RU2058669C1 - Device for bidirectional amplification of signals for two-wire line - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: invention relates to high-frequency communication. In device for two-way amplification of signals in two-wire line Ll first lead of resistor R2 is linked to center lead 4 of first winding of differential transformer 1 and second lead of resistor and second lead of output of amplifier 2 are grounded to expand application field of bidirectional amplifier of two-wire lines, to conduct contactless inductive high-frequency communication over unidirectional lines, to enhance reliability and to simplify communication system. EFFECT: expanded application field and enhanced operational reliability of device. 1 dwg

Description

 The invention relates to techniques for high-frequency communication in coal mines and provides two-way amplification of a signal of a single frequency or frequency band in a single-wire line.

 Studies in our country and abroad have established that for covering large distances, as well as for radio communications in an extensive network of mine workings, contactless systems of high-frequency (HF) inductive radio communications along guiding conductors using linear amplifiers can be industrially reliable (Olaf J. Royters H. Propagation of electromagnetic waves underground.Glukauf N 23, Dec. 1984, p.15-22; Investigate the principles of organization and develop functional requirements for a system for the general notification of workers about accidents on the basis of wearable radiotelephone devices. Report on research at the MakNII, led by Redzio A.G. Babkov S.V. topic N 1714321000, N state registration 01890021317. Makeevka-Donbass, 1990, p.118). Moreover, since the connection must be two-way from any point in the mine with any other point in the same or other mine, the amplifiers must be bi-directional.

 Amplifiers are known that are used for bi-directional amplification of speech signals transmitted over two-wire lines (Baguts V.P. Tyurin V.L. Multichannel telephone communication in railway transport, M. Transport, 1988, pp. 20-28). On these circuits, currents of the same frequency band are transmitted in both directions. Two-sided amplifiers of this type use two amplifying elements, each of which amplifies the currents passing in one direction of transmission. To distinguish transmission directions, amplifying elements are included in two-wire circuits through differential systems.

 The disadvantage of such amplifiers is the difficulty in selecting the resistance of the balanced circuit equal to the resistance of the linear circuit. Moreover, this condition must be satisfied on both sides of the amplifier. As you know, the line resistance varies from climatic factors, and in mine workings it also depends on geological and mining factors. As a consequence, the differential systems of two-sided amplifiers are usually unbalanced to one degree or another, which leads to their self-excitation. The currents of the oscillator generation frequency propagate along a linear circuit on both sides of the amplifier and are perceived in the apparatus as interference. In addition, such amplifiers are designed to amplify low-frequency telephone signals in two-wire lines and cannot be used in RF communication lines in which ground is used as the second wire.

 Known bidirectional amplifier used for such a line (ed. St. USSR N 1575292, CL N 04 B 3/36, 1990).

 Its disadvantage is the impossibility of simultaneously amplifying signals in two directions, and the direction of transmission of the amplified signal is achieved by switching a negative or positive voltage along the power supply circuit.

 Using a single-wire line compared to a two-wire line is more acceptable for economic reasons (there is no need to physically lay two insulated wires as an RF line). In addition, the use of a two-wire line for non-contact HF radio communication has a significant drawback associated with the fact that in order to improve the transmit-receive properties of the wire line, it must be spaced about 0.2-0.5 m apart (the best option is on opposite sides of the workings walls ) (Lindeman V. Ratz V. Vogt. Radio remote control and radiotelephone communication device for underground rail transport, Gluckauf N 5, p. 30. Therefore, in mining workings, it is most advisable to use two-wire lines in which the second gadfly is the "ground" (ie, single-ended lines) and bi-directional amplifiers.

 A known system that uses the "ground" as a second wire for RF communication with mines (ed. St. USSR N 1411982, class N 04 B 3/36, 1986). This system uses an artificial circuit to wire the ground line as a guide system for the propagation of electromagnetic waves along it. To ensure the necessary range and quality of radio communication along this line, pairs (even and odd) of amplifiers are installed, which are connected in a special way to a two-wire line and ground.

 For the functioning of this system, a two-wire line is needed to connect a pair of amplifiers. It is not possible to use single amplifiers of this system for a single-wire line.

 A technical solution is known, taken as a prototype (ed. St. USSR N 1309320, class N 04 B 3/36, 1987), allowing to replace a pair of amplifiers with one and eliminating the need to select elements of a balanced circuit. The device contains a differential transformer (DT) and an amplifier. One winding of the DT is connected in series in the first wire of the two-wire line, one in the second wire of the line, and the third winding of the DT is connected to the inputs of the amplifier. The amplified signal is fed into the line through the terminals of the first and second windings of the DT, respectively, when the signal propagates in both directions.

 The disadvantage of this device is that it is designed to amplify low-frequency signals in two-wire lines and it cannot be used in HF single-wire communication lines in which the earth serves as the second wire. Direct use of the device in a single-wire line is impossible, since the connection to the ground of the winding makes it short-circuited.

 The purpose of the invention is the expansion of the scope of the two-sided amplifier of two-wire lines for amplifying signals in single-wire lines (the second wire is ground), as well as improving the reliability and simplification of the communication system.

 The goal is achieved in that in a two-way signal amplification device for a two-wire line containing a differential transformer, the primary winding of which is connected in series to the first wire of the two-wire line loaded on both sides with resistors, the secondary winding is connected to the inputs of the amplifier, one output terminal of which is connected to the middle the output of the primary winding of the differential transformer, and the other output of the output with the second wire of the two-wire line, between the middle terminal of the primary winding of the differential transformer ceiling elements and the second two-wire line wire resistor is included, wherein the second lead wire line is "land".

 The presence of the above distinguishing features ensures the achievement of a positive effect of the proposed technical solution.

 The drawing shows the proposed device for two-way signal amplification, comprising a transformer 1, amplifier 2, a single-wire line L1 (second ground wire), load resistors R1, R2, R3 equal to the wave impedance of the line. Transformer 1 has a primary winding 3-5 with a middle terminal 4, connected in series to a single-wire line L1, and a secondary winding 6-7 connected to the input of amplifier 2. The output of amplifier 2 is connected to the midpoint 4 of transformer 1 and to one terminal of resistor R2. The ends of the line L1 are loaded on the resistors R1 and R3. The second terminals of the resistors R1, R2, R3 and the second terminal of the amplifier 2 are grounded.

 The device operates as follows.

 Induced from the radiotelephone, for example, in the left shoulder of the L1 line, the signal current flowing through the half-winding 3-4 of transformer 1 induces an EMF in the winding 6-7. After amplification by amplifier 2, the signal enters the load resistor R2, the middle terminal 4 of transformer 1 and is fed to both sides of the line. The currents flowing through the semi-windings 3-4 and 4-5 create counter magnetic fluxes in the magnetic circuit of the transformer 1, which does not cause the induction of an additional EMF in the windings 6-7 of the transformer 1, thereby providing the effect of amplifying a signal of one frequency in both directions. Similarly, the amplification process takes place in the opposite direction when applying signals from the other shoulder of the line due to the symmetry of the circuit. The maximum possible gain of the device is equal to the common-mode rejection ratio of the transformer 1 and reaches in practice 50 dB. With a large gain of the device and the occurrence of asymmetry of the lines, the device is excited, which can be used to monitor the status of the lines. With a device gain of about 15 dB, excitation is not observed with line asymmetry.

 The use of a double-sided linear amplifier circuit will make it possible to create simple systems of general-mine technological systems of RF inductive radio communications.

 An example of a practical implementation of the device.

 The device for bilateral amplification of radio signals in a single-wire line is made on a 40x80 mm-thick foil fiberglass board and contains a core transformer M1000NI-AO 284, one operational amplifier KR140UD1, transistors KT315B 1 pc. KT815G 1 pc. The device is placed in a plastic case measuring 45x85x20 mm and tested at the Novodonetskaya mine of the Dobropolye Coal Production Association in recoil drifts at a horizon of 320 m. The amplifier is powered by a constant voltage of 10 V from an autonomous power source. A single-wire line at the Novodonetskaya mine was a single core of telephone cable laid along the route in a northerly direction: the Northern field haulage drift, the northern root haulage drift to the L3 formation, a crosshitch, a bypass slope of the L3 formation (the total length of the northern direction was about 4 km) , as well as southward from the trunk along the route: Southern field haulage, southern haulage of the K7 layer, southern drainage line of the K7 formation (the total length of the southern direction was about 3 km). The total length of the line is approximately 7 km. At the beginning, end and middle of the line, one device for two-way signal amplification was installed.

 Radio communication in the development was carried out using wearable type Dnepro-NSh radio telephones operating at a carrier frequency of 250 kHz (wearable radio station Dnipro-NSh. Technical description and instruction manual. ILGD. 464511.001 TO. Dnepropetrovsk, 1991, p.63) .

 The line was balanced at the terminal amplifiers by connecting an RC chain with an adjustable resistor to the free arm of the amplifier. Wearable radio stations were connected with a single-wire waveguide line using a frame (magnetic) antenna.

 Compared with the prototype, the proposed technical solution allows you to expand the scope of the bi-directional amplifier on two-wire lines, one wire on which is the "ground" (ie on single-wire lines), which gives an economic effect, since laying a single-wire line in comparison with a two-wire requires less material for the line and labor; improve reliability and simplify the communication system using bi-directional amplifiers for non-contact inductive RF radio communication along one guide conductor. This consists in the ability to communicate from anywhere in the mine in which the guide wire is laid. The use of bi-directional amplifiers in a two-wire line provides communication only with stationary devices installed in strictly defined places.

Claims (1)

 A TWO-WAY SIGNAL AMPLIFICATION DEVICE FOR A TWO-WIRE LINE, comprising a differential transformer, the primary winding of which is connected in series to the first wire of the two-wire line, the secondary winding is connected to the inputs of the amplifier, one output terminal of which is connected to the middle output of the primary winding of the differential transformer, and the other is connected to the second wire of a two-wire line, characterized in that between the middle terminal of the primary winding of the differential transformer and torym included two-wire line wire resistor, wherein the second wire is an earth wire line.