JPH0440110A - Cable converting transmitter for paired balanced coaxial cables - Google Patents

Abstract

PURPOSE:To eliminate the introduction of noise from a ground line or noise from a power line to paired balanced cables by using in combining a conversion transformer which grounds the lead wire of an intermediate contact to a coil on the side of the paired balanced cables, with a conversion transformer which is not fitted with the lead wire between opposite transmitters using the coaxial cables for transmission media. CONSTITUTION:An electric communication signal to be transmitted from a transmitter 4-1 is guided through a coaxial cable 1-1 to a conversion transformer 2-1, converted to an imbalanced signal to a balanced signal by the conversion transformer 2-1, passed through balanced paired cables 5, converted to the imbalanced signal by a conversion transformer 3-1 and reached through a coaxial cable 1-2 to a transmitter 4-2. An electric communication signal to be transmitted from the transmitter 4-2 is reached through an inverse route to the transmitter 4-1. In such a case, the lead wire of the intermediate contact is provided at the coil on the side of the paired balanced cables in the inside of the conversion transformer 3-1 and connected to the outside cable conductor side of an imbalanced side coil. The lead wire of the intermediate contact is not provided at the conversion transformer 2-1. Thus, an operation is executed to suppress the noise to be mixed from a ground line 6 and the noise to be induced from a power line 7 to the paired balanced cables 5, and any influence of guidance is hardly received.

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention replaces the coaxial cable with a balanced pair cable for balanced transmission as the transmission medium of a communication system that transmits telecommunications signals using a coaxial cable for unbalanced transmission. This technology relates to equipment that performs two-way transmission, particularly after converting the output signal of the transmission equipment from an unbalanced signal to a balanced signal and transmitting it using a balanced pair cable. The present invention relates to a cable conversion transmitter that obtains a signal by converting it into a balanced signal.

(2) Prior Art Figure 1 shows an embodiment of a device for transmitting data by replacing coaxial cables with balanced pair cables, in which 1-1 and 1-2 are coaxial cables, 2-1 and 2-2 are Conversion transformer, 4-1 and 4-2 are transmission devices, 4-a and 4-b are stray capacitances in the transmission device, 5 is a balanced pair cable, 6 is a ground line, 7 is a power line, 8 is between ground A noise generation source corresponding to the potential difference, 9 is the virtual midpoint of the balanced pair cable, VL is the induced longitudinal voltage induced in the balanced pair cable, and 2 is the induced product voltage induced in the balanced pair cable.

The telecommunication signal sent from the transmission device 4-1 is guided to the conversion transformer 2-1 via the coaxial cable 1-1, and after being converted from an unbalanced signal to a balanced signal by the conversion transformer 2-1, It passes through the balanced pair cable 5 to the conversion transformer 2-2,
This conversion transformer converts the balanced signal into an unbalanced signal, which reaches the transmission device 4-2 via the coaxial cable 1-2. The telecommunication signal sent out from the transmission device 4-2 is guided to the conversion transformer 2-2 via the reverse path, that is, the coaxial cable 1-2, and is converted into a balanced signal by the conversion transformer 2-2. It passes through the balanced pair cable 5, is converted into an unbalanced signal by the conversion transformer 2-1, and is sent to the transmission device 4-1 via the coaxial cable 1-1.
reach. The conversion transformers 2-1 and 2-2 have a primary winding and a secondary winding inside. The side windings are matched to the characteristic impedance of the balanced pair cable 5, and the internal structures of the conversion transformers 2-1 and 2-2 are exactly the same.

Coaxial cable 1-1 or 1-2 using this conversion transformer
When transmitting by substituting the balanced pair cable 5 for transmission, there is a drawback that noise is induced from the power line 7 to the balanced pair cable 5. In the configuration shown in FIG. 1, the voltage induced from the power line 7 to the communication line is the induced longitudinal voltage VL (between the virtual midpoint of the pair of twisted wires and the ground) in the pair of twisted wires inside the balanced pair cable 5. Due to the unbalanced attenuation of the transformer, twisted pair wires and equipment, it is converted into an induced product voltage V, (the line voltage between a pair of balanced cables), and as a noise voltage. It has the disadvantage of contaminating telecommunications signals.

FIG. 2 shows another conventional example that improves the drawbacks of the conventional example shown in FIG. It is connected to the outer conductor side of the coaxial cable side winding. When using this conversion transformer to replace a coaxial cable with a balanced pair cable for transmission, the method of transmitting signals between the transmission devices is the same as the method shown in Figure 1, or one of the balanced pair cables is used for transmission.
Since the twisted pair wires are grounded to the outer conductor of the coaxial cable through the outlet of the intermediate junction inside the conversion transformers 3-1 and 3-2, the distance between the virtual midpoint 9 of the twisted pair wires and the ground is The impedance becomes extremely low, and almost no induced vertical voltage VL is induced from the power line 7 to the balanced pair cable 5, and the induction from the power line 7 has almost no effect. However, in this improvement method, if there is a potential difference (8) between the ground 6, the noise current induced by this potential difference (8) between the ground wire 6 and the ground wire inside the transmission device 4-1 Stray capacitance 4-a between and coaxial cable 1-1, coaxial cable 1-1, conversion transformer 3-1, balanced pair cable 5,
Conversion transformer 3-2, coaxial cable l-2, transmission device 4-
A loop is formed between the stray capacitance 4-b between the coaxial cable 1-2 and the grounding wire 6 inside the 2, and a loop flowing through the grounding wire 6. -2 and the unbalanced attenuation of the transmission device 4-2, it is converted into a lateral voltage V1 and is mixed into the telecommunication signal as a noise voltage, which has the drawback of causing a new problem.

(3) Purpose of the Invention The purpose of the present invention is to connect a ground line to An object of the present invention is to provide a coaxial cable balanced-to-cable conversion transmitter that can perform stable telecommunications signal transmission by solving the problems of noise contamination and noise induced from a power line to a balanced-pair cable.

(4) Structure of the Invention The coaxial cable balanced-to-cable conversion transmitter of the present invention is applied between opposing transmission devices using a coaxial cable as a transmission medium, and converts an unbalanced signal outputted from the transmission device via the coaxial cable into an unbalanced signal. A conversion transformer with a balance conversion function is used to convert the signal into a balanced signal, which is then transmitted to the other transmission device via a balanced pair cable, and a conversion transformer with a balance-unbalance conversion function is used to convert the balanced signal into an unbalanced signal. In a configuration in which the conversion transformer is converted into an unbalanced converter and connected to the other transmission device via a coaxial cable, the balance inside one converter is The most important feature is that an outlet for the intermediate junction is provided in the winding on the cable side and the intermediate junction is connected to the coaxial outer conductor on the unbalanced pair cable, that is, the coaxial cable side.

The conventional technology is to install an outlet for the intermediate connection on the winding on the balanced cable side inside the conversion transformer of either a conversion transformer with an unbalanced/balanced conversion function or a conversion transformer with a balanced/unbalanced function. The difference is that a coaxial cable balanced-to-cable conversion transmitter can be used by combining a conversion transformer with a conventional connection and a conversion transformer without an intermediate connection outlet.

(5) Embodiment FIG. 3 is a detailed diagram of the present invention, in which 1-1 and 1-2 are coaxial cables, 2-1 and 3-1 are conversion transformers, and 4-1 and 4- 2 is the transmission device, 5 is the balanced pair cable, 6 is the ground wire, 7 is the power line, 8 is the noise source, 9 is the virtual midpoint of the balanced pair cable, and L is the induced longitudinal voltage induced in the balanced pair cable. vl is the induced detection voltage induced in the balanced pair cable.

The telecommunication signal sent from the transmission device 4-1 is guided to the conversion transformer 21 via the coaxial cable 1-1, and after being converted from an unbalanced signal to a balanced signal by the conversion transformer 2-1, it is converted into a balanced pair cable. 5, is converted into an unbalanced signal by a conversion transformer 3-1, and is sent to a transmission device 4- via a coaxial cable 1-2.
Reach 2. The telecommunication signal sent from the transmission device 4-2 reaches the transmission device 4-1 through a reverse path. In this example, an outlet for the intermediate junction is provided in the balanced pair cable side winding inside the conversion transformer 3-1, and is connected to the cable external conductor side of the unbalanced side winding, and is connected to the cable external conductor side of the unbalanced side winding. does not have an opening for intermediate points.

Due to this structure, there is a suppressing effect as described below against the noise mixed in from the grounding wire 6 and the induced noise induced in the balanced pair cable 5 from the power line 7, so the influence of induction is suppressed. Hard to accept.

Regarding the noise coming in from the grounding wire 6, in the configuration shown in Fig. 3, the noise coming from the grounding wire 6 is isolated from the primary winding and the secondary winding in the transformer 2-1, so it is not a noise current. Since it is cut off, the ground wire 6, the stray capacitance 4-a between the ground wire of the transmission device 4-1 and the coaxial cable, the coaxial cable 1-1, the conversion transformer 2-1, the balanced pair cable 5, and the conversion transformer 3 -1,
Noise current mixes from the grounding wire 6 to the balanced pair cable 5 without circulating to the coaxial cable l-2, the stray capacitance 4-b between the coaxial cable and the grounding wire of the transmission device 4-2, and the grounding wire 6. Does not occur. Regarding induced noise from the power line 7, since the balanced pair cable side winding in the conversion transformer 3-1 is connected to the outer conductor side of the coaxial cable side winding, one pair of the balanced pair cable 5 is connected to the outer conductor side of the coaxial cable side winding. Since the impedance between the virtual midpoint 9 of the stranded wire and the ground is extremely low, the power line 7
The vertical voltage V induced from the balanced pair cable 5 to the balanced pair cable 5 is hardly generated, and the induction from the power line 7 has almost no effect.

As a result, the transmission speed is 2.4MHbit/sec.
We have a transmission device that transmits using the AMl coding system, a coaxial cable with a characteristic impedance of 93 ohms, and a balanced pair cable with a characteristic impedance of 100 ohms, and create wiring for transmitting telecommunication signals to transmit the signals. When transmission is performed using the conventional example shown in Figure 1, the transmission distance, that is, the length of the balanced pair cable, is approximately 300 meters, and when transmission is performed using the conventional example shown in Figure 2, the transmission distance is approximately 300 meters. Table 1 shows the transmission distance when using the coaxial cable balanced-to-cable converter transmitter of the present invention as shown in Figure 3 under an indoor electromagnetic noise environment as shown in Table 1, which is about 90 meters. As shown in the figure, the transmission distance has increased to approximately 360 meters. As is clear from this result, there was an improvement in the transmission distance compared to the conventional technology.

Table 1 Examples of transmission distances between the conventional example and the present invention, and stable transmission is possible without noise contamination from the ground line, but there is a risk of noise current contamination from the ground line or induction from the power line. If unshielded balanced pair cable is used as a transmission medium indoors, etc., it is cheaper than coaxial cable, expands the service range, and improves the workability of laying cables, significantly reducing initial investment and operating costs. The advantage is that it can be reduced to

(6) As described in detail of the invention, the coaxial cable balanced pair cable conversion transmitter of the present invention does not allow induction from the power line even if a balanced pair cable is used instead of a coaxial cable.

[Brief explanation of drawings]

Fig. 1 is a connection system diagram showing a conventional coaxial cable balanced to cable conversion transmitter; Fig. 2 is a connection system diagram showing an improved version of the conventional coaxial cable balanced to cable conversion transmitter shown in Fig. 1; FIG. 3 is a connection system diagram showing an embodiment of the present invention. 1-1.1-2... Coaxial cable, 2-1.2-2.
...Conversion transformer, 3-1.3-2...Conversion transformer in which the outlet of the intermediate junction of the balanced pair cable side windings is connected to the outer conductor of the coaxial cable, 4-1. 4-2... Transmission device, 4-a, 4-b... Stray capacitance inside the transmission device, 5.
・Balanced pair cable, 6... Ground wire, 7... Power line, 8... Noise source corresponding to potential difference between grounds, 9...
・Virtual midpoint of a pair of twisted wires in a balanced pair cable, V
L...Induced longitudinal voltage induced in the balanced pair cable, vl
...Induced detection voltage induced in the balanced cable. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Scope of Claims] Two transmission devices facing each other using an unbalanced coaxial cable as a transmission medium are provided, and the unbalanced transmission of the coaxial cable is provided at the transmission signal output section of one of the two transmission devices. A first transformer having an unbalanced/balanced conversion function for converting the transmission method from transmission to balanced transmission using a balanced pair cable is installed, and the unbalanced transmission signal is converted to a balanced signal, and the second transformer is converted using the balanced pair cable. a second transformer having a balanced/unbalanced conversion function in order to convert the balanced signal into an unbalanced signal at the transmission signal input section of the other device; In a coaxial cable balanced-to-cable conversion transmitter that is attached and inputs a converted unbalanced signal to the coaxial cable, the first transformer having an unbalanced-to-balanced conversion function or the second transformer having a balanced-to-unbalanced function. An outlet of the intermediate junction is installed in the winding on the balanced pair cable side in either transformer of the transformer, and the outlet of the intermediate junction is connected to the external conductor terminal of the coaxial cable side. A coaxial cable balanced pair cable conversion transmitter, characterized in that the winding on the balanced pair cable side has only an outlet of an intermediate junction connected to an external conductor terminal on the coaxial cable side.