JPH03253139A - Emi detection system in communication system - Google Patents

Abstract

PURPOSE:To accurately recognize the influence of an EMI upon a communication system by using an amplifier, a detection circuit, a high frequency noise detection part, a pulse noise detection part, a listenable noise detection part, and an EMI detector. CONSTITUTION:The electro-magnetic interference(EMI) detector 1 is constituted of the amplifier 11 for amplifying an input signal, the high frequency noise detection part X consisting of a detection circuit 12, a detection circuit by-pass part 19b and a level setting circuit 15a, the pulse noise detection part Y consisting of a pulse shaping circuit 13 and a level setting circuit 15b, the listenable noise detection part Z consisting of a level setting circuit 15c, and a display circuit 16. An idle pair lines are connected to the amplifier 11, the output of the amplifier 11 is impressed to respective detection parts X, Y, Z and the outputs of the detection parts X, Y, Z are displayed on the display circuit 16. Thus, whether a communication system such as an ISDN system and a home bus system is influenced by EMI or not can be decided only by connecting a modular jack to the bus wiring of the system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention is directed to electro-magnetic technology that affects the normal operation of a communication system using bus wiring such as an I5DN system or a home network system.
etic interference) This is related to the detection method number.

[Prior Art 1] Conventionally, whether or not a communication system is influenced by radio waves from amateur radio, CB radio, commercial broadcasting stations, etc. has been detected and measured using a method as shown in FIG.

In FIG. 2, 1 is a bus wiring, 3 is a terminal device, 4 is a dipole antenna, and 5 is an EMI detector.

In the method shown in FIG. 2, EMI near the terminal device 3 or bus wiring 1 is measured with a dipole antenna 4, and the measured EMI is guided to the terminal device 3 or the bus wiring 1, causing noise in the terminal device 3. The influence of EMI was estimated by changing the direction and distance of the dipole antenna 4 to determine whether the antenna is operating or malfunctioning. For this reason, even if the EMI detector 5 is able to detect radio waves, it is unclear whether they actually have an effect on the communication system such as the bus wiring 1 or the terminal device 3 (for example, depending on the presence or absence of a shield in the bus arrangement! 1). (the effects differ depending on the measurement person's experience and know-how). Furthermore, in order to check the presence or absence of noise on the bus arrangement i1, etc., measurements were performed using the method shown in FIG.

In FIG. 3, 1 is a bus wiring, 3 is a terminal device, 5 is an EMI detector, and 6 is a current clamp.

In the method shown in FIG. 3, the current clamp 6 is attached to the cord of the terminal device 3 or the bus wiring 1 for measurement, which is time-consuming. On the other hand, regarding the magnetic field component, since a loop antenna was connected in place of the dipole antenna 4 shown in FIG. 2, there was a problem similar to that which occurred when the dipole antenna 4 was used.

As mentioned above, conventional methods reduce EMI to communication systems.
The influence of this method often depends on the experience and know-how of the measurer, and since it was necessary to change the measurement position (distance), direction, etc., there was a drawback that it required a lot of operation.

An object of the present invention is to provide an EMI detection method that can determine whether a communication system such as an 15DN system or a home bus system is affected by EMI by simply connecting it to the bus wiring of the communication system using a modular jack. .

[Means for Solving the Problems] An EMI detection method in a communication system according to the present invention includes an amplifier that amplifies an input signal, a high frequency noise detection section consisting of a detection circuit, a detection circuit bypass section, and a level setting circuit, and a pulse shaping section. Using an EMI detection device consisting of a pulse noise detection section consisting of a circuit and a level setting circuit, an audible noise detection section consisting of a level setting circuit, and a display circuit, an empty pair of wires is connected to an amplifier, and the output of the amplifier is converted into a high frequency signal. The signal is applied to a noise detection section, a pulse noise detection section and an audible noise detection section, and the outputs thereof are displayed on a display circuit.

Further, in the present invention, the empty pair wire is grounded when the immunity level (noise tolerance) is exceeded.

[Operation] In this invention, a vacant pair of wires in the bus wiring is connected to an amplifier, the output of the amplifier is applied to the high frequency noise detection section, the pulse noise detection section, and the audible noise detection section, and the output at that time is applied to the display circuit. EMI is detected by displaying the information.

And when EMI exceeds the immi-unity level,
EMI induced noise is reduced by grounding the empty pair of wires.

[Example] An embodiment of this invention is shown in FIG.

In Figure 1, 1 is the bus wiring for the l5DN system, home bus system, etc., 1a, 1b, and Ic are pair wires, and l5D
Pair wires 1a and 1b are unused in N, 18 in home bus
~1C information channels are normally unused. 2a, 2
b is a terminating resistor with a resistance value equal to the characteristic impedance of the cable, 3 is a terminal device for 15DN or home bus system, 10 is an EMI detection device, 11 is an amplifier for the band from DC to about 30 MHz, and 12 is an AM/FM high frequency A detection circuit 13 is a pulse shaping circuit that shapes pulses synchronized with the AC power supply, 14a and 14b are switches that turn off AM/FM high frequency detection, pulse noise detection, and audible noise detection, respectively.
Interlock. 15a, 15b, and 15c are level setting circuits that set the level according to the immunity level of equipment, systems, etc. Level setting is performed for each noise type;
Decide how much noise to detect. For example, terminal device 3
The bus is #! If a malfunction or noise occurs when the noise level induced from 1 is 50 dBm, the level setting circuit 15
a is set to detect noise of 50 dBm or more.

The same applies to the level setting circuits 15b and 15c.

16 is a display circuit such as an LED or a meter, and 17a and 17b are switches for selecting an empty bare wire, which are interlocked. 18a, 1
8b is a switch for installing bare cotton after detecting EMI, which is interlocked. 19a and 19b are the detection circuits 1 for detecting malfunction of the system due to high frequency components;
This switch is used to bypass 2. 20
Reference numeral 21 indicates a detection circuit bypass section, and 21 indicates a grounding terminal for connecting and grounding the vacant pair of wires to a protector ground or the like. and,
Detection circuit 12. Level setting circuit 15a, switch 19a
, 19b, a high frequency noise detection section X is configured by the detection circuit bypass section 2o, a pulse shaping circuit 13, and a level setting circuit 1.
5b constitutes a pulse noise detection section Y, and furthermore, the level setting circuit 15c constitutes an audible noise detection section 2.

Next, the operation shown in FIG. 1 will be explained.

This embodiment is an example applied to an 15DN system, and in FIG. 1, an empty pair 1a or 1b of two pairs of bus wiring 1 is selected by operating the switches 17a and 17b. By operating the switches 14a and 14b, the AM/FM high frequency noise detector X, pulse noise detector Y, or audible noise detector 2 is selected, and EMI induced onto the bus wiring 1 is detected.

The detection circuit 12 detects AM and FM high frequencies.
The frequency band to be detected is limited. Therefore, the terminal device 3
In order to detect high frequency components that may cause the detector to malfunction, the detector circuit 12 is connected to the detector circuit bypass section 20 and the switch 19a.
, 19b.

When EMI on bus wiring 1 is detected, switch 18a,
By operating 18b and grounding the empty pair wire to the protector earth, etc., a shielding effect is created and the EMI on the bus wiring 1 is
Induced noise can be reduced.

Note that although the above embodiment has been described in which the amplifier 11 is shared by various types of noise, it is also possible to separately configure the amplifier 11 for each type of noise. Furthermore, the switch 14a is not used and the amplifier 11
The output of the switch 14b is applied in common to the high frequency noise detection section X, the pulse noise detection section Y, and the audible noise detection section Z.
One of them may be selected and displayed on the display circuit 16, or the outputs of each section X, Y, and Z may be displayed simultaneously on the display circuit 16 without using the switch 14b.

Further, the level setting circuits 15a, 15b, and 15c are for setting the immunity level of the communication system.
By setting the immunity level of the communication system in advance and incorporating such a circuit into the terminal device 3, maintenance and operation of the communication system can be reduced.

In this embodiment, a switch 14a is shown as a principle diagram.

14b, 17a, 17b, 18a, 18b is shown as an example of manual operation, but the switches 14a, 14
b is set to automatic switching, and as a result, switches 18a and 1
8b is also easy to operate.

Note that the detection method of the present invention is based on the IS shown in the embodiment.
It can be applied not only to DN systems but also to home bus systems and subsystems between devices (for example, D2B systems).

[Effects of the Invention] As explained above, the present invention includes an amplifier that amplifies an input signal, a high frequency noise detection section consisting of a detection circuit, a detection circuit bypass section, and a level setting circuit, and a pulse shaping circuit and a level setting circuit. a pulse noise detection section,
Using an EMI detection device consisting of an audible noise detection section consisting of a level setting circuit and a display circuit, empty bare cotton is connected to an amplifier, and the output of the amplifier is connected to a high frequency noise detection section, a pulse noise detection section and an audible noise detection section. Since EMI is applied to the communication system and the output thereof is displayed on the display circuit, the influence of EMI on the communication system can be accurately grasped, making it easy to take countermeasures and significantly reducing maintenance operations.

Furthermore, in this invention, the empty pair wires are grounded when the immunity level is exceeded, so that EM on the bus wiring
This has the advantage of reducing I-induced noise.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining an example of detecting a conventional electric field component, and FIG. 3 is a diagram showing an example of detection using a conventional current clamp.

Claims (2)

[Claims] (1) Consists of an amplifier that amplifies the input signal, a high-frequency noise detection section consisting of a detection circuit, a detection circuit bypass section, and a level setting circuit, a pulse noise detection section consisting of a pulse shaping circuit and a level setting circuit, and a level setting circuit. Using an EMI detection device composed of an audible noise detection section and a display circuit, an empty pair of wires is connected to the amplifier, and the output of the amplifier is applied to the high frequency noise detection section, the pulse noise detection section, and the audible noise detection section. EMI in a communication system characterized by detecting and displaying the noise level to the communication system by displaying these outputs on the display circuit.
Detection method. (2) Consists of an amplifier that amplifies the input signal, a high-frequency noise detection section consisting of a detection circuit, a detection circuit bypass section, and a level setting circuit, a pulse noise detection section consisting of a pulse shaping circuit and a level setting circuit, and a level setting circuit. Using an EMI detection device composed of an audible noise detection section and a display circuit, an empty pair wire is connected to the amplifier, and the output of the amplifier is applied to the high frequency noise detection section, the pulse noise detection section, and the audible noise detection section. An EMI detection method in a communication system, characterized in that these outputs are displayed on the display circuit, and the empty pair of wires is grounded when the immunity level is exceeded.