal equalized by the reference equalization processing unit 50 and the known teacher signal generated by the teacher signal generation unit 22 of the transmission unit 20. Furthermore, during periodic calibration, the coefficient setting unit 70 dynamically updates the filter coefficients set in the output equalization processing unit 40 based on the communication signal equalized by the reference equalization processing unit 50 and the communication signal regenerated by the communication signal regeneration unit 60. Details of the output equalization processing unit 40, the reference equalization processing unit 50, the communication signal regeneration unit 60, and the coefficient setting unit 70 will be described later.

[0033] 3. Output Equalization Processing Unit, Reference Equalization Processing Unit, Communication Signal Regeneration Unit, and Coefficient Setting Unit Figure 3 is a block diagram showing the detailed configuration of the receiving unit 30 of the communication circuit 10. As shown in Figure 3, the output equalization processing unit 40 includes a plurality of delay elements 41, a plurality of multipliers 42, and an adder 43. The plurality of delay elements 41 and the plurality of multipliers 42 correspond to each other, and the plurality of delay elements 41, the plurality of multipliers 42, and the adder 43 constitute an FIR filter. The number of delay elements 41, i.e., the number of taps in the FIR filter, is not limited.

[0034] Multiple delay elements 41 are connected in series. The signal output from the signal adjustment unit 32 is input to the upstream delay element 41, i.e., the first-stage delay element 41. The signals output from the preceding delay element 41 are input to the second-stage and subsequent delay elements 41. Each delay element 41 delays the input signal by a predetermined time (1 clock cycle) and outputs it.

[0035] Each multiplier 42 receives a signal output by its corresponding delay element 41. Each multiplier 42 also has a filter coefficient set by the coefficient setting unit 70. Each multiplier 42 multiplies the input signal by the set filter coefficient and outputs the result. The adder 43 receives signals output by multiple multipliers 42. The adder 43 adds the input signals and outputs the added signal as an equalized signal.

[0036] The reference equalization processing unit 50 includes a buffer circuit 51 and an FIR filter 52. The buffer circuit 51 stores signals from the signal adjustment unit 32 one frame at a time, buffers the stored communication signals for a time equivalent to one frame, and then outputs them. The buffer circuit 51 is used to supply the FIR filter 52 with signals of the same frame as the communication signals output by the buffer circuit 61 of the communication signal regeneration unit 60, which will be described later. The FIR filter 52 has the same configuration as the FIR filter of the output equalization processing unit 40 and performs equalization processing on the signals output by the buffer circuit 51.

[0037] The communication signal regeneration unit 60 includes a buffer circuit 61, a modulation unit 62, a frame generation unit 63, and a filter circuit 64. During periodic calibration, the buffer circuit 61 stores the communication signal from the demodulation unit 34 one frame at a time, buffers the stored communication signal for a time equivalent to one frame, and then outputs it.

[0038] The modulation unit 62 and the frame generation unit 63 have configurations similar to those of the modulation unit 24 and frame generation unit 25 of the transmission unit 20 in Figure 2. The modulation unit 62 modulates the communication signal output by the buffer circuit 61. The frame generation unit 63 frames the communication signal modulated by the modulation unit 62. The filter circuit 64 includes, for example, a roll-off filter and filters the communication signal framed by the frame generation unit 63. As a result, a communication signal equivalent to the communication signal equalized by the output equalization processing unit 40 is regenerated.

[0039] The coefficient setting unit 70 includes an error calculation unit 71, a coefficient calculation unit 72, and an update determination unit 73. The error calculation unit 71 acquires a signal from the reference equalization processing unit 50. In addition, during initial calibration, the error calculation unit 71 acquires a known teacher signal from the teacher signal generation unit 22 of the transmission unit 20, and during periodic calibration, it acquires a communication signal from the communication signal regeneration unit 60. The error calculation unit 71 calculates the error between the signal acquired from the reference equalization processing unit 50 and the teacher signal acquired from the teacher signal generation unit 22 or the communication signal acquired from the communication signal regeneration unit 60.

[0040] The coefficient calculation unit 72 calculates, frame by frame, the filter coefficients to be set in each multiplier 42 of the output equalization processing unit 40 in order to perform equalization processing on the signal output by the signal adjustment unit 32, based on the error calculated by the error calculation unit 71. A known adaptive algorithm can be used to calculate the filter coefficients. In this example, the filter coefficients are calculated using the least mean squares method so as to minimize the error calculated by the error calculation unit 71. The coefficient calculation unit 72 dynamically updates the set filter coefficients by setting the calculated filter coefficients in each multiplier 42 for each frame.

[0041] The update determination unit 73 detects the amount of noise mixed into the signal for each frame. In this example, the amount of noise mixed into the signal is calculated as the EVM (Error Vector Magnitude) value. Figure 4 is a diagram illustrating an example of EVM value calculation. As described above, the signal adjustment unit 32 in Figure 3 adjusts the gain and frequency of the signal according to the gain parameter and frequency parameter determined in the initial calibration. Therefore, as shown in Figure 4, if no noise is mixed into the signal, the symbol corresponding to the signal is located at a predetermined coordinate C1 on the signal space diagram. The reference vector V1 from the origin of the signal space diagram to coordinate C1 is a known quantity.

[0042] On the other hand, if noise is mixed into the signal, the symbol corresponding to that signal will be located at coordinate C2, which is different from coordinate C1 on the signal space diagram. Therefore, for the signal identified by the signal identification unit 33, the coordinate C2 where the symbol is located is measured, and the measured vector V2 from the origin of the signal space diagram to coordinate C2 is identified. In addition, the error vector Ve(V2-V1) is calculated, and the EVM value (unit: dB) is calculated by dividing the absolute value of the error vector Ve by the absolute value of the reference vector V1. When the amount of noise mixed in is relatively small, the EVM value will be below a predetermined threshold. Conversely, when the amount of noise mixed in is relatively large, the EVM value will exceed the threshold.

[0043] The update determination unit 73 determines, frame by frame, whether or not to update the filter coefficients based on the detected noise level. In frames where the noise level is relatively low, it is determined that the filter coefficients should be updated. On the other hand, in frames where the noise level is relatively high, it is determined that the filter coefficients should not be updated. Therefore, for frames where the update determination unit 73 has determined not to update the filter coefficients, the coefficient calculation unit 72 does not set the calculated filter coefficients in each multiplier 42 of the output equalization processing unit 40. As a result, the update of the filter coefficients is postponed.

[0044] 4. Calibration of Filter Coefficient (1) Overall Process FIG. 5 is a flowchart showing the calibration of filter coefficients executed by the communication circuits 10A and 10B. As shown in FIG. 5, in the calibration of filter coefficients, first, initial calibration is executed at startup before the communication circuit 10 starts steady operation (step S10). After the completion of the initial calibration, the communication circuit 10 starts steady operation. Periodic calibration is executed during the steady operation period of the communication circuit 10 (step S30). The periodic calibration is repeatedly executed as long as the transmission and reception of communication signals continue between the communication circuits 10A and 10B.

[0045] Hereinafter, the details of the initial calibration and the periodic calibration will be described while referring to FIGS. 2 and 3. Here, in this example, the calibration of filter coefficients is executed by the primary / secondary method. In the primary device and the secondary device, the procedure of the periodic calibration is the same, but the procedure of the initial calibration is different. Therefore, for the initial calibration, the operations of the primary device and the secondary device will be separately described as necessary.

[0046] (2) Initial Calibration FIGS. 6 and 7 are flowcharts showing an example of the initial calibration in FIG. 5. First, each communication circuit 10 determines whether its own device is a primary device (step S11). In this example, based on the value preset in each communication circuit 10, it is determined whether its own device is a primary device or a secondary device. When it is determined that its own device is a primary device, the transmission unit 20 starts transmitting a teacher signal (step S12). When it is determined that its own device is a secondary device, the reception unit 30 determines whether it has received the teacher signal (step S13).

[0047] In steps S20 and S24, the same determination as in step S11 is also made. In the following description, for ease of understanding, the flowcharts of FIGS. 6 and 7 are separated into the flowchart of FIG. 8 related to the primary device and the flowchart of FIG. 9 related to the secondary device. Also, the communication circuit 10A is used as the primary device, and the communication circuit 10B is used as the secondary device to continue the explanation.

[0048] (3) Primary device FIG. 8 is a flowchart showing an example of initial calibration related to the primary device. Specifically, FIG. 8 is a flowchart when the own device is determined to be the primary device in steps S11, S20, and S24 of FIGS. 6 and 7. In FIG. 8, the illustration of steps S11, S20, and S24 is omitted, and the illustration of steps S22 and S25 that are not executed in the primary device is also omitted.

[0049] As shown in FIG. 8, in the communication circuit 10A determined to be the primary device in step S11 of FIG. 6, the transmission unit 20A starts transmitting the teaching signal (step S12). Next, the reception unit 30A determines whether the teaching signal has been received (step S13). If the teaching signal is not received, the reception unit 30A waits until the teaching signal is received. In the communication circuit 10B, the teaching signal is received by executing step S22 of FIG. 9 described later.

[0050] When the teaching signal is received, the signal adjustment unit 32A determines whether the gain parameter and the frequency parameter are appropriate (step S14). If the gain parameter or the frequency parameter is not appropriate, the signal adjustment unit 32A adjusts the gain parameter or the frequency parameter (step S15). Thereafter, the process returns to step S13. Steps S13 to S15 are repeated until the gain parameter and the frequency parameter become appropriate.

[0051] The gain parameter and frequency parameter may be determined and adjusted one at a time. For example, in step S14, it may be determined whether the gain parameter is appropriate, and if it is not appropriate, the gain parameter may be adjusted in step S15. After the gain parameter is deemed appropriate, the same determination and adjustment may be performed on the frequency parameter in steps S14 and S15.

[0052] If the gain parameters and frequency parameters are appropriate, the reference equalization processing unit 50A equalizes the teacher signal received in step S13 (step S16). Next, the coefficient setting unit 70A calculates the filter coefficients of the output equalization processing unit 40A based on the error between the teacher signal equalized by the reference equalization processing unit 50A in step S16 and a known teacher signal (step S17). Subsequently, the coefficient setting unit 70A updates the filter coefficients set in the output equalization processing unit 40A with the filter coefficients calculated in step S17 (step S18).

[0053] Next, the coefficient setting unit 70A calculates the EVM value and determines whether the calculated EVM value is appropriate (step S19). If the EVM value is below a predetermined threshold, the EVM value is determined to be appropriate. If the EVM value is not appropriate, the process returns to step S13. Steps S13 to S19 are repeated until the EVM value becomes appropriate. If the EVM value is appropriate, the transmission unit 20A transmits a notification signal indicating that the initial calibration is complete (step S21).

[0054] Subsequently, the receiving unit 30A determines whether or not it has received a notification signal (step S23). If no notification signal is received, the receiving unit 30A waits until a notification signal is received. In the communication circuit 10B, the notification signal is received when step S25 in Figure 9, which will be described later, is executed. If a notification signal is received, the transmitting unit 20A stops transmitting the teacher signal (step S26). This completes the initial calibration of the primary device.

[0055] (4) Secondary device Figure 9 is a flowchart showing an example of initial calibration related to a secondary device. Specifically, Figure 9 is a flowchart showing the case when the device is determined to be a secondary device in steps S11, S20, and S24 of Figures 6 and 7. In Figure 9, steps S11, S20, and S24 are not shown, and steps S12 and S21, which are not performed in a secondary device, are not shown.

[0056] As shown in Figure 9, in the communication circuit 10B, which was determined to be a secondary device in step S11 of Figure 6, the receiving unit 30B determines whether or not it has received a teacher signal (step S13). If the teacher signal is not received, the receiving unit 30B waits until the teacher signal is received. In the communication circuit 10A, the teacher signal is received when step S12 of Figure 8 is executed.

[0057] When a teacher signal is received, steps S14 to S19 become executable in the communication circuit 10B. This allows the same initial calibration as in the communication circuit 10A to be performed in the communication circuit 10B. If the EVM value is appropriate in step S19, the transmitter 20B starts transmitting the teacher signal (step S22). Next, the receiver 30B determines whether or not a notification signal has been received (step S23). If no notification signal is received, the receiver 30B waits until a notification signal is received. In the communication circuit 10A, the notification signal is received when step S21 in Figure 8 is executed.

[0058] If a notification signal is received, the transmitter 20B transmits a notification signal indicating that the initial calibration is complete (step S25). Subsequently, the transmitter 20B stops transmitting the teacher signal (step S26). This completes the initial calibration of the secondary device.

[0059] (5) Periodic Calibration Figure 10 is a flowchart showing an example of periodic calibration in Figure 5. Once the initial calibration of communication circuits 10A and 10B is completed, the communication circuit 10 starts steady operation. During the steady operation period, communication signals are sent and received between communication circuits 10A and 10B. Periodic calibration is performed during the steady operation period of the communication circuit 10. Therefore, when periodic calibration is performed, communication circuit 10A appropriately transmits drive signals as communication signals to communication circuit 10B. Also, communication circuit 10B appropriately transmits status signals as communication signals to communication circuit 10A.

[0060] First, the receiving unit 30 determines whether or not it has received a communication signal that is transmitted as appropriate (step S31). If no communication signal is received, the receiving unit 30 waits until it receives a communication signal. If a communication signal is received, the output equalization processing unit 40 equalizes the communication signal received in step S31 (step S32). Next, the signal identification unit 33 synchronizes the communication signal that was equalized by the output equalization processing unit 40 in step S32 (step S33).

[0061] Next, the demodulation unit 34 demodulates the portion of the communication signal that includes the main data sequence identified by the synchronization process in step S33 (step S34). The communication signal demodulated in step S34 is decoded by the decoding unit 35 and output by the output I / F 36. Subsequently, the communication signal regeneration unit 60 performs a series of processes on the communication signal demodulated in step S34 to regenerate the communication signal that was equalized by the output equalization processing unit 40 in step S32 (step S35).

[0062] Furthermore, the reference equalization processing unit 50 buffers the communication signal received in step S31 for one frame (step S36). After that, the reference equalization processing unit 50 equalizes the communication signal buffered in step S35 (step S37). Steps S32 to S35 and steps S36 and S37 are executed in parallel. Here, in step S35, the communication signal has been buffered for one frame by the buffer circuit 61 of the communication signal regeneration unit 60, so the frame of the communication signal equalized in step S37 is the same as the frame of the communication signal regenerated in step S35.

[0063] Next, the coefficient setting unit 70 calculates the filter coefficients for the output equalization processing unit 40 based on the communication signal regenerated in step S35 and the communication signal equalized in step S37 (step S38). After that, the coefficient setting unit 70 determines whether or not noise has been mixed into the communication signal received in step S31 (step S39). In this example, if the maximum EVM value among the EVM values ​​calculated during the period of one frame exceeds the threshold, it is determined that noise has been mixed into the communication signal. If the maximum EVM value is below the threshold, it is determined that there is no noise mixed into the communication signal.

[0064] If it is determined that noise has been introduced into the communication signal, the process returns to step S31. As a result, the periodic calibration is repeated without updating the filter coefficient set in the output equalization processing unit 40. On the other hand, if it is determined that there is no noise introduced into the communication signal, the coefficient setting unit 70 updates the filter coefficient set in the output equalization processing unit 40 to the filter coefficient calculated in step S38 (step S40). After that, the process returns to step S31. As a result, the periodic calibration is repeated with the filter coefficient set in the output equalization processing unit 40 updated.

[0065] 5. Effects In the communication circuit 10 according to this embodiment, communication signals are transmitted and received between this circuit and other communication circuits 10 via the cable 310 during the steady-state operation period. The communication signals transmitted by other communication circuits 10 are equalized by the output equalization processing unit 40 based on a set equalization coefficient. The communication signals transmitted by other communication circuits 10 are equalized by the reference equalization processing unit 50.

[0066] Based on the communication signal equalized by the output equalization processing unit 40 and the communication signal equalized by the reference equalization processing unit 50, the coefficient setting unit 70 calculates the equalization coefficient. Furthermore, the equalization coefficient set in the output equalization processing unit 40 is updated to the calculated equalization coefficient. With this configuration, there is no need to send or receive a teacher signal for calculating the equalization coefficient during the steady-state operation period. This allows for equalization processing of communication signals while preventing an increase in latency.

[0067] Prior to the periodic calibration described above, an initial calibration is performed. Specifically, at startup prior to the steady-state operation period, a known teacher signal transmitted by another communication circuit 10 is equalized by the reference equalization processing unit 50. Based on the teacher signal equalized by the reference equalization processing unit 50 at startup, the equalization coefficient is calculated by the coefficient setting unit 70. The calculated equalization coefficient is then set in the output equalization processing unit 40.

[0068] In this case, during periodic calibration, the equalization coefficient set in the output equalization processing unit 40 at startup can be referenced to efficiently calculate the equalization coefficient during the steady-state operation period. Furthermore, during startup, when no communication signals are transmitted or received, sending and receiving a teacher signal to calculate the equalization coefficient does not increase latency. This prevents an increase in latency while enabling the output equalization processing unit 40 to perform equalization processing on the communication signal more efficiently.

[0069] In this case, if noise is suddenly introduced into the communication signal, the equalization coefficient may not be calculated correctly. Therefore, the amount of noise introduced into the communication signal transmitted by another communication circuit 10 is detected by the coefficient setting unit 70. If the detected amount of noise exceeds a predetermined threshold, the update of the equalization coefficient set in the output equalization processing unit 40 is suspended. This prevents the set equalization coefficient from being updated to an inappropriate equalization coefficient. The amount of noise introduced into the communication signal is detected based on the coordinates on the signal space diagram of the symbol corresponding to the communication signal transmitted by the other communication circuit 10. In this case, the amount of noise introduced into the communication signal can be easily detected.

[0070] Each of the communication modules 120 and 220 includes the communication circuit 10 described above. Therefore, the communication circuit 10 can be provided in any device including the control device 100 or the drive device 200. Furthermore, the communication circuit 10 can perform equalization processing on the communication signal while preventing an increase in latency.

[0071] Communication module 120 is connected to communication circuit 10 and further includes a filter unit 122 that separates communication signals and power from each other. Communication module 220 is connected to communication circuit 10 and further includes a filter unit 222 that separates communication signals and power from each other. In this case, the filter units 122 and 222 make it possible to separate communication signals and power from each other. Therefore, communication signals and power can be transmitted and received between communication module 120 and communication module 220 through a common cable 310.

[0072] The communication system 300 includes a control device 100 and a drive device 200. A communication module 120 of the control device 100 and a communication module 220 of the drive device 200 are connected by a cable 310. Communication signals are transmitted and received between the communication modules 120 and 220 through the cable 310. This allows each of the control device 100 and the drive device 200 to perform equalization processing on the communication signals while preventing an increase in latency.

[0073] 6. Other Embodiments (1) In the above embodiment, initial calibration is performed before periodic calibration is performed, but the embodiment is not limited thereto. Initial calibration does not have to be performed.

[0074] (2) In the above embodiment, it is determined whether or not noise has been introduced into the signal based on the EVM value, but the embodiment is not limited thereto. For example, it may be determined whether or not noise has been introduced into the signal based on fluctuations in the amplitude or frequency of the signal. Also, if the communication system 300 is used in an environment where the amount of noise introduced into the signal is small, it is not necessary to determine whether or not noise has been introduced into the signal. Furthermore, it is not necessary to postpone updating the filter coefficients.

[0075] (3) In the above embodiment, the cable 310 is a PLC (Power Line Communication) cable, and power is supplied from the control device 100 to the drive device 200 through the cable 310, but the embodiment is not limited to this. Power may be supplied to the drive device 200 without going through the cable 310. In this case, the communication module 120 does not need to be provided with a power supply unit 121 and a filter unit 122. Also, the communication module 220 does not need to be provided with a power receiving unit 221 and a filter unit 222.

[0076] (4) The functions of the elements disclosed above may be implemented using circuit configurations or processing circuit configurations, including general-purpose processors, dedicated processors, integrated circuits, ASICs (application-specific integrated circuits), conventional circuit configurations and / or combinations thereof, which are configured to perform the disclosed elements or programmed to perform the disclosed functions. A processor is considered a processing circuit configuration or circuit configuration if it includes transistors and other circuit configurations within it. In this disclosure, a circuit configuration, unit or means is hardware that performs the listed functions or hardware programmed to perform such functions. Hardware may be any hardware disclosed herein or other known hardware programmed to perform the listed functions or configured to perform such functions. When hardware is a processor which may be considered a type of circuit configuration, a circuit configuration, means or unit is a combination of hardware and software, software used to configure the hardware and / or processor.

[0077] 7. Correspondence between each component of the claim and each part of the embodiment The following describes examples of the correspondence between each component of the claim and each element of the embodiment, but the present invention is not limited to the following examples. Various other elements having the configuration or function described in the claim can also be used as each component of the claim.

[0078] In the above embodiment, cable 310 is an example of a cable, communication circuit 10 is an example of a communication circuit or a second communication circuit, output equalization processing unit 40 is an example of an output equalization processing unit or a second output equalization processing unit, reference equalization processing unit is an example of a reference equalization processing unit or a second reference equalization processing unit, and coefficient setting unit 70 is an example of a coefficient setting unit or a second coefficient setting unit.

[0079] Communication module 120 or communication module 220 is an example of a communication module or a second communication module, and filter unit 122 or filter unit 222 is an example of a filter unit. Control device 100 or drive device 200 is an example of a first device or a second device, and communication system 300 is an example of a communication system.

[0080] 8. Summary of Embodiments (Paragraph 1) The communication circuit according to Paragraph 1 is a communication circuit that transmits and receives communication signals to and from another device via a cable during a steady-state operation period, and comprises: an output equalization processing unit that equalizes the communication signal transmitted by the other device based on a set equalization coefficient; a reference equalization processing unit that equalizes the communication signal transmitted by the other device; and a coefficient setting unit that calculates an equalization coefficient based on the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit, and updates the equalization coefficient set in the output equalization processing unit to the calculated equalization coefficient.

[0081] In this communication circuit, during the steady-state operation period in which communication signals are sent and received with other devices, the equalization coefficient is calculated by the coefficient setting unit based on the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit. Therefore, there is no need to send and receive a teacher signal to calculate the equalization coefficient during the steady-state operation period. This prevents an increase in latency while enabling the output equalization processing to be performed on the communication signal.

[0082] (Paragraph 2) In the communication circuit described in Paragraph 1, the reference equalization processing unit may equalize a known teacher signal transmitted by the other device when it is started up before the steady-state operation period, and the coefficient setting unit may calculate an equalization coefficient based on the teacher signal that has been equalized by the reference equalization processing unit when it is started up, and set the calculated equalization coefficient in the output equalization processing unit.

[0083] In this case, the equalization coefficient is calculated based on the training signal during startup, prior to the steady-state operation period, and the calculated equalization coefficient is set in the output equalization processing unit. Therefore, by referring to the equalization coefficient set in the output equalization processing unit, it is possible to efficiently calculate the equalization coefficient during the steady-state operation period. Furthermore, during startup, when no communication signals are transmitted or received, sending and receiving training signals to calculate the equalization coefficient does not increase latency. This prevents an increase in latency while enabling more efficient equalization processing of communication signals by the output equalization processing unit.

[0084] (3) In the communication circuit described in either paragraph 1 or 2, the coefficient setting unit may detect the amount of noise mixed into the communication signal transmitted by the other device, and if the detected amount of noise exceeds a predetermined threshold, it may postpone updating the equalization coefficient set in the output equalization processing unit.

[0085] If noise is suddenly introduced into the communication signal, the equalization coefficient may not be calculated correctly. Even in such cases, this configuration allows the update of the equalization coefficient set in the output equalization processing unit to be withheld. This prevents the equalization coefficient set in the output equalization processing unit from being updated to an inappropriate equalization coefficient.

[0086] (Clause 4) In the communication circuit described in paragraph 3, the coefficient setting unit may detect the amount of noise mixed into the communication signal based on the coordinates on the signal space diagram of the symbol corresponding to the communication signal transmitted by the other device.

[0087] In this case, the amount of noise mixed into the communication signal can be easily detected.

[0088] (Paragraph 5) The communication module relating to Paragraph 5 includes the communication circuit described in any one of Paragraphs 1 to 4.

[0089] This communication module allows communication circuits to be installed in any device. Furthermore, the communication circuit can perform equalization processing on communication signals using an output equalization processing unit while preventing an increase in latency.

[0090] (Clause 6) The communication module described in paragraph 5 may further include a filter unit connected to the communication circuit for separating communication signals and power from each other.

[0091] In this case, the filter unit can separate the communication signal and the power. Therefore, the communication signal and power can be transmitted and received through a common cable.

[0092] (Paragraph 7) The communication system relating to Paragraph 7 comprises a cable, a first device provided with a communication module as described in Paragraph 5 or 6, and a second device provided with a second communication module that transmits and receives communication signals between the first device and the communication module via the cable.

[0093] In this communication system, communication signals are transmitted and received between the communication module of the first device and the second communication module of the second device via a cable. Since the first device is equipped with the above-mentioned communication module, it is possible to perform equalization processing on the communication signals by an output equalization processing unit while preventing an increase in latency.

[0094] (Clause 8) In the communication system described in paragraph 7, the second communication module may include a second communication circuit having: a second output equalization processing unit that equalizes a communication signal transmitted by the communication module based on a set equalization coefficient; a second reference equalization processing unit that equalizes a communication signal transmitted by the communication module; and a second coefficient setting unit that calculates an equalization coefficient based on the communication signal equalized by the second output equalization processing unit and the communication signal equalized by the second reference equalization processing unit, and updates the equalization coefficient set in the second output equalization processing unit to the calculated equalization coefficient.

[0095] In this case, the second device is also provided with a second communication module similar to the communication module described above, so that the communication signal can be equalized by the second output equalization processing unit while preventing an increase in latency.

[0096] (Paragraph 9) The communication method relating to Paragraph 9 is a communication method performed by a communication circuit that transmits and receives communication signals to and from another device through a cable during a steady-state operation period, and includes: equalizing the communication signal transmitted by the other device by an output equalization processing unit based on a set equalization coefficient; equalizing the communication signal transmitted by the other device by a reference equalization processing unit; calculating an equalization coefficient based on the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit; and updating the equalization coefficient set in the output equalization processing unit to the calculated equalization coefficient.

[0097] According to this communication method, during the steady-state operation period in which communication signals are sent and received between the communication circuit and other devices, the equalization coefficient is calculated based on the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit. Therefore, there is no need to send and receive a teacher signal to calculate the equalization coefficient during the steady-state operation period. This prevents an increase in latency while enabling the output equalization processing of the communication signal.

Claims

1. A communication circuit that transmits and receives communication signals to and from another device via a cable during a steady-state operation period, comprising: an output equalization processing unit that equalizes a communication signal transmitted by the other device based on a set equalization coefficient; a reference equalization processing unit that equalizes a communication signal transmitted by the other device; and a coefficient setting unit that calculates an equalization coefficient based on the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit, and updates the equalization coefficient set in the output equalization processing unit to the calculated equalization coefficient.

2. The communication circuit according to claim 1, wherein the reference equalization processing unit equalizes a known teacher signal transmitted by the other device at startup prior to the steady-state operation period, and the coefficient setting unit calculates an equalization coefficient based on the teacher signal equalized by the reference equalization processing unit at startup, and sets the calculated equalization coefficient in the output equalization processing unit.

3. The communication circuit according to claim 1 or 2, wherein the coefficient setting unit detects the amount of noise mixed into the communication signal transmitted by the other device, and if the detected amount of noise exceeds a predetermined threshold, it suspends updating the equalization coefficient set in the output equalization processing unit.

4. The communication circuit according to claim 3, wherein the coefficient setting unit detects the amount of noise mixed into the communication signal based on the coordinates on the signal space diagram of the symbol corresponding to the communication signal transmitted by the other device.

5. A communication module comprising the communication circuit described in claim 1 or 2.

6. The communication module according to claim 5, further comprising a filter unit connected to the communication circuit for separating communication signals and power from each other.

7. A communication system comprising a cable, a first device provided with the communication module described in claim 5, and a second device provided with a second communication module that transmits and receives communication signals between the first device and the communication module via the cable.

8. The communication system according to claim 7, wherein the second communication module includes a second output equalization processing unit that equalizes a communication signal transmitted by the communication module based on a set equalization coefficient, a second reference equalization processing unit that equalizes a communication signal transmitted by the communication module, and a second coefficient setting unit that calculates an equalization coefficient based on the communication signal equalized by the second output equalization processing unit and the communication signal equalized by the second reference equalization processing unit, and updates the equalization coefficient set in the second output equalization processing unit to the calculated equalization coefficient.

9. A communication method performed by a communication circuit that transmits and receives communication signals to and from another device via a cable during a steady-state operation period, comprising: equalizing a communication signal transmitted by the other device using an output equalization processing unit based on a set equalization coefficient; equalizing a communication signal transmitted by the other device using a reference equalization processing unit; calculating an equalization coefficient based on the communication signal equalized by the output equalization processing unit and the communication signal equalized by the reference equalization processing unit; and updating the equalization coefficient set in the output equalization processing unit to the calculated equalization coefficient.

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