JP2015198303A - coaxial communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of an error.SOLUTION: A controller 11 and a head 12 in a data transmission system 10 are communicatively connected with each other via a coaxial cable 13. The coaxial cable 13 includes an inner conductor 21 and an outer conductor 22, and the outer conductor 22 is placed in a cylindrical shape centering on the one inner conductor 21. The inner conductor 21 is connected to a plus input terminal of a differential receiver 33, and an outer conductor 22a is connected to a minus input terminal of the differential receiver 33 via a termination resistor R1. In addition, the outer conductor 22a is connected to a signal ground SG1 via an impedance element Z1 and also connected to a frame ground FG via a capacitor C8.

Description

  The present invention relates to a coaxial communication device that communicates via a coaxial cable.

  Conventionally, when a high-frequency signal is transmitted between two devices (for example, a controller and a peripheral device), an inexpensive single-core coaxial cable having a good impedance characteristic is used for connection between the devices (for example, Patent Document 1). Moreover, it connects using the communication cable which has a signal line, a signal ground line, and a frame ground line (for example, refer patent document 2).

US Patent Application Publication No. 2011/0103267 JP 2006-278259 A

  By the way, a communication error may occur in a system that transmits a signal using a single-core coaxial cable as described above. The outer conductor of the single-core coaxial cable is connected to the signal ground of the device. For this reason, the signal ground potential of the apparatus changes due to noise applied to the external conductor. This voltage change causes a reception error in the apparatus.

  In addition, in a device that performs communication using a communication cable having a signal line, a signal ground line, and a frame ground line, a reception error is prevented when the frequency of noise applied to the frame ground of the device includes the frequency of a signal transmitted by the communication cable. It is not possible.

  The present invention has been made to solve the above-described problems, and an object thereof is to suppress the occurrence of errors.

  A coaxial communication device that solves the above-described problem is a coaxial communication device that receives a signal via a coaxial cable including one inner conductor and an outer conductor, and a positive input terminal is connected to the inner conductor, and the outer conductor A differential receiver to which a negative input terminal is connected, a first termination resistor connected between the outer conductor and the negative input terminal of the differential receiver, and a positive input terminal of the differential receiver A second terminator connected between the signal ground and the signal ground, a third terminator connected between the negative input terminal of the differential receiver and the signal ground, the external conductor and the signal Connected between the external conductor and the frame ground, and an impedance element having a characteristic of being connected between the ground, passing a signal in a low frequency region, and blocking a signal in a high frequency region And a capacitor, with a.

  According to this configuration, the impedance element acts as a resistance in the high frequency region, and attenuates noise that is a high frequency component superimposed on a signal transmitted by the external conductor. The capacitor passes an alternating current of the supplied signal and blocks a direct current component by capacitive coupling between the two electrodes. Therefore, the noise reflected by the impedance element passes through the capacitor and flows to the frame ground. Therefore, it is possible to reduce the influence of noise on the level of the signal ground to which the impedance element is connected. The signal at the input terminal of the differential receiver is not easily affected by noise applied to the external conductor. Therefore, the occurrence of errors in the differential receiver is suppressed.

  The coaxial communication device is a coaxial communication device connected to the coaxial communication device via a coaxial cable composed of one inner conductor and an outer conductor, and a positive output terminal is connected to the inner conductor, A differential transmitter whose negative output terminal is connected to the outer conductor via a terminating resistor, and connected between the outer conductor and the signal ground, allows signals in the low frequency region to pass and blocks signals in the high frequency region And an impedance element having the characteristics of:

  According to this configuration, the external conductor is connected to the signal ground via the impedance element. It acts as a resistor in the high frequency region, and attenuates noise that is a high frequency component superimposed on a signal transmitted by the external conductor. Therefore, the influence of noise on the signal ground can be reduced. And the influence of the noise in the differential transmitter connected to the signal ground is reduced.

  The coaxial communication device is a coaxial communication device having a first communication device and a second communication device connected via a coaxial cable composed of one inner conductor and an outer conductor, the first communication device comprising: A differential receiver in which a positive input terminal is connected to the inner conductor and a negative input terminal is connected to the outer conductor via a first termination resistor, and a positive input terminal of the differential receiver and a first signal A second terminal resistor connected between the ground, a third terminal resistor connected between the negative input terminal of the differential receiver and the first signal ground, the external conductor, and the An impedance element connected between the first signal ground and having a characteristic of passing a signal in a low frequency region and blocking a signal in a high frequency region, and a capacitor connected between the external conductor and the frame ground. A differential transmitter having a positive output terminal connected to the inner conductor and a negative output terminal connected to the outer conductor via a fourth termination resistor; And an impedance element connected between the outer conductor and the second signal ground and having a characteristic of allowing a signal in a low frequency region to pass and blocking a signal in a high frequency region.

  According to this configuration, in the first communication device, the impedance element acts as a resistor in the high frequency region, and attenuates noise that is a high frequency component superimposed on a signal transmitted by the external conductor. The capacitor passes an alternating current of the supplied signal and blocks a direct current component by capacitive coupling between the two electrodes. Therefore, the noise reflected by the impedance element passes through the capacitor and flows to the frame ground. Therefore, it is possible to reduce the influence of noise on the level of the signal ground to which the impedance element is connected. The signal at the input terminal of the differential receiver is not easily affected by noise applied to the external conductor. Therefore, the occurrence of errors in the differential receiver is suppressed.

  In the second communication device, the external conductor is connected to the signal ground via the impedance element. It acts as a resistor in the high frequency region, and attenuates noise that is a high frequency component superimposed on a signal transmitted by the external conductor. Therefore, the influence of noise on the signal ground can be reduced. And the influence of the noise in the differential transmitter connected to the signal ground is reduced.

In the coaxial communication device, the impedance element is preferably an element including a magnetic material.
According to this configuration, it is possible to easily obtain a characteristic of passing a signal in a low frequency region and blocking a signal in a high frequency region by the magnetic material.

In the coaxial communication device, the capacitor is preferably a high voltage capacitor.
According to this configuration, it is possible to prevent the capacitor from being damaged even when the noise level is a high voltage or the potential difference between the frame ground and the signal ground is a high voltage.

In the above coaxial communication device, the capacitor is preferably a nonpolar capacitor.
According to this configuration, it is possible to prevent the capacitor from being damaged even if the noise level exists both on the plus side and the minus side with respect to the frame ground level.

  According to the present invention, the occurrence of errors can be suppressed.

It is a schematic block diagram of a data transmission system. It is a block circuit diagram of a data transmission system. It is a wave form diagram of the signal in a data transmission system. It is a wave form diagram of the signal in a data transmission system. It is a wave form diagram of the signal in a data transmission system.

Hereinafter, an embodiment will be described.
As shown in FIG. 1, the data transmission system 10 includes a controller 11 and a head 12, and the controller 11 and the head 12 are connected via a coaxial cable 13. The data transmission system 10 is, for example, an image processing system, the head 12 is a FA (Factory Automation) camera device that transmits captured image information, and the controller 11 performs image processing on the received image information. It is a processing device. The data transmission system may be an illumination system including an illumination unit and a control unit, a detection system including a sensor such as a proximity sensor and a control unit, and the like.

  The controller 11 is connected to the power supply 14 via the positive power supply wiring VP and the negative power supply wiring VN, and a drive voltage is supplied from the power supply 14. The controller 11 is connected to a frame ground FG (ground line). The controller 11 operates based on the drive voltage supplied from the power source 14 and outputs an operation signal VD of the head 12 and an uplink signal SU including a control signal for controlling the head 12. The operating voltage VD and the uplink signal SU are supplied to the head 12 via the coaxial cable 13. The head 12 operates based on the operating voltage VD and the uplink signal SU, and outputs a downlink signal SD. The downlink signal SD is supplied to the controller 11 via the coaxial cable 13. Thus, the head 12 and the controller 11 are connected to each other via the coaxial cable 13 so as to communicate with each other.

FIG. 2 shows a configuration related to the connection by the coaxial cable 13.
The coaxial cable 13 is a single-core coaxial cable, and has an inner conductor 21 and an outer conductor 22. The inner conductor 21 is, for example, a single conducting wire (copper wire), and the outer conductor 22 is a shield wire (mesh wire) arranged in a cylindrical shape with the inner conductor 21 as the center.

  The coaxial cable 13 is connected between the controller 11 and the head 12. Therefore, each of the inner conductor 21 and the outer conductor 22 of the coaxial cable 13 has an end connected to the controller 11 and an end connected to the head 12. In the following description, in order to distinguish the end on the controller 11 side and the end on the head 12 side as necessary, the reference numerals of the inner conductor and the outer conductor are denoted by “a” and “b”, respectively. .

The controller 11 includes a line filter 31, a voltage conversion circuit (denoted as “LDO”) 32, a differential receiver (differential receiver) 33, and a low-speed signal transmission circuit 34.
The input terminal of the line filter 31 is connected to the power supply wirings VP and VN. The input terminal of the line filter 31 is connected to one end of each of the capacitors C1 and C2, and the other end of the capacitors C1 and C2 is connected to the frame ground FG. The positive output terminal of the line filter 31 is connected to the voltage conversion circuit 32, and the negative output terminal of the line filter 31 is connected to the signal ground SG1. The low potential power supply terminal (ground terminal) of the voltage conversion circuit 32 is connected to the signal ground SG1. The output terminal of the voltage conversion circuit 32 is connected to the internal conductor 21a via the coil L1 and the ferrite bead FB1. The voltage conversion circuit 32 outputs the operating voltage VD of the head 12 based on the output voltage of the line filter 31.

  The inner conductor 21a of the coaxial cable 13 is connected to the plus input terminal of the differential receiver 33 via the capacitor C3. The outer conductor 22a of the coaxial cable 13 is connected to the negative input terminal of the differential receiver 33 via a termination resistor R1 and a capacitor C4. One end of the termination resistor R2 is connected between the capacitor C3 and the differential receiver 33, and the other end of the termination resistor R2 is connected to the signal ground SG1. One end of the termination resistor R3 is connected between the capacitor C4 and the differential receiver 33, and the other end of the termination resistor R3 is connected to the signal ground SG1.

  The differential receiver 33 receives signals RDp and RDn transmitted through the inner conductor 21a and the outer conductor 22a of the coaxial cable 13, and outputs differential signals S1p and S1n. The differential signals S1p and S1n are supplied to a processing circuit (not shown). The processing circuit processes image information based on the differential signals S1p and S1n. Further, the processing circuit outputs a signal (for example, a control signal) S2 for the head 12 to the low-speed signal transmission circuit 34.

  The output terminal of the low-speed signal transmission circuit 34 is connected to the inner conductor 21a of the coaxial cable 13 via the capacitor C7. The power supply terminal (low potential power supply terminal) of the low-speed signal transmission circuit 34 is connected to the signal ground SG1. The low-speed signal transmission circuit 34 outputs a so-called single-ended transmission signal SO to the internal conductor 21a based on the signal S2.

  The outer conductor 22a of the coaxial cable 13 is connected to the signal ground SG1 via the impedance element Z1 and to the frame ground FG via the capacitor C8. The impedance element Z1 has impedance characteristics corresponding to the frequency band. The impedance of the element Z1 has a characteristic obtained by combining (summing) the inductance component (X) and the resistance component (R) corresponding to the frequency. For example, high impedance is shown in a high frequency region (for example, several tens of MHz or more), and low impedance is shown in a low frequency region (for example, several tens of MHz or less). Therefore, the impedance element Z1 reduces (attenuates) the signal in the high frequency band and passes the low frequency band and direct current. In other words, the impedance element Z1 is equivalent to an inductance (coil) in the low frequency region and equivalent to a resistance in the high frequency region. On the other hand, the capacitor C8 passes alternating current by capacitive coupling. The impedance element Z1 is an element including a magnetic material, such as a ferrite bead or a coil using ferrite as a core. By using such an impedance element Z1, it is possible to easily obtain a characteristic of passing a signal in a low frequency region and blocking a signal in a high frequency region.

  The capacitor C8 connected to the frame ground FG is a nonpolar capacitor. This is because the level of noise applied to the outer conductor 22a of the coaxial cable 13 exists both on the plus side and the minus side with respect to the level of the frame ground FG. For this reason, the capacitor C8 can suppress the voltage change of the signal ground SG1 by flowing noise in the high frequency region to the frame ground FG.

  The capacitor C8 is preferably a high withstand voltage capacitor. This is because the potential difference between the frame ground FG and the power supply wiring VN (signal ground SG1) may be increased (for example, about 100 volts) by the AC power supply voltage supplied to the power supply 14. For this reason, damage to the capacitor C8 can be prevented by using a capacitor with a high breakdown voltage as the capacitor C8.

  In the head 12, the outer conductor 22b of the coaxial cable 13 is connected to the signal ground SG2 via the impedance element Z2. The impedance element Z2 has the same characteristics as the impedance element Z2 connected between the external conductor 22b and the signal ground SG1 in the controller 11. That is, the impedance element Z2 has impedance characteristics corresponding to the frequency band, exhibits high impedance in the high frequency region, and exhibits low impedance in the low frequency region. The impedance element Z2 is an element including a magnetic material, and is, for example, a ferrite bead. By using such an impedance element Z2, it is possible to easily obtain a characteristic of passing a signal in a low frequency region and blocking a signal in a high frequency region.

  The head 12 has a differential driver 41. Image information output from an image sensor (not shown) is supplied to the differential driver 41 as differential signals S11p and S11n. The positive output terminal of the differential driver 41 is connected to the inner conductor 21b of the coaxial cable 13 via the capacitor C11. The negative output terminal of the differential driver 41 is connected to the outer conductor 22b of the coaxial cable 13 via a capacitor C12 and a terminating resistor R11.

  The positive output terminal of the differential driver 41 is connected to one end of the output resistor R12, and the other end of the output resistor R12 is supplied with the high potential voltage VCC. The negative input terminal of the differential driver 41 is connected to one end of the output resistor R13, and the high potential voltage VCC is supplied to the other end of the output resistor R13. The high potential voltage VCC is supplied to the differential driver 41 as a drive voltage. That is, the high potential power terminal of the differential driver 41 is connected to a wiring (hereinafter referred to as wiring VCC) to which the high potential voltage VCC is supplied, and the low potential power terminal of the differential driver 41 is connected to the signal ground SG2. Yes.

  The inner conductor 21b of the coaxial cable 13 is connected to a load (not shown) via the ferrite bead FB11 and the coil L2. The load is, for example, an imaging unit that outputs the differential signals S11p and S11n, a power supply circuit that generates the high potential voltage VCC, and the like. The operating voltage VD supplied from the controller 11 is supplied to these loads via the coaxial cable 13. An imaging unit (not shown) operates based on the operating voltage VD and outputs differential signals S11p and S11n. A power supply circuit (not shown) generates a high potential voltage VCC based on the operating voltage VD.

  The inner conductor 21b of the coaxial cable 13 is connected to the input terminal of the low-speed signal receiving circuit 42 via the capacitor C13. The low potential power supply terminal of the low speed signal receiving circuit 42 is connected to the signal ground SG2. The low-speed signal receiving circuit 42 outputs a signal S12 to the load (for example, the imaging unit) of the head 12 based on the signal RD2 supplied from the controller 11 via the coaxial cable 13.

Next, the operation of the data transmission system 10 will be described.
The controller 11 and the head 12 of the data transmission system 10 are connected to each other via a coaxial cable 13 so that they can communicate with each other.

  FIG. 3 shows the differential signals SDp and SDn output from the differential driver 41 of the head 12. The differential driver 41 outputs differential signals SDp and SDn based on the differential signals S11p and S11n. Based on the signals SDp and SDn, an equivalent current (alternating current component) flows through the transmission path between the head 12 and the controller 11. For example, current flows from the output resistor R12 toward the negative output terminal of the differential driver 41 via the inner conductor 21 of the coaxial cable 13, termination resistors R2, R3, and R1, the outer conductor 22 of the coaxial cable 13, and the termination resistor R11. Flowing. Similarly, a current flows from the output resistor R13 through the termination resistor R11, the outer conductor 22, the termination resistors R1, R3, and R2, and the inner conductor 21. In addition, since it is an equivalent (alternating current) current, the capacitor is omitted in the description. Termination resistors R1, R2, and R3 of the controller 11 generate a voltage corresponding to the current flowing through the transmission line. Thereby, the signals SDp and SDn of the head 12 are transmitted as signals RDp and RDn.

  FIG. 5 shows the level difference between the negative input terminal and the positive input terminal of the differential receiver 33. The differential receiver 33 determines the level difference of the positive signal RDp with respect to the negative signal RDn and outputs signals S1p and S1n.

  The coaxial cable 13 includes an inner conductor 21 and an outer conductor 22, and the outer conductor 22 is disposed in a cylindrical shape centered on one inner conductor 21. Therefore, the outer conductor 22 functions as a shield line for the inner conductor 21. For this reason, noise applied to the coaxial cable 13 from the outside is hindered by the outer conductor 22 and is not added to the inner conductor 21. That is, the outer conductor 22 reduces the influence of noise on a signal transmitted through the inner conductor 21. Therefore, as shown in FIG. 4, the level of the signal S <b> 22 transmitted through the outer conductor 22 varies depending on the noise applied to the outer conductor 22.

  As shown in FIG. 2, a termination resistor R <b> 1 is connected between the outer conductor 22 a and the differential receiver 33. The external conductor 22a is connected to the signal ground SG1 via the impedance element Z1 and is connected to the frame ground FG via the capacitor C8. Capacitor C8 passes alternating current out of the supplied signal and blocks direct current components by capacitive coupling between the two electrodes. The impedance between the outer conductor 22 of the coaxial cable 13 and the frame ground FG is sufficiently higher than the impedance between the outer conductor 22 of the coaxial cable 13 and the negative input terminal of the differential receiver 33 and the negative output terminal of the differential driver 41. Low. The impedance between the external conductor 22 and the frame ground FG is sufficiently lower than the impedance between the external conductor 22 and the signal ground SG1 of the controller 11 and the signal ground SG2 of the head 12. Therefore, the high frequency component of noise superimposed on the signal S22 transmitted by the external conductor 22 passes through the capacitor C8 and flows to the frame ground FG.

  Since the termination resistor R1 is a resistor, it attenuates high-frequency noise superimposed on the signal S22. Therefore, the level of the signal RDn at the negative input terminal of the differential receiver 33 reduces the influence of noise. Therefore, the level difference between the minus input terminal and the plus input terminal of the differential receiver 33 changes as shown in FIG. 5 as in the case where noise is not mixed.

  Similarly, the impedance element Z1 acts as a resistance in the high frequency region, and attenuates noise that is a high frequency component superimposed on the signal S22 transmitted by the external conductor 22. Therefore, the influence of noise is reduced with respect to the level of the signal ground SG1 to which the impedance element Z1 is connected.

  In the head 12, the external conductor 22b is connected to the signal ground SG2 via the impedance element Z2. Therefore, similarly to the signal ground SG1 in the controller 11, the influence of noise on the signal ground SG2 in the head 12 is reduced.

  Note that the noise applied to the external conductor 22b is transmitted to the frame ground FG via the capacitor C8 as described above. Therefore, in the controller 11, the level of the frame ground FG varies according to noise. Due to the level fluctuation of the frame ground FG, the levels of the power supply wirings VP and VN may vary. However, the controller 11 has a line filter 31 connected to the power supply wirings VP and VN. Therefore, the level fluctuation of the frame ground FG is unlikely to affect the signal ground SG1 of the controller 11 by the line filter 31.

  The output terminal of the low-speed signal transmission circuit 34 is connected to the inner conductor 21a of the coaxial cable 13 via the capacitor C7. The inner conductor 21b of the coaxial cable 13 is connected to the input terminal of the low-speed signal receiving circuit 42 via the capacitor C13. The low-speed signal transmission circuit 34 outputs a so-called single-ended transmission signal SO to the internal conductor 21a based on the signal S2. The low-speed signal receiving circuit 42 outputs a signal S12 to the load (for example, the imaging unit) of the head 12 based on the signal RD2 supplied from the controller 11 via the coaxial cable 13. Therefore, the data transmission system 10 performs low-speed signal transmission from the controller 11 to the head 12 and high-speed signal transmission from the head 12 to the controller 11 via one coaxial cable 13, that is, bidirectional communication.

  The output terminal of the voltage conversion circuit 32 is connected to the internal conductor 21a via the coil L1 and the ferrite bead FB1. The voltage conversion circuit 32 outputs the operating voltage VD of the head 12 based on the output voltage of the line filter 31. Therefore, the data transmission system 10 transmits a signal and supplies the operating voltage VD to the head 12 using one coaxial cable 13. According to this configuration, it is not necessary to use a cable for supplying the operating voltage VD to the head 12 connected via the coaxial cable 13, and the installation of the head 12 becomes easy.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The controller 11 and the head 12 of the data transmission system 10 are connected via a coaxial cable 13 so as to communicate with each other. The coaxial cable 13 includes an inner conductor 21 and an outer conductor 22, and the outer conductor 22 is disposed in a cylindrical shape centered on one inner conductor 21. The inner conductor 21 is connected to the plus input terminal of the differential receiver 33, and the outer conductor 22a is connected to the minus input terminal of the differential receiver 33 via the termination resistor R1. The external conductor 22a is connected to the signal ground SG1 via the impedance element Z1 and is connected to the frame ground FG via the capacitor C8.

  The impedance element Z1 acts as a resistor in the high frequency region, and attenuates noise that is a high frequency component superimposed on the signal S22 transmitted by the external conductor 22. Capacitor C8 passes alternating current out of the supplied signal and blocks direct current components by capacitive coupling between the two electrodes. Therefore, the noise reflected by the impedance element Z1 passes through the capacitor C8 and flows to the frame ground FG. Therefore, it is possible to reduce the influence of noise on the level of the signal ground SG1 to which the impedance element Z1 is connected. The signals RDp and RDn at the input terminals of the differential receiver 33 are not easily affected by noise applied to the external conductor 22. Therefore, the occurrence of errors in the differential receiver 33 can be suppressed.

  (2) In the head 12, the external conductor 22b is connected to the signal ground SG2 via the impedance element Z2. Therefore, similarly to the signal ground SG1 in the controller 11, the influence of noise on the signal ground SG2 in the head 12 can be reduced. Then, it is possible to suppress the occurrence of errors in the differential driver 41 and the low-speed signal receiving circuit 42 connected to the signal ground SG2.

  (3) The capacitor C8 connected to the frame ground FG is a nonpolar capacitor. This is because the level of noise applied to the outer conductor 22a of the coaxial cable 13 exists both on the plus side and the minus side with respect to the level of the frame ground FG. For this reason, the capacitor C8 can suppress the voltage change of the signal ground SG1 by flowing noise in the high frequency region to the frame ground FG.

  (4) The capacitor C8 is preferably a high voltage capacitor. This is because the AC power supply voltage supplied to the power supply 14 may be used in an environment where the potential difference between the frame ground FG and the power supply wiring VN (signal ground SG1) is high (for example, about 100 volts). In some cases, the noise level is high (for example, about several kilovolts). For this reason, damage to the capacitor C8 can be prevented by using a capacitor with a high breakdown voltage as the capacitor C8.

In addition, you may implement each said embodiment in the following aspects.
In the above embodiment, the operating voltage VD of the head 12 is supplied from the controller 11, but a power source may be connected to the head 12 so that the operating voltage is supplied from the power source to the head 12. In this case, elements related to generation and supply of the operating voltage VD from the controller 11 can be omitted.

  In the above embodiment, signals are transmitted from the controller 11 to the head 12 using the low-speed signal transmission circuit 34 and the low-speed signal reception circuit 42, but these may be omitted depending on the configuration of the data transfer system.

In the above embodiment, the operating voltage VD is supplied to the head 12 using the coaxial cable 13, but the operating voltage VD may be supplied to the head 12 using another cable.
In the above embodiment, the signal from the low-speed signal transmission circuit 34 to the low-speed signal reception circuit 42 is transmitted using the coaxial cable 13. However, the signal may be transmitted using a cable other than the coaxial cable 13.

The technical idea grasped from each of the above forms will be described below.
(A) The coaxial communication device according to claim 1, further comprising a voltage conversion circuit that generates an operating voltage of the device connected to the inner conductor and connected via the coaxial cable. According to this configuration, it is possible to receive a signal and supply an operating voltage with a single coaxial cable. And it becomes unnecessary to use the cable for supplying an operating voltage to the apparatus connected via the coaxial cable, and installation of an apparatus can be made easy.

  (B) The coaxial communication device according to claim 1, further comprising a low-speed signal transmission circuit having an output terminal connected to the internal conductor. According to this configuration, signal reception and low-speed signal transmission, that is, bidirectional communication can be performed via one coaxial cable.

  (C) The first communication device includes a voltage conversion circuit that generates an operating voltage of the second communication device connected to the inner conductor and connected via the coaxial cable. 4. The coaxial communication device according to 3. According to this configuration, it is possible to receive a signal and supply an operating voltage with a single coaxial cable. And it becomes unnecessary to use the cable for supplying an operating voltage to the apparatus connected via the coaxial cable, and installation of an apparatus can be made easy.

  (D) The first communication device includes a low-speed signal transmission circuit having an output terminal connected to the internal conductor, and the second communication device includes a low-speed signal reception circuit having an input terminal connected to the internal conductor. The coaxial communication device according to claim 3, wherein According to this configuration, signal reception and low-speed signal transmission, that is, bidirectional communication can be performed via one coaxial cable.

  DESCRIPTION OF SYMBOLS 11 ... Controller (coaxial communication apparatus, 1st communication apparatus), 12 ... Head (coaxial communication apparatus, 2nd communication apparatus), 13 ... Coaxial cable, 21 ... Internal conductor, 22 ... External conductor, 33 ... Differential receiver (difference) Dynamic receiver), 41 ... differential driver (differential transmitter), R1 ... termination resistor (first termination resistor), R2 ... termination resistor (second termination resistor), R3 ... termination resistor (third termination resistor) Resistance), R11 ... termination resistance, R12, R13 ... output resistance, C8 ... capacitor, Z1, Z2 ... impedance element, SG1 ... signal ground (first signal ground), SG2 ... signal ground (second signal ground), FG: Frame ground.

Claims (6)

A coaxial communication device for receiving a signal via a coaxial cable composed of one inner conductor and an outer conductor,
A differential receiver in which a positive input terminal is connected to the inner conductor and a negative input terminal is connected to the outer conductor;
A first termination resistor connected between the outer conductor and the negative input terminal of the differential receiver;
A second termination resistor connected between the positive input terminal of the differential receiver and a signal ground;
A third termination resistor connected between the negative input terminal of the differential receiver and the signal ground;
An impedance element connected between the outer conductor and the signal ground, having a characteristic of passing a signal in a low frequency region and blocking a signal in a high frequency region;
A capacitor connected between the outer conductor and a frame ground;
A coaxial communication device comprising: A coaxial communication device connected to the coaxial communication device according to claim 1 via a coaxial cable comprising one inner conductor and an outer conductor,
A differential transmitter in which a positive output terminal is connected to the inner conductor and a negative output terminal is connected to the outer conductor via a terminating resistor;
An impedance element connected between the outer conductor and a signal ground, having a characteristic of passing a signal in a low frequency region and blocking a signal in a high frequency region;
A coaxial communication device comprising: A coaxial communication device having a first communication device and a second communication device connected via a coaxial cable composed of one inner conductor and an outer conductor,
The first communication device is
A differential receiver having a positive input terminal connected to the inner conductor and a negative input terminal connected to the outer conductor via a first termination resistor;
A second termination resistor connected between the positive input terminal of the differential receiver and a first signal ground;
A third termination resistor connected between the negative input terminal of the differential receiver and the first signal ground;
An impedance element connected between the outer conductor and the first signal ground, having a characteristic of passing a signal in a low frequency region and blocking a signal in a high frequency region;
A capacitor connected between the outer conductor and a frame ground;
With
The second communication device is
A differential transmitter having a positive output terminal connected to the inner conductor and a negative output terminal connected to the outer conductor via a fourth termination resistor;
An impedance element connected between the outer conductor and the second signal ground, having a characteristic of passing a signal in a low frequency region and blocking a signal in a high frequency region;
A coaxial communication device comprising:   The coaxial communication device according to claim 1, wherein the impedance element is an element including a magnetic material.   The coaxial communication device according to claim 1, wherein the capacitor is a high voltage capacitor.   The coaxial communication device according to claim 1, wherein the capacitor is a nonpolar capacitor.