JP4778463B2 - Modem equipment - Google Patents

Description

  The present invention relates to a modem device used for wired communication using a pair of wire lines. More specifically, the present invention relates to a transmission system circuit of a modem device, and differentially drives and transmits each of a pair of wire lines. The present invention relates to a modem device having a transmission output adjustment function for adjusting output characteristics of a differential transmission signal to be adapted to restrictions and restrictions on common mode current.

  Many wired communication systems using wire lines for transmitting and receiving information have been put into practical use and are still under development. Such a wired communication system, for example, a telephone subscriber line defined by ITU g992.1, a home network using a power line defined by HomePlug-AV specification 1.1.00 (December 16, 2005), etc. In order to establish communication between two modem devices, differential transmission is usually performed using a pair of wire lines. In differential transmission, a pair of wire lines is usually driven separately by two signals with inverted phases, that is, signals with the sum of the signal outputs of both signals being zero. Differential transmission has several advantages over transmission schemes that use a single wire line. One of them is that when the wire line has ideal line characteristics, almost no radiant energy is generated. However, the actual line characteristics are never ideal, and the line impedance changes for each line pair. Also, the hardware of the modem device is not ideal as well as the wire line. A common mode current is generated on the communication line due to imperfections in hardware of the modem device and fluctuations in line characteristics. The leaked radio wave intensity due to the common mode current depends on the line characteristics of the pair of wire lines and the transmitted differential transmission signal power. In general, since the influence of parasitic components such as a small capacitance becomes significant as the frequency increases, the importance of the common mode current signal increases with the frequency.

  The energy of leaked radio waves radiated by the common mode current is a harmful signal to radio equipment such as radio receivers and is potentially harmful. Interference in the operating frequency band increases, causing a reduction in the function of the system. In order to cope with fluctuations in line impedance, it is possible to reduce the leaked radio wave intensity due to a certain common mode current by adapting impedance in the AFE (Analog Front End) of the modem device (first conventional technique, for example, , See Patent Document 1 below). However, since a recent system uses a relatively wide frequency band extending to several tens of MHz, accurate impedance matching in a wide band is difficult and the cost is high. Furthermore, the line characteristics can potentially be very wide, and such an impedance matching system must also be able to handle very diverse environments.

  In order to control and regulate the impact on other equipment of the transmitter, the supervisory body typically regulates the differential transmit signal power that can be transmitted, typically by defining a power mask to be adapted. In addition, there are cases where there are specific restrictions on the level of the common mode current generated from the wired communication modem device (see, for example, a report on high-speed power line carrier communication, December 2005). As a technique for satisfying these regulations, conventionally, a method of attenuating the differential transmission signal power has been used in consideration of the relative line impedance as a relative disadvantage (second method). Conventional technology).

  Further, a power line carrier communication device that measures the common mode current of the power line and controls the output of the power line communication signal superimposed on the power line according to the magnitude of the common mode current is disclosed (third prior art, for example, , See Patent Document 2 below).

US Pat. No. 6,724,890 JP 2006-203481 A

  However, when the differential transmission signal power is attenuated by the second prior art technique, system performance such as bit rate and communication distance is degraded. However, in most cases, the actual transmission line characteristics have characteristics that are significantly more advantageous than the standards considered, so that the differential transmission signal can be output with higher power without exceeding the regulation value of the common mode current. It was done. That is, as a result, better communication quality, for example, a higher bit rate and a longer communication distance have been obtained. In addition, in the wideband transmission method, the leakage wave intensity of the common mode current is usually frequency-dependent, and the frequency that makes the line impedance most unfavorable is used as a reference. Therefore, only the gain control of the transmission signal power is insufficient. . Therefore, compared to the above conventional method, if the differential transmission signal power is controlled based on the leakage radio wave intensity actually radiated from the communication line, the transmission output can be further secured, and the system performance is optimized while satisfying the regulations. There is room for it.

  Hereinafter, the common mode current in the differential transmission signal will be described more specifically. As shown in FIG. 6, in differential transmission, a driving circuit of a transmission system circuit of a modem device differentially drives a pair of wire lines with two signals determined to be signal positive, and signals are transmitted. The Here, the common mode current ic is expressed as a vector sum of currents i1 and i2 on a pair of wire lines forming a differential pair. As shown in FIG. 6A, when a pair of wire lines have ideal line characteristics, the first current i1 flowing out on one (first line) of the pair of wire lines and the other (first) Since the absolute values of the second currents i2 flowing in the two lines) are equal, the vector sum of the currents i1 and i2, that is, the common mode current ic is zero. However, when a pair of wire lines have practical line characteristics, as shown in FIG. 6B, the vector sum of the currents i1 and i2 does not become zero, and a common mode current ic is generated. The magnitude of the generated common mode current ic is determined depending on the power of the differential transmission signal transmitted to the pair of wire lines as well as the hardware of the modem device and the line characteristics of the pair of wire lines. In a broadband system, the common mode current generally has frequency dependence and tends to increase as the frequency increases.

  If the supervisory authority sets restrictions on the common mode current that can be generated by the system, the transmitter of the modem device must be within the allowable range of the common mode current over the full range of expected operating conditions before shipping to the factory. The adjustment is made so that the worst case is assumed. If there is a possibility that an adaptive system such as an impedance matching circuit exists, it contributes to the reduction of the common mode current generated when trying to reduce the common mode current achievable with the device in one adjustment procedure. . However, the power of the differential transmission signal that is actually used is almost always lower than the power that can be used to accurately achieve the regulation value of the common mode current in the entire frequency band of the signal.

  FIG. 5 shows an example in which the allowable value of the common mode current (indicated by a broken line in the figure) is defined depending on the frequency corresponding to the restriction value to be considered. If there is a frequency range (see arrows 500, 502, and 504) where the measured value of the common mode current (indicated by the solid line in the figure) exceeds the allowable value of the common mode current in the initial state, the differential transmission signal The power must be reduced so that the common mode current is within an acceptable range over the entire frequency range. However, in the example shown in FIG. 5, the measured value of the common mode current is less than the allowable value in most frequency ranges in the initial state, and only exceeds the allowable value in a small frequency range. .

  By reducing the transmission power of the differential transmission signal, the signal level is lowered on the reception side. The decrease in the received signal level results in a deterioration in communication quality or reliability in a non-adaptive system, and in an adaptive system such as DSL (data communication system for digital subscribers), a decrease in bit rate or a predetermined bit rate. The communication distance is shortened. To ensure system performance, power suppression of the differential transmission signal over the entire frequency should be avoided, and in general, the transmission power of the differential transmission signal is maximum under all conditions to be considered. Must be adjusted to be.

  Further, as shown in FIG. 7, the third prior art power line carrier communication device (modem device) is provided between the external device 40 and the power line 39, and transmits and receives power line communication signals using the power line 39 as a medium. The modem device 30 includes a signal / power source coupling circuit 34 for inputting / outputting a power line communication signal to / from the power line 39, and a power source circuit 35 for operating the modem device 30 by the electric power extracted from the signal / power source coupling circuit 34. A modulation circuit 31 that modulates transmission data passed from the external device 40 into a power line communication signal; a demodulation circuit 32 that demodulates the power line communication signal received via the power line 39 and passes it to the external device 40 as received data; The common mode current measuring device 36 that measures the current value Ic of the common mode current flowing through the power line 39, and the measured current value Ic of the common mode current An A / D conversion circuit 37 for converting to a digital current value Id; an output control circuit 38 for controlling the output of the modulation circuit 31 to be a predetermined value based on the current value measured by the common mode current measuring device 36; , And is configured. With such a configuration, the current value of the common mode current of the power line 39 is measured and fed back so that the output of the modulation circuit 31 becomes a predetermined value, so that the output of the modem device 30 is automatically generated by the change of the common mode current. Is adjusted so that the magnitude of the leakage electric field does not exceed the set value. However, in the configuration shown in FIG. 7, a receiving circuit such as an A / D conversion circuit 37 for appropriately processing the current value of the common mode current measured by the common mode current measuring device 3 so that it can be processed by the output control circuit 38. In addition, a dedicated output control circuit 38 is required separately. Although not disclosed in detail in Patent Document 2, in order to appropriately process the common mode current so that it can be processed by the output control circuit 38, in addition to the A / D conversion circuit 37, a fast Fourier transform or the like is used. Signal conversion processing from the time domain to the frequency domain is also required. Further, the common mode current needs to be monitored over the entire frequency band of the differential signal transmitted or received by the modem device 30, and the performance of the receiving circuit such as the separately provided A / D conversion circuit 37 is determined by the modem device. 30 is required to be equivalent to a differential signal receiving circuit (demodulation circuit 32) related to original transmission / reception. Therefore, the provision of these processing devices separately causes a rise in the manufacturing cost of the entire modem device.

  The present invention has been made in view of the above problems, and an object of the present invention is to satisfy the regulations on the common mode current and maintain the high communication quality, and output characteristics of the differential transmission signal transmitted from the modem device. Is to provide a modem device that can be adjusted at low cost.

In order to achieve the above object, a modem device according to the present invention is a modem device that performs wired communication using a pair of wire lines, which modulates digital data by a predetermined digital modulation method and converts it into an analog signal. A transmission system circuit that differentially drives and transmits each of the pair of wire lines as a first differential transmission signal and a second difference transmitted from the other modem device to the pair of wire lines. A differential signal is detected after a dynamic transmission signal is converted into a digital signal and demodulated by a demodulation method corresponding to the digital modulation method to reproduce digital data, and from the transmission system circuit to the pair of wire lines Common mode current detection means for detecting a common mode current of the transmitted differential transmission signal; and the second differential transmission signal received at the input terminal of the reception system circuit and the common mode. Input switching means for switching the detection output of the current detection means and inputting it to a circuit downstream from the input end of the reception system circuit, and the differential to the pair of wire lines with respect to the transmission system circuit Transmitting a transmission signal, switching the input of the input switching means to the detection output of the common mode current detection means, and so that one or more characteristic values of the common mode current are within a predetermined specified range, A control circuit that adjusts output characteristics of the first differential transmission signal that is differentially driven by the transmission system circuit according to the detection output of the common mode current detection means processed by the reception system circuit. This is the first feature.

  According to the modem device of the first feature, the output characteristics of the differential transmission signal transmitted from the transmission system circuit of the modem device can be adjusted according to the detection output of the common mode current detection means. Since the output characteristics (for example, transmission power) of the differential transmission signal can be adjusted so that the common mode current generated in the pair of wire lines does not exceed the specified value, the signal strength of the differential transmission signal is not unnecessarily decreased. Therefore, the communication quality such as the bit rate and the communication distance can be optimized within a range satisfying the restriction on the common mode current.

  Due to the randomness of the line characteristics of a pair of wire lines, it is not realistic to predict the common mode current and adjust the transmission power of the differential transmission signal. By measuring the mode current, a precise common mode current can be evaluated, and the output characteristics of the differential transmission signal can be optimally adjusted. Also, by directly measuring the common mode current, the line characteristics such as the impedance of the wire line and the line characteristics such as the balance between the lines are not directly considered in the adjustment process of the transmission power of the differential transmission signal. The combined effect of the modem device hardware characteristics will be evaluated by the common mode current.

  Furthermore, signal processing such as amplification processing and analog / digital conversion can be performed on the detection output, which is an analog value of the common mode current detection means, using a receiving system circuit used in normal operation. As such, a processor or the like that can process a normal digital signal input incorporated in the modem device can be used.

  In other words, when the communication method used in the modem device is a communication method capable of transmitting and receiving data in the same frequency band, such as a time division multiplexing method, the common system current detection is performed on the receiving circuit of the modem device. In the transmission output adjustment circuit, a circuit necessary for processing of the detection signal of the common mode current detection means is inherently provided in the modem device because it can be used to acquire and process the detection signal of the means. The circuit configuration can be simplified.

  In the modem device according to the present invention, in addition to the first feature, the differential transmission signal is a signal obtained by differentially driving a multicarrier-modulated signal. A common mode current of the differential transmission signal is detected for each frequency of a carrier wave used for multicarrier modulation, and the control circuit has a predetermined rule in which the characteristic value of the common mode current is set for each frequency for each frequency. A second feature is that output characteristics of the differential transmission signal transmitted from the transmission system circuit are adjusted in accordance with a detection output of the common mode current detection means so as to fall within a range.

  According to the modem device of the second feature, in the multi-carrier modulation method, which is a broadband transmission method, when the line characteristic has frequency dependency, or the common mode current is regulated by frequency (or by frequency band). In this case, the output characteristics (for example, transmission power) of the differential transmission signal can be adjusted for each frequency within a range satisfying the restriction on the common mode current, so that the communication quality can be further optimized and improved.

  In the case of a multicarrier communication system such as OFDM, the transmission power of the differential transmission signal can be finely adjusted by controlling the frequency for each carrier, and the common mode current depends on the transmission power of the differential transmission signal. Therefore, as with the adjustment of the transmission power of the differential transmission signal, the frequency can be adjusted so as to be within a specified range for each frequency.

  In the modem device according to the present invention, in addition to the first or second feature described above, the control circuit further processes the detection output of the common mode current detection unit, and outputs the differential transmission signal output characteristics. A third feature is that a microprocessor for predicting the adjustment amount is provided.

  According to the modem device of the third feature, it is possible to realize an adjustable forward control system for the output characteristics of the differential transmission signal based on the predicted adjustment value, and the operation according to the first or second feature configuration. An effect can be specifically produced.

  In addition to any of the above features, the modem device according to the present invention further includes a first process in which the control circuit derives at least one characteristic value based on a detection output of the common mode current detection unit. A second process for comparing the derived characteristic value derived in the first process with a reference value of the characteristic value; and if the derived characteristic value is equal to or less than the reference value and within a predetermined range of the reference value, If the output characteristic of the differential transmission signal is not controlled and the derived characteristic value is outside the predetermined range of the reference value, the transmission power of the differential transmission signal is set when the derived characteristic value is greater than the reference value. Performing a third process for performing at least one of a process for reducing and a process for increasing the transmission power of the differential transmission signal when the derived characteristic value is smaller than the reference value. Features.

  In the modem device according to the present invention, in addition to the fourth feature described above, the control circuit further sets the transmission power of the differential transmission signal to a predetermined low level, and sets the output characteristics of the differential transmission signal. The fifth feature is that control is started, control is performed to gradually increase the transmission power of the differential transmission signal in the third process, and the derived characteristic value is maintained below the reference value during the control period. To do.

  In the modem device according to the present invention, in addition to the fourth feature described above, the control circuit further sets the transmission power of the differential transmission signal to a predetermined reference level and sets the output characteristics of the differential transmission signal. Control is started, and only when the derived characteristic value is larger than the reference value, a process of reducing the transmission power of the differential transmission signal is performed until the derived characteristic value becomes equal to or less than the reference value. It is characterized by.

  In addition to any of the above features, the modem device according to the present invention further includes a pseudo-differential dedicated for adjustment that does not induce reception by another modem device with respect to the transmission system circuit. Transmitting the transmission signal randomly so that one or more predetermined statistical values of the pseudo differential transmission signal approximate the predetermined statistical value in a normal data signal transmitted and received between the modem devices The seventh feature is to perform the control.

  In the modem device according to the present invention, in addition to any one of the above features, the one or more characteristic values of the common mode current may be an average value, a peak value, a quasi-peak value of the common mode current, and The eighth characteristic is that it is at least one of the other statistical values.

  According to the modem device having any one of the fourth to eighth characteristics, the output characteristics of the differential transmission signal for each frequency within a range satisfying the restriction on the common mode current, in the entire frequency band or for each frequency. (For example, transmission power) can be adjusted.

  In particular, according to the modem device having the seventh feature, unnecessary interference with other modem devices connected on the same wire line 7 can be prevented by adjusting the output characteristics of the differential transmission signal.

  In addition to any one of the above characteristics, the modem device according to the present invention has the predetermined prescribed range set for a plurality of the characteristic values of the common mode current, and one of the characteristic values However, when the degree of suppression by the specified range is larger than the other characteristic value, the control circuit detects the common mode current detecting unit so that one characteristic value having the large degree of suppression is within the specified range. Adjusting the output characteristics of the differential transmission signal transmitted from the transmission system circuit in accordance with the detected output of the transmission system circuit so that all the characteristic values are individually within the specified range. Features.

  According to the modem device of the ninth feature, when a predetermined specified range is set for each of a plurality of characteristic values of the common mode current, all the characteristic values are within individual specified ranges. Adjustment of the output characteristics of the differential transmission signal can be easily performed so as to fit.

  In addition to any one of the above features, the modem device according to the present invention further includes, after initial adjustment of an output characteristic of the first differential transmission signal, the control circuit, the receiving system circuit being the second differential signal. When the transmission signal is not received, the input of the input switching unit is set so that the reception system circuit can process the detection output of the common mode current detection unit and monitor the variation of the characteristic value of the common mode current. A tenth feature is to perform control to switch to the detection output of the common mode current detection means.

  In addition to the tenth feature, the modem device according to the present invention further includes, after initial adjustment of an output characteristic of the first differential transmission signal, detecting a change in the characteristic value of the common mode current, An eleventh feature is that the control circuit performs control to transmit a message related to readjustment of the output characteristic of the differential transmission signal to another modem device.

  According to the modem device of the tenth or eleventh feature, even if the characteristic value of the common mode current fluctuates after the initial adjustment of the output characteristic of the first differential transmission signal, the fluctuation is suppressed and the regulation range is suppressed. The output characteristics of the first differential transmission signal can be readjusted so as to be within the range. In particular, according to the modem device of the fourth feature, the other modem device of the communication partner can confirm in advance that the output characteristics of the first differential transmission signal are readjusted. Cutting can be avoided.

  In addition to any of the above-described features, the modem device according to the present invention further includes the reception system circuit when the control circuit switches the input of the input switching unit to the detection output of the common mode current detection unit. The characteristic or gain of at least a part of the circuit parts or circuit elements constituting the predetermined value is set to a predetermined value, and the output characteristic of the first differential transmission signal is set in consideration of the characteristic or gain set to the predetermined value. Adjustment is the twelfth feature.

  According to the modem device of the twelfth feature, the output characteristics of the first differential transmission signal can be accurately adjusted in consideration of the characteristics of the reception system circuit used for signal processing of the detection output of the common mode current detection means. .

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a modem device according to the present invention (hereinafter simply referred to as “the present device” as appropriate) will be described below with reference to the drawings. In the following embodiments, the present invention apparatus will be described on the assumption that a multicarrier communication system such as Orthogonal Frequency Division Multiplexing (OFDM) is used as the communication system to be used. The communication method is not limited to a multicarrier communication method such as OFDM.

  FIG. 1 schematically shows a schematic system configuration of the device of the present invention. The device of the present invention shown in FIG. 1 includes a transmission system circuit 1, a reception system circuit 2, a microcontroller 3 as a control circuit, a differential signal coupling device 4, a common mode current detection means 5, and an input switching means 6. Composed. The transmission system circuit 1 and the reception system circuit 2 are a transmission system circuit and a reception system circuit 2 of a general modem device that performs data transmission / reception in a broadband multicarrier communication system.

  The transmission system circuit 1 is a circuit that converts an OFDM signal obtained by OFDM-modulating the digital data Din into an analog signal and differentially drives a pair of wire lines 7 to transmit the signal to the preceding digital signal processing region. It includes an IFFT circuit unit 11 that performs fast Fourier transform processing (IFFT), an intermediate processing unit 12 that performs intermediate processing such as cyclic prefix addition processing, and a DA converter 13 that performs digital / analog conversion processing. The analog signal processing area includes an amplifier 14 and a drive circuit 15 that generates and drives a differential transmission signal based on an output signal from the amplifier 14. The OFDM modulation processing is realized by intermediate processing such as IFFT processing and cyclic prefix addition processing. The differential transmission signal differentially driven by the drive circuit 15 is transmitted to the pair of wire lines 7 via the differential signal coupling device 4.

  In contrast to the transmission system circuit 1, the reception system circuit 2 amplifies and filters the differential reception signal received from the pair of wire lines 7 via the differential signal coupling device 4, and converts it into a digital signal. A circuit that reproduces the digital data Dout of the transmission source by performing OFDM demodulation, and includes an amplifier 21, a filter circuit 22, and an AD converter 23 that performs analog-digital conversion processing in the analog signal processing area of the previous stage, and the digital of the subsequent stage The signal processing area includes an intermediate processing unit 24 that performs intermediate processing such as cyclic prefix removal processing and an FFT circuit unit 25 that performs fast Fourier transformation (FFT). The OFDM demodulation processing is realized by intermediate processing such as cyclic prefix removal processing and FFT processing.

  In the transmission operation, the microcontroller 3 performs predetermined processing required for the input digital data Din in accordance with a communication method such as encoding and loading, and the processed digital data is transferred to the IFFT circuit unit. 11 and receives the digital data after OFDM demodulation from the FFT circuit unit 25 in the reception operation, and performs a predetermined process opposite to the transmission operation.

  The differential signal coupling device 4 is commonly used in the transmission operation and the reception operation of the device of the present invention. In the transmission operation, the differential transmission signal differentially driven by the drive circuit 15 is coupled to a pair of wire lines 7. In a receiving operation, a circuit that couples a differential signal on a pair of wire lines 7 to an input of an amplifier 21 of the receiving system circuit 2 as an input terminal of the receiving system circuit 2, and a conventional wired modem device such as a transformer The ones used in are available.

  The common mode current detection means 5 is provided on a pair of wire lines 7, and its detection output can be input to the amplifier 21 of the reception system circuit 2 via the input switching means 6. The detection output is output as a pair of differential signals in the same manner as the output from the differential signal coupling device 4 so that it can be processed by the amplifier 21 of the reception system circuit 2. As long as the common mode current detection means 5 is a physical device capable of detecting the common mode current generated on the pair of wire lines 7, the current detection principle and structure are not limited. For example, a pair of current probes that detect each current on the pair of wire lines 7 using a transformer, a coil, or the like can be used.

  The input switching means 6 selects either the differential reception signal output from the differential signal coupling device 4 or the differential signal output from the common mode current detection means 5 by switching control from the microcontroller 3. The switch circuit is input to the amplifier 21.

  The microcontroller 3 further controls the transmission system circuit 1 and the reception system circuit 2 in a normal transmission / reception operation. In the operation for adjusting the output characteristics of a differential transmission signal, which will be described later, the input of the input switching means 6 is The control to switch to the detection output from the common mode current detection means 5 is performed, and the reception system circuit 2 can appropriately process the detection output of the common mode current detection means 5 for some circuits of the reception system circuit 2. Perform additional control to

  Depending on the characteristics of the common mode current detection means 5 used in the adjustment operation of the output characteristics of the differential transmission signal, the signal amplitude and power (average value, peak value) of the detection output (differential signal) can be changed in the normal reception operation. There is a possibility that the differential reception signal input to the amplifier 21 is greatly different. For example, the signal amplitude of the detection output (differential signal) may be large, and conversely, the differential reception signal on the wire line 7 received via the differential signal coupling device 4 may be greatly attenuated. If the additional control is not performed on the amplifier 21, the detection output of the common mode current detection means 5 may be saturated at the subsequent stage of the amplifier 21. When it takes time to adjust the additional control or the like for the amplifier 21, for example, the input of the input switching means 6 is detected from the detection output from the common mode current detection means 5 and the differential signal in the normal reception operation. When the control for switching between them is performed relatively quickly and the adjustment time for the additional control is too long for the switching control time of the input switching means 6 to be accepted, the output characteristics of the differential transmission signal The adjustment operation is not sufficient. Further, in order to compensate the influence of the detection output on the amplifier 21 and the filter circuit 22 of the reception system circuit 2 so that the detection output of the common mode current detection means 5 can be processed by the microcontroller 3, the control on each circuit is performed. Is required.

  In this embodiment, the detection output of the common mode current detection means 5 is input to the microcontroller 3 built in the device of the present invention via the input switching means 6 and the receiving system circuit 2 built in the device of the present invention. It is the composition which becomes.

  Hereinafter, by using the device of the present invention, an output from the transmission system circuit 1 is made so that a common mode current generated in a modem device of a multicarrier communication system such as OFDM falls within a specified range determined by a supervisory organization, for example. A procedure for adjusting the output characteristics of the differential transmission signal will be described.

  First, as a general flow, when the apparatus of the present invention is started, the apparatus of the present invention is self-contained so as to satisfy the regulation value of the common mode current determined for the frequency band used at the place of use of the apparatus of the present invention. The output characteristic (output power) of the differential transmission signal (first differential transmission signal) transmitted from the transmission system circuit 1 is adjusted. As the adjustment procedure, there may be several methods depending on the regulation contents and the communication method. Once the initial adjustment is completed, actual data transmission / reception in accordance with the communication protocol to be used is started as usual using a differential transmission signal having an output characteristic adjusted by the adjustment procedure.

  Next, an example of the adjustment procedure in the multicarrier communication system will be described with reference to FIG. Here, assuming that each carrier has moderate linearity, each step of the adjustment procedure shown below is executed independently for each carrier. In addition, when each carrier does not maintain the linearity appropriately, the following procedure is developed and applied.

  As a first step, a differential transmission signal is output from the transmission system circuit 1 to the pair of wire lines 7 via the differential signal coupling device 4 based on an arbitrarily set initial characteristic (# 100). At the same time, the microcontroller 3 controls the input switching means 6 to set the detection output of the common mode current detection means 5 to be input to the reception system circuit 2, and the reception system circuit 2 processes the detection output, A common mode current generated on the pair of wire lines 7 is estimated (# 102). The estimation of the common mode current is based on the detection output of the common mode current detection means 5 based on the detection circuit of a predetermined circuit of the reception system circuit 2 which is set to be able to extract the detection output with high reliability by the control from the microcontroller 3. It is executed in consideration of characteristics or gain. The control of the reception system circuit 2 by the microcontroller 3 includes extraction of the circuit state of each circuit of the reception system circuit 2. In the process of estimating the common mode current, other characteristic values such as an average value, a peak value, a quasi-peak value, and other statistical values of the common mode current are extracted in accordance with the target regulation content. Calculation processing is included.

  Next, the microcontroller 3 compares the estimated value of the common mode current (corresponding to the derived characteristic value) with the maximum allowable value (corresponding to the reference value) (# 104). Here, when the estimated value of the common mode current exceeds the allowable range (maximum allowable value) of the common mode current (YES branch of # 104), the microcontroller 3 Control to reduce the transmission output of the differential transmission signal is performed (# 106). Here, as a method of determining the amount of decrease in the transmission output of the differential transmission signal, several methods are conceivable depending on conditions such as the subject regulation content and possible design options. If the estimated value of the common mode current is equal to or less than the maximum allowable value of the common mode current (# 104 NO branch), the transmission output of the differential transmission signal may be further increased. Therefore, if it is determined in step # 104 that the estimated value of the common mode current is less than or equal to the maximum allowable value, it is determined whether the estimated value of the common mode current is considerably lower than the maximum allowable value. 2 is determined (# 108). Here, when the difference between the estimated value of the common mode current and the maximum allowable value is equal to or smaller than the predetermined value (NO branch of # 108), the series of adjustment processing is ended (# 112). In the second determination, a margin for the estimation error of the common mode current is given by providing the predetermined value. When the difference between the estimated value of the common mode current and the maximum allowable value exceeds the predetermined value in the second determination (YES branch of # 108), the microcontroller 3 makes a difference with respect to the transmission system circuit 1. Control to increase the transmission output of the dynamic transmission signal is performed (# 110). Here, as a method of determining the increase amount of the transmission output of the differential transmission signal, several methods are conceivable depending on conditions such as the target regulation contents and possible design options. The predetermined value used for the second determination is a design parameter. The above steps # 102 to # 110 are repeated until a series of adjustment processing ends (# 112).

  The adjustment procedure illustrated in FIG. 2 is obvious when, for example, individual regulation ranges to be satisfied simultaneously are defined for a plurality of characteristic values such as an average value and a peak value of a common mode current. Can be easily extended with changes. Furthermore, as described above, various different methods are possible as methods for determining the amount of decrease or increase in the transmission output of the differential transmission signal in steps # 106 and # 110 of the adjustment procedure illustrated in FIG.

  In one embodiment of the adjustment procedure illustrated in FIG. 2, in the first step (# 100), very low power is used as the power of the differential transmission signal to be output first in the entire frequency band of the differential transmission signal. Then, through steps # 102, # 104, # 108, and # 110, until the second determination (# 108) determines that the difference between the estimated common mode current value and the maximum allowable value is equal to or less than a predetermined value. Gradually increase the power of the differential transmission signal. Here, the increase amount of the transmission output of the differential transmission signal in step # 110 is decreased as the estimated value of the common mode current approaches the maximum allowable value. With such a procedure, the estimated value of the common mode current is always maintained below the maximum allowable value. In this embodiment, step # 106 is not executed.

  In another embodiment of the adjustment procedure illustrated in FIG. 2, in steps # 106 and # 110, in order to quickly converge the processing procedure, respective initial values of the decrease amount and increase amount of the transmission output of the differential transmission signal are set. Set larger. In the second and subsequent steps # 106 and # 110, the decrease amount and the increase amount are reduced in order to finely adjust the transmission output of the differential transmission signal.

  In still another embodiment of the adjustment procedure illustrated in FIG. 2, in the first step (# 100), the restriction applied simultaneously as the power of the differential transmission signal to be output first in all frequency bands of the differential transmission signal. The maximum allowable value (corresponding to the reference level) of the differential transmission signal defined in the contents is used. The second determination (# 108) is invalidated to intentionally end the adjustment procedure. That is, if the estimated value of the common mode current is equal to or less than the maximum allowable value of the common mode current in the first determination (# 104), the series of adjustment processing is terminated (# 112). In the present embodiment, when the estimated value of the common mode current exceeds the allowable range (maximum allowable value) of the common mode current in the first determination (# 104) (YES branch of # 104), The microcontroller 3 controls the transmission system circuit 1 to reduce the transmission output of the differential transmission signal (# 106), and steps # 102, # 104, and # 106 are the first determination (# 104). This is repeated until the estimated value of the common mode current is equal to or less than the maximum allowable value of the common mode current. By the adjustment procedure, when the differential transmission signal itself is regulated, it is possible to prevent the output characteristics of the differential transmission signal from exceeding the regulation value.

  In still another embodiment of the adjustment procedure illustrated in FIG. 2, in the first step (# 100), when the first differential transmission signal is output and step # 106 or # 110 is reached, the microcontroller 3 is based on the assumption that the common mode current changes in proportion to the transmission power of the differential transmission signal, and uses the estimated value of the common mode current and the transmission power of the first differential transmission signal to perform differential transmission. The amount of decrease or increase in signal transmission output is estimated, and the transmission power of the differential transmission signal is adjusted based on the estimated amount of decrease or increase. According to the processing procedure, either one of the transmission power adjustment steps of steps # 106 and # 110 is executed only once and is not repeated, so that the processing time of the adjustment processing can be greatly shortened.

  From the above exemplary embodiments, many other embodiments can be derived to suit a particular situation, design needs, etc. Next, a simplified embodiment where a plurality of restrictions are applied to both the common mode current and the transmission output of the differential transmission signal will be described in detail with reference to FIG. In the present embodiment, description will be made assuming that the common mode current is regulated by both the average value and the peak value, and the differential transmission signal is regulated by the average power.

  As a first step, a differential transmission signal initially set to a minute power so that all the regulation values are satisfied is transferred from the transmission system circuit 1 to the pair of wire lines 7 via the differential signal coupling device 4. Output (# 200). Here, the power increase parameter (power increase rate or power increase amount) α of the differential transmission signal is set to a predetermined initial value.

  At the same time, the microcontroller 3 controls the input switching means 6 to set the detection output of the common mode current detection means 5 to be input to the reception system circuit 2, and the reception system circuit 2 processes the detection output, The average value and peak value of the common mode current generated on the pair of wire lines 7 are estimated (# 202). Next, the microcontroller 3 compares the estimated values (average value and peak value) of the common mode current with respective maximum allowable values (# 204). Here, when all the estimated values (average value and peak value) of the common mode current are not more than the corresponding maximum allowable values (NO branch of # 204), each estimated value of the common mode current is individually A second determination is made as to whether or not the maximum allowable value is considerably below (# 208). Here, when any one of the differences between the estimated values (average value, peak value) of the common mode current and the corresponding maximum allowable value is equal to or smaller than a predetermined value (NO branch of # 208), a series of adjustment processes Is finished (# 218). In the second determination, when the difference between each estimated value (average value, peak value) of the common mode current and the corresponding maximum allowable value exceeds both predetermined values (YES branch of # 208), When the transmission power of the differential transmission signal is increased with the power increase parameter α, a third determination is made as to whether the average power does not exceed the maximum allowable value (# 210). If the average power does not exceed the maximum allowable value in the third determination (# 210 YES branch), the transmission power of the differential transmission signal is increased by the current power increase parameter α (# 212). If the average power exceeds the maximum allowable value in the third determination, that is, if the power increase parameter α is too large (NO branch of # 210), the power increase parameter α is decreased (# 214) and decreased. A fourth determination is made as to whether or not the increased power increase parameter α is smaller than the lower limit αmin of the increased power parameter α (# 216). In the fourth determination, if the decreased power increase parameter α is smaller than the predetermined lower limit αmin (# 216 YES branch), it is determined that the transmission power of the differential transmission signal cannot be increased, and a series of adjustments are performed. The process ends (# 218). In the fourth determination, when the decreased power increase parameter α is equal to or greater than the lower limit αmin (NO branch of # 216), the process returns to step # 210 and the third determination is performed again.

  Here, at the passing point (# 220) between step # 204 and step # 208 in the processing procedure illustrated in FIG. 3, all the regulation values for both the common mode current and the transmission output of the differential transmission signal are satisfied. It is noted that. If the first determination is positive, that is, if the estimated value (average value, peak value) of at least one of the common mode currents is larger than the corresponding maximum allowable value (YES branch of # 204), differential The transmission output of the transmission signal is increased too much, and the estimated value of the common mode current exceeds the maximum allowable value. In this embodiment, in order to correct the situation, the transmission output of the differential transmission signal is reduced by a reduction amount corresponding to half of the power increase parameter α, that is, the transmission output of the differential transmission signal before the power increase and At the same time, the power increase parameter α is set to half (# 206). Then, it returns to step # 202 and repeats the process after step # 202. As a result, the transmission output of the differential transmission signal is suppressed so that the plurality of estimated values of the common mode current satisfy the corresponding maximum allowable values. In the first determination (# 204), when one characteristic value of the plurality of characteristic values of the common mode current has a greater degree of suppression by the maximum allowable value (specified range) than the other characteristic values, that is, the maximum When the excess degree with respect to the allowable value is large, as a result, the transmission output of the differential transmission signal is suppressed so that the characteristic value with the large degree of suppression (excess degree) satisfies the maximum allowable value.

  FIG. 4 schematically shows the power spectrum density (PSD) of the differential transmission signal before and after adjustment of the transmission output of the differential transmission signal by the adjustment procedure illustrated in FIG. 2 or FIG. . In the illustration of FIG. 4, the PSD before adjustment is flat within the operating frequency band (Fmin to Fmax). As shown in FIG. 4, by adjusting the transmission output of the differential transmission signal, the transmission output of the differential transmission signal increases in one frequency range (400, 402), and in another frequency range (404, 406), The transmission output of the differential transmission signal is reduced. Corresponding to the adjustment of the transmission output of the differential transmission signal shown in FIG. 4, as schematically shown in FIG. 5, the common mode current (indicated by a dotted line in the figure) is an allowable value of the common mode current (dashed line in the figure). Will be satisfied in all frequency bands.

  Although the present invention apparatus has been described in detail above, it should be noted that the reception system circuit 2 of the present invention apparatus has the power or power spectral density of the transmission output of the differential transmission signal in the transmission system circuit 1 of the present invention apparatus. It is not adversely affected by the adjustment. This is because, from the reception system circuit 2, the characteristic change of the differential transmission signal is seen as a random influence of the communication line (for example, frequency selective attenuation of the signal level on the wire line 7). That is, once the power or power spectral density of the transmission output of the differential transmission signal is adjusted, the transmission system circuit 1 can start normal data transmission. In the apparatus of the present invention, the reception system circuit 2 does not include adjustments as to the transmission system circuit 1, so that the adjustment method and adjustment performance in the apparatus of the present invention are not affected by the reception system circuit 2. Therefore, in the transmission system circuit of another device of the present invention connected on the common wire line 7, when the power or power spectral density of the transmission output of the differential transmission signal is adjusted and optimized, normal reception is performed. In operation, the reception system circuit of each modem device can receive a higher-quality differential reception signal, and, for example, communication quality such as bit rate can be improved.

  Hereinafter, another embodiment of the present invention will be described.

  <1> In the above embodiment, when adjusting the transmission output of the differential transmission signal, the differential transmission signal output on the pair of wire lines 7 is limited for signal attributes other than the output characteristics. However, it is also preferable to use a pseudo differential transmission signal dedicated for adjustment that is not received by another modem device connected on the same wire line 7. By using the pseudo differential transmission signal dedicated to the adjustment, while the device of the present invention is adjusting the transmission output of the differential transmission signal, another modem device transmits the differential transmission signal transmitted from the device of the present invention. By receiving this, it is possible to prevent the initialization process and waste of trying to establish a communication connection with the device of the present invention.

  Furthermore, when the apparatus of the present invention is started, a long adjustment period can be set for the initial adjustment of the transmission output of the differential transmission signal. When the device of the present invention on the pair of wire lines 7 adjusts the transmission output of the differential transmission signal during the adjustment period, the reception system circuit 2 inputs the detection output of the common mode current detection means 5 However, since the differential signal from the other modem device is not received, the other modem device on the pair of wire lines 7 tries to establish communication connection with the device of the present invention which is being initially adjusted. However, the device of the present invention does not receive the packet data for establishing the communication connection. Therefore, during the adjustment period, it is preferable that the device of the present invention uses a pseudo differential transmission signal dedicated for adjustment that cannot be misread by other modem devices attempting communication connection.

  However, the pseudo differential transmission signal dedicated for adjustment needs to match the characteristic value of the protocol signal corresponding to the regulation to be considered. For example, the above condition is important when characteristic values such as peak value and quasi-peak value are regulated. Since the characteristic value directly depends on the signal attribute such as the modulation method, the characteristics of the pseudo differential transmission signal dedicated for adjustment must be carefully designed so that the characteristic value of the protocol signal can be simulated. I must. Specifically, one or a plurality of predetermined statistical values of the pseudo differential transmission signal dedicated for adjustment are approximated to the predetermined statistical values in a normal differential transmission signal transmitted and received between modem devices. The pseudo differential transmission signal dedicated for adjustment is randomly transmitted.

  <2> Further, as a preferable application example of the device of the present invention, a plurality of the devices of the present invention connected on the common wire line 7 may be independently connected at the start-up or before the start of normal operation. Even when there is no data to be transmitted, the power or power spectral density of the transmission output of the differential transmission signal is adjusted. Furthermore, since the preferred adjustment procedure is a single-ended type that does not communicate with other modem devices as described in <1> above, the adjustment operation can be quickly started at the time of startup.

  <3> The common mode current characteristics may change over time. For example, while a gradual characteristic fluctuation occurs due to a temperature fluctuation in the transmission system circuit 1 of the present invention device, for example, a new device is connected to the wire line 7 or an existing device connected to the wire line 7. A sudden characteristic change occurs due to a change in the configuration of the wire line 7 accompanied by a change in the line impedance due to the removal of the wire.

  In the embodiment described above, the adjustment of the power or power spectral density of the transmission output of the differential transmission signal has been described on the assumption that it is performed once at the time of start-up or before the start of normal operation. In order to keep the common mode current within the regulated range by appropriately responding to fluctuations in the mode current characteristics, the characteristic fluctuations are monitored and the power or power spectral density of the differential transmission signal is adjusted in a timely manner. Is also a preferred embodiment.

  In this case, in the device of the present invention, when the normal reception operation of the reception system circuit 2 is stopped, the microcontroller 3 controls the input switching unit 6 to output the detection output of the common mode current detection unit 5 to the reception system circuit 2. The reception system circuit 2 processes the detection output, determines whether there is a change in the common mode current characteristic based on the estimated value of the common mode current, and re-adjusts based on the determination result Is required, the transmission output of the differential transmission signal is readjusted as described above.

  Although it depends on the characteristics of the communication method used, the schedule for monitoring the fluctuation of the common mode current characteristics can be set sufficiently. For example, in the case of the time division multiplexing method, even when the transmission system circuit 1 transmits data, it is possible to always monitor the variation of the common mode current characteristic. In other communication methods, various methods can be used for detection of the timing of fluctuation monitoring without affecting the schedule of fluctuation monitoring or normal reception operation.

  Here, it should be noted that the fluctuation monitoring of the common mode current characteristic is different from the adjustment of the transmission output of the differential transmission signal, and is not a differential transmission signal dedicated for adjustment but a differential transmission signal used for actual data transmission. It can be executed using.

  Furthermore, before starting the readjustment of the transmission output of the differential transmission signal, the adjustment of the transmission output of the differential transmission signal is started with respect to another modem device connected to the common wire line 7. It is also a preferred embodiment to control to send higher protocol level messages. Thereby, when readjustment of the transmission output of a differential transmission signal is requested | required, it can prevent that the communication connection between other modem apparatuses is cut | disconnected. As a last resort, the present invention device can independently readjust the transmission output of the differential transmission signal by cutting off the communication connection and efficiently re-initializing the communication connection of the modem devices on both sides. Yes.

  INDUSTRIAL APPLICABILITY The present invention can be used for a wired communication modem device. In particular, the output characteristics of a differential transmission signal transmitted by differential driving with respect to each of a pair of wire lines by a transmission system circuit of the modem device are common. The present invention is useful for a wired communication modem apparatus that can be adjusted so as to adapt to regulations and restrictions on mode current.

1 is a block diagram schematically showing a schematic system configuration in an embodiment of a modem device according to the present invention. The flowchart which shows an example of the adjustment procedure of the output characteristic of the differential transmission signal in one Embodiment of the modem apparatus which concerns on this invention The flowchart which shows another example of the adjustment procedure of the output characteristic of the differential transmission signal in one Embodiment of the modem apparatus which concerns on this invention. The figure which shows typically the comparison of the power spectrum density of the differential transmission signal before and after the output characteristic adjustment of the differential transmission signal by this invention The figure which shows typically the comparison of the initial state of common mode current, an allowable value, and the state after the output characteristic adjustment of the differential transmission signal by this invention The common mode current induced on a pair of wire lines that are differentially driven from the transmission system circuit of the wired communication modem device is compared between the case where the line characteristics are ideal (A) and the case where it is practical (B). Figure to explain A block diagram schematically showing an example of a schematic system configuration of a conventional modem device

Explanation of symbols

1: Transmission system circuit 2: Reception system circuit 3: Microcontroller (control circuit)
4: Differential signal coupling device 5: Common mode current detection means 6: Input switching means 7: A pair of wire lines 11: IFFT circuit section (inverse fast Fourier transform processing circuit section)
12: Intermediate processing part (cyclic prefix addition processing, etc.)
13: DA converter 14: Amplifier 15: Drive circuit 21: Amplifier 22: Filter circuit 23: AD converter 24: Intermediate processing section (cyclic prefix removal processing)
25: FFT circuit (fast Fourier transform processing circuit)

Claims (14)

A modem device that performs wired communication using a pair of wire lines,
A transmission system circuit that modulates digital data by a predetermined digital modulation method, converts the digital data into an analog signal, and differentially drives and transmits each of the pair of wire lines as a first differential transmission signal;
The second differential transmission signal transmitted from the other modem device to the pair of wire lines is differentially detected, converted to a digital signal, and demodulated by a demodulation method corresponding to the digital modulation method to reproduce the digital data. Receiving system circuit,
Common mode current detection means for detecting a common mode current of the differential transmission signal transmitted from the transmission system circuit to the pair of wire lines;
Input switching means for switching between the second differential transmission signal received at the input terminal of the reception system circuit and the detection output of the common mode current detection means and inputting the signal to a circuit subsequent to the input terminal of the reception system circuit When,
The transmission circuit is caused to transmit the differential transmission signal to the pair of wire lines, the input of the input switching unit is switched to the detection output of the common mode current detection unit, and the common mode Differentially driven by the transmission system circuit according to the detection output of the common mode current detection means processed by the reception system circuit so that one or more characteristic values of the current fall within a predetermined specified range. Ri Na and and a control circuit for adjusting the output characteristics of the first differential transmission signal,
Wherein the control circuit processes the detection output of the common mode current detection means, the modem apparatus according to claim Rukoto a microprocessor for predicting the amount of adjustment for the output characteristics of the differential transmission signal. The control circuit transmits a pseudo-differential transmission signal dedicated for adjustment that does not induce reception by another modem device to the transmission system circuit, and one or a plurality of predetermined pseudo-differential transmission signals. 2. The modem apparatus according to claim 1, wherein control is performed so that a statistical value is randomly transmitted so as to approximate the predetermined statistical value in a normal data signal transmitted and received between the modem apparatuses. A modem device that performs wired communication using a pair of wire lines,
A transmission system circuit that modulates digital data by a predetermined digital modulation method, converts the digital data into an analog signal, and differentially drives and transmits each of the pair of wire lines as a first differential transmission signal;
The second differential transmission signal transmitted from the other modem device to the pair of wire lines is differentially detected, converted to a digital signal, and demodulated by a demodulation method corresponding to the digital modulation method to reproduce the digital data. Receiving system circuit,
Common mode current detection means for detecting a common mode current of the differential transmission signal transmitted from the transmission system circuit to the pair of wire lines;
Input switching means for switching between the second differential transmission signal received at the input terminal of the reception system circuit and the detection output of the common mode current detection means and inputting the signal to a circuit subsequent to the input terminal of the reception system circuit When,
The transmission circuit is caused to transmit the differential transmission signal to the pair of wire lines, the input of the input switching unit is switched to the detection output of the common mode current detection unit, and the common mode Differentially driven by the transmission system circuit according to the detection output of the common mode current detection means processed by the reception system circuit so that one or more characteristic values of the current fall within a predetermined specified range. Ri Na and and a control circuit for adjusting the output characteristics of the first differential transmission signal,
The control circuit transmits a pseudo-differential transmission signal dedicated for adjustment that does not induce reception by another modem device to the transmission system circuit, and one or a plurality of predetermined pseudo-differential transmission signals. A modem device, characterized in that control is performed to randomly transmit a statistical value so as to approximate the predetermined statistical value in a normal data signal transmitted and received between the modem devices. The predetermined specified range is set for a plurality of the characteristic values of the common mode current, and one of the characteristic values has a greater degree of suppression by the specified range than the other characteristic values. In this case, the control circuit transmits the difference transmitted from the transmission system circuit in accordance with a detection output of the common mode current detection means so that the one characteristic value having a large degree of suppression falls within the specified range. to adjust the output characteristic of the dynamic transmission signal, the modem apparatus according to any one of claim 1 to 3, characterized in that all the characteristic values to fit within an individual of the specified range in each different. A modem device that performs wired communication using a pair of wire lines,
A transmission system circuit that modulates digital data by a predetermined digital modulation method, converts the digital data into an analog signal, and differentially drives and transmits each of the pair of wire lines as a first differential transmission signal;
The second differential transmission signal transmitted from the other modem device to the pair of wire lines is differentially detected, converted to a digital signal, and demodulated by a demodulation method corresponding to the digital modulation method to reproduce the digital data. Receiving system circuit,
Common mode current detection means for detecting a common mode current of the differential transmission signal transmitted from the transmission system circuit to the pair of wire lines;
Input switching means for switching between the second differential transmission signal received at the input terminal of the reception system circuit and the detection output of the common mode current detection means and inputting the signal to a circuit subsequent to the input terminal of the reception system circuit When,
The transmission circuit is caused to transmit the differential transmission signal to the pair of wire lines, the input of the input switching unit is switched to the detection output of the common mode current detection unit, and the common mode Differentially driven by the transmission system circuit according to the detection output of the common mode current detection means processed by the reception system circuit so that one or more characteristic values of the current fall within a predetermined specified range. Ri Na and and a control circuit for adjusting the output characteristics of the first differential transmission signal,
The predetermined specified range is set for a plurality of the characteristic values of the common mode current, and one of the characteristic values has a greater degree of suppression by the specified range than the other characteristic values. In this case, the control circuit transmits the difference transmitted from the transmission system circuit in accordance with a detection output of the common mode current detection means so that the one characteristic value having a large degree of suppression falls within the specified range. to adjust the output characteristic of the dynamic transmission signal, the modem apparatus all characteristic values, wherein to Rukoto to fit within each of the specified range in each different. When the control circuit switches the input of the input switching means to the detection output of the common mode current detection means, the characteristics or gains of at least some circuit parts or circuit elements constituting the reception system circuit are predetermined. set to a value, taking into account the characteristics or gain is set to the predetermined value, to any one of claim 1 to 5, characterized in that to adjust the output characteristic of the first differential transmission signal The modem device described. A modem device that performs wired communication using a pair of wire lines,
A transmission system circuit that modulates digital data by a predetermined digital modulation method, converts the digital data into an analog signal, and differentially drives and transmits each of the pair of wire lines as a first differential transmission signal;
The second differential transmission signal transmitted from the other modem device to the pair of wire lines is differentially detected, converted to a digital signal, and demodulated by a demodulation method corresponding to the digital modulation method to reproduce the digital data. Receiving system circuit,
Common mode current detection means for detecting a common mode current of the differential transmission signal transmitted from the transmission system circuit to the pair of wire lines;
Input switching means for switching between the second differential transmission signal received at the input terminal of the reception system circuit and the detection output of the common mode current detection means and inputting the signal to a circuit subsequent to the input terminal of the reception system circuit When,
The transmission circuit is caused to transmit the differential transmission signal to the pair of wire lines, the input of the input switching unit is switched to the detection output of the common mode current detection unit, and the common mode Differentially driven by the transmission system circuit according to the detection output of the common mode current detection means processed by the reception system circuit so that one or more characteristic values of the current fall within a predetermined specified range. Ri Na and and a control circuit for adjusting the output characteristics of the first differential transmission signal,
When the control circuit switches the input of the input switching means to the detection output of the common mode current detection means, the characteristics or gains of at least some circuit parts or circuit elements constituting the reception system circuit are predetermined. modem apparatus set to a value, taking into account the characteristics or gain is set to the predetermined value, characterized that you adjust the output characteristic of the first differential transmission signal. The differential transmission signal is a signal obtained by differentially driving a multi-carrier modulated signal,
The common mode current detection means detects the common mode current of the differential transmission signal for each frequency of the carrier used for the multicarrier modulation,
In accordance with the detection output of the common mode current detection means, the transmission system is configured so that the characteristic value of the common mode current falls within a predetermined specified range set for each frequency. the modem apparatus according to any one of claims 1-7, characterized in that to adjust the output characteristic of the differential transmission signal transmitted from the circuit. The control circuit comprises:
A first process for deriving at least one characteristic value based on a detection output of the common mode current detection means;
A second process for comparing the derived characteristic value derived in the first process with a reference value of the characteristic value;
If the derived characteristic value is equal to or less than the reference value and within the predetermined range of the reference value, the output characteristic of the differential transmission signal is not controlled, and if the derived characteristic value is outside the predetermined range of the reference value The process of reducing the transmission power of the differential transmission signal when the derived characteristic value is larger than the reference value, and the transmission power of the differential transmission signal when the derived characteristic value is smaller than the reference value A third process for executing at least one of the processes;
The modem apparatus according to any one of claims 1-8, characterized in that the run. The control circuit sets the transmission power of the differential transmission signal to a predetermined low level and starts controlling the output characteristics of the differential transmission signal. In the third process, the transmission power of the differential transmission signal is reduced. The modem apparatus according to claim 9 , wherein control is performed to gradually increase, and the derived characteristic value is maintained below the reference value during a control period. The control circuit starts the control of the output characteristics of the differential transmission signal by setting the transmission power of the differential transmission signal to a predetermined reference level, and only when the derived characteristic value is larger than the reference value, The modem device according to claim 9 , wherein a process of reducing transmission power of the differential transmission signal is performed until the derived characteristic value becomes equal to or less than the reference value. The one or more characteristic values of the common mode current are at least one of an average value, a peak value, a quasi-peak value, and other statistical values of the common mode current. The modem device according to any one of claims 1 to 11 . After the initial adjustment of the output characteristics of the first differential transmission signal, when the control circuit does not receive the second differential transmission signal, the reception circuit detects the common mode current detection means. The control of switching the input of the input switching means to the detection output of the common mode current detecting means is performed so that the fluctuation of the characteristic value of the common mode current can be monitored by processing the detected output of the common mode current. Item 15. The modem device according to any one of Items 1 to 12 . After the initial adjustment of the output characteristic of the first differential transmission signal, when detecting a change in the characteristic value of the common mode current, the control circuit sends a message regarding readjustment of the output characteristic of the differential transmission signal. the modem apparatus according to claim 1 3, characterized in that performing control of transmitting to another modem device.

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