Active combiner of DRTD optical fiber repeater

Abstract

The utility model relates to an active combiner of a DRTD optical fiber repeater. The active combiner comprises a single-chip microcomputer, and an uplink communication interface, a DC stabilized power supply module, an ALC automatic level control circuit and an optical module alarm signal discrimination and radio frequency switch switching circuit which are connected with the single-chip microcomputer. A plurality of paths of uplink input radio frequency signals are respectively subjected to gain adjustment and attenuation through a radio frequency digital attenuation chip, are combined by a radio frequency power divider and then are input into an ALC (Automatic Level Control) circuit; the ALC automatic level control circuit filters the radio frequency signal through a 400MHz filter and a 450MHz filter which are connected in parallel and then outputs the radio frequency signal; a radio frequency signal of an output end is coupled and then converted into a voltage analog quantity signal, and the voltage analog quantity signal is compared with a reference level and then fed back to the attenuator so as to adjust output power. Compared with the prior art, the output ALC function is supported, the threshold of the output power is set by adjusting the reference level, and the attenuation amount is automatically adjusted, so that the stable output power is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of railway communication, in particular to an active combiner specially used for a DRTD optical fiber repeater station. Background Art

[0002] With the continuous development of high-speed railways and the continuous improvement of information technology, radio frequencies have been re-planned and adjusted. The 450MHz train modulation frequency point of the railway has been withdrawn, and digital wireless communication frequency points have been allocated to the railway in the 400MHz frequency band. The railway wireless train modulation system has changed from the original analog communication system to the current digital communication system.

[0003] The railway 400MHz digital wireless train dispatching communication system (DRTD) is an important communication system for the next generation of railway train dispatching. It can not only meet the various business needs of railway dispatching communication services, wireless train number verification information transmission, operation and maintenance services, but also has the advantages of occupying less frequency resources, higher receiving sensitivity, lower spurious emission, better anti-interference ability, and flexible system structure.

[0004] Fiber optic repeaters are an important part of the railway DRTD communication system, and they undertake the important task of extending the coverage of fixed radio signals. In the DRTD system, fiber optic repeaters are basically the same as those used in other systems in principle. They all use optical fiber as the transmission medium, and use direct coupling to extract signals from fixed radio stations. Then, the fixed radio station signals are transmitted through optical fiber to weak field areas that need to be covered, such as tunnels, hills, and gullies on the railway line, and antennas or leaky cables are used for signal coverage.

[0005] The DRTD fiber repeater transmits the uplink RF signals received by each remote unit to the near-end unit through optical fiber, and amplifies, combines, processes and outputs these RF signals to the base station in the near-end unit, thereby amplifying and returning the uplink signals of handheld terminals or vehicle-mounted equipment in the wireless signal coverage area of ​​the repeater. The active combiner is an important component of the uplink communication link in the near-end unit of the DRTD fiber repeater system. It is an active RF unit module with the functions of signal selection, amplification, combining and monitoring. Utility Model Content

[0006] The purpose of the utility model is to provide an active combiner dedicated to a DRTD optical fiber repeater station in order to realize the above-mentioned scene applications and functions.

[0007] The purpose of the utility model can be achieved through the following technical solutions:

[0008] A DRTD optical fiber repeater active combiner, multiple uplink input radio frequency signals respectively pass through digital controlled attenuators, the output ends of multiple digital controlled attenuators are connected to radio frequency power dividers, and the output ends of the radio frequency power dividers are connected to ALC level control circuits.

[0009] The ALC level control circuit comprises a PIN attenuator, a first radio frequency amplifier tube, a first bridge, a 400MHz filter and a 450MHz filter arranged in parallel, a second bridge, a second radio frequency amplifier tube and a third radio frequency amplifier tube connected in sequence;

[0010] The output end of the third RF amplifier tube is connected to the PIN attenuator through feedback provided in sequence with a coupler, a RF power detection chip and a comparison circuit, one input end of the comparison circuit is connected to the output end of the RF power detection chip, and the other input end is connected to the reference level, and the output end of the comparison circuit is connected to the PIN attenuator.

[0011] As a preferred technical solution, the active combiner is connected to the proximal machine main control board via a data power line, and the proximal machine main control board provides power supply.

[0012] As a preferred technical solution, the active combiner further includes: a single-chip microcomputer and an uplink communication interface connected to the single-chip microcomputer, a DC regulated power supply module, and an optical module alarm signal determination and radio frequency switch switching circuit.

[0013] As a preferred technical solution, each of the RF signals inputted uplink is provided with a RF switch, and the optical module alarm signal discrimination and RF switch switching circuit comprises: a bus transceiver and an alarm signal discrimination circuit;

[0014] The input end data of the bus transceiver is connected to the uplink communication interface; the output end of the bus transceiver is connected to the input end of the alarm signal discrimination circuit, and the output end of the alarm signal discrimination circuit is connected to the radio frequency switch.

[0015] As a preferred technical solution, the alarm signal discrimination circuit has two input terminals, including a NOT gate and an AND gate;

[0016] One of the input terminals of the alarm signal discrimination circuit is connected to one of the input terminals of the AND gate after passing through a NOT gate.

[0017] Another input end of the alarm signal discrimination circuit is connected to another input end of the AND gate.

[0018] As a preferred technical solution, a serial port bidirectional automatic level conversion chip is arranged between the uplink communication interface and the single-chip microcomputer, and a TVS tube is arranged near the uplink communication interface.

[0019] As a preferred technical solution, the DC regulated power supply module includes a two-stage voltage stabilizing module, wherein the input of the first-stage voltage stabilizing module is an externally input DC voltage, and outputs a first DC regulated voltage to the RF amplifier, operational amplifier and second-stage voltage stabilizing module; the second-stage voltage stabilizing module outputs a second DC regulated voltage to the remaining components inside the combiner.

[0020] As a preferred technical solution, the active combiner further includes an onboard temperature and humidity sensor, and the onboard temperature and humidity sensor is connected to the single-chip microcomputer via an I2C bus communication mode.

[0021] As a preferred technical solution, the active combiner further includes a storage chip, and the storage chip is connected to the single-chip microcomputer using an SPI bus communication method.

[0022] As a preferred technical solution, the active combiner further includes a DIP switch.

[0023] Compared with the prior art, the utility model has the following beneficial effects:

[0024] 1. The utility model supports the output ALC function. According to the comparison between the detected output power voltage and the reference level voltage by the comparison circuit, the attenuation of the PIN attenuator is automatically adjusted, thereby achieving the purpose of stabilizing the output power.

[0025] 2. The utility model supports the optical module alarm signal identification and RF switch switching functions, which are automatically identified through hardware circuits, making it more convenient for debugging and user operation.

[0026] 3. The utility model is modular in design and simple in structure, compatible with 450MHz frequency modulation point and 400MHz digital wireless communication frequency point. It has 4 pairs of main and standby inputs, 1 output, 9 SMA RF interfaces in total, power consumption is less than 3W, and maximum gain is 5dB.

[0027] 4. Except for the passband filter, the chips and components used in the circuit of the utility model are relatively common, with a high overall cost performance, which can reduce construction costs and maintenance costs. At the same time, the module has low power consumption, strong durability, and is not easy to damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the hardware circuit structure of an active combiner of a DRTD optical fiber repeater station of the utility model;

[0029] Figure 2 The utility model is a schematic diagram of an active combiner ALC circuit of a DRTD optical fiber repeater station. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0031] Example 1

[0032] The DRTD optical fiber repeater station active combiner provided by the utility model is installed in the near-end machine of the DRTD optical fiber repeater station. Figure 1 As shown, it includes communication RS485 serial port bidirectional automatic level conversion chip, DC voltage regulated power supply module, single chip microcomputer, storage chip, onboard temperature and humidity sensor, RF digital attenuation chip, RF power divider, ALC automatic level control circuit, optical module alarm signal discrimination and RF switch switching circuit, operation status indication and fault alarm light, DIP switch, etc. The active combiner is connected to the near-end machine main control board through the data power line, and the near-end machine main control board provides it with DC12V power supply.

[0033] The utility model has the functions of RF combining, ALC automatic level control, output power monitoring, RF power amplification, gain adjustment, passband filtering, optical module alarm signal input judgment and RF switch switching, RF output temperature compensation, host computer data parameter query and setting, remote upgrade and maintenance, etc.

[0034] Specifically, as a preferred implementation of the utility model, in this embodiment:

[0035] The voltage regulator module includes MC7805BDT and AMS1117-3.3. The voltage regulator module MC7805BDT converts the external input DC5~24V into a regulated DC5V. The wide voltage input is more adaptable to different types of repeater near-end machines, providing an output current of more than 1A, mainly for the RF amplifier tube, operational amplifier and voltage regulator module AMS1117-3.3. The voltage regulator module AMS1117-3.3 converts DC5V into DC3.3V to power other internal chips, providing a maximum current of 800mA.

[0036] The storage chip SST25VF016B uses SPI bus communication to connect to the microcontroller and can be used for the remote upgrade function of the active combiner. When receiving the upgrade command sent by the host computer, the storage chip can store the new software upgrade package, so that the microcontroller can perform the upgrade action to complete the remote upgrade.

[0037] The serial port bidirectional automatic level conversion chip MAX3485EESA is set between the uplink communication interface RS485 and the single-chip computer for communication between the active combiner and the near-end machine of the repeater. A TVS tube is added near the interface for surge protection.

[0038] The onboard temperature and humidity sensor HDC2080DMBT uses the I2C bus communication method to communicate with the microcontroller, collects the temperature and humidity data inside the active combiner and reports it to the microcontroller.

[0039] The RF digital attenuation chip PE4312 is suitable for the frequency range of 1MHz to 4GHz, with a characteristic impedance of 50 ohms. The microcontroller can control its internal register to adjust the attenuation value in 0.5dB steps through the 6-bit serial input interface of the RF digital attenuation chip. The adjustable attenuation range is 0 to 31.5dB, and the insertion loss is a maximum of 1.5dB at 1MHz to 1GHz. The active combiner uses a total of 4 digitally controlled attenuators, which can adjust different gains and attenuation sizes for each RF channel, and can adjust the output power and gain of each RF channel under different temperature and humidity conditions.

[0040] The RF power divider SCA-4-10+ is suitable for the frequency range of 5MHz to 1GHz, with a characteristic impedance of 50 ohms, four ports for input (output) and one port for output (input). It can combine the signals received from multiple remote devices into one RF signal output after passing through 4-channel RF digital attenuation chips, thereby realizing the RF combining function.

[0041] like Figure 2 As shown, the ALC automatic level control circuit includes a PIN attenuator HSMP3814, a 400MHz filter, a 450MHz filter, a 10dB coupler, a RF power detection chip MAX4003EUA, the first and second 3dB bridges, the first, second and third RF amplifiers ADL5602, and the first, second and third operational amplifiers LMV358. The RF signal synthesized by the RF power divider is input into the PIN attenuator, amplified by 20dB by the first RF amplifier, and then divided into two paths using the first 3dB bridge, and filtered by the 400MHz filter and the 450MHz filter respectively, so that the passband characteristics meet the requirements of -3dB bandwidth>f0±1MHz, -40dB bandwidth<f0±5MHz; after passing through the filter, the two-path signal is re-combined using the second 3dB bridge, input into the second and third RF amplifiers for two-stage amplification, and finally output to the output port;

[0042] A 10dB coupler is used at the output port to couple the RF signal, and a slightly smaller RF signal is obtained for power detection through the MAX4003EUA power detection chip. The RF signal amplitude is converted into a voltage analog signal. After amplification by the first operational amplifier, it is input to the microcontroller for ADC sampling on the one hand, and compared with the reference level on the other hand. If it is smaller than the reference level, the output pin of the third op amp maintains the maximum output unchanged. At this time, the PIN attenuator is in the minimum attenuation state, generally 3dB insertion loss. If it is larger than the reference level, the pin voltage output from the third op amp to the PIN attenuator will decrease, and the attenuation value of the PIN attenuator will increase, causing the RF output power to decrease, resulting in a decrease in the power detected by the power detection tube, and then its detection voltage decreases, eventually forming negative feedback, so that the output power remains constant. By adjusting the reference level, the maximum output power can be controlled, thereby realizing the ALC automatic level control function.

[0043] The optical module alarm signal identification and RF switch switching circuit includes 74LVC245APW octal bus transceiver, SN74HC165PWR shift register, NOT gate, AND gate, SN74HC257PW data selector, ESDA6V1W5 electrostatic protection diode. Among them, the alarm signal input by the optical module first passes through the 74LVC245APW octal bus transceiver, whose input pin is compatible with +5V or +3.3V signal input, and the output signal high level is +3.3V, so that the combiner can adapt to different types of optical modules.

[0044] Then, the alarm signal is input into the SN74HC165PWR shift register on the one hand, so that 8-way alarm signals are input into the single-chip microcomputer through 3 pins; on the other hand, the optical module alarm signal is input into the alarm discrimination circuit, that is, the alarm signal of the main optical module is input into the AND gate after passing through a NOT gate, and the alarm signal of the backup optical module is directly input into the AND gate. The two are logically compared and judged, so that when the main optical module alarms and the backlight module is normal, the output is 1, and the other states are all 0, thereby realizing hardware collection, discrimination and switching.

[0045] The dip switch SW DIP-2 is a 2-bit state dip switch, which is connected to the digital I / O port of the microcontroller. The device number and address of the current combiner can be set through different states of the dip switch.

[0046] The preferred specific embodiments of the utility model are described in detail above. It should be understood that ordinary technicians in this field can make many modifications and changes based on the concept of the utility model without creative work. Therefore, all technical solutions that can be obtained by technicians in this technical field based on the concept of the utility model through logical analysis, reasoning or limited experiments on the basis of the existing technology should be within the scope of protection determined by the claims.

Claims

1. A DRTD optical fiber repeater active combiner, wherein multiple uplink input RF signals pass through digital controlled attenuators respectively, and the output ends of the multiple digital controlled attenuators are connected to the RF power divider, characterized in that: The output end of the RF power divider is connected to the ALC level control circuit. The ALC level control circuit comprises a PIN attenuator, a first radio frequency amplifier tube, a first bridge, a 400MHz filter and a 450MHz filter arranged in parallel, a second bridge, a second radio frequency amplifier tube and a third radio frequency amplifier tube connected in sequence; The output end of the third RF amplifier tube is connected to the PIN attenuator through feedback provided in sequence with a coupler, a RF power detection chip and a comparison circuit, one input end of the comparison circuit is connected to the output end of the RF power detection chip, and the other input end is connected to the reference level, and the output end of the comparison circuit is connected to the PIN attenuator.

2. The DRTD optical fiber repeater active combiner according to claim 1, characterized in that: The active combiner is connected to the proximal machine main control board through a data power line, and is powered by the proximal machine main control board.

3. The DRTD optical fiber repeater active combiner according to claim 1, characterized in that: The active combiner further comprises: a single chip microcomputer and an uplink communication interface connected to the single chip microcomputer, a DC voltage regulated power supply module, and an optical module alarm signal determination and radio frequency switch switching circuit.

4. The DRTD optical fiber repeater active combiner according to claim 3, characterized in that: Each of the RF signals inputted upstream is provided with a RF switch, and the optical module alarm signal discrimination and RF switch switching circuit comprises: a bus transceiver and an alarm signal discrimination circuit; The input end data of the bus transceiver is connected to the uplink communication interface; the output end of the bus transceiver is connected to the input end of the alarm signal discrimination circuit, and the output end of the alarm signal discrimination circuit is connected to the radio frequency switch.

5. The DRTD optical fiber repeater active combiner according to claim 4, characterized in that: The alarm signal discrimination circuit has two input terminals, including a NOT gate and an AND gate; One of the input terminals of the alarm signal discrimination circuit is connected to one of the input terminals of the AND gate after passing through a NOT gate. Another input end of the alarm signal discrimination circuit is connected to another input end of the AND gate.

6. The DRTD optical fiber repeater active combiner according to claim 3, characterized in that: A serial port bidirectional automatic level conversion chip is arranged between the uplink communication interface and the single-chip microcomputer, and a TVS tube is arranged near the uplink communication interface.

7. The DRTD optical fiber repeater active combiner according to claim 3, characterized in that: The DC regulated power supply module includes a two-stage voltage stabilizing module, wherein the input of the first-stage voltage stabilizing module is an externally input DC voltage, and outputs a first DC regulated voltage to the radio frequency amplifier, operational amplifier and second-stage voltage stabilizing module; the second-stage voltage stabilizing module outputs a second DC regulated voltage to the remaining components inside the combiner.

8. The DRTD optical fiber repeater active combiner according to claim 1, characterized in that: The active combiner also includes an onboard temperature and humidity sensor, which is connected to the single-chip microcomputer via an I2C bus communication mode.

9. The DRTD optical fiber repeater active combiner according to claim 1, characterized in that: The active combiner also includes a storage chip, and the storage chip is connected to the single-chip microcomputer using an SPI bus communication method.

10. The DRTD optical fiber repeater active combiner according to claim 1, characterized in that: The active combiner also includes a DIP switch.

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