JP3131857B2 - Pseudo communication network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simulated communication network for measuring an interference wave appearing at a terminal connecting a communication line of a communication device and evaluating whether or not the interference affects other devices. is there.

[0002]

2. Description of the Related Art There is a problem that unnecessary radio waves generated from a device having a digital signal processing circuit inside a personal computer or the like interfere with a radio receiver or the like. For this reason, unnecessary radio waves radiated from these devices themselves and interference voltage generated at the power line terminals of the devices are in a direction of being internationally regulated (for example, IEC / CISPR Pub. 2).
2).

[0003] Of course, the communication device is also subject to the above-mentioned regulation, but the communication device has a terminal connected to a communication line (hereinafter referred to as a communication line terminal) in addition to a power line terminal. For this reason, it is necessary to regulate the communication line terminal disturbance voltage in addition to the radiation disturbance electric field strength and the power supply line terminal disturbance voltage.

In order to measure the communication line terminal interference wave voltage, it is reasonable to connect a circuit simulating the communication line connected to the communication line terminal of the apparatus (pseudo communication network) to perform the measurement. In some countries, a pseudo communication network is used to measure the disturbance voltage at the communication line terminal of an analog communication device such as a facsimile (for example, West Germany).

[0005] On the other hand, with the advance of communication technology, a number of devices having a communication line for extension communication, such as a key telephone device and a multifunctional home telephone, have been introduced into business establishments and general homes. Most of these communication lines for extension communication use communication cables of four or more lines, and the necessity of measuring a communication line terminal interference voltage of a device connected to such a communication line increases. I have.

Therefore, a pseudo communication network for four wires and eight wires has been proposed (for example, Japanese Patent Application No. Hei.
0).

FIG. 12 shows an example of a pseudo communication network. In FIG. 12, reference numeral 1 denotes a device to be measured, 2 denotes a measuring device of an interference wave voltage, 3 denotes a conventionally proposed 4-wire pseudo communication network,
Is a current probe for measuring an interference wave current, 5 is an auxiliary device for bringing a device under test into an operating state, 6 is a DC cut capacitor, 7 is a terminal impedance between a core wire and ground, and 8 is a common mode choke. is there.

[0008]

[Table 1]

Table 1 shows conditions required for the pseudo communication network. In Table 1, the common mode insertion loss is a condition for preventing an interference wave generated by the auxiliary device of the communication device from affecting the measurement, and is a common mode interference wave propagating from the auxiliary device 5 to the device under test 1. Is the insertion loss of the quasi-communication network. The unbalanced attenuation indicates the magnitude of the signal voltage converted to the common mode, and the ratio between the level of the interference wave to be measured and the signal voltage must be larger than this value. The common mode impedance indicates the impedance when the communication line side is viewed from the communication line terminal of the device under test, and needs to be a constant value in order to enhance the reproducibility of measurement. The signal propagation loss is a condition necessary to keep the device under test in an operating state. For an analog communication device, a value of the characteristic impedance of the line of 600Ω is used, and for a digital communication device, a value of the characteristic impedance of the line of 100Ω is used.

Next, the operation of the pseudo communication network shown in FIG. 12 will be described below. (1) A direct current for supplying power to the communication device is applied to the communication line. The capacitor 6 is a capacitor for cutting this DC component. (2) The pseudo communication network must simulate a communication line. The impedance 7 simulates the input impedance between the core of the communication line and the ground. (3) The simulated communication network must be able to separate interference waves from communication lines. For this reason, the common mode choke 8 prevents a common mode disturbance wave propagating through the communication line from entering the disturbance wave voltage measuring device 2.

The simulated communication network shown in FIG. 12 can measure an interference wave radiated through a communication line from a communication device having four communication line terminals, but has the following disadvantages. (1) Since a plurality of large-diameter ferrite cores are used for the common mode choke coil 8, the pseudo communication network becomes large. (2) The connection is inconvenient because the input terminal does not match the shape of the connector normally used in the communication device. (3) Since the current probe is used for measuring the interference wave, the measurement level fluctuates depending on the arrangement of the coaxial cable of the current probe and the position of the cable in the current probe, and the measurement accuracy deteriorates. (4) Since the current probe is used, the measurement level is low and accurate measurement cannot be performed. (5) Since the current probe is required separately from the pseudo communication network, it is expensive.

[0012]

SUMMARY OF THE INVENTION The present invention solves these problems and can accurately measure a communication line terminal interference wave of a communication device having four or more communication line terminals. An object of the present invention is to provide an easy-to-use pseudo communication network.

[0013]

SUMMARY OF THE INVENTION A feature of the present invention is that the communication device and the communication device are connected to each other in order to measure an interference wave radiated through the communication line from the communication device using the balanced line as the communication line. In a pseudo communication network inserted into the communication line for connecting an auxiliary device to be operated, a terminal for connecting to the communication device, and a first equal-valued first terminal connected to one end of each core wire of the terminal. A series circuit of impedance and a first capacitance, a second impedance provided between a common connection point at the other end of the series circuit and a ground point, and a choke coil provided between the terminal and the auxiliary device. The choke coil is a common mode choke coil having little loss for a communication signal and a large loss for an interference wave appearing between the communication line and the ground. The choke coil has a terminal for connecting to an auxiliary device in an integrated configuration, and the first capacitance is a reference value of a transmission condition of a signal used for communication and a reference value of an impedance between a core wire of a pseudo communication network and a ground. And a simulated communication network for evaluating an interference wave appearing between the communication line terminal of the communication device and the ground by measuring the voltage across the second impedance.

[0014]

FIG. 1 shows the basic configuration of the present invention. FIG.
3a is a simulated communication network according to the present invention, 9 is a terminal for connecting to a device under test, 10 is a terminal for connecting to an auxiliary device, 11 is an impedance 8 between a core wire and ground for measuring current. 12 is an impedance for matching with the input impedance of the disturbance wave measuring device 3, and 13 is a core material having a smaller magnetic permeability than the core material used for the common mode choke coil 8. Auxiliary common mode choke used, 1
Reference numeral 4 denotes a capacitor inserted between the core wire and the ground.

Next, the operation of the pseudo communication network of the present invention will be described.

A conventional pseudo communication network uses a banana plug or the like for a terminal connected to a device under test. However, most communication devices now use modular sockets. Therefore, in the present invention, a modular socket having terminals for connecting to the device under test and terminals for connecting to the auxiliary device is used. With such a structure, it is possible to easily connect to the device to be measured and the auxiliary device, and measurement efficiency is increased. Further, since it is not necessary to insert a conversion connector or the like between the device under test and the pseudo communication network, measurement accuracy can be improved.

Further, in the conventional pseudo communication network, since the common mode choke is a combination of a plurality of toroidal cores having a diameter of about 25 mm, the common mode choke becomes large.
The pseudo communication network was large. In the present invention,
The size of the pseudo communication network is reduced by using a small choke coil.

FIG. 2 shows a common mode choke coil used in the present invention. In FIG. 2, 15 is a core obtained by combining one E-shaped core 15 'and another E-shaped core 15 ", 16 is a winding, 17 is a modular socket, and 18 is a module for connecting the modular socket to a printed circuit board. The feature of this common mode choke coil is that in the conventional toroidal core, the winding had to be wound directly around the core, but in the present invention, one E-shaped core and another E-shaped core are combined. Since the core is used, the winding can be wound on a bobbin or the like in advance and then assembled, so that cost can be reduced for mass production.
It is easy to reduce the size. Furthermore, since the two windings constituting the communication path are brought close to each other and used as a logarithmic bundle required for communication, the unbalanced attenuation required for communication can be easily obtained.

FIG. 3 shows the unbalanced attenuation when the two windings are aligned and the unbalanced attenuation when the pseudo winding is not aligned. As shown in the figure, the unbalanced attenuation can be improved by at least 20 dB by bringing the windings close to each other. By using such a common mode choke coil, the volume can be reduced to one tenth or less as compared with a pseudo communication network conventionally used.

Since the common mode choke coil shown in FIG. 2 is small, the electrostatic coupling between the input side and the output side is large, and at around 30 MHz, the insertion loss with respect to the common mode interference wave decreases. Therefore, in the present invention, the auxiliary common mode choke coil 13 is inserted between the common mode choke coil and the input terminal 9. The common mode choke coil 13 is a common mode choke coil 1
In order to improve the insertion loss in the high frequency band of No. 5, the permeability of the core is made smaller than that of the core of the common mode choke coil 15 and the number of windings is reduced. Therefore, the auxiliary common mode choke coil 13 can be made small, and has little effect on increasing the volume of the pseudo communication network.

The auxiliary common mode choke coil 1
In order to increase the effect of 3, it is effective to insert a capacitor 14 on the auxiliary device side of the auxiliary common mode choke coil 13 to lower the impedance between the communication line and the ground for high frequencies. FIG. 4 shows the structure of the capacitor. 4, reference numeral 19 denotes a printed circuit board on which a pseudo communication network is formed, reference numeral 20 denotes a ground plane formed on the back side of the printed circuit board 19, reference numeral 21 denotes a communication line formed on the surface of the printed circuit board, and reference numeral 22 denotes a width of the line. This is the part that is widened to increase the capacitance with the ground plane. As shown in the figure, the capacitor 14 is realized by increasing the capacitance of the communication line with the ground plane by increasing the width of the communication line. In order to increase the amount of unbalanced attenuation of the communication line, it is necessary to adjust the capacitance between each line and the ground so that they have the same value. By doing so, the shape of the print pattern can be made the same. This makes it very precisely possible to make this capacity the same value. Further, by using glass epoxy or the like having a good frequency characteristic as a material of the printed circuit board, a capacitor having a good frequency characteristic can be realized.

FIG. 5 shows the insertion loss of the pseudo communication network when the auxiliary common mode choke coil 13 and the capacitor 14 are used. As shown in FIG. 5, the insertion loss is 30 MHz.
z can be improved by 20 dB or more.

In the conventional pseudo communication network, the interference wave of the device under test is measured using a current probe. Therefore,
The operator had to purchase a current probe in addition to the pseudo communication network, which was economically burdensome. In addition, the measurement value of the current probe is easily affected by the arrangement of the coaxial cable connected to the current probe and the position of the communication line passing through the current probe, resulting in poor measurement accuracy. Therefore,
In the present invention, the ground side of the impedance 8 constituting the common mode impedance is bundled together, the impedance 11 is inserted between the bundled connection portion and the ground, and the voltage appearing at both ends is measured, so that the disturbance wave current is measured. Is measured. In FIG. 1, the impedance 12 is for matching with the input impedance of the measuring instrument 2. By adopting such a structure, Z _A (impedance 7), Z _B (impedance 11), Z _D (impedance 12 ), The relations of equations (1) and (2) hold. _{Z A = N * (Z C} -Z B) (1) Z D = Z IN -Z B (2)

In the equations (1) and (2), Z _C is the impedance between the core of the pseudo communication network and the ground (common mode impedance), and Z _IN is the input impedance of the measuring instrument 3. The value of Z _B following Z _C is less than one tenth of (150 ohms) 15 [Omega] is a measure.

With such a structure, an expensive current probe is not required. In addition, since the outer conductor of the coaxial cable is directly connected to the casing of the pseudo communication network,
The influence of the arrangement method of the coaxial cable can be reduced. Also,
The problem of the position of the communication line in the current probe, which is a problem in the case of the current probe, is also eliminated, and economical and accurate measurement can be performed.

[0026]

【Example】

Embodiment 1 FIG. 6 shows a first embodiment of a pseudo communication network according to the present invention. In FIG. 6, 3b is a simulated communication network according to the present invention, 6 is a DC cut capacitor, 7 is a terminal impedance between the core and the ground, and 11 is an impedance between the core and the ground 8 for measuring current between the ground and the ground. The inserted impedance 12 is an impedance for matching with the input impedance of the measuring device 3 for the interference wave.

In FIG. 6, the value of the DC cut capacitor needs to be determined so as not to affect the common mode impedance and the insertion loss shown in Table 1.
It is given by (3) and (4). ΔZ _C > | (R _A + 1 / (j2πf _C C _A )) / N | −Z _C (3) α <20 * log ₁₀ | 1 + Z ₀ / (N * (R _A + 1 / (j2πf _D C _A ))) ) | (4) In the equations (3) and (4), _RA is the value of the impedance 7 and is represented by a resistance in the present embodiment. C _A is a DC cut capacitor, ΔZ _C is a permissible deviation of the common mode impedance, and is a value shown in Table 1 (20Ω in this embodiment).

F _C is a frequency at which the influence of the capacitor on the standard of the common mode impedance is the largest, and in the case of this embodiment, as shown in Table 1, the common mode impedance is defined in the range of 0.15 to 30 MHz. , The lowest 0.15 MHz. F _D is the frequency at which the value of the capacitor has the greatest effect on the insertion loss. When the characteristic impedance of the line is 600Ω, the frequency wave number range is 10 kHz or less according to Table 1, so the highest 10 kHz is adopted. I do. Incidentally, the larger the characteristic impedance Z _0, a large effect of C _A. In addition, the insertion loss α is 2 dB from Table 1 when the characteristic impedance is 600Ω, so this value was used.

Capacitor C _A obtained using equations (3) and (4)
Fig. 7 shows the relationship between impedance, common mode impedance, and insertion loss.
Shown in In the figure, N is the number of core wires, and the hatched straight line is the reference value of the common mode impedance deviation and the insertion loss described in Table 1. From the figure, when the value of the capacitor is reduced, the reference value of the insertion loss is satisfied, but the reference value of the impedance is not satisfied.When the value of the capacitor is increased, the reference value of the impedance is satisfied, but the reference value of the insertion loss is It is no longer satisfied, and it can be seen that there is an optimum capacitor value range. It can also be seen that as the number of cores increases, the allowable range of capacitor values increases. From the figure, even in the case of 2W, which is the most severe condition,
It can be seen that if the value of the capacitor is 10 nF or more and 50 nF or less, the condition of the insertion loss and the condition of the common mode impedance can be satisfied simultaneously. In this embodiment, C _A
Was used as 33 nF. Table 2 shows the characteristic evaluation results of this example. Table 2 shows that the present embodiment satisfies the conditions shown in Table 1 and required for the pseudo communication network.

[0030]

[Table 2]

FIGS. 8 and 10 show examples of measurement of an interference wave appearing at a communication line terminal of a communication device, measured using the present embodiment. FIG. 8 shows the result of measurement using the current probe, and FIG. 9 shows the result of measurement using this embodiment. As shown in the figure, by using this embodiment, it is possible to obtain the same result as the measurement result using the current probe which is standardized by the International Organization for Standardization. In addition, comparing FIGS. 8 and 9, the measurement limit of the interference wave (the lower line in the figure) is smaller in the case of the present embodiment, and is higher in the present embodiment than in the case of using the current probe. Disturbance can be measured with sensitivity.

[0032]

Embodiment 2 FIG. 10 shows a second embodiment of the present invention. As shown in the figure, by preparing a DC cut capacitor and the number of core wires that require the impedance R _A and determining the value of R _A using the equation (1), communication of not only 2W and 4W but also an arbitrary logarithm is performed. A pseudo communication network corresponding to the line can be easily realized.

[0033]

Embodiment 3 FIG. 11 shows a third embodiment of the present invention. In FIG. 11, reference numeral 23 denotes an input impedance of a measuring instrument for measuring an interference wave. As shown in the figure, the input impedance of a measuring instrument for measuring an interfering wave can be used as the impedance 8 between the core wire and the ground for measuring the current and the impedance inserted between the ground.

[0034]

As described above, according to the present invention, a small, economical and highly sensitive pseudo communication network can be provided, so that the effect is very large.

[Brief description of the drawings]

FIG. 1 shows a basic configuration of the present invention.

FIG. 2 shows the structure of a common mode choke coil used in the present invention.

FIG. 3 shows an unbalanced attenuation amount when two windings are aligned with each other and an unbalanced attenuation amount of a pseudo communication network when the two windings are not aligned.

FIG. 4 shows the structure of a capacitor.

FIG. 5 shows insertion loss of a pseudo communication network.

FIG. 6 shows a first embodiment of a pseudo communication network according to the present invention.

FIG. 7 shows the relationship between the capacitor C _A and the common mode impedance and the insertion loss obtained using the equations (3) and (4).

FIG. 8 shows a measurement obtained by using the present example and a current probe together;
An example of measuring an interference wave appearing at a communication line terminal of a communication device.

FIG. 9 is a measurement example of an interference wave appearing at a communication line terminal of a communication device measured using only the present embodiment.

FIG. 10 shows a second embodiment of the present invention.

FIG. 11 shows a third embodiment of the present invention.

FIG. 12 is a conventional pseudo communication network.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Device to be measured 2 Measuring device of interference wave voltage 3 Conventionally proposed 4-wire pseudo communication network 3a to 3d Pseudo communication network according to the present invention 4 Current probe for measuring interference wave current 5 Device to be measured Auxiliary device for operating state 6 DC cut capacitor 7 Terminating impedance between core wire and ground 8 Common mode choke 9 Terminal to connect to device under test 10 Terminal to connect to auxiliary device 11 To measure current The impedance 8 between the core wire and the ground and the impedance inserted between the ground 12 The impedance for matching the input impedance of the measuring device 3 for the disturbing wave 13 The magnetic permeability of the core material used for the common mode choke coil 8 Auxiliary common mode choke using small core material 14 Condenser inserted between core wire and ground 15 A core obtained by combining one E-shaped core 15 'and another E-shaped core 15 "16 Winding 17 Modular socket 18 Pin for connecting the modular socket to a printed circuit board 19 A pseudo communication network is formed. Printed circuit board 20 Ground plane formed on the back side of printed circuit board 21 Communication line formed on the surface of printed circuit board 22 Portion where line width is increased to increase capacitance with ground plane 23 Measuring instrument for measuring interference wave Input impedance of

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 29/08 H04B 17/00 H04L 29/14

Claims (4)

(57) [Claims] 1. A communication line for connecting a communication device and an auxiliary device for operating the communication device to measure an interference wave radiated through the communication line from a communication device using a balanced line as the communication line. A terminal for connecting to the communication device, and a series circuit of a first impedance and a first capacitance having mutually equal values and having one end connected to each core of the terminal. And a second impedance provided between a common connection point at the other end of the series circuit and a ground point; and a choke coil provided between the terminal and the auxiliary device. This is a common mode choke coil that has almost no loss and has a large loss with respect to an interference wave that appears between the communication line and the ground. The first capacitance satisfies both the transmission condition of the signal used for communication and the reference value of the impedance between the core of the pseudo communication network and the ground. A pseudo communication network characterized by evaluating a disturbance wave appearing between a communication line terminal of a communication device and a ground by measuring a voltage between both ends of the second impedance. 2. The choke coil according to claim 1, wherein the choke coil comprises a series circuit of first and second choke coils, and the first choke coil has almost no loss with respect to a communication signal and has an interference wave appearing between the communication line and the ground. The second choke coil has an auxiliary core having a magnetic permeability smaller than the magnetic permeability of the core used for the first choke coil. And a capacitance is provided between a connection point of the two choke coils and a ground point, and the capacitance is provided between a common ground plane on one side of the printed circuit board and a signal line on the other side. The pseudo communication network according to claim 1, wherein 3. The pseudo communication network according to claim 1, wherein the first common mode choke coil comprises an E-shaped first core and another E-shaped second core,
A pair of cores constituting a communication path are twisted with each other in a middle magnetic path of a closed magnetic path formed by connecting the first core and the second core to each other, and the twisted core is connected to a communication device. Has a configuration in which a logarithmic bundle necessary for normal operation is wound. 4. The pseudo communication network according to claim 1, wherein the other end of the series circuit of impedance and capacitance connected to each core of the communication line is connected to each other, and between the connection point and ground. A simulated communication network, wherein an input impedance of a level meter for measuring an interference wave is used as the second impedance to be inserted.