A microwave photon distributed radar system based on existing optical access networks

Abstract

The present application relates to the field of microwave photon radar, in particular to a kind of microwave photon distributed radar system based on existing optical access network, including, according to the topological structure of existing passive optical access network architecture is different, is divided into tree passive optical network and ring passive optical network, in tree passive optical network proposes the distributed radar system of point-to-multipoint transmission radar analog signal, in ring passive optical network proposes the distributed radar system of point-to-point transmission radar analog signal.The distributed radar system proposed in the application is based on the widely laid passive optical access network, only needs to increase part of optical device to complete the construction of distributed radar system, reduces the construction cost of radar system, uses the optical fiber network widely laid in current optical fiber communication system as the signal transmission medium of radar networking, does not need to lay optical cable again, can quickly, conveniently, widely, flexibly construct distributed radar system.

Description

Technical Field

[0001] This invention relates to the field of microwave photonic radar, and in particular to a microwave photonic distributed radar system based on existing optical access networks. Background Technology

[0002] With the continuous development of modern electronic warfare technology, radar systems face four major threats: stealth targets, low-altitude penetration, anti-radiation missiles, and integrated electronic jamming. This places increasingly stringent demands on radar performance, particularly on target identification range, positioning accuracy, and data processing speed. When using monostatic radar, it is difficult to achieve high-precision, omnidirectional target positioning within the monitored area. Distributed radar systems, however, possess more transmitters and receivers, forming a network for transmitting and receiving electromagnetic waves. This enables wide-area detection and allows for target monitoring from different angles, acquiring echo signals from targets in different directions, thus possessing a certain anti-stealth capability. Furthermore, the distributed deployment of distributed radar ensures that even if some transmitters or receivers are attacked, the system can still continue to operate. For continuous operation and strong resistance to destruction, distributed radar systems require all transmitters and receivers to work together and collect data at the central station. To avoid transmitting large amounts of raw data, some solutions choose to perform signal preprocessing at the transmitters and receivers, and then transmit the simplified information back to the central station for processing via a data link. However, this solution requires each transmitter and receiver to have a high-precision time signal and maintain synchronization. Another solution is to directly establish a reliable high-bandwidth data transmission link to transmit the raw data of the transmitted and received signals directly to the central station. This solution does not require data processing at each base station. This solution places high demands on the data transmission link. Traditional cable transmission solutions have limited bandwidth, huge transmission loss, and are easily affected by electromagnetic interference, making it difficult to meet transmission requirements.

[0003] With the maturity of fiber optic communication technology, the advantages of fiber optics as a transmission carrier, such as its broadband and low loss, can be used to easily achieve high-bandwidth, high-speed, long-distance parallel transmission, which is very suitable for distributed radar systems where the transmitter, receiver, and central station are separately arranged.

[0004] Chinese Patent Publication No. CN114660543A discloses a radar system in which multiple radar transceivers are synchronized with a common clock signal. The radar system includes: a control module; a processing module; multiple radar transceivers; and a communication bus connecting the control module to one or more of the multiple radar transceivers. The control module is configured to generate a first clock signal and transmit the first clock signal to one or more of the multiple transceivers via the communication bus, and to receive radar data from the multiple transceivers via the communication bus. Each of the multiple transceivers is configured to generate a second clock signal extracted from the first clock signal, and to transmit and receive frequency-synchronized radar signals based on the second clock signal. The processing module is configured to: calculate the phase difference between the frequency-synchronized radar signals; compensate for the measured phase difference; and process the received radar signals from the multiple transceivers.

[0005] Current radar systems are costly to deploy and have poor resistance to destruction. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a microwave photonic distributed radar system based on existing optical access networks, which has the advantages of low deployment cost and strong resistance to destruction of distributed radar systems.

[0007] To achieve the above objectives, this invention provides a microwave photonic distributed radar system based on existing optical access networks, comprising differentiating passive optical network topologies according to the different topologies of existing passive optical access network architectures, including tree-shaped passive optical networks and ring-shaped passive optical networks. The tree-shaped passive optical network proposes a distributed radar system for point-to-multipoint transmission of analog radar signals. The proposed ring passive optical network enables a distributed radar system for point-to-point transmission of analog radar signals.

[0008] Furthermore, the distributed radar system for point-to-multipoint transmission of analog radar signals includes, The optical fiber routing terminal is a hardware device at the endpoint of the passive optical network, used to control, manage, and measure distances to user-end devices; A data center unit, connected in parallel at the optical routing terminal, is used to generate optical radar signals and process echo signals; A 1×2 optical switch is used to achieve selective switching of parallel structures, enabling rapid networking of distributed radars. An optical network unit (ONU) is a terminal device in the passive optical network that uses optical fiber access. It is used to receive and respond to ranging and power control commands issued by the optical fiber routing terminal and make corresponding adjustments. The tree-shaped radar transceiver base station is connected in parallel to the optical network unit to complete the radiation and reception of radio frequency radar signals, and to complete the conversion of optical-to-electric and electrical-to-optical signals. A wavelength division multiplexer / demultiplexer is used to combine / separate wavelengths, allowing light of different wavelengths to travel through different transmission paths to the designated tree-shaped radar transceiver base station.

[0009] Furthermore, the distributed radar system for point-to-multipoint transmission of analog radar signals achieves rapid distributed radar networking by controlling the optical switch to switch between tree-shaped conventional communication mode and tree-shaped radar signal transmission mode. The optical routing terminal, the wavelength division multiplexer / demultiplexer, the optical network unit, and the optical fiber constitute a conventional tree-shaped passive optical network structure. The system initiates the conventional tree-shaped communication mode. In the conventional tree-shaped passive optical network structure, the optical routing terminal and the optical network unit are respectively connected in parallel to the data center unit and the radar transceiver base station. The data center unit and each radar transceiver base station form a tree network structure, and the system enables the tree-shaped radar signal transmission mode.

[0010] Furthermore, the data center unit includes a laser array, a wavelength division multiplexer, a wavelength demultiplexer, a modulator, an optical filter, an optical circulator, a photodetector, a radio frequency signal source, and an echo signal processing module. The laser array is capable of generating optical carriers of different wavelengths and transmitting the optical carriers to each of the tree-shaped radar transceiver base stations. The modulator is used to modulate radio frequency signals onto an optical carrier.

[0011] Furthermore, the distributed radar system for point-to-multipoint transmission of analog radar signals includes several tree-shaped radar transceiver base stations. Each tree-shaped radar transceiver base station includes an optical circulator, an optical beam splitter, a phase modulator, a photodetector, a power amplifier, a low-noise amplifier, an electrical circulator, and a transceiver antenna assembly. The optical circulator includes a first path, a second path, and a third path. The first and second paths are used to allow the optical radio frequency signal to enter the optical distribution network of the tree-shaped passive optical network for transmission. The second and third paths are used to allow the optical radio frequency signal to re-enter the optical distribution network for transmission to the data center unit. After the optical radio frequency signal is transmitted to the tree-shaped radar transceiver base station, the optical beam splitter splits the optical radio frequency signal into two beams. One beam is used to convert it into a radar signal for radiation, and the other beam is used as the optical carrier of the optical radio frequency signal received by the antenna.

[0012] Furthermore, the distributed radar system for point-to-point transmission of analog radar signals includes, An optical circulator is used to reflect signals transmitted to the optical routing terminal back to the loop, ensuring that radar signals can be transmitted to any ring radar transceiver base station in the loop. A ring-shaped radar transceiver base station, connected in parallel to the optical network unit, is used to generate, transmit, receive, and process signals. A total light reflector, connected in parallel at the light routing terminal, is used to reflect light; A reference signal generation module is used to generate a reference signal, modulate it onto a fixed-wavelength optical carrier, and transmit it to each of the radar transceiver base stations.

[0013] Furthermore, the distributed radar system that transmits analog radar signals point-to-point achieves rapid networking of distributed radars by controlling the optical switch to switch between the ring conventional communication mode and the ring radar signal transmission mode. The optical routing terminal, the optical circulator, the optical network unit, and the optical fiber constitute a conventional ring passive optical network structure. The system initiates the conventional ring communication mode. In the conventional ring passive optical network structure, the optical routing terminal and the optical network unit are respectively connected in parallel to the all-optical reflector and the ring radar transceiver base station. The reference signal generation module is sequentially connected to each ring radar transceiver base station to form a ring network structure, and the system enables the ring radar signal transmission mode.

[0014] Furthermore, the reference signal generation module includes an upload / download multiplexer, an optical filter, and a reference signal generator. The reference signal generator generates a reference signal, which is uploaded to the main loop and transmitted to all ring radar transceiver base stations via the upload / download multiplexer as the unified reference signal of the system. When the reference signal is transmitted to the reference signal generation module again, the optical filter at the front end filters out the remaining reference signal in the system to avoid interference with the newly generated reference signal.

[0015] Furthermore, the distributed radar system for point-to-point transmission of radar analog signals includes several ring radar transceiver base stations, each of which includes an upload / download multiplexer, a photodetector, a tunable laser, an electro-optic modulator, an optical filter, an optical beam splitter, an optical coupler, an electro-directional coupler, a power amplifier, a low-noise amplifier, a radio frequency signal source, and an echo signal processing module. The upload / download multiplexer downloads the radar signal and the reference signal of a specified wavelength from the main loop or uploads a radar signal of any operating wavelength to the main loop. Different wavelengths correspond to different ring radar transceiver base stations. Point-to-point transmission can be achieved in the ring passive optical network through the upload / download multiplexer. The coupling ratio of the optical coupler can be adjusted appropriately according to the number of ring radar transceiver base stations connected in the loop. It is necessary to ensure that most of the reference signals can continue to be transmitted to other ring radar transceiver base stations in the loop. The tunable laser generates laser of any wavelength used in the distributed radar system for point-to-point transmission of radar analog signals. The generated radar optical signal is transmitted to any ring radar transceiver base station in the distributed radar system for point-to-point transmission of radar analog signals. The photodetector and the electro-optic modulator realize the optical-to-electrical signal conversion and electro-optical signal conversion in the system, respectively.

[0016] Furthermore, both the tree-shaped passive optical network-based distributed radar system for point-to-multipoint transmission of radar analog signals and the ring-shaped passive optical network-based distributed radar system for point-to-point transmission of radar analog signals are coherent radar systems. In the distributed radar system for point-to-multipoint transmission of radar analog signals proposed by the tree-shaped passive optical network, the reference signals used by the data center unit for signal generation and echo signal processing are all provided by the same radio frequency signal source. In the distributed radar system for point-to-point transmission of radar analog signals proposed by the ring passive optical network, the reference signals used by the ring radar transceiver base station for signal generation and processing are all generated by the reference signal generation module. The number of the tree-shaped radar transceiver base stations and the ring-shaped radar transceiver base stations can be increased or decreased according to system needs. The maximum number is determined based on the number of optical network units allowed to be accessed in the protocol followed by the tree / ring passive optical network.

[0017] Compared with existing technologies, the advantages of this invention are that it proposes to build a distributed radar system based on the widely deployed passive optical access network. Only a few optical components need to be added to the existing network to easily and flexibly build the radar system, greatly reducing the deployment cost of the distributed radar system. At the same time, due to the easy access characteristics of fiber optic networks, radar base stations can be quickly added, improving the survivability of the distributed radar system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a distributed radar system that transmits analog radar signals point-to-multipoint based on an existing optical access network, as described in an embodiment of the present invention. Figure 2This is a schematic diagram of the data center unit in a distributed radar system that transmits analog radar signals from point to multiple points based on an existing optical access network, as described in this embodiment of the invention. Figure 3 This is a schematic diagram of the structure of a tree-shaped radar transceiver base station in a distributed radar system that transmits analog radar signals from point to multiple points based on an existing optical access network, as described in this embodiment of the invention. Figure 4 This is a schematic diagram of the structure of a distributed radar system for point-to-point transmission of analog radar signals based on an existing optical access network, as described in this embodiment of the invention. Figure 5 This is a schematic diagram of the reference signal generation module in a distributed radar system that transmits analog radar signals point-to-point based on an existing optical access network, according to an embodiment of the present invention. Figure 6 This is a schematic diagram of the structure of a radar transceiver base station in a distributed radar system that transmits analog radar signals point-to-point based on an existing optical access network, according to an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Please see Figures 1-6 As shown, Figure 1This is a schematic diagram of the structure of a distributed radar system that transmits analog radar signals point-to-multipoint based on an existing optical access network, as described in an embodiment of the present invention. Figure 2 This is a schematic diagram of the data center unit in a distributed radar system that transmits analog radar signals from point to multiple points based on an existing optical access network, as described in this embodiment of the invention. Figure 3 This is a schematic diagram of the structure of a tree-shaped radar transceiver base station in a distributed radar system that transmits analog radar signals from point to multiple points based on an existing optical access network, as described in this embodiment of the invention. Figure 4 This is a schematic diagram of the structure of a distributed radar system for point-to-point transmission of analog radar signals based on an existing optical access network, as described in this embodiment of the invention. Figure 5 This is a schematic diagram of the reference signal generation module in a distributed radar system that transmits analog radar signals point-to-point based on an existing optical access network, according to an embodiment of the present invention. Figure 6 This is a schematic diagram of the radar transceiver base station structure in a distributed radar system that transmits analog radar signals point-to-point based on an existing optical access network, as described in an embodiment of the present invention. Figure 1 In the OLT, the optical routing terminal is a 1×2 optical switch, the ONUi is the i-th optical network unit (i=1,2...n), and the TR1i is the i-th tree-shaped radar transceiver base station (i=1,2...n). Figure 2 In this diagram, PM represents the phase modulator, OF represents the optical filter, and PDi represents the i-th photodetector, where i = 1, 2, ..., n. Figure 3 In this context, PD stands for photodetector and PM stands for phase modulator. Figure 4 In the OLT, the optical routing terminal is the optical system, the OS is a 1×2 optical switch, the ONUi is the i-th optical network unit (i=1,2...n), the TR2i is the i-th ring radar transceiver base station (i=1,2...n), and the OF is an optical filter. Figure 5 In the image, OF stands for optical filter and ADM stands for upload / download multiplexer; Figure 6 In the diagram, ADMj is the j-th upload / download multiplexer, j=1,2,3,4; OC is the optical coupler; OF is the optical filter; PM is the phase modulator; and PDk is the k-th photodetector, k=1,2,3.

[0024] This invention provides a microwave photonic distributed radar system based on an existing optical access network, comprising: Based on the different topologies of existing passive optical access network architectures, passive optical network formations are distinguished, including tree-shaped passive optical networks and ring-shaped passive optical networks. The tree-shaped passive optical network proposes a distributed radar system for point-to-multipoint transmission of analog radar signals. The proposed ring passive optical network enables a distributed radar system for point-to-point transmission of analog radar signals.

[0025] Specifically, in this embodiment, the distributed radar system for point-to-multipoint transmission of analog radar signals includes, The optical fiber routing terminal is a hardware device at the endpoint of the passive optical network, used to control, manage, and measure distances to user-end devices; A data center unit, connected in parallel at the optical routing terminal, is used to generate optical radar signals and process echo signals; A 1×2 optical switch is used to achieve selective switching of parallel structures, enabling rapid networking of distributed radars. An optical network unit (ONU) is a terminal device in the passive optical network that uses optical fiber access. It is used to receive and respond to ranging and power control commands issued by the optical fiber routing terminal and make corresponding adjustments. The tree-shaped radar transceiver base station is connected in parallel to the optical network unit to complete the radiation and reception of radio frequency radar signals, and to complete the conversion of optical-to-electric and electrical-to-optical signals. A wavelength division multiplexer / demultiplexer is used to combine / separate wavelengths, allowing light of different wavelengths to travel through different transmission paths to the designated tree-shaped radar transceiver base station.

[0026] Specifically, in this embodiment, the distributed radar system for transmitting analog radar signals from point to multiple points achieves rapid networking of distributed radar by controlling the optical switch to switch between tree-shaped conventional communication mode and tree-shaped radar signal transmission mode. The optical routing terminal, the wavelength division multiplexer / demultiplexer, the optical network unit, and the optical fiber constitute a conventional tree-shaped passive optical network structure. The system initiates the conventional tree-shaped communication mode. In the conventional tree-shaped passive optical network structure, the optical routing terminal and the optical network unit are respectively connected in parallel to the data center unit and the radar transceiver base station. The data center unit and each radar transceiver base station form a tree network structure, and the system enables the tree-shaped radar signal transmission mode.

[0027] Specifically, in this embodiment, the data center unit includes a laser array, a wavelength division multiplexer, a wavelength demultiplexer, a phase modulator, an optical filter, an optical circulator, a photodetector, a radio frequency signal source, and an echo signal processing module. The phase modulator is used to modulate the radio frequency signal onto the optical carrier, and the phase modulator includes a first phase modulator and a second phase modulator. The laser array can generate optical carriers of different wavelengths, including a first optical carrier λ1...the nth optical carrier λn, and the optical carriers will be transmitted to each of the tree-shaped radar transceiver base stations respectively; The radio frequency (RF) signal source is a dual-output RF signal source. The RF signal source modulates the RF signal emitted by the RF signal source onto the optical carrier by driving the first phase modulator and the second phase modulator in series, generating an optical RF signal and transmitting it to each of the tree-shaped radar transceiver base stations. After the tree-shaped radar transceiver base station receives the optical RF signal, converts it into an RF electrical signal, and transmits it to the data center unit, it first passes through the filter to filter out the single-sided first-order sideband generated by phase modulation, and then passes through the photodetector to perform beat frequency detection to recover the RF electrical signal, which is then transmitted to the echo signal processing module for processing. The echo signal processing module includes an intermediate frequency amplifier, an analog-to-digital converter, and a signal processing host computer. After the radar signal enters the echo signal processing module, it is first amplified by the intermediate frequency amplifier, the analog-to-digital converter completes the sampling and digitization of the radar signal, and finally it is sent to the signal processing host computer to complete the extraction of target information.

[0028] Specifically, in this embodiment, the distributed radar system for point-to-multipoint transmission of analog radar signals includes several tree-shaped radar transceiver base stations, including a first tree-shaped radar transceiver base station TR11, a second tree-shaped radar transceiver base station TR12, ..., an nth tree-shaped radar transceiver base station TR1n. Each tree-shaped radar transceiver base station includes an optical circulator, an optical beam splitter, a phase modulator, a photodetector, a power amplifier, a low-noise amplifier, an electrical circulator, and a transceiver antenna assembly. The optical circulator includes a first path, a second path, and a third path. The first path and the second path are used to allow the optical radio frequency signal to enter the optical distribution network of the tree-shaped passive optical network for transmission. The second path and the third path are used to allow the optical radio frequency signal to re-enter the optical distribution network for transmission to the data center unit. The transceiver antenna assembly described in this embodiment uses a separate transceiver antenna. Of course, other transceiver antenna assemblies can also be used, such as a shared transceiver antenna or an antenna array. This embodiment does not limit the use of transceiver antennas. After the optical radio frequency signal is transmitted to the tree-shaped radar transceiver base station, the optical beam splitter splits the optical radio frequency signal into two beams. One beam is used to convert it into a radar signal and radiate it out. The other beam is used as the optical carrier of the optical radio frequency signal received by the antenna again.

[0029] Specifically, in this embodiment, when the system activates the tree-shaped radar signal transmission mode, the laser array in the data center unit outputs light of different wavelengths, including λ1…λn. After being multiplexed by the wavelength division multiplexer, the light is modulated by the phase modulator under the drive of the radio frequency signal source to generate an optical radio frequency signal. The optical radio frequency signal enters the optical distribution network of the tree-shaped passive optical network through the first and second paths of the optical circulator. After passing through the wavelength division multiplexer, the optical radio frequency signal reaches the designated tree-shaped radar transceiver base station through different transmission paths. After passing through the first and second paths of the optical circulator, the optical radio frequency signal is split into two by the optical beam splitter. One branch of the optical radio frequency signal is converted into a radio frequency electrical signal by the photodetector and then passed through the power amplifier. After amplification, the radar signal is radiated by the antenna, thus completing the generation and radiation of the radar signal. The other branch of the optical beam splitter carries the radio frequency signal, which is reused as a light source. The radar signal received by the antenna is amplified by the low-noise amplifier and drives the phase modulator to remodulate it into an optical signal. It then re-enters the optical distribution network through the second and third paths of the optical circulator and is transmitted to the data center unit. At the data center unit, the signals of different tree-shaped radar transceiver base stations are distinguished by different wavelengths. The received radar signal passes through the second and third paths of the circulator to the filter. After the filter filters out the single-sided first-order sideband generated by phase modulation, it is subjected to beat frequency detection by the photodetector and finally enters the echo signal processing module for processing, thus completing the reception and processing of the radar signal.

[0030] Specifically, in this embodiment, the distributed radar system for point-to-point transmission of analog radar signals includes, The optical fiber routing terminal is a hardware device at the endpoint of the passive optical network, used to control, manage, and measure distances to user-end devices; A 1×2 optical switch is used to achieve selective switching of parallel structures, enabling rapid networking of distributed radars. An optical circulator is used to reflect signals transmitted to the optical routing terminal back to the loop, ensuring that radar signals can be transmitted to any ring radar transceiver base station in the loop. An optical network unit (ONU) is a terminal device in the passive optical network that uses optical fiber access. It is used to receive and respond to ranging and power control commands issued by the optical fiber routing terminal and make corresponding adjustments. A ring-shaped radar transceiver base station, connected in parallel to the optical network unit, is used to generate, transmit, receive, and process signals. A total light reflector, connected in parallel at the light routing terminal, is used to reflect light; A reference signal generation module is used to generate a reference signal, modulate it onto a fixed-wavelength optical carrier, and transmit it to each of the ring radar transceiver base stations.

[0031] Specifically, in this embodiment, the distributed radar system for point-to-point transmission of analog radar signals achieves rapid distributed radar networking by controlling the optical switch to switch between the ring conventional communication mode and the ring radar signal transmission mode. The optical routing terminal, the optical circulator, the optical network unit, and the optical fiber constitute a conventional ring passive optical network structure. The system initiates the conventional ring communication mode. In the conventional ring passive optical network structure, the optical routing terminal and the optical network unit are respectively connected in parallel to the all-optical reflector and the ring radar transceiver base station. The reference signal generation module is sequentially connected to each ring radar transceiver base station to form a ring network structure, and the system enables the ring radar signal transmission mode.

[0032] Specifically, the reference signal generation module in this embodiment includes an upload / download multiplexer, an optical filter, and a reference signal generator; Specifically, the wavelength of the reference signal generated by the reference signal generator is set to λ0. The reference signal is uploaded to the main loop and transmitted to all ring radar transceiver base stations through the upload / download multiplexer as the unified reference signal of the system. When the reference signal is transmitted to the reference signal generation module again, the residual reference signal in the system is filtered out by the pre-filter to avoid interference with the newly generated reference signal.

[0033] Specifically, the distributed radar system for point-to-point transmission of analog radar signals described in this embodiment includes several ring radar transceiver base stations, including a first ring radar transceiver base station TR21, a second ring radar transceiver base station TR22, ..., an nth ring radar transceiver base station TR2n. Each ring radar transceiver base station includes an upload / download multiplexer, a photodetector, a tunable laser, an electro-optic modulator, an optical filter, an optical beam splitter, an optical coupler, an electro-directional coupler, a power amplifier, a low-noise amplifier, an RF signal source, and an echo signal processing module. The upload / download multiplexer downloads the radar signal and the reference signal of a specified wavelength from the main loop or uploads a radar signal of any operating wavelength to the main loop. Different wavelengths correspond to different ring radar transceiver base stations. Point-to-point transmission can be achieved in the ring passive optical network through the upload / download multiplexer. The coupling ratio of the optical coupler can be adjusted appropriately according to the number of ring radar transceiver base stations connected in the loop. It is necessary to ensure that most of the reference signals can continue to be transmitted to other ring radar transceiver base stations in the loop. The tunable laser generates laser of any wavelength used in the distributed radar system for point-to-point transmission of radar analog signals. The generated radar optical signal is transmitted to any ring radar transceiver base station in the distributed radar system for point-to-point transmission of radar analog signals. The photodetector and the electro-optic modulator realize the optical-to-electrical signal conversion and electro-optical signal conversion in the system, respectively.

[0034] Specifically, in this embodiment, when the system enables the ring radar signal transmission mode, the reference signal generation module generates a reference signal λ0. The reference signal λ0 is uploaded to the main loop and transmitted to the ring radar transceiver base station. After reaching the ring radar transceiver base station, it is downloaded to each ring radar transceiver base station via the upload / download multiplexer. All ring radar transceiver base stations can download the reference signal λ0. After the reference signal λ0 is downloaded from each ring radar transceiver base station, it passes through the optical coupler at a ratio of 1:9. 10% of the reference signal is recovered into an electrical signal by the photodetector and transmitted to the echo signal processing module and the radio frequency signal source for processing. As a reference signal for echo signal processing and signal generation, 90% of the reference signal is re-uploaded to the main loop via the upload / download multiplexer for further transmission to other ring radar transceiver base stations. Each ring radar transceiver base station receives radar optical signals of a specified wavelength. Different ring radar transceiver base stations are distinguished by different wavelengths. After the radar optical signal arrives at the ring radar transceiver base station, it is downloaded to the specified wavelength via the upload / download multiplexer. The signal is then split into two paths by the optical beam splitter. One radar optical signal is converted into a radio frequency electrical signal after passing through a photodetector and a power amplifier and is radiated by the antenna, completing the radar signal transmission process. The radar signal received by the antenna is amplified by a low-noise amplifier and then drives the modulator. Another radar optical signal is remodulated as a light source. After being detected by the photodetector, it enters the echo signal processing module for signal processing. The intelligence information processed by each ring radar transceiver base station is converted into a digital signal and transmitted to the headquarters through conventional digital communication, completing the radar signal reception and processing process. Under the drive of the radio frequency signal source, the optical carrier λx generated by the tunable laser, 1≤x≤n, where n is the number of ring radar transceiver base stations in the system, is modulated by the modulator and then uploaded to the main ring link for transmission through the upload / download multiplexer until it is received by a ring radar receiving base station capable of downloading the wavelength, completing the radar signal generation and point-to-point transmission process.

[0035] Specifically, in this embodiment, both the distributed radar system proposing point-to-multipoint transmission of radar analog signals via the tree-shaped passive optical network and the distributed radar system proposing point-to-point transmission of radar analog signals via the ring passive optical network are coherent radar systems. In the distributed radar system proposed by the tree-shaped passive optical network for point-to-multipoint transmission of radar analog signals, the reference signals used by the data center unit for signal generation and echo signal processing are all provided by the same radio frequency signal source. In the distributed radar system for point-to-point transmission of analog radar signals proposed by the ring passive optical network, the reference signals used for signal generation and processing by the ring radar transceiver base station are all generated by the reference signal generation module.

[0036] Specifically, in this embodiment, the number of the tree-shaped radar transceiver base stations and the ring-shaped radar transceiver base stations can be increased or decreased according to system needs. The maximum number is determined based on the number of optical network units allowed to be accessed in the protocol followed by the tree / ring passive optical network.

[0037] This invention, based on the different topologies of existing passive optical access network architectures, divides them into tree-shaped passive optical networks and ring-shaped passive optical networks. For the tree-shaped passive optical network, a distributed radar system for point-to-multipoint transmission of radar analog signals is proposed; for the ring-shaped passive optical network, a distributed radar system for point-to-point transmission of radar analog signals is proposed. The proposed distributed radar systems are based on widely deployed passive optical access networks, requiring only the addition of some optical components to complete the construction of the distributed radar system, thus reducing the construction cost. Utilizing the widely deployed fiber optic networks in current fiber optic communication systems as the signal transmission medium for radar networking, there is no need to lay new optical cables. This allows for the rapid, convenient, widespread, and flexible construction of distributed radar systems. Furthermore, the easy access characteristics of fiber optic networks improve the survivability of the distributed radar systems.

[0038] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A microwave photonic distributed radar system based on an existing optical access network, characterized in that, This includes differentiating passive optical network (PON) topologies based on existing PON architectures, including tree-structured PONs and ring-structured PONs. The tree-shaped passive optical network proposes a distributed radar system for point-to-multipoint transmission of analog radar signals. The proposed ring passive optical network enables a distributed radar system for point-to-point transmission of analog radar signals.

2. The microwave photonic distributed radar system based on an existing optical access network according to claim 1, characterized in that, The distributed radar system for point-to-multipoint transmission of analog radar signals includes, The optical fiber routing terminal is a hardware device at the endpoint of the passive optical network, used to control, manage, and measure distances to user-end devices; A data center unit, connected in parallel at the optical routing terminal, is used to generate optical radar signals and process echo signals; A 1×2 optical switch is used to achieve selective switching of parallel structures, enabling rapid networking of distributed radars. An optical network unit (ONU) is a terminal device in the passive optical network that uses optical fiber access. It is used to receive and respond to ranging and power control commands issued by the optical fiber routing terminal and make corresponding adjustments. The tree-shaped radar transceiver base station is connected in parallel to the optical network unit to complete the radiation and reception of radio frequency radar signals, and to complete the conversion of optical-to-electric and electrical-to-optical signals. A wavelength division multiplexer / demultiplexer is used to combine / separate wavelengths, allowing light of different wavelengths to travel through different transmission paths to the designated tree-shaped radar transceiver base station.

3. The microwave photonic distributed radar system based on an existing optical access network according to claim 2, characterized in that, The distributed radar system that transmits analog radar signals from point to multiple points achieves rapid networking of distributed radars by controlling the optical switch to switch between tree-shaped conventional communication mode and tree-shaped radar signal transmission mode. The optical routing terminal, the wavelength division multiplexer / demultiplexer, the optical network unit, and the optical fiber constitute a conventional tree-shaped passive optical network structure. The system initiates the conventional tree-shaped communication mode. In the conventional tree-shaped passive optical network structure, the optical routing terminal and the optical network unit are respectively connected in parallel to the data center unit and the radar transceiver base station. The data center unit and each radar transceiver base station form a tree network structure, and the system enables the tree-shaped radar signal transmission mode.

4. The microwave photonic distributed radar system based on an existing optical access network according to claim 3, characterized in that, The data center unit includes a laser array, a wavelength division multiplexer, a wavelength demultiplexer, a modulator, an optical filter, an optical circulator, a photodetector, a radio frequency signal source, and an echo signal processing module. The laser array is capable of generating optical carriers of different wavelengths and transmitting the optical carriers to each of the tree-shaped radar transceiver base stations. The modulator is used to modulate radio frequency signals onto an optical carrier.

5. The microwave photonic distributed radar system based on an existing optical access network according to claim 3, characterized in that, The distributed radar system for point-to-multipoint transmission of analog radar signals includes several tree-shaped radar transceiver base stations. Each tree-shaped radar transceiver base station includes an optical circulator, an optical beam splitter, a phase modulator, a photodetector, a power amplifier, a low-noise amplifier, an electrical circulator, and a transceiver antenna assembly. The optical circulator includes a first path, a second path, and a third path. The first and second paths are used to allow the optical radio frequency signal to enter the optical distribution network of the tree-shaped passive optical network for transmission. The second and third paths are used to allow the optical radio frequency signal to re-enter the optical distribution network for transmission to the data center unit. After the optical radio frequency signal is transmitted to the tree-shaped radar transceiver base station, the optical beam splitter splits the optical radio frequency signal into two beams. One beam is used to convert it into a radar signal for radiation, and the other beam is used as the optical carrier of the optical radio frequency signal received by the antenna.

6. The microwave photonic distributed radar system based on an existing optical access network according to claim 2, characterized in that, The distributed radar system for point-to-point transmission of analog radar signals includes, An optical circulator is used to reflect signals transmitted to the optical routing terminal back to the loop, ensuring that radar signals can be transmitted to any ring radar transceiver base station in the loop. A ring-shaped radar transceiver base station, connected in parallel to the optical network unit, is used to generate, transmit, receive, and process signals. A total light reflector, connected in parallel at the light routing terminal, is used to reflect light; A reference signal generation module is used to generate a reference signal, modulate it onto a fixed-wavelength optical carrier, and transmit it to each of the radar transceiver base stations.

7. The microwave photonic distributed radar system based on an existing optical access network according to claim 6, characterized in that, The distributed radar system that transmits analog radar signals point-to-point achieves rapid networking of distributed radars by controlling an optical switch to switch between a ring-shaped conventional communication mode and a ring-shaped radar signal transmission mode. The optical routing terminal, the optical circulator, the optical network unit, and the optical fiber constitute a conventional ring passive optical network structure. The system initiates the conventional ring communication mode. In the conventional ring passive optical network structure, the optical routing terminal and the optical network unit are respectively connected in parallel to the all-optical reflector and the ring radar transceiver base station. The reference signal generation module is sequentially connected to each ring radar transceiver base station to form a ring network structure, and the system enables the ring radar signal transmission mode.

8. The microwave photonic distributed radar system based on an existing optical access network according to claim 7, characterized in that, The reference signal generation module includes an upload / download multiplexer, an optical filter, and a reference signal generator. The reference signal generator generates a reference signal, which is uploaded to the main loop and transmitted to all ring radar transceiver base stations via the upload / download multiplexer to serve as the unified reference signal for the system. When the reference signal is transmitted to the reference signal generation module again, the optical filter filters out any remaining reference signals in the system to avoid interference with the newly generated reference signal.

9. The microwave photonic distributed radar system based on an existing optical access network according to claim 7, characterized in that, The distributed radar system for point-to-point transmission of radar analog signals includes several ring radar transceiver base stations. Each ring radar transceiver base station includes an upload / download multiplexer, a photodetector, a tunable laser, an electro-optic modulator, an optical filter, an optical beam splitter, an optical coupler, an electro-directional coupler, a power amplifier, a low-noise amplifier, a radio frequency signal source, and an echo signal processing module. The upload / download multiplexer downloads the radar signal and the reference signal of a specified wavelength from the main loop or uploads a radar signal of any operating wavelength to the main loop. Different wavelengths correspond to different ring radar transceiver base stations. Point-to-point transmission can be achieved in the ring passive optical network through the upload / download multiplexer. The coupling ratio of the optical coupler can be adjusted appropriately according to the number of ring radar transceiver base stations connected in the loop. It is necessary to ensure that most of the reference signals can continue to be transmitted to other ring radar transceiver base stations in the loop. The tunable laser generates laser of any wavelength used in the distributed radar system for point-to-point transmission of radar analog signals. The generated radar optical signal is transmitted to any ring radar transceiver base station in the distributed radar system for point-to-point transmission of radar analog signals. The photodetector and the electro-optic modulator realize the optical-to-electrical signal conversion and electro-optical signal conversion in the system, respectively.

10. The microwave photonic distributed radar system based on an existing optical access network according to any one of claims 2-9, characterized in that, Both the tree-shaped passive optical network-based distributed radar system for transmitting radar analog signals from point to multiple points and the ring-shaped passive optical network-based distributed radar system for transmitting radar analog signals from point to point are coherent radar systems. In the distributed radar system for point-to-multipoint transmission of radar analog signals proposed by the tree-shaped passive optical network, the reference signals used by the data center unit for signal generation and echo signal processing are all provided by the same radio frequency signal source. In the distributed radar system for point-to-point transmission of radar analog signals proposed by the ring passive optical network, the reference signals used by the ring radar transceiver base station for signal generation and processing are all generated by the reference signal generation module. The number of the tree-shaped radar transceiver base stations and the ring-shaped radar transceiver base stations can be increased or decreased according to system needs. The maximum number is determined based on the number of optical network units allowed to be accessed in the protocol followed by the tree / ring passive optical network.

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