Low-altitude cooperative target fusion monitoring device and method based on ADS-B and RID modules

Abstract

The invention relates to a low-altitude cooperative target fusion monitoring device and method based on a sum module, and belongs to the technical field of low-altitude monitoring. According to the equipment method, a module is used for receiving a radio frequency signal of a corresponding frequency band according to a correspondingly-arranged external interface, the radio frequency signal is filtered through a radio frequency front end, baseband signal extraction is carried out through a digital down-conversion unit, and finally the signal is detected and decoded through a DSP unit to obtain corresponding monitoring information. An external interface which is also correspondingly arranged in the module receives a radio frequency signal of a corresponding frequency band, a built-in integrated chip carries out amplification, down-conversion, demodulation and decoding processing to obtain an MAC layer data packet, the data packet is read through a main processor, and corresponding monitoring information is extracted from the data packet. According to the invention, diversified signal types from various aircrafts and unmanned aerial vehicles can be received and processed at the same time, and seamless coverage and comprehensive perception of all cooperative targets in a low-altitude airspace are realized.

Description

Technical Field

[0001] This invention belongs to the field of low-altitude surveillance technology and relates to a low-altitude cooperative target fusion surveillance device and method based on ADS-B and RID modules. Background Technology

[0002] As the global low-altitude economy enters a period of rapid development, its scale has exceeded 5 trillion yuan. The utilization mode of low-altitude airspace is undergoing profound changes from single to multiple, and from low frequency to high frequency. In the civilian sector, drone applications have penetrated into more than 30 industry scenarios, including logistics and distribution, emergency rescue, aerial surveying and mapping, and agricultural plant protection, forming a complete industrial chain ecosystem.

[0003] From a technological perspective, low-altitude traffic is exhibiting three major characteristics: "three-dimensionality, density, and intelligence." In terms of three-dimensionality, airspace below 1000 meters is divided into multiple altitude layers, with different types of aircraft operating in vertically layered configurations. Regarding density, it has become common for 5-10 aircraft to be present simultaneously per square kilometer of airspace in core urban areas. In terms of intelligence, the application of new technologies such as autonomous flight and swarm collaboration has significantly increased the difficulty of flight trajectory prediction. This change has directly driven a qualitative shift in surveillance requirements: the traditional "passive reception" model can no longer meet the needs, necessitating the construction of a surveillance system with "full-element perception, full-time and spatial coverage, and fully intelligent analysis" capabilities.

[0004] The current low-altitude surveillance system has the following problems: single-source sensing technology has significant limitations; traditional secondary radar has a blind spot at the top due to building obstruction in urban environments; and its detection range for micro UAVs with an RCS (radar cross-section) of less than 0.1㎡ is less than 500 meters; photoelectric surveillance systems are susceptible to rain and fog, and the accuracy of nighttime identification drops by 40%; radio monitoring relies on the aircraft actively emitting signals, and is completely ineffective against illegal aircraft using silent mode. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a low-altitude cooperative target fusion monitoring device and method based on ADS-B and RID modules, for receiving ADS-B and RemoteID signals, and for monitoring and early warning of the flight status of aircraft.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules includes an ADS-B module, an RID module, a PoE switching module, a power conversion module, internal interfaces, and external interfaces. The ADS-B module receives RF signals of the corresponding frequency band through its external interface. First, the RF front-end filters the RF signal. Then, the digital down-conversion unit extracts the baseband signal. Finally, the DSP unit detects and decodes the signal to obtain the corresponding monitoring information. Similarly, the RID module receives RF signals of the corresponding frequency band through its external interface. Its built-in integrated chip amplifies, down-converts, demodulates, and decodes the signals to obtain MAC layer data packets. The main processor then reads these MAC layer data packets and extracts the corresponding monitoring information. The monitoring information acquired by the ADS-B and RID modules is transmitted to externally connected computer devices through internal interfaces and the PoE exchange module, where data analysis and display are performed.

[0007] Furthermore, the RF front-end of the ADS-B module includes a low-noise amplifier, a mirror filter, a mixer processor, a filter bank, and an analog-to-digital converter. The filter bank includes an IF low-pass filter and an anti-aliasing filter. After the antenna receives an RF signal containing an ADS-B signal, the received signal is amplified by the low-noise amplifier, then passed through the RF mirror filter, and then the signal is mixed. After passing through the filter bank, the signal is digitized and then enters the subsequent digital down-conversion unit for digital processing.

[0008] Furthermore, the digital down-conversion unit of the ADS-B module includes an A / D converter, an NCO digitally controlled oscillator, a CIC filter, an FIR filter, and two decimators. The A / D converter converts the intermediate frequency signal into a digital signal. The digital signal is then used by the NCO oscillator to generate I-channel and Q-channel quadrature signals. The I-channel and Q-channel quadrature signals are filtered out by the CIC filter to remove high-frequency signals. Then, the sampling rate is reduced by one decimator to reduce the computational burden. The signal after the sampling rate reduction is filtered out again by the FIR filter to remove high-frequency signals. Finally, the sampling rate is reduced by another decimator to obtain the final output signal.

[0009] Furthermore, the generation process of the two orthogonal signals of the digital down-conversion unit is represented as follows: First, the intermediate frequency signal is converted into a digital signal by an A / D converter:

[0010] in, This indicates the amplitude of the input intermediate frequency signal. Indicates the frequency of the intermediate frequency signal. Indicates the sampling rate of the signal. It is a sequence of sampling points. Indicates the phase of the signal.

[0011] Then, the NCO oscillator first generates two quadrature signals:

[0012]

[0013] Then the digital signal After mixing with an NCO oscillator, the I-channel signal and the Q-channel signal are obtained:

[0014]

[0015] After mixing, the I-channel and Q-channel signals are moved to the baseband and high-frequency sections.

[0016] Furthermore, the processes of the CIC filter filtering out high-frequency signals and the first decimator reducing the sampling rate, as well as the processes of the FIR filter filtering out high-frequency signals and the second decimator reducing the sampling rate, are as follows: Let the decimation factor of the CIC filter be... The output I-channel and Q-channel signals of the CIC filter are:

[0017]

[0018] in, The index of the CIC filter coefficients is 0 to 1. , The order of the CIC filter; This is for CIC filter operation; the sampling rate of the two signals output by the CIC filter is... ; Let the extraction factor of the first extractor be... Then the output signal of the extractor is:

[0019]

[0020] in The sampling rate of the output signal of the first decimator is ; The output signal after the FIR filter removes high-frequency signals is:

[0021]

[0022] in, This indicates FIR filter operation, where the sampling rate of the output signal is... ; The extraction factor of the second extractor is The output signal is represented as:

[0023]

[0024] in At this time, the sampling rate of the output signal is .

[0025] Furthermore, the two output signals are then input into the DSP processor for signal detection and decoding. Data inspection includes header inspection, data decision, and CRC check. Header inspection uses correlation operations to find known sequences to locate data frames. Data decision compares the energy of the preceding and following data within each window to determine whether it is 0 or 1. CRC check ensures the correctness of the data; if it is incorrect, it is discarded. Signal decoding includes parsing the binary data stream that has passed CRC check, extracting the DF field, confirming the accuracy of the message type, and then parsing the ICAO address, latitude and longitude, altitude, and speed information from the data field according to the message type; The data parsed by the DSP processor is encapsulated according to the output protocol defined by the device, and the data stream is uploaded to the low-altitude monitoring and management platform software in real time via UART serial port or Ethernet.

[0026] Furthermore, in the RID module, the omnidirectional antenna captures 2.4 GHz / 5.8 GHz signals, which are then processed by an integrated chip. The integrated chip internally performs low-noise amplification, down-conversion, demodulation, and decoding of the signals, ultimately outputting MAC layer data packets. The main processor reads the MAC layer data packets from the integrated chip, performs message filtering to determine their validity, and extracts the UAV ID, location, altitude, and speed fields from the valid message data, completing the information processing and parsing. The parsed Remote ID data is then uploaded in real time to the low-altitude monitoring and management platform software via UART serial port or Ethernet, according to the output protocol defined by the device.

[0027] Furthermore, the external interfaces include a power supply interface, a network interface, and a signal receiving interface; The power supply interface is used to supply power to the device. The power supply interface is connected to the AC / DC current conversion module in the device. The current conversion module supplies power to the PoE switching module, ADS-B module, RID module and internal interfaces. The network interface is set to a TTL serial port for reporting aircraft information to external systems. The signal receiving interface includes several N-type connectors, including at least one N-type connector for receiving ADS-B signals, which are used to receive 1090MHz radio frequency signals; and two N-type connectors for receiving Remote ID signals, one for receiving 2.4GHz radio frequency signals and the other for receiving 5.8GHz radio frequency signals.

[0028] Furthermore, the PoE switching module serves as the internal network switching hub of the device. Its main functions include: building an internal local area network, connecting various functional modules within the device (such as the Remote ID receiving module, main processor, etc.) via Ethernet to form a standardized, high-speed internal communication network; and also being responsible for receiving, verifying, forwarding, and routing data packets between different modules. Its working process follows the principle of a standard network switch and can be summarized into the following continuous operation stages: The first stage is address learning, that is, when a functional module sends data for the first time, the PoE switching module will check the source MAC address of the data frame and record the address along with the physical port number that received the frame in its internal MAC address table, thereby dynamically learning and building the topology of the entire internal network of the device, knowing which module is connected to which port; The second stage is frame forwarding and filtering, that is, when the PoE switching module receives a data frame from a port, it checks the destination MAC address of the data frame, then queries the MAC address table, and completes the data transmission according to certain rules.

[0029] On the other hand, a monitoring method for a low-altitude cooperative target fusion monitoring device based on the aforementioned ADS-B and RID modules is also provided. This method includes an ADS-B signal processing procedure and a Remote ID signal processing procedure. The ADS-B signal processing procedure includes the following steps: The aircraft obtains position, attitude, flight information and 24-bit ICAO address from the airborne GNSS receiver, inertial reference system, flight management system and airborne transponder, packages them into a message containing DF field and CRC check code according to standard protocol, converts it into an analog signal using pulse position-pulse width modulation, tunes it to the 1090MHz frequency band and transmits it through the antenna; The antenna receives 1090MHz ADS-B radio frequency signals, which are then amplified by a low-noise amplifier. The image signal is filtered out by an RF image filter, mixed to an intermediate frequency, and then digitized by a filter bank. The digital intermediate frequency signal is mixed with the NCO oscillator signal to the baseband, and then the sampling rate is reduced by CIC, FIR filters and decimator to output the baseband I and Q signals; The DSP is used to detect and locate the data frame in the preamble, the data is judged to be 0 / 1, and after CRC check, the message is parsed to extract ICAO address, latitude and longitude, altitude and speed information; The parsed data is encapsulated according to the output protocol and uploaded to the low-altitude monitoring and management platform in real time via UART serial port or Ethernet. The Remote ID signal processing includes the following steps: The UAV flight control system collects ID, position, altitude, speed and track angle information, encapsulates it into network data packets according to the ASTM F3411 protocol, modulates and encodes it in the 2.4GHz / 5.8GHz frequency band, amplifies the power and broadcasts it through the antenna; An omnidirectional antenna captures 2.4GHz / 5.8GHz signals, and an integrated chip performs low-noise amplification. The chip internally demodulates the baseband signal and decodes it into raw data packets. The main processor executes protocol stack processing, filters valid messages, and extracts drone ID, location, altitude, and speed information; The parsed data is encapsulated according to the output protocol and uploaded to the low-altitude monitoring and management platform in real time via UART serial port or Ethernet.

[0030] The beneficial effects of this invention are as follows: This invention deeply integrates two advanced surveillance technologies, ADS-B (Automatic Dependent Surveillance-Broadcast) and RID (Remote Identification), to construct a comprehensive, multi-layered, and high-precision low-altitude cooperative target surveillance system. This invention can simultaneously receive and process diverse signal types from various aircraft (such as fixed-wing aircraft and helicopters) and UAVs, including but not limited to precise position information, instantaneous speed, flight altitude, and unique identification IDs. It also achieves seamless coverage and comprehensive perception of all cooperative targets within the low-altitude airspace.

[0031] This unprecedented all-element perception capability is a milestone in improving the safety and efficiency of low-altitude economic monitoring. In terms of safety, by grasping the dynamic information of each cooperative target in real time and accurately, the system can immediately detect and warn of potential collision risks, illegal intrusions, or other emergencies, providing traffic management departments with sufficient reaction time and decision-making basis, thereby effectively avoiding air traffic accidents and ensuring the safe and orderly operation of low-altitude airspace.

[0032] In terms of efficiency improvement, the comprehensive sensing capability enables traffic management departments to manage traffic flow, plan routes, and allocate resources based on more comprehensive and accurate data. This reduces traffic congestion and waiting time caused by information asymmetry or delays, thereby improving the overall operational efficiency of low-altitude transportation. At the same time, this capability lays a solid foundation for the intelligent and automated development of low-altitude transportation, propelling low-altitude traffic management towards a more efficient, precise, and sustainable direction.

[0033] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the functional modules of a low-altitude cooperative target fusion monitoring device based on ADS-B and RID modules according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the data processing flow of the radio frequency front-end processing module of the ADS-B module in an embodiment of the present invention; Figure 3 This is a schematic diagram of the data processing flow of the digital down-conversion unit of the ADS-B module in an embodiment of the present invention; Figure 4 This is a schematic diagram of the data processing flow of the DSP unit of the ADS-B module in an embodiment of the present invention. Detailed Implementation

[0035] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0036] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0037] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0038] Please see Figures 1-4 This invention relates to a low-altitude cooperative target fusion monitoring device and method based on ADS-B and RID modules.

[0039] Example 1 This embodiment describes in detail a low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules, such as... Figure 1 As shown, it includes an ADS-B module, a RID module, a PoE switching module, a power conversion module, internal interfaces, and external interfaces. The ADS-B module receives RF signals of the corresponding frequency band through its external interface. It first filters the RF signal through an RF front-end, then extracts the baseband signal through a digital down-conversion unit, and finally detects and decodes the signal through a DSP unit to obtain the corresponding monitoring information. Similarly, the RID module receives RF signals of the corresponding frequency band through its external interface, and its built-in integrated chip amplifies, down-converts, demodulates, and decodes the signals to obtain MAC layer data packets. The main processor then reads the MAC layer data packets and extracts the corresponding monitoring information from them. The monitoring information acquired by the ADS-B and RID modules is transmitted to externally connected computer devices through internal interfaces and the PoE exchange module, where data analysis and display are performed.

[0040] In this embodiment, Automatic Dependent Surveillance-Broadcast (ADS-B) is a novel surveillance technology where the aircraft determines its position via satellite navigation and periodically broadcasts information, enabling it to be tracked. For Air Traffic Control (ATC) ground stations, ADS-B will replace secondary surveillance radar in the future. Because it does not require ground interrogation signals, ADS-B can also be received by other aircraft to improve situational awareness and for application in traffic coordination systems. ADS-B is "automatic," requiring no pilot or additional input; however, it is "dependent," requiring data from the aircraft's navigation system and other systems. Traditional hardware receivers mostly use application-specific integrated circuits (ASICs), resulting in poor scalability, inability to upgrade algorithms, and long product update cycles. With the emergence and continuous development of software-defined radio (SDR) technology, SDR receivers are gradually replacing traditional receivers for the design of receiving various signals. The receiver processes digital signal processing modules through software, maximizing the receiver's flexibility.

[0041] ADS-B signals are divided into aircraft-transmitted signals and ADS-B receiver modules that receive and process signals. First, the aircraft acquires data from various systems, such as core position data from the onboard GNSS receiver, attitude data from the inertial reference system, flight information (flight number, destination, etc.) from the flight management system, and the aircraft's 24-bit ICAO address from the onboard transponder. Then, the collected information is packaged into messages according to standard protocols, including DF fields (such as DF17 and DF18) to determine the message type, and a CRC checksum is added to ensure data integrity. Pulse-width modulation (PPM-PWM) is used to convert the message data into an analog signal suitable for wireless transmission. Finally, the signal is tuned to the 1090MHz frequency band and transmitted through the antenna. This is the ADS-B signal transmission process.

[0042] The ADS-B receiver module first receives the signal through the antenna. The received signal is amplified by a low-noise amplifier, then passed through an RF image filter to remove unwanted image signals. The signal is then mixed to convert it to an intermediate frequency (IF), and after passing through a filter bank, it is digitized. The digital IF signal is mixed with the signal generated by the NCO oscillator, thus shifting the signal spectrum to baseband. Subsequently, it passes through a CIC decimation filter, an FIR filter, and a decimator to reduce the sampling rate to a level suitable for DSP processing, outputting the final baseband I and Q signals.

[0043] Subsequently, the baseband signal is detected and decoded using a DSP. Data detection includes preamble detection: using correlation operations to find known sequences to locate data frames; data decision: comparing the energy of the preceding and following 0.5 microseconds within each 1-microsecond window to determine if it is 0 or 1; CRC check: ensuring data correctness, discarding incorrect data. Signal decoding includes: parsing the binary data stream that has passed the CRC check, extracting the DF field to confirm it is a DF17 / DF18 message, and then, based on the message type, parsing information such as the ICAO address, latitude and longitude, altitude, and speed from the data field.

[0044] The data parsed by ADS-B is then encapsulated according to the output protocol defined by the device (e.g., ADS-B outputs DF17 raw messages or plaintext), and the data stream is uploaded to the low-altitude monitoring and management platform software in real time via UART serial port or Ethernet.

[0045] In the RF front-end of the ADS-B module, the following is used: Figure 2 The low-complexity low-IF structure shown includes a low-noise amplifier, a mirror filter, a mixer processor, a filter bank, and an analog-to-digital converter. The filter bank includes an IF low-pass filter and an anti-aliasing filter. After the antenna receives an RF signal containing an ADS-B signal, the received signal is amplified by the low-noise amplifier, then filtered out by the RF mirror filter to remove unnecessary mirror signals, and then the signal is mixed. After passing through the filter bank, it is digitized and enters the digital processing section.

[0046] In the digital downconversion unit of the ADS-B module, the intermediate frequency (IF) signal is downconverted to a baseband signal. The sampled signal is multiplied by two orthogonal signals generated by a numerically controlled oscillator (NCO) for quadrature demodulation. Specifically, it includes an A / D converter, an NCO, a CIC filter, an FIR filter, and two decimators. The A / D converter converts the IF signal into a digital signal. The digital signal is then used by the NCO to generate I-channel and Q-channel quadrature signals. The I-channel and Q-channel quadrature signals are filtered out by the CIC filter to remove high-frequency signals. Then, a decimator reduces the sampling rate to reduce computational burden. The signal with the reduced sampling rate is then filtered out again by the FIR filter to remove high-frequency signals, and finally, another decimator reduces the sampling rate to obtain the final output signal.

[0047] To reduce data volume for easier processing and computation, the signal undergoes multi-rate reception processing, reducing the signal sampling rate. To prevent signal aliasing, the signal with the reduced sampling rate needs to be filtered to obtain in-phase and quadrature components, which are then decimated and filtered to obtain the baseband symbol signal. For example... Figure 3 The specific processing procedure of the digital down-converter unit is shown, which includes the following steps: The intermediate frequency signal is converted into a digital signal by an A / D converter, and is represented in the following form:

[0048] The two orthogonal signals generated by the NCO numerically controlled oscillator are represented in the following forms:

[0049]

[0050] The intermediate frequency signal is then mixed with the NCO digitally controlled oscillator to obtain the following I-channel signal:

[0051] After mixing, the I-channel signal is shifted to the baseband and high-frequency range. The resulting Q-channel signal is shown below:

[0052] The signal sampling rate at this time is .

[0053] The signal is then passed through a CIC filter to remove the high-frequency portion. The CIC filter consists of two parts: an integrator and a comb filter. The integrator is essentially an accumulator, providing a low-pass effect, but also allowing high-frequency noise to accumulate. The comb filter is a differential converter that reduces the data sampling rate and suppresses the back amplification of high-frequency noise caused by the integrator. Together with the integrator, they form a low-pass filter with a flat passband. The system function expression of the CIC filter is:

[0054] This is an Nth-order CIC filter with a decimation factor of R and a differential delay of D=1.

[0055] Assume the decimation factor of the CIC filter is Then the output I and Q signals of the CIC filter are in the following form;

[0056]

[0057] The sampling rate of the output signal at this time is .

[0058] Further downsampling of the CIC output reduces the computational burden on the subsequent complex FIR filter. The decimation factor of the decimator is assumed to be... The output signal of the extractor is

[0059]

[0060] in At this time, the sampling rate of the output signal is .

[0061] To further reduce the sampling rate and avoid signal aliasing, the output signal is first filtered by an FIR filter to remove high-frequency signals. The output signal is shown below:

[0062]

[0063] The sampling rate of the output signal at this time is .

[0064] The signal finally passes through a decimator to further reduce the sampling rate, thereby reducing the amount of data processing and computation. Assume the decimator's decimation factor is... The output signal is shown below:

[0065]

[0066] in At this time, the sampling rate of the output signal is .

[0067] In the DSP unit of the ADS-B module, the signal consists of two parts, such as... Figure 4 The figures show an 8μs preamble pulse and a 112μs data bit pulse, respectively, with the data bits encoded using Pulse Position Modulation (PPM). The header contains a total of four pulses, each 0.5μs wide, which, in actual reception, is within ±0.05μs. The positions of the four pulses are fixed, with intervals of 1.0μs, 3.0μs, and 4.5μs.

[0068] According to the 1090ES ADS-B signal standard, the data processing module of the ADS-B receiving system can be divided into two main parts: header detection and data bit processing. Header detection employs a correlation-based header detection algorithm, which uses locally known headers to perform correlation calculations with the signal, and uses this correlation to find the correct header location.

[0069] During data bit processing, within a single code element, the preceding chip is named chip0 and the following chip is named chip1. If chip0 is a high pulse and chip1 is a low pulse, then this code element is 1. The first 5 bits of the 112-bit data downlink format (DF) segment are converted to decimal and checked against 17. If they are correct, a Cyclic Redundancy Check (CRC) is performed. The CRC checksum is then used to verify the correctness of the received ADS-B signal. Following the DO260B standard, the received valid ADS-B signal is parsed to obtain relevant aircraft information.

[0070] The RID (Remote ID) receiver module is primarily used in remote identification systems for drones and other aircraft to ensure that they can be identified and tracked while in flight, thus ensuring flight safety. According to the Federal Aviation Administration (FAA) requirements for drone remote identification, Remote ID data typically includes information such as the aircraft's identity, location, speed, and flight status, and is usually transmitted via wireless communication protocols.

[0071] The Remote ID receiver chip receives radio frequency signals from wireless routers or other devices via its internal antenna. These signals are then amplified and filtered before entering the chip's radio frequency receiver.

[0072] Radio frequency (RF) receivers convert received signals into baseband signals, or digital signals, using demodulation techniques. These digital signals contain data encoded using modulation techniques such as QFDM.

[0073] The baseband signal is further processed by decoding to convert the modulated data back into the original data, such as data packets.

[0074] The decoded data is then handed over to the chip's internal processor for processing. The processor is responsible for executing the functions of various protocol stacks, including the TCP / IP protocol stack, transport layer / network layer / data link layer processing, etc.

[0075] More specifically, the Remote ID signal transmission and reception process is as follows: First, during the data acquisition phase, the UAV flight control system acquires information such as the UAV ID, latitude and longitude, altitude (including atmospheric altitude and relative altitude), ground speed, vertical speed, and track angle. Simultaneously, the remote controller link provides the control station's location (latitude and longitude). This data is encapsulated according to Remote ID standard protocols such as ASTM F3411, forming network data packets, and transmitted at the Wi-Fi MAC layer. Subsequently, in the RF modulation and transmission phase, the signal is modulated to the 2.4 GHz and / or 5.8 GHz frequency bands, using modulation and coding techniques (compliant with IEEE 802.11a / g / n protocols) to segment the high-speed data stream into multiple orthogonal subcarriers, enhancing multipath interference resistance. The signal is then amplified (typically with a transmit power of 100mW to 1W, or 20 to 30dBm) and broadcast via antenna.

[0076] In the reception and processing flow, the omnidirectional antenna captures 2.4 GHz / 5.8 GHz signals, which are then processed by the integrated chip PAN9026. This chip internally performs low-noise amplification (LNA), down-conversion, demodulation, and decoding of the signals, ultimately outputting MAC layer data packets. The main processor (such as an STM32) reads these data packets from the PAN9026, performs message filtering to determine their validity, and extracts fields such as UAV ID, location, altitude, and speed from valid message data, completing the information processing and parsing.

[0077] The parsed Remote ID data is then uploaded in real time to the low-altitude monitoring and management platform software via UART serial port or Ethernet, according to the output protocol defined by the device (Remote ID outputs hexadecimal raw message or plaintext).

[0078] The external interfaces include a power supply interface, a network interface, and a signal receiving interface. Specifically, in this embodiment, the power supply interface uses a three-pin aviation connector, with one unit, for powering the device. The power supply interface connects to the AC / DC current conversion module in the device, which supplies power to the PoE switching module, ADS-B module, RID module, and internal interfaces. In this embodiment, the current conversion module outputs a 5V voltage. The network interface is a TTL serial port using an RJ45 connector, with one unit, primarily used for reporting aircraft information externally. The signal receiving interface includes several N-type connectors. In this embodiment, at least one N-type connector is used to receive ADS-B signals, specifically 1090MHz radio frequency signals. A spare identical N-type connector can also be provided. Two N-type connectors are used to receive Remote ID signals, one for receiving 2.4GHz radio frequency signals and the other for receiving 5.8GHz radio frequency signals.

[0079] The PoE switching module serves as the internal network switching hub of the device. Its main functions include: building an internal local area network, connecting various functional modules within the device (such as the Remote ID receiving module, main processor, etc.) via Ethernet to form a standardized, high-speed internal communication network; and receiving, verifying, forwarding, and routing data packets between different modules.

[0080] Its working process follows the principles of a standard network switch and can be summarized into the following continuous operation stages: The first stage is address learning, that is, when a functional module sends data for the first time, the PoE switching module checks the source MAC address of the data frame and records the address along with the physical port number that received the frame in its internal MAC address table, thereby dynamically learning and building the topology of the entire internal network of the device, knowing which module is connected to which port; The second stage is frame forwarding and filtering, that is, when the PoE switching module receives a data frame from a port, it checks the destination MAC address of the data frame, then queries the MAC address table, and completes the data transmission according to certain rules.

[0081] Example 2 This embodiment provides a low-altitude cooperative target fusion surveillance method based on ADS-B and Remote ID modules, including an ADS-B signal processing flow and a Remote ID signal processing flow. The ADS-B signal processing includes the following steps: Signal broadcasting: The aircraft obtains position, attitude, flight information and 24-bit ICAO address from the airborne GNSS receiver, inertial reference system, flight management system and airborne transponder, packages them into a message containing DF field and CRC check code according to standard protocol, converts it into an analog signal using pulse position-pulse width modulation, tunes it to 1090MHz frequency band and transmits it through antenna; Signal reception and amplification: 1090MHz ADS-B RF signal is received through the antenna and amplified by a low-noise amplifier; Filtering and mixing: The image signal is filtered out by an RF image filter, mixed to an intermediate frequency, and then digitized by a filter bank; Digital downconversion and filtering: The digital intermediate frequency signal is mixed with the NCO oscillator signal to the baseband, and then the sampling rate is reduced by CIC, FIR filters and decimator to output the baseband I and Q signals; Signal detection and decoding: The DSP is used to detect and locate the data frame in the preamble, determine the 0 / 1 of the data, and parse the message after CRC check to extract ICAO address, latitude and longitude, altitude and speed information; Data upload: The parsed data is encapsulated according to the output protocol and uploaded to the low-altitude monitoring and management platform in real time via UART serial port or Ethernet.

[0082] The Remote ID signal processing includes the following steps: Signal broadcasting: The UAV flight control system collects ID, position, altitude, speed and track angle information, encapsulates it into network data packets according to the ASTM F3411 protocol, modulates and encodes it in the 2.4GHz / 5.8GHz frequency band, and broadcasts it through the antenna after power amplification; Signal reception and amplification: The omnidirectional antenna captures 2.4GHz / 5.8GHz signals, and the integrated chip performs low-noise amplification; Signal demodulation and decoding: The chip internally demodulates the baseband signal and decodes it into the original data packet; Data processing and extraction: The main processor executes protocol stack processing, filters valid messages, and extracts UAV ID, location, altitude, and speed information; Data upload: The parsed data is encapsulated according to the output protocol and uploaded to the low-altitude monitoring and management platform in real time via UART serial port or Ethernet.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules, characterized in that: It includes an ADS-B module, a RID module, a PoE switching module, a power conversion module, internal interfaces, and external interfaces. The ADS-B module receives RF signals of the corresponding frequency band through its external interface. First, the RF front-end filters the RF signal. Then, the digital down-conversion unit extracts the baseband signal. Finally, the DSP unit detects and decodes the signal to obtain the corresponding monitoring information. Similarly, the RID module receives RF signals of the corresponding frequency band through its external interface. Its built-in integrated chip amplifies, down-converts, demodulates, and decodes the signals to obtain MAC layer data packets. The main processor then reads these MAC layer data packets and extracts the corresponding monitoring information. The monitoring information acquired by the ADS-B and RID modules is transmitted to externally connected computer devices through internal interfaces and the PoE exchange module, where data analysis and display are performed.

2. The low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules according to claim 1, characterized in that: The RF front-end of the ADS-B module includes a low-noise amplifier, a mirror filter, a mixer processor, a filter bank, and an analog-to-digital converter. The filter bank includes an IF low-pass filter and an anti-aliasing filter. After the antenna receives an RF signal containing an ADS-B signal, the received signal is amplified by the low-noise amplifier, then passed through the RF mirror filter, and then the signal is mixed. After passing through the filter bank, the signal is digitized and then enters the subsequent digital down-conversion unit for digital processing.

3. A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules according to claim 2, characterized in that: The digital down-conversion unit of the ADS-B module includes an A / D converter, an NCO digitally controlled oscillator, a CIC filter, an FIR filter, and two decimators. The A / D converter converts the intermediate frequency signal into a digital signal. The digital signal is then used by the NCO oscillator to generate I-channel and Q-channel quadrature signals. The I-channel and Q-channel quadrature signals are filtered out by the CIC filter to remove high-frequency signals. Then, the sampling rate is reduced by one decimator to reduce the computational burden. The signal after the sampling rate reduction is filtered out again by the FIR filter to remove high-frequency signals. Finally, the sampling rate is reduced by another decimator to obtain the final output signal.

4. A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules according to claim 3, characterized in that: The generation process of the two orthogonal signals of the digital downconverter unit is represented as follows: First, the intermediate frequency signal is converted into a digital signal by an A / D converter: in, This indicates the amplitude of the input intermediate frequency signal. Indicates the frequency of the intermediate frequency signal. Indicates the sampling rate of the signal. It is a sequence of sampling points. Indicates the phase of the signal. Then, the NCO oscillator first generates two quadrature signals: Then the digital signal After mixing with an NCO oscillator, the I-channel signal and the Q-channel signal are obtained: After mixing, the I-channel and Q-channel signals are moved to the baseband and high-frequency sections.

5. A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules according to claim 4, characterized in that: The processes of CIC filter filtering out high-frequency signals and the first decimator reducing the sampling rate, and the processes of FIR filter filtering out high-frequency signals and the second decimator reducing the sampling rate are as follows: Let the decimation factor of the CIC filter be... The output I-channel and Q-channel signals of the CIC filter are: in, The index of the CIC filter coefficients is 0 to 1. , The order of the CIC filter; This is for CIC filter operation; the sampling rate of the two signals output by the CIC filter is... ; Let the extraction factor of the first extractor be... Then the output signal of the extractor is: in The sampling rate of the output signal of the first decimator is ; The output signal after the FIR filter removes high-frequency signals is: in, This indicates FIR filter operation, where the sampling rate of the output signal is... ; The extraction factor of the second extractor is The output signal is represented as: in At this time, the sampling rate of the output signal is .

6. A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules according to claim 5, characterized in that: The final two output signals are input into the DSP processor for signal detection and decoding. Data inspection includes header inspection, data decision, and CRC check. Header inspection uses correlation operations to find known sequences to locate data frames. Data decision compares the energy of the preceding and following data within each window to determine whether it is 0 or 1. CRC check ensures the correctness of the data; if it is incorrect, it is discarded. Signal decoding includes parsing the binary data stream that has passed CRC check, extracting the DF field, confirming the accuracy of the message type, and then parsing the ICAO address, latitude and longitude, altitude, and speed information from the data field according to the message type; The data parsed by the DSP processor is encapsulated according to the output protocol defined by the device, and the data stream is uploaded to the low-altitude monitoring and management platform software in real time via UART serial port or Ethernet.

7. A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules according to claim 1, characterized in that: In the RID module, the omnidirectional antenna captures 2.4GHz / 5.8GHz signals, which are then processed by an integrated chip. The integrated chip performs low-noise amplification, down-conversion, demodulation, and decoding of the signals, and finally outputs MAC layer data packets. The main processor reads the MAC layer data packets from the integrated chip, performs message filtering to determine their validity, and extracts the UAV ID, location, altitude, and speed fields from the valid message data to complete the information processing and parsing. The parsed Remote ID data is then uploaded in real time to the low-altitude monitoring and management platform software via UART serial port or Ethernet, according to the output protocol defined by the device.

8. A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules according to claim 1, characterized in that: External interfaces include power supply interface, network interface, and signal receiving interface; The power supply interface is used to supply power to the device. The power supply interface is connected to the AC / DC current conversion module in the device. The current conversion module supplies power to the PoE switching module, ADS-B module, RID module and internal interfaces. The network interface is set to a TTL serial port for reporting aircraft information to external systems. The signal receiving interface includes several N-type connectors, including at least one N-type connector for receiving ADS-B signals, which are used to receive 1090MHz radio frequency signals; and two N-type connectors for receiving Remote ID signals, one for receiving 2.4GHz radio frequency signals and the other for receiving 5.8GHz radio frequency signals.

9. A low-altitude cooperative target fusion surveillance device based on ADS-B and RID modules according to claim 1, characterized in that: The PoE switching module serves as the internal network switching hub of the device. It is used to build an internal local area network, connecting various functional modules within the device via Ethernet to form an internal communication network. Simultaneously, it receives, verifies, forwards, and routes data packets between different modules. The PoE switching module includes the following continuously operating phases: The first phase is address learning, where the PoE switching module checks the source MAC address of the data frame when a functional module sends data for the first time, and records the address along with the physical port number that received the frame in its internal MAC address table, dynamically learning and building the topology of the entire internal network of the device; The second phase is frame forwarding and filtering, where the PoE switching module receives a data frame from a port, checks the destination MAC address of the data frame, then queries the MAC address table, and completes the data transmission according to certain rules.

10. A monitoring method for a low-altitude cooperative target fusion monitoring device based on ADS-B and RID modules according to any one of claims 1-9, characterized in that: The method includes an ADS-B signal processing flow and a Remote ID signal processing flow. The ADS-B signal processing flow includes the following steps: The aircraft obtains position, attitude, flight information and 24-bit ICAO address from the airborne GNSS receiver, inertial reference system, flight management system and airborne transponder, packages them into a message containing DF field and CRC check code according to standard protocol, converts it into an analog signal using pulse position-pulse width modulation, tunes it to the 1090MHz frequency band and transmits it through the antenna; The antenna receives 1090MHz ADS-B radio frequency signals, which are then amplified by a low-noise amplifier. The image signal is filtered out by an RF image filter, mixed to an intermediate frequency, and then digitized by a filter bank. The digital intermediate frequency signal is mixed with the NCO oscillator signal to the baseband, and then the sampling rate is reduced by CIC, FIR filters and decimator to output the baseband I and Q signals; The DSP is used to detect and locate the data frame in the preamble, the data is judged to be 0 / 1, and after CRC check, the message is parsed to extract ICAO address, latitude and longitude, altitude and speed information; The parsed data is encapsulated according to the output protocol and uploaded to the low-altitude monitoring and management platform in real time via UART serial port or Ethernet. The Remote ID signal processing includes the following steps: The UAV flight control system collects ID, position, altitude, speed and track angle information, encapsulates it into network data packets according to the ASTM F3411 protocol, modulates and encodes it in the 2.4GHz / 5.8GHz frequency band, amplifies the power and broadcasts it through the antenna; An omnidirectional antenna captures 2.4GHz / 5.8GHz signals, and an integrated chip performs low-noise amplification. The chip internally demodulates the baseband signal and decodes it into raw data packets. The main processor executes protocol stack processing, filters valid messages, and extracts drone ID, location, altitude, and speed information; The parsed data is encapsulated according to the output protocol and uploaded to the low-altitude monitoring and management platform in real time via UART serial port or Ethernet.

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