JPH0539026U - Coaxial cable / balanced cable converter string - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a string that has the function of mutual conversion between unbalance and equilibrium. [Structure] A balanced-to-unbalanced converter in which a transformer using a core and an inductor and a capacitor are connected to the windings of this transformer at constants in a specified order, one of which is a coaxial cable and the other is a balanced pair. Configure the cable so that it can be connected.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a converter that converts an electric signal from unbalanced transmission using a coaxial cable to balanced transmission using a balanced cable and enables communication of the electric signal using the coaxial cable and the balanced cable.

[0002]

[Prior Art]

 Conventionally, when connecting data terminals via a host computer to form a network, there are a peripheral type that is used on the premises and a line type that uses lines such as switched lines and leased lines. In each of these terminals, a terminal is connected to a host computer via a network management device (hereinafter referred to as "NMC"), and a coaxial cable is used for connection between the NMC and the terminal. A balanced cable (pair cable) is used between the linear communication control unit and the communication control unit because of balanced transmission.

FIG. 6 shows a connection form between NMC and terminals, which is currently the most common. In the figure, 1 is an NMC and 2 is a terminal. Reference numeral 3 is a coaxial cable, and BNC connectors 4 and 4'are connected to both ends thereof. The NMC 1 and the terminal 2 include those having an input / output impedance of 50Ω, 75Ω, 95Ω or the like. Reference numeral 5 is a BNC connector for connecting the NMC 1 and 5'for connecting the terminal 2, respectively, which are connected to the connectors 4, 4'of the coaxial cable 3, respectively. For these, coaxial cables and connectors corresponding to the input / output impedances of the terminal 2 and the NMC 1 are used.

[0004]

[Problems to be solved by the device]

 On the other hand, recently, wiring using coaxial cables has drawbacks in use, such as an increase in cable cost and the need for rewiring due to terminal movements.Therefore, there are more and more forms of network construction using balanced cables. Therefore, a coaxial cable and a balanced cable are often used together.

For this reason, what is called “unbalanced-balanced conversion” or “balanced-unbalanced conversion” for converting a coaxial cable into a balanced cable for transmission is required. In this regard, for example, Japanese Patent Publication No. 61-33616 (balance / unbalance conversion transformer), JP-A-55-155135 (balance / unbalance conversion transformer device), JP-A-62-49212 (balance) Unbalanced conversion transformer), Japanese Patent Laid-Open No. 57-26120 (balanced unbalanced transformer), and the like. Only the technical contents relating to the conversion means themselves are disclosed in these documents.

Japanese Patent Application No. 2-148904 (coaxial cable balanced cable conversion transmitter) proposes a communication of this type. FIG. 7 explains the contents. In the figure, 6-1 and 6-2 are transmission devices, 7-1 and 7-2 are coaxial cables, 8-1 and 8-2 are conversion transformers, 9 is a balanced pair cable, and 10 is a balanced pair cable pair. The virtual center of the twisted pair, VH is the induced longitudinal voltage induced in the balanced pair cable (voltage between the virtual midpoint of one pair of twisted pair and ground), and VL is between the pair of twisted pair of the balanced pair. Indicates the induced lateral voltage. Reference numerals 11a and 11b denote ground wires, and 12a and 12b denote stray capacitance between the ground of the transmission device and the coaxial cable. The transmission signal from the transmission device 6-1 is guided to the 8-1 conversion transformer via the coaxial cable 7-1, the unbalanced signal is converted into a balanced signal, and the balanced signal is transferred to the balanced pair cable 9. Sent out. Further, it is configured such that it enters the conversion transformer 8-2 on the receiving side, is converted into an unbalanced signal, and reaches the transmission device 6-2 corresponding to the terminal via the coaxial cable 7-2. ..

In the example of FIG. 7, a balanced pair is formed by connecting the outer conductor side of the coaxial cable side winding to the balanced pair cable side winding (secondary side) in the conversion transformers 8-1 and 8-2. Since the impedance between the virtual center of the twisted pair of cables and the ground is extremely low, the vertical voltage VH from the outside is hardly generated. However, some terminals require connection at both ends, and this situation is not entirely satisfied. Further, in the example of FIG. 7, there is a problem that the noise propagating from the terminal or the surroundings through the cable becomes a great obstacle to the electric signal, and the terminals nearby cannot be used during use.

An object of the present invention is to use a cord equipped with a converter having such an unbalanced-balanced conversion function and a balanced-unbalanced conversion function to convert noise to a different cable and transmit the noise from the terminal. It is intended to solve the problems of radiation noise propagating through a cable and the problems of signal destruction due to induction noise from power lines to a balanced cable, and to enable easy and stable transmission of electrical signals.

[0009]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention provides a cord having a converter for converting unbalanced transmission to balanced transmission and balanced transmission to unbalanced transmission at one end of a coaxial cable or a balanced pair cable. A transformer with a core and an inductor and a capacitor connected to the winding of this transformer at constants in the specified order.One of the converters can be connected to a coaxial cable and the other to a balanced pair cable. What is done is a basic feature.

[0010]

[Action]

 Since the present invention has such a configuration, by connecting one to the coaxial cable and the other to the balanced pair cable, the converter converts the electrical signal on the unbalanced transmission to the normal electrical signal on the balanced transmission. The signal can be converted into a signal, and conversely, the electric signal on the balanced transmission can be converted into a normal electric signal on the unbalanced transmission, and moreover, a stable electric signal can be transmitted without being affected by induction noise.

[0011]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a specific example of the internal circuit of the converter used in the present invention. FIG. 1 (a) shows a midpoint grounding type converter composed of a T-type circuit and a balun coil. Reference numeral 13 is a core that constitutes a balun that converts unbalance to balance and balance to unbalance. An insulated primary coil 14 is wound around the core 13, one of which is connected to an inner conductor of a BNC connector described later that is connected to a coaxial cable, and the other of which is connected to an outer conductor of the BNC. 31 is connected. Reference numeral 15 is a secondary coil connected to the balanced cable, in which the insulated lead wire 16 (solid line) and the other lead wire 17 (broken line) are wound in a coil shape from opposite directions as shown in the drawing to bundle two cores. It is as a configuration. That is, the lead wire 16 is wound on the lower surface 18, and the other lead wire 17 is wound on the upper surface 19 to form a transformer. At this time, the respective lead wires 16 and 17 are physically connected at the midpoint 20, and the connection point is extended to be connected to the BNC external conductor connection terminal 31 on the primary side. One of the secondary side coils 15 is connected to the terminal 22 which is connected to the balanced cable, and the other side 17 is connected to the terminal 23.

Inductors 25 and 26 (here, a tertiary circuit configuration) are connected between the lead wire 24 of the primary coil 14 and the terminal 30. One end of the capacitor 27 is connected to the connection point of the inductors 25 and 26, and the other end of the capacitor 27 is connected to the lead wire 24 ′ from the primary side coil 14 (connection point 29). An unbalanced-balanced converter using a balun coil is constructed by connecting with a connection terminal 31 connected with a conductor. At this time, if the balun coil needs impedance conversion, it is converted by changing the wire diameter and the number of turns on the primary side and the secondary side. For example, when the impedance 93Ω of the primary side coaxial cable is converted into the impedance 110Ω of the secondary side balanced cable, it can be realized by setting the number of windings to correspond to the impedance. Of course, at this time, the wire diameter of the coil may be changed and wound.

Further, one end of the inductor 26 on the primary side is connected to the internal conductor connection terminal 30 of the BNC connector to form an unbalanced connection terminal.

When a coaxial cable is converted into a balanced cable by using this converter and then transmitted, a pair of twisted wires of the balanced cable output a signal between the NMC and the terminal from the midpoint 20 inside the converter. Since it is grounded to the outer conductor of the outer conductor of the coaxial cable, the impedance between the balanced cable and ground becomes extremely low, and there is almost no induction to the balanced cable. Further, with respect to the noise from the primary side, this noise can be cut by the third-order filter composed of the inductors 25 and 26 and the capacitor 27.

The cut-off frequency can be calculated from the circuit configuration of the converter, but here, the constants shown in Tables 1 and 2 are formed into a circuit from the relationship with the allowable delay time of the terminal to be connected, and the converter is combined with the balun coil. Make up.

FIG. 1B is an example of a converter without a midpoint in which a T-type circuit and a balun coil are integrated. The basic structure is the same as that of the example shown in FIG. 1A, but the feature is that the winding method of the secondary coil is one. The winding ratio for impedance conversion is the same as in the case of FIG. This example is useful when the terminal does not have to be grounded.

[Table 1]

[Table 2] For the constants of the inductors 25 and 26 and the capacitor 27 on the primary side, use the A type of Table 1 and Table 2. At this time, it is necessary to use the value in the table that matches the input impedance of the unbalanced coaxial cable side.

FIG. 2 is a specific example of the converter when the Π-type circuit is used.

First, in FIG. 2A, a primary side coil 33 having an insulation treatment is wound around a core 32, one end of which is connected to an internal conductor of a BNC connector described later for connecting a coaxial cable. The other end is connected to the terminal 41 which is connected to the outer conductor of the BNC connector. A secondary coil 34 is a side to which a balanced cable is connected. In the secondary coil, the insulated lead wire 35 is wound, the other lead wire 36 is also wound in the direction of the dotted line, and two cores of the respective output lead wires 37 and 38 are bundled to form a midpoint 39, thereby forming a transformer. To do. The lead wire 40 extending from the midpoint 39 is extended and connected to the BNC external conductor connection terminal 41 on the primary side. The lead wire 35 on the secondary side is connected to the terminal 42 for connection of the balanced cable, and the other lead wire 36 is connected to the terminal 43.

To the lead wire 44 of the primary side coil 33, capacitors 45 and 49 and an inductor 48 are connected in a Π type (described in the tertiary circuit). That is, the capacitors 45 and 49 are connected to both ends of the inductor 48. The connection point 46 between the inductor 48 and the capacitor 45 is connected to the lead wire 44 of the primary coil 33, and the other end of the capacitor 45 is connected to the lead wire 44 ^′ at the connection point 47. A connection point 51 between the capacitor 49 and the inductor 48 is connected to an internal conductor connection terminal 52 of the BNC connector described later. The other end of the capacitor 49 is connected to a connection extension line between the coil terminal 44 'on the primary coil side and the capacitor 45 (connection point 50), and further connected to the BNC connector outer conductor connection terminal 41. In this way, an unbalanced-balanced converter using a balun coil is constructed. At this time, in the case of impedance conversion, the balun coil can be converted by changing the number of turns on the primary side and the secondary side or the winding diameter.

When this converter is used to convert a coaxial cable into a balanced cable for transmission, a signal between the NMC and the terminal is such that a pair of twisted wires of the balanced cable are transmitted from the midpoint 39 inside the converter. Since the output is connected to the outer conductor of the coaxial cable, the impedance between the balanced cable and ground is extremely low. Further, with respect to the noise from the primary side, the noise can be cut by the circuit composed of the inductor 48 and the capacitors 45 and 49. The signal waveform is impedance-converted and transmitted to the partner communication terminal through a balanced cable. The other terminal receives the balanced signal, and the converter connected to the terminal converts the balanced signal into an unbalanced signal and impedance conversion, and the induced noise propagated from the surroundings during communication is removed by the circuit inside the converter. Then, the terminal receives a signal.

FIG. 2B shows a converter without a midpoint in which a Π-type circuit and a balun coil are integrated. The basic configuration is the same as that of the type shown in FIG. 2 (a), but the winding method of the secondary coil does not take the center point. The same winding method is used for impedance conversion. This converter is useful for terminals where it would be inconvenient to connect the midpoint ground to the outer conductor of the coaxial cable.

Tables 1 and 2 are constants in each element of the converter circuit, Table 1 is a constant corresponding to the impedance characteristic of the unbalanced cable portion when the conversion circuit is T type, and Table 2 is a conversion circuit. It is a constant corresponding to the impedance of the unbalanced cable in the case of Π type. There are circuit types from the second-order A type to the seventh-order F type. The characteristics are almost the same for both T type and Π type. The converter circuit can be calculated from the cutoff frequency, but it is necessary to determine the values of the inductor and capacitor from the relationship with the allowable delay time of the connected terminal, and the values in the table are combined with the balun coil. To configure the converter.

FIG. 3 shows an embodiment of the present invention. That is, an example of the configuration of a leash equipped with a converter, a coaxial cable, a connector for connecting a balanced cable, etc. for facilitating connection of the converter with the terminal and the NMC is shown.

In FIG. 3A, 67 is a BNC connector, and there are three types of connectors: 50Ω, 75Ω, and 93Ω. Reference numeral 68 denotes a converter, which is connected to a coaxial cable and a connection terminal as shown in FIG. 1 or 2. A balanced cable 69 is similarly connected as shown in FIG. 1 or 2. Reference numeral 70 is a modular-type plug terminal or the like, which forms a machine cord by inserting and crimping a balanced cable 69 connected to the converter into a specified pin number. The connector 67 is a means for connecting to a coaxial counterpart cable, and various types of connectors are connected according to the connecting means. The plug terminal 70 is connected to a terminal (jack) that is connected to a balanced cable that is a wiring cable.

In FIG. 3 (b), the BNC connector 71 and the coaxial cable 73 are crimp-connected by the mounting metal fitting 72, the converter 74 is connected to the coaxial cable 73, and the same balance cable 75 as in FIG. 3 (a) is connected to the other end. , And a plug 76 at the other end to form a cable for converting a coaxial cable to a balanced cable by incorporating the converter.

FIG. 4 shows an example of use when the terminal and the NMC are connected using the machine cord of FIG. 3 incorporating the converter shown in FIG. 1 or 2. In FIG. 4, the device strings of FIG. 3 are connected to the terminal or NMC side, respectively, but the structure of the connector, plug, etc. for connection is omitted.

In the example of FIG. 4A, 53 is a 93Ω NMC, and 54 is a terminal. 55-1 and 55-2 are coaxial cables for connecting the NMC and terminals, 56-1 and 5 6-2 are converters incorporated in a string equipped with a T-type circuit, and 57 is a balanced pair cable. It has an impedance of 110Ω. The signal transmitted from the terminal 54 of 93Ω is guided to the converter 56-2 via 55-2, and is converted from the unbalanced signal to the balanced signal in the converter 56-2. Further, the impedance 93Ω of the terminal 54 is converted into 110Ω of the balanced pair cable 57 by the balun coil in the converter 56-2. The signal passing through the equilibrium cable 57 is transmitted while satisfying the condition of passing through the balanced cable, and after passing through the balanced cable 57, is guided to the other converter 56-1 and is converted into an unbalanced signal again, and then the coaxial cable 57 Reach NMC 53 via 55-1. Upon receiving this communication signal, the NMC 53 sends a signal from the NMC 53 to the terminal 54 via the route reverse to the above.

In this example, the balanced-to-cable-side winding inside the converter 56-1 is provided with a lead-out point that is a midpoint ground, and is connected to the coaxial connector outer conductor of the unbalanced-side winding. The converter 56-2 on the 54 side is not provided with an intermediate contact lead. In the case of this structure, the primary side and the secondary side of the converter 56-2 side are insulated from the noise mixed from the ground lines 58 and 59 and the induced noise induced in the balanced pair cable 57. Therefore, the noise current is cut off and a loop is not taken between the NMC 53, the terminal 54 and the ground, and the single-point grounding provides a relatively strong structure against noise.

FIG. 4B is an embodiment in which a machine string incorporating converters 63-1 and 63-2 having a midpoint grounding point is connected to both sides of the NMC 60 and the terminal 61. The communication signal is transmitted through the same route as in FIG. 4 (a), but this example is effective for the configuration in which it is necessary to connect the terminals.

FIGS. 4 (c) and 4 (d) show the same connection form as FIGS. 4 (a) and 4 (b), and show the case where the converter circuit incorporated in the cord is the Π type shown in FIG. .. The operation and characteristics in this case are the same as those in FIGS. 4 (a) and 4 (b).

FIG. 5 shows a characteristic comparison regarding radiated noise with and without the converter circuit according to the above-described embodiment. In this embodiment, a T-type circuit having an impedance of 93 Ω is incorporated in the configuration of FIG. 1, and the capacitances of the inductor and the capacitor are e1 = O.50 μH, e2 = 166 PF, e3 = 3.26 μH.

FIG. 5A shows a reflection noise characteristic when a conventionally used coaxial cable is used. Fig. 5 (b) shows the radiated noise characteristics under the condition of Fig. 5 (a) when data is transmitted by the balanced twisted pair cable using the converter of the present invention. The radiated noise uses a coaxial cable. It turns out that it is obviously less than when compared.

[0034]

[Effect of the device]

 By selecting and using a machine string incorporating the converter of the present invention, an unbalanced-balanced conversion function matching the impedance or various characteristics is provided between the terminal and the NMC. You can In the embodiment of the present invention, it was possible to confirm wide band transmission with a transmission speed corresponding to 1 MHz to 3 MHz. In addition, stable transmission can be performed without receiving induction from the power line and noise from the ground line, and data communication can be performed using normal telephone wiring. It has the merit of being much cheaper than the wiring cost of the coaxial cable, such as the improvement of work and the significant reduction of initial investment and operation cost.

In the embodiment of the present invention, only the unbalanced balanced-balanced unbalanced transmission conversion was discussed, but it is not possible to use it as a balanced unbalanced-unbalanced balanced parallel transmission by reversing the communication form. Of course, it is possible by changing the input port in the form of conversion. In addition, the coaxial cable or balanced cable that is the transmission medium is not integrated, but one or all are separated, or only one is connectable. Needless to say, this can be done with the separated configuration.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an internal circuit of a converter used in the present invention.

FIG. 2 is a diagram showing another internal circuit example of the converter used in the present invention.

FIG. 3 is a diagram showing an embodiment of the present invention.

FIG. 4 is a diagram showing a configuration example of a connection system using the present invention.

FIG. 5 is a diagram for explaining a radiation noise characteristic comparison in the vicinity of a terminal connecting cord when the present invention is used.

FIG. 6 is a diagram illustrating a conventional NMC and terminal connection form.

FIG. 7 is a diagram illustrating a conventional coaxial cable balanced cable conversion transmitter.

[Explanation of symbols]

13,32 Core 14,33 Primary coil 16,34 Secondary coil 20,39 Midpoint 22,23,42,43 Balance cable connection terminal 25,26,48 Inductor 27,45,49,30 Capacitor 52 BNC internal conductor Connection terminal 31,41 BNC external conductor connection terminal 53,60 NMC 54,61 Terminal 55-1,55-2 Coaxial cable 56-1,56-2,63-1,63-2,6 8,7
4 Converter 57,64,69 Balanced cable 67,71,73 Coaxial cable 70,76 Plug

Claims (1)

[Scope of utility model registration request] 1. A cord having a converter for converting unbalanced transmission to balanced transmission and balanced transmission to unbalanced transmission, which is connected to one end of a coaxial cable or a balanced pair cable, wherein the converter uses a core. The transformer and the windings of the transformer are connected to an inductor and a capacitor at constants in the specified order, and one of the converters can be connected to the coaxial cable and the other to the balanced pair cable. A coaxial cable / balanced cable converter string.