JPH02131032A - Transmission method for densely coupled signal - Google Patents

Abstract

PURPOSE:To attain immunity against external noise and to prevent reception electric field intensity from being changed due to the movement of an electric equipment by arranging a signal cable with two insulation conductors twisted in pairs and coupling the antenna with the signal in the TEM mode formed when a signal is propagated between the insulation conductors. CONSTITUTION:A couple of loop antennas 32, 32' are provided on an opposite position to a pair twisted cable 11 at a prescribed interval via a supporting member 31. When parallel conductors are twisted at a prescribed pitch, an electromagnetic field is changed in a sinusoidal shape in the axial direction with respect to the direction of the parallel conductors perpendicular to the aperture, that is, the direction of the loop antenna 32. Then the electromagnetic field at a sufficiently remote location from the twist pitch P is cancelled by the electromagnetic fields of opposite phase to each other from line segments by P/2 and the electromagnetic field strength is rapidly attenuated. Thus, the noise coming from a remote location is cancelled by all the line segments of the pair twisted cable, thereby forming a transmission system with a high noise elimination capability. Moreover, the stable transmission system is formed by twisting the parallel conductors 14, 14' without capacitance unbalance with the earth system.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a signal transmission method, and more specifically, between a signal cable arranged along a trolley conductor and an antenna facing the signal cable, The present invention relates to a tightly coupled signal transmission method for transmitting information to and from a mobile device in a non-contact manner.

[Prior art] Used for automatic transportation of parts in assembly processes, automatic transportation of products between processes, unmanned monitoring in poor environments, etc.
Much of the power supply to automatic equipment moving on lines is accomplished by sliding trolley conductors. Furthermore, the transmission of control information to the mobile equipment and the transmission of monitoring information from the mobile equipment are carried out using a single wire disposed along the trolley conductor.
This is performed using a tightly coupled signal transmission device between an open transmission line such as a parallel conductor or a leaky coaxial cable, and an antenna facing the open transmission line.

Hereinafter, a conventional tightly coupled signal transmission device will be explained with reference to FIG. In the figure, a hanger 21 in which three parallel rails 22, 22' are formed is fixed to a long wiring rail main body 20, and a hanger 21 in which three parallel rails 22, 22' are formed is fixed to the long wiring rail main body 20. Two trolley conductors 23 for supplying power are fixed via an insulator 24. Further, in the other groove 22', a signal leakage line 41 formed of a leaky coaxial cable or the like is buried in the large diameter part, and a gourd-shaped sheath 42 in which a hanging wire 43 is buried in the small diameter part is fixed.

Furthermore, the trolley conductor 23 is electrically contacted with a brush 25 which is biased to protrude outward by a spring 26 provided on the main body 27 of the electrical equipment, and is located at a position facing the signal leakage line 41. , the support member 3 while maintaining a predetermined distance.
A loop antenna 30 is provided via 1.

Therefore, power is supplied to the electrical equipment main body 27 by the two trolley conductors 23 via the two brushes 25, and the signal supplied to the signal leakage line 41 is transmitted to the electrical equipment main body 27 via the loop antenna 30. Also, the electrical equipment body 2
Signal transmission is performed by supplying the signal from 7 to the signal leakage line 41 via the loop antenna 30.

However, due to the inherently high noise level of the environment in which this type of equipment is installed and the noise generated when the trolley conductor slides, conventional equipment cannot perform stable signal transmission with moving electrical equipment. The problem was that there was no. This problem can be solved by increasing the electromagnetic field strength, but
It was also difficult to meet the regulations of the Radio Law for weak radio stations (field strength of 500 μV/m = 54 dBμV/m or less at a point 3 meters away from the antenna).

[Problems to be Solved by the Invention] The present invention has been devised in view of the above-mentioned points. Another object of the present invention is to provide a tightly coupled signal transmission method in which the received electric field strength does not change due to movement of electrical equipment.

[Means and effects for solving the problem] In the tightly coupled signal transmission method of the present invention, a signal cable is arranged along a wiring rail that supplies power to moving electrical equipment in a sliding manner. In a signal transmission method, the signal cable is an insulated conductor, and the signal cable is an insulated conductor. It is characterized in that it is made by twisting two wires in pairs, and the antenna is coupled to a TEM mode that is formed when a signal propagates between the insulated conductors.

By using the twisted pair signal cable as described above, the electromagnetic field formed around the cable is canceled out and weakened, and generation of the electromagnetic field into the external space can be suppressed. Furthermore, by using two loop antennas arranged at an interval of (2n+1)/4 times the twisting pitch of the insulated conductors, the electromagnetic field strength in the length direction of the signal cable can be made constant.

[Example] An embodiment of this invention will be described below.

First, the structure of the embodiment will be explained with reference to FIG. In the figure, a hanger 21 in which three mutually parallel grooves 22, 22° 22' are formed is fixed to a long wiring rail main body 20, and an electrical equipment main body 27 is provided in the grooves 22 of the hanger 21. Two trolley conductors 23 for supplying power to are fixed via an insulator 24. Further, a gourd-shaped sheath 42 in which a twisted pair cable 11 made of parallel conductors twisted at a constant pitch is embedded is fixed in the other groove 22''.

Furthermore, the trolley conductor 23 is electrically contacted with a brush 25 which is given an outward protruding force by a spring 26 provided on the electrical equipment main body 27, and is placed in a predetermined position opposite to the twisted pair cable 11. Support member 31 while keeping a distance
A pair of loop antennas 32, 32' are provided via the antenna.

Therefore, power is supplied to the electrical equipment body 27 by the pair of trolley conductors 23 via the pair of brushes 25, and the signal supplied to the twisted pair cable 11 is transmitted to the antenna 3.
2.32'' to the electrical equipment main body 27, and signals from the electrical equipment main body 27 are supplied to the twisted pair cable 11 via the antenna 32.32', thereby performing signal transmission. .

Next, the embodiment will be described in further detail with reference to FIGS. 2 to 4.

Figure 2 shows the electric field E and magnetic field H1, that is, the TEM wave (tr
anverse electromagnetic wave). Here, the direction perpendicular to the aperture plane of the parallel conductors 14, 14', that is, the direction of the loop antenna 32 is used as a reference (
When θ=0), the magnetic field strength ΔH3□ generated around the unit line segment of the parallel conductor 14.14' is ΔH3゜-A(r)・B(q)・CO8θ...(1)
However, the distance of the unit line segment of parallel conductor 14.14' is A
(r), and the Hertzian dipole efficiency of the unit line segment of the parallel conductor 14, 14' is B (q).

From this equation, it is predicted that when parallel conductors are twisted at a constant pitch, the electromagnetic field changes sinusoidally in the axial direction.

Next, the electromagnetic field formed around the twisted pair cable 11 will be explained with reference to FIG. In the figure, the parallel conductors 14.14' of the twisted pair cable 11 are twisted at a constant pitch P, and as shown in the figure, the parallel conductors 14.14'
If the axial deviation of the loop antenna 32 is Z and the twisting pitch is P, starting from the position where the aperture of the parallel conductor 14.14' faces the loop antenna 32, then the angle α between the aperture of the parallel conductor 14 and 14' and the antenna 32 is is α=2πZ/P (2). Therefore, using equation (1), the magnetic field strength from all segments of the parallel conductor 14, 14' at the distance of the loop antenna 32 is calculated as follows: H32= f A (r) ・B (Q) ・cos
(θ+2πZ/P)dθ (3). Here, cos (θ+2 yr Z / P) cos θ
-c o s (2πZ/P) -s i
Transforming equation (3) using the mathematical formula n (2'rZ/P)・sinθ, H32=J' A (r) ・B (q) ・COSθ
-cos (2πZ/P)dθ, FA(r) ・B (q)-sinθ-sin
(2πZ/P)dθ---(4) is obtained. Since the function B (q) in the equation is a quantity proportional to the signal, it can be considered constant for now, and since the function A (r) is symmetrical with respect to θ, the right-hand side of the above equation (4) The second term becomes O.

Therefore, with C as a constant, H32-J'A (r) ・B (q)
・ cos θ−cos (2πZ/P) dθ = C−cos (2π・Z/P) is derived, and it is understood that the electromagnetic field formed around the twisted pair cable changes sinusoidally in the axial direction. Ru.

Now, when the electromagnetic field changes sinusoidally in the axial direction in this way, the electromagnetic field sufficiently far away from the twist pitch P is canceled out by the electromagnetic fields with mutually opposite phases from line segments separated by P/2, and the electromagnetic field rapidly changes. The intensity will be reduced. This electromagnetic field characteristic is shown in FIG. 4 together with the electromagnetic field characteristic of the conventional example.

From the above explanation, it is clear that the twisted pair cable forms an electromagnetic field that is sufficiently strong over the transmission distance and rapidly attenuates at a distance, and for the same reason, the noise coming from a long distance is transmitted over the entire length of the twisted pair cable. In addition, the parallel conductor 14
．． It is easily understood that by twisting the strands of 14", a stable transmission system can be formed without a capacitance imbalance with the ground system.

However, the fact that the electromagnetic field changes sinusoidally with respect to movement in the axial direction means that signal transmission may not occur depending on the position of the loop antenna, and this method cannot be used immediately for signal transmission. . Therefore, the present invention has been developed so that the twist pitch of the twisted pair cable 11 is (2n + 1
) / 4 times (n0.1, 2. . . ) by arranging two loop antennas 32, 32' at an interval of n0.1, 2, . . . to solve this problem. Note that the value of n can be arbitrarily determined in consideration of the twisting pitch or the mutual interference of the loop antennas.

Let's continue the explanation. Similarly to the derivation of equation (5) above, the magnetic field strength H32 of the loop antenna 32' is determined as follows: H32= =C-cos (2πZ/P+π/2)
C-s in (2πZ/P) (6). The output of the loop antenna 32° that detects this magnetic field is phase-shifted by π/2 or π/2 by the phase shifter 15, mixed with the output of the other loop antenna 32, and output to the terminal T. Therefore, the received voltage ■ generated at the terminal T is expressed by the following equation.

V=C(cos (2rZ/P) ± j -sin (2'rZ/P))
. . . 17) Equation (7) expresses that although the phase of the received voltage ■ changes as Z changes, that is, as the loop antenna 32, 32' moves, the amplitude remains constant. As a result, the present invention not only enables stable signal transmission, but also allows the position of electrical equipment to be determined by detecting changes in phase.

In addition, instead of the method of phase-shifting and adding the signals obtained from one loop antenna as described above, the same purpose can also be achieved by generating the absolute value of the signals obtained from both loop antennas using a detection means etc. and adding them. It is possible to achieve this. That is, VOcICO52πZ/P +1sin2πZ/Pl (8) has a relatively constant amplitude, and with a simple configuration it is possible to perform stable signal transmission regardless of the position of the electrical equipment main body 27. be.

[Effects of the Invention] As described above, according to the present invention, (1) Sufficient electric field strength can be obtained over a transmission distance, and electromagnetic field characteristics can be obtained that rapidly attenuate at a long distance.

(2) Stable signal transmission is possible because there is no capacity imbalance between the twisted pair cable and the ground system.

(3) Induced voltages from adjacent trolley conductors and other external noises are canceled out.

(4) The moving distance of the electrical equipment can be determined from the phase change of the received signal.

It is possible to provide a tightly coupled transmission method that achieves this remarkable effect.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view explaining the structure of an embodiment of the present invention, Figure 2 is a diagram explaining TEM waves formed by parallel conductors, and Figure 3 is the geometric relationship between the twisted pair cable and the loop antenna. FIG. 4 is an electromagnetic field characteristic diagram, and FIG. 5 is a cross-sectional view explaining the structure of a conventional example. 11 ・ 14, 14' 15 ・ 23 ・ 27 ・ 32, 32'

Claims (2)

[Claims] (1) A signal cable is arranged along a wiring rail that supplies power to moving electrical equipment in a sliding manner, and the signal cable is connected to the signal cable through an antenna that is electrically coupled to the signal cable in a non-contact state. In a signal transmission method for transmitting an information signal to or receiving an information signal from an electrical device, the signal cable is made up of two insulated conductors twisted in pairs, and when the signal propagates between the insulated conductors, A tightly coupled signal transmission method, characterized in that the antenna is coupled to a TEM mode formed in a TEM mode. (2) The tightly coupled signal transmission method according to claim 1, wherein the antenna comprises two loop antennas arranged at an interval of (2n+1)/4 times the twisting pitch of the insulated conductor.