JPS5943346B2 - automatic gain adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ATC (self-adjusted trolley control) device, and more particularly to an automatic gain adjustment device for keeping the receiving input of a receiving device installed on a train constant.

In the case of conventional ATC, the level difference between the transmitting end and the ground receiving end is about 20 dB, so the on-vehicle receiver must cover this level difference for reception. Therefore, the input level range of the on-vehicle receiver needs to be extremely wide. Furthermore, if the input level difference is large, the amount of out-of-band attenuation of the filter of the on-vehicle receiver must be correspondingly large, which has the disadvantage that the entire device becomes uneconomical. SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic gain adjustment device that eliminates the above-mentioned drawbacks and can maintain a constant receiving current of an on-board receiver no matter where the train is located.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. In the figure, reference numeral 1 indicates an arithmetic circuit that detects the transmitting end current and transmitting end voltage and calculates the ratio thereof, and reference numeral 2 indicates the arithmetic circuit 1.
An analog-to-digital converter (A/D converter) that converts the calculation result into digital data is shown. Reference numeral 3 indicates a read-only memory (ROM) that generates a digital value corresponding to the input digital value, and reference numeral 4 indicates a digital-to-analog converter (D/A converter) that converts the digital value into an analog value. . Reference numeral 5 is a controller that controls the amplifier 6 based on the output of the D/A converter 4. Reference numeral T designates a transmission amplifier, reference numeral 8 a transmission coupler for transmitting the signal to the track circuit, reference numeral 9 a current transformer for measuring the transmission current and reference numeral 10 a transmission signal line. Also, reference number 1
1 indicates the receiver installed in the evening storage 12, and the reference number 1
3 indicates a track (rail). Further, reference numerals 100 and 200 indicate transmitting current receiving sections and receiving current extracting sections provided at predetermined distances on the track 13. Second
The figure shows an equivalent circuit of the line in FIG. 1, and the operation of the automatic gain adjustment device will be explained with reference to this figure and FIG.

In FIG. 2, V1 and 11 are respectively the transmitting end voltage and transmitting end current of the transmitting amplifier T in FIG. 1, Vx and I
x is the track voltage and track current at the train position at a point XKm from the transmitting current receiving section, I is the equivalent current to the onboard receiver, V2 and 12 are the ground receiving end voltage and ground receiving end current, and Zo is Track circuit characteristic impedance,
If γ is the propagation constant, Z' is the impedance when looking at the receiving end from the train position, and Za is the equivalent impedance of the on-board receiver 11, then the track current at the train position 1X1 The impedance when looking at the receiving end from the train position Z' and the line voltage Vx at the train position are respectively expressed as follows. Therefore, from equations (1) and (2), line current 1x is expressed as:

In reality, the relationship between the characteristic impedance ZO and the impedance Za of the on-board receiver is ZO>>Za, so equation (4) can be expressed as follows. On the other hand, the transmission end voltage and the transmission end current 1 are expressed as follows. Using these equations (5) and (6), the transmitting end impedance, /11, is expressed as follows.

However, since Tanhθ Z' Za lO-1'R 50rr
LA, the orbit length of one section is 1.5A77Z1 characteristic impedance 1Z01 is 51Ω and propagation constant 1γl is 1.54
/b, the ratio of the transmitting end voltage V1 to the transmitting end current 11 in each winter storage of the train at this time and the transmitting end current 11 are calculated in advance using equations (9) and (8), These relationships are shown in FIG.

Therefore, by writing the transmitting current 1 corresponding to the transmitting end impedance B in the ROM 3, the transmitting end current required at that time is calculated from the transmitting end impedance Vtance 1 at each position of the train calculated by the calculator 1. 1, so if you adjust the transmitting end current so that it becomes this I, the on-board receiver always receives 1.
The receiving current 1x of 1 can be kept constant.

In other words, the calculation unit 1 calculates the transmitting end impedance of V at point
, is read from the ROM 3, this value is compared with the transmitting end current 12 at point Adjust as follows.

As described above, according to the present invention, the receiving current of the receiver on the train can be kept constant regardless of where the train is on the track, so the receiver can be small and easily configured.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is an equivalent circuit of a line circuit, and Fig. 3 is a diagram showing the relationship between distance and voltage/current ratio, and when the current at the receiving end of the receiver is kept constant. FIG. 3 is a diagram showing the relationship between transmitting end currents.

Claims (1)

[Claims] 1. A computing unit that calculates the ratio of the transmitting end voltage to the transmitting end current at each position of the train, and a calculator that calculates the ratio of the transmitting end voltage and the transmitting end current at each position of the train, and a calculator that calculates the ratio of the transmitting end voltage and the transmitting end current at each position of the train, and a calculator that calculates the ratio of the transmitting end voltage and the transmitting end current at each position of the train, and the unit that is necessary to flow a constant current to the receiver installed on the train at each position of the train. a read-only memory in which a transmitting end current is stored and addressed by the output of the arithmetic unit; means for comparing the output of this memory with a transmitting end current at a point before the current location of the train; and the comparing means. 1. An automatic gain adjustment device comprising: means for controlling a transmitting end current using an output from the transmitter.