Optical fiber digital repeater

Abstract

The invention relates to the technical field of train communication, in particular to an optical fiber digital repeater which comprises a near-end machine and a far-end machine, the near-end machine and the far-end machine are connected through an optical fiber, and the far-end machine comprises a far-end machine digital board, a multiplexer, a 3dB bridge, a main power amplifier, a standby power amplifier, a radio frequency switch and a same and different frequency control module. The far-end machine digital board is electrically connected with the 3dB bridge, the main power amplifier and the standby power amplifier are both electrically connected with the 3dB bridge, and the main power amplifier and the standby power amplifier are both electrically connected with the 3dB bridge. The same and different frequency control module is added in the far-end machine, so that the digital repeater has 450M same and different frequency work and is compatible with 400M and 450M simultaneous work; the 400M train digital wireless dispatching communication system and the 450M analog wireless train dispatching system can work at the same time, the application requirement of the DRTD system is met, and train communication can be guaranteed in the transition stage of the train communication system from the current 450M analog wireless train dispatching system to the 400M digital wireless dispatching system.

Description

Technical Field

[0001] The invention relates to the technical field of train communications, in particular to an optical fiber digital repeater. Background Art

[0002] Digital repeaters are an effective means to solve weak fields and blind spots in relay systems. The 450MHz analog wireless train modulation communication currently used in railway dedicated mobile communications has problems such as low frequency resource utilization, poor anti-interference ability, aging equipment, and serious over-service, and is facing renovation.

[0003] According to the "General Technical Requirements for Train Digital Wireless Dispatching and Communication Systems (Interim)" (Railway Industry

[2023] No. 33), it is recommended that conventional railways and local railways use the train digital wireless dispatching and communication system (DRTD) in the future, and will transition from the current 450M analog wireless train dispatching to the 400M digital wireless dispatching system (DRTD). During the transition period, the two systems should be supported for simultaneous use.

[0004] The repeater in the existing technology can only support a single 450M analog wireless train modulation or 400M digital wireless train modulation. Therefore, there is an urgent need for a fiber optic digital repeater as a relay remote device of the DRTD system, which is compatible with the existing 450M analog wireless train modulation system and can meet the transition needs of railway wireless train modulation from 450M analog to 400M digital wireless train modulation. Summary of the invention

[0005] The object of the present invention is to provide a fiber optic digital repeater to solve the problems raised in the above background technology.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A fiber optic digital repeater comprises a near-end unit and a far-end unit, wherein the near-end unit and the far-end unit are connected via an optical fiber, wherein the far-end unit comprises a far-end unit digital board, a multiplexer, a 3dB bridge, a main power amplifier, a backup power amplifier, a radio frequency switch and a same-frequency and different-frequency control module, wherein the far-end unit digital board is electrically connected to the 3dB bridge, the main power amplifier and the backup power amplifier are both electrically connected to the 3dB bridge, and the main power amplifier and the backup power amplifier are both electrically connected to the radio frequency switch for transmitting signals to the radio frequency switch.

[0008] The same-frequency and different-frequency control module includes an ATN and a radio frequency electronic switch, which are electrically connected to receive 400M and 450M same-frequency and different-frequency downlink signals, and the ATN and the radio frequency electronic switch are electrically connected to connect the downlink same-frequency signals to the radio frequency electronic switch, and the radio frequency electronic switch is electrically connected to the remote digital board.

[0009] Preferably, the proximal machine includes a proximal machine digital board and a duplex filter, which are electrically connected. The proximal machine digital board is used for downlink input of 400M band and 450M band, and the duplex filter is used for uplink output of 400M band and 450M band.

[0010] The near-end digital board and the far-end digital board are connected via optical fiber. The far-end digital board is used to receive the downlink signal input by the near-end digital board, output it to the 3dB bridge at the far-end output RF port, and send the uplink signal to the near-end digital board.

[0011] Preferably, the remote digital board is electrically connected to the main power amplifier and the backup power amplifier to control redundant switching of the main power amplifier and the backup power amplifier.

[0012] Preferably, the multiplexer is provided with a radio frequency port, and the uplink 400M and 450M signals are respectively input into the multiplexer through the radio frequency port.

[0013] Preferably, the multiplexer is electrically connected to the remote digital board for directly inputting the 400M uplink signal to the remote digital board.

[0014] Preferably, the multiplexer is electrically connected to the radio frequency electronic switch, and is used to input the 450M uplink signal to the radio frequency electronic switch, and the radio frequency electronic switch then inputs it to the remote digital board.

[0015] Beneficial effects of the present invention:

[0016] 1. The present invention adds a same-frequency and different-frequency control module inside the remote machine, and the same-frequency and different-frequency control module enables the digital repeater to have 450M same-frequency and different-frequency operation, and is compatible with 400M and 450M simultaneous operation, so as to realize the simultaneous operation of 400M train digital wireless dispatching communication system and 450M analog wireless train dispatching, meet the application requirements of DRTD system, and ensure train communication during the transition stage of the train communication system from the current 450M analog wireless train dispatching to the 400M digital wireless dispatching system.

[0017] 2. The present invention adopts digital repeater technology, which adds digital processing circuits compared to analog repeaters. The cost of this part of the hardware is relatively high, but one digital board can achieve compatibility between 400M and 450M systems, and the number of passive components is also less than that of analog, so the overall cost of the equipment is comparable to that of analog repeaters. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is a schematic diagram of the 400M digital repeater system;

[0020] Figure 2 This is the radio frequency block diagram of the 400M digital optical fiber digital repeater proposed by the present invention;

[0021] Figure 3 yes Figure 2 Schematic diagram of the connection between the digital board of the near-end machine and the digital board of the far-end machine;

[0022] Figure 4 yes Figure 2 RF block diagram of the mid- and remote-end parts;

[0023] Figure 5 This is a block diagram of uplink signal processing of an optical fiber digital repeater in the present invention;

[0024] Figure 6 This is a downlink signal processing block diagram of the optical fiber digital repeater in the present invention;

[0025] Figure 7 It is a schematic diagram of a double-chain network between a near-end machine and a far-end machine in the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] A fiber optic digital repeater comprises a near-end unit and a far-end unit, wherein the near-end unit and the far-end unit are connected via an optical fiber, wherein the far-end unit comprises a far-end unit digital board, a multiplexer, a 3dB bridge, a main power amplifier, a backup power amplifier, a radio frequency switch and a same-frequency and different-frequency control module, wherein the far-end unit digital board is electrically connected to the 3dB bridge, the main power amplifier and the backup power amplifier are both electrically connected to the 3dB bridge, and the main power amplifier and the backup power amplifier are both electrically connected to the radio frequency switch for transmitting signals to the radio frequency switch.

[0028] The same-frequency and different-frequency control module includes an ATN (different-frequency combiner) and a radio frequency electronic switch. The ATN and the radio frequency switch are electrically connected to receive 400M and 450M same-frequency and different-frequency downlink signals. The ATN and the radio frequency electronic switch are electrically connected to connect the downlink same-frequency signals to the radio frequency electronic switch. The radio frequency electronic switch is electrically connected to the remote digital board.

[0029] like Figure 1The optical fiber digital repeater proposed in the present invention is a WJB-II 400MHz optical fiber digital repeater, which serves as a relay device of a DRTD system (400Mhz train digital wireless dispatching communication system). The system consists of a near-end machine, a far-end machine, an optical fiber, an antenna feed system, and a network management system.

[0030] In addition to the remote digital board, multiplexer, 3dB bridge, main power amplifier, backup power amplifier, RF switch and frequency control module, the remote machine also includes a power module, an optical module, a chassis and other structures. In addition to the digital board and duplex filter, the near-end machine also includes a power module, a power filter, an interface board, an optical module, a chassis and other structures. The structures not shown in the figure are irrelevant to the technical problems to be solved by the present invention and will not be described in detail here.

[0031] The power supply mode of the proximal machine is: DC power supply DC40V~57V;

[0032] The power supply mode of the remote machine is: DC power supply DC40V~57V; AC power supply AC220V±44V, 45Hz~55Hz; supports remote power supply.

[0033] The near-end and far-end devices support star, chain, daisy, ring, and dual-chain networking. Figure 7 As shown:

[0034] like Figure 7 , Figure 7 This is a schematic diagram of the dual-link network between the near-end machine and the far-end machine. The far-end machine digital board has four optical ports. The near-end machine A optical port and the far-end machine 1, 2, 3, 4 A and B optical ports form the main link, and the near-end machine B optical port and the far-end machine 1, 2, 3, 4 C and D optical ports form the backup link. Under normal circumstances, the dual link works in the main link; when the main link fails, the near-end machine detects the failure and controls the repeater system to switch to the backup link. Similarly, the near-end machine C and D optical ports and the far-end machines 5, 6, 7, 8 form the main and backup dual links to achieve redundant backup function. The dual-link network has a small delay, and the delay will not increase significantly when working in the backup link, which is very helpful for engineering applications. Because the railway sets up repeaters along a straight line, the ring network must require the farthest far-end machine to have a long optical fiber and a large delay.

[0035] The near-end machine includes a near-end machine digital board and a duplex filter, which are electrically connected. The near-end machine digital board is used for downlink input of 400M band and 450M band, and the duplex filter is used for uplink output of 400M band and 450M band.

[0036] like Figure 2 and Figure 3The near-end machine adopts a standard 19-inch 2U chassis design and provides four RF ports, which are 450M and 400M uplink output and downlink input respectively. The 400M digital optical fiber amplifier provides two independent input and output channels, which provide independent processing channels for the 450M and 400M systems respectively. They are isolated from each other and do not interfere with each other. The downlink 400M and 450M signals are respectively input to the RF input port of the near-end digital board through the RF port. The near-end digital board transmits the signal to the remote digital board through optical fiber. The near-end digital board receives the 400M and 450M uplink signals input by the remote digital board through optical fiber, and outputs them to the duplex filter at the RF output port of the digital board. The duplex filter finally outputs the signal through the RF output port of the near-end machine.

[0037] The near-end digital board and the far-end digital board are connected via optical fiber. The far-end digital board is used to receive the downlink signal input by the near-end digital board, output it to the 3dB bridge at the far-end output RF port, and send the uplink signal to the near-end digital board.

[0038] The remote digital board is electrically connected to the main power amplifier and the backup power amplifier, and is used to control the redundant switching of the main power amplifier and the backup power amplifier.

[0039] like Figure 2 , Figure 3 and Figure 4 The remote machine adopts a cast aluminum chassis and provides two RF ports, which are 400M and 450M antenna system interfaces respectively. The two independent output channels of 400M and 450M downlink are output to the main power amplifier and the backup power amplifier through the bridge. The remote machine digital board communicates with the main power amplifier and the backup power amplifier through RS485, and controls the RF switch through an IO port. The power amplifier realizes main and backup redundancy switching through the RF switch. It works in the main power amplifier by default. When the remote machine digital board detects a failure of the main power amplifier, it switches to the backup power amplifier through the RF switch.

[0040] The multiplexer is provided with a radio frequency port, and the uplink 400M and 450M signals are respectively input into the multiplexer through the radio frequency port.

[0041] The multiplexer is electrically connected to the remote digital board and is used to directly input the 400M uplink signal to the remote digital board.

[0042] The multiplexer is electrically connected to the radio frequency electronic switch and is used to input the 450M uplink signal to the radio frequency electronic switch, which then inputs it to the remote digital board.

[0043] The near-end digital board and the far-end digital board are the core components of the system, responsible for the RF signal processing of the repeater equipment, digital mixing of baseband digital signals, digital filtering, digital gain adjustment, CPRI (common radio interface, mainly used for information transmission between the wireless equipment control center (REC) and the wireless equipment (RE) for wireless communication) transmission protocol analysis and framing, squelch threshold adjustment, simultaneous operation of the same and different frequencies, and fiber optic link networking. The system clock is locked by an AD9528 chip and outputs multiple clock signals; the RF transceiver consists of an AD9370 chip with four channels of dual-receive and dual-transmit, and the digital baseband processing The processing and transmission part is mainly composed of FPGA chip XC7A100T and ARM chip STM32F407. The FPGA chip completes baseband signal processing, including data interaction with the RF transceiver, digital local oscillator generation, orthogonal modulation and demodulation, upper and lower spectrum shifting, FIR filter, CIC filter, digital gain adjustment, same-frequency and different-frequency detection, uplink power detection, CPRI transmission protocol analysis and framing, MCU data interaction interface, etc.; the ARM chip is responsible for powering on and loading the FPGA chip, communicating with the upper-layer network management software through the network port, and is responsible for parameter setting, status detection and software upgrades of the entire system.

[0044] like Figure 5 The uplink frequency band of the optical fiber digital repeater system is 403.7±0.5M, 413.2±0.5M, and 458±1M. The AD9370 chip first performs 431MHz mixing to move the signal to -27.3±0.5M, -17.8±0.5M, and 27±1M respectively. The 122.88Mhz clock generated by the AD9528 samples the signal, and the half-bag filter inside the AD9370 chip performs double decimation filtering to reduce the sampling rate from 122.88Mhz to 61.44Mhz. Finally, the FIR filter inside the AD9370 filters out the sampling image.

[0045] The FPGA chip realizes data interaction with the RF transceiver AD9370 through the JESD204B protocol interface, and receives two signals with original working frequencies of 450M and 400M respectively after being sampled and filtered by the AD9370. The FPGA acts as a digital oscillator NCO to generate three digital local oscillators, which are 27.3M, 17.8M, and 27M respectively. The trigonometric function characteristics are used to realize up-conversion of the 400M channel signal to 27.3M and 17.8M respectively, and down-conversion of the 450M channel signal to 27M. The center frequencies of the three working frequency bands are moved to zero frequency respectively, and the IQ signals are obtained through orthogonal modulation;

[0046] The 400M signal is filtered by a FIR filter with a bandwidth of 1M, and the 450M signal is filtered by a FIR filter with a bandwidth of 2M. Both FIR filters use 4x decimation filtering to reduce the sampling rate from 61.44M to 15.36M. The selection of the filter order refers to the standard requirements of system delay, out-of-band suppression, and in-band fluctuation. The sampling frequency of 15.36M is twice the highest frequency of the signal, which conforms to the Nyquist sampling theorem;

[0047] The digital optical fiber digital repeater consists of a near-end machine and one or more far-end machines, which transmit data through optical fiber, and the interface adopts the CPRI protocol specification. The basic unit of CPRI protocol transmission is called a basic frame, and the transmission rate of each basic frame is 3.84MHz. A basic frame contains 16 words, of which the first word is used to transmit the control word; the remaining 15 words are used to transmit IQ data. In addition to transmitting the judgment signal of the main and standby optical ports, the control word also bears the MCU monitoring channel hdlc and fe channel;

[0048] The remote machine encapsulates the control signal and three groups of filtered IQ signals into CPRI frames through the FPGA serializer, and the near-end machine completes the CPRI de-framing work through the FPGA deserializer, and decodes the control signal and the three groups of IQ signals. The three groups of IQ signals are then FIR4x interpolation filtered to increase the sampling rate to 61.44M, and filter out the images generated by the interpolation. The digital up-conversion moves the center frequency of the original 400M signal to -27.3M and -17.8M respectively, and moves the center frequency of the original 450M signal to 27M. The two original 400M signals are synthesized into one signal by signal superposition;

[0049] Finally, the FPGA realizes data interaction with the RF transceiver AD9370 through the JESD204B protocol interface, and transmits the original 450M signal and the original 400M signal to the two channels of AD9370 respectively. After the AD9370 performs digital-to-analog conversion, it mixes and filters the two channels of signals with 431M, and restores them to the original working frequency bands of 403.7±0.5M, 413.2±0.5M, and 458±1M.

[0050] The working principle of an optical fiber digital repeater provided by the present invention is as follows:

[0051] like Figure 2-4 The same and different frequency controller modules include 1 ATN and 1 RF electronic switch. The remote digital board receives the downlink signal input by the near-end digital board through optical fiber, and outputs it to the 3dB bridge at the remote RF output port. The 3dB bridge outputs the signal to the main and backup power amplifiers. The main and backup power amplifiers output the signal to the RF electronic switch respectively. The remote digital board controls the RF electronic switch to switch the main and backup power amplifiers through high and low levels, and the RF switch outputs the signal to the same and different frequency control modules.

[0052] ATN receives 400M and 450M downlink signals of the same and different frequencies from the RF switch. The downlink signals of the same frequency are connected to the RF electronic switch. The switching of the 450M wireless train modulation same and different frequency functions is controlled by the RF electronic switch. The remote digital board controls the switching of the RF electronic switch through high and low levels.

[0053] The same-frequency and different-frequency control module outputs the downlink signal to the multiplexer, and the downlink 450M different-frequency mode and the downlink 400M digital mode share one channel to output to the multiplexer; the uplink 400M and 450M signals are respectively input to the multiplexer through the RF port, and the multiplexer inputs the 400M uplink signal directly to the remote digital board, and the multiplexer inputs the 450M uplink signal first into the RF switch, and the RF switch inputs it into the remote digital board, and the remote digital board transmits the uplink 400M and 450M signals to the near-end digital board through optical fiber.

[0054] like Figure 1-4 The digital board of the optical fiber digital repeater detects the signal power of the base station signal in the 457-459M frequency band to determine whether the 450M wireless modulation is working in the same frequency mode or the different frequency mode. When the near-end digital board receives the 450M same-frequency downlink signal, it notifies the remote digital board through the optical fiber, and the remote digital board controls the switching of the RF switch through an IO port; in the same frequency mode, the remote digital board outputs a high level, and the RF switch of the same and different frequency control module receives the 450M downlink signal and sends it to the multiplexer; in the different frequency mode, the remote digital board outputs a low level, and the RF switch of the same and different frequency control module receives the 450M uplink signal and sends it to the remote digital board. The same and different frequency control modules enable the digital repeater to have 450M same and different frequency operation, and is compatible with 400M and 450M working at the same time.

[0055] like Figure 6 Compared with the uplink RF signal processing of the optical fiber digital repeater system, the downlink RF signal processing adds a 450M co-frequency channel, and the uplink working frequency band is 413.7±0.5M, 423.2±0.5M, 458±1M, and 468±1M. The AD9370 chip moves the signal to -27.3±0.5M, -17.8±0.5M, 17±1M, and 27±1M respectively through 441MHz mixing; then realizes analog-to-digital conversion, digital mixing, extraction filtering, and mirror filtering. The FPGA chip completes the baseband signal processing, including data interaction with the RF transceiver, digital local oscillator generation, orthogonal modulation and demodulation, upper and lower spectrum shifting, FIR filter, CIC filter, CPRI transmission protocol analysis and framing, MCU data interaction interface, etc. Finally, the AD9370 realizes 441M mixing, DAC, and mirror filtering.

[0056] Compared with the related art, the optical fiber digital repeater provided by the present invention has the following beneficial effects:

[0057] The present invention adds a same-frequency and different-frequency control module inside the remote machine, and the same-frequency and different-frequency control module enables the digital repeater to have 450M same-frequency and different-frequency operation, and is compatible with 400M and 450M simultaneous operation, so as to realize the simultaneous operation of 400M train digital wireless dispatching communication system and 450M analog wireless train dispatching, meet the application requirements of the DRTD system, and ensure train communication in the transition stage of the train communication system from the current 450M analog wireless train dispatching to the 400M digital wireless dispatching system.

[0058] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. An optical fiber digital repeater, comprising a near-end unit and a far-end unit, the near-end unit and the far-end unit being connected via an optical fiber, characterized in that: The remote device includes a remote device digital board, a multiplexer, a 3dB bridge, a main power amplifier, a backup power amplifier, a radio frequency switch and a same-frequency and different-frequency control module. The remote device digital board is electrically connected to the 3dB bridge, the main power amplifier and the backup power amplifier are both electrically connected to the 3dB bridge, and the main power amplifier and the backup power amplifier are both electrically connected to the radio frequency switch, for transmitting signals to the radio frequency switch; The same-frequency and different-frequency control module includes an ATN and a radio frequency electronic switch, which are electrically connected to receive 400M and 450M same-frequency and different-frequency downlink signals, and the ATN and the radio frequency electronic switch are electrically connected to connect the downlink same-frequency signals to the radio frequency electronic switch, and the radio frequency electronic switch is electrically connected to the remote digital board.

2. The optical fiber digital repeater according to claim 1, characterized in that: The near-end machine includes a near-end machine digital board and a duplex filter, which are electrically connected. The near-end machine digital board is used for downlink input of 400M band and 450M band, and the duplex filter is used for uplink output of 400M band and 450M band.

3. The optical fiber digital repeater according to claim 2, characterized in that: The near-end digital board and the far-end digital board are connected via optical fiber.

4. The optical fiber digital repeater according to claim 3, characterized in that: The remote digital board is used to receive the downlink signal input by the near-end digital board, output it to the 3dB bridge at the remote RF output port, and send the uplink signal to the near-end digital board.

5. The optical fiber digital repeater according to claim 3, characterized in that: The remote digital board is electrically connected to the main power amplifier and the backup power amplifier, and is used to control the redundant switching of the main power amplifier and the backup power amplifier.

6. The optical fiber digital repeater according to claim 3, characterized in that: The multiplexer is provided with a radio frequency port, and the uplink 400M and 450M signals are respectively input into the multiplexer through the radio frequency port.

7. The optical fiber digital repeater according to claim 6, characterized in that: The multiplexer is electrically connected to the remote digital board and is used to directly input the 400M uplink signal to the remote digital board.

8. The optical fiber digital repeater according to claim 7, characterized in that: The multiplexer is electrically connected to the radio frequency electronic switch and is used to input the 450M uplink signal to the radio frequency electronic switch, which then inputs it to the remote digital board.

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