An airborne collision avoidance system direction finding method and system

Abstract

The present invention discloses a method and system for direction finding of an airborne collision avoidance system. The method includes obtaining corresponding channel compensation data according to the type of the selected directional antenna; performing channel amplitude and phase compensation on the signals received by the directional antenna by using the channel compensation data; performing digital shaping processing on the signals after amplitude and phase compensation, and parallelly outputting three groups of signals: the received signals in the amplitude monopulse system, the received signals in the phase monopulse system, and the weighted combined signals; parallelly processing the three groups of signals output after the shaping processing to obtain the azimuth information in the amplitude monopulse system and the azimuth information in the phase monopulse system, and making a decision on the azimuth information of the two systems to determine the target azimuth information. The present invention can realize the complementary advantages of the two direction finding systems, and improve the anti-interference performance and accuracy of TCAS direction finding.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar direction finding, and particularly relates to a direction finding method and system for an airborne collision avoidance system. Background Art

[0002] The airborne collision avoidance system (i.e., ACAS - Airborne Collision Avoidance System, also known as TCAS - Traffic Alert and Collision Avoidance System) is defined by the Federal Aviation Administration (FAA) of the United States. Currently, the generally used civil and military ACAS is the TCAS II type collision avoidance system, which can provide traffic alert (TA) and resolution advisory (RA). TCAS is an essential device to prevent dangerous proximity and collision accidents of aircraft in the air and can work independently of the ground traffic control system. It is mainly used to provide air safety separation assurance for aircraft. The system uses the secondary radar method to detect approaching aircraft in the nearby airspace. When necessary, it reminds the pilot to take evasive measures to maintain an appropriate safety distance from other aircraft to achieve the purpose of anti - collision. Through flight practice in recent years, it has been proved that this system is the last line of defense to prevent aircraft collisions in the air and is also one of the most effective means at present. It overcomes the limitations of ground air traffic control, can provide flight safety assurance capabilities beyond those of ground air traffic control, and plays a huge role in coping with sudden dangerous proximity in the air and avoiding mid - air collisions.

[0003] The ACAS transceiver host of the system is the key to realizing the anti - collision function. It scans and interrogates the four regions in front of, behind, left, and right of the aircraft by controlling the pointing direction of the antenna beam. Aircraft equipped with an air traffic control transponder (S - mode / ATCRBS transponder) nearby (hereinafter referred to as the target aircraft) will make a response. The ACAS transceiver host obtains information such as the altitude, relative distance, and azimuth of the target aircraft according to the received response signal, and then calculates its altitude change rate and relative distance change rate. Combining the position and motion information of the own aircraft, it evaluates the threat level of the target aircraft (OT: other aircraft, PT: approaching aircraft, TA: traffic alert, RA: resolution advisory), and displays different target aircraft in a corresponding graphical manner. The typical configuration of the airborne collision avoidance system includes: 1 ACAS transceiver host, 2 S - mode transponders, 2 directional antennas, 2 omnidirectional antennas, 2 traffic / resolution displays, and 1 control box; in the enhanced configuration, it includes: 1 integrated collision avoidance host (integrating the ACAS transceiver host and the S - mode transponder), 1 directional antenna, 1 omnidirectional antenna, and can be optionally cross - linked with the integrated control and display system or configured with independent display and control sub - units.

[0004] In an airborne collision avoidance system, according to different direction-finding systems, there are currently two direction-finding systems worldwide, namely: direction-finding based on amplitude monopulse system and direction-finding based on phase monopulse system.

[0005] Taking the TCAS2000 airborne collision avoidance system equipment produced by Thales as an example, it belongs to the direction-finding method of the amplitude monopulse system. For the direction-finding of the amplitude monopulse system, the directional antenna uses an antenna design with an internal RF network. Through the RF network, the antenna pattern shaping is completed to form a specific directional beam. This direction-finding method is similar to the amplitude monopulse angle measurement method of ground SSR radar. It relies on comparing the amplitude differences between the sum channel and the difference channel (the combination of adjacent channel patterns), and then performs a look-up table operation based on the "amplitude difference - azimuth angle" formed in the microwave anechoic chamber to obtain the azimuth information of the target.

[0006] Taking the TTR4000 airborne collision avoidance system equipment produced by Collins as an example, it belongs to the direction-finding method of the phase monopulse system. For the direction-finding of the phase monopulse system, the directional antenna does not have an internal RF network, but it is necessary to arrange the antenna elements symmetrically to meet the wavelength requirements of typical 1030 / 1090 MHz signals. Its direction-finding principle is similar to that of an interferometer direction finder. This direction-finding method performs direction-finding calculations based on the phase relationship of the signals output by 4 receiving channels in the backend digital processing according to the determined arrangement of the antenna elements to obtain the azimuth information of the target.

[0007] The difficulty of the direction-finding method of the amplitude monopulse system lies in the design of the directional antenna itself, and its design quality directly affects the accuracy and consistency of the antenna pattern; the key lies in the amplitude leveling of the receiving channel, and its leveling degree directly affects the accuracy of direction-finding. This direction-finding method has no special requirements for the phase of the receiving channel, so it has good adaptability to installation elements such as installation and cable length, and strong anti-interference ability. However, due to being restricted by the design and processing accuracy of the directional antenna, it is difficult to accurately control the null depth position and consistency difference of the antenna pattern, which affects the accuracy of direction-finding.

[0008] The key points and difficulties of the direction-finding method of the phase monopulse system lie in the phase calibration between the receiving channels. When the phase relationship between the receiving channels is stable, the azimuth information obtained through phase discrimination has high accuracy. However, due to being sensitive to phase, this direction-finding method is greatly affected by installation elements such as installation and cable length, and has weak anti-interference ability. Summary of the Invention

[0009] Aiming at the limitations of the above-mentioned direction-finding technologies based on amplitude monopulse system or phase monopulse system, the present invention provides a direction-finding method for an airborne collision avoidance system (TCAS) that combines the advantages of the two direction-finding systems, which can realize the complementary advantages of the two direction-finding systems and improve the anti-interference ability and accuracy of TCAS direction-finding.

[0010] The present invention is achieved through the following technical solutions:

[0011] A method for direction finding of an airborne collision avoidance system, comprising:

[0012] Obtain the corresponding channel compensation data according to the type of the selected directional antenna;

[0013] Use the channel compensation data to perform channel amplitude and phase compensation on the signals received by the directional antenna;

[0014] Perform digital shaping processing on the signals after amplitude and phase compensation, and output three groups of signals in parallel: the received signals in amplitude monopulse system, the received signals in phase monopulse system, and the weighted combined signals;

[0015] Process the three groups of signals output after shaping processing in parallel, obtain the azimuth information in amplitude monopulse system and the azimuth information in phase monopulse system, and make a decision on the azimuth information of the two systems to determine the target azimuth information.

[0016] Preferably, the directional antenna of the present invention is composed of 4 antenna elements;

[0017] The 4 antenna elements are arranged at the four vertices of a square, and meet the standing wave requirements, 50-ohm characteristic impedance matching requirements at typical application frequency points of 1030 MHz and 1090 MHz, have a DC main impedance different from that of traditional amplitude system / phase system directional antennas, and support antenna connection state detection.

[0018] Preferably, the channel compensation data of the present invention is obtained through the following steps:

[0019] The calibration signal is fed into the antenna A1 channel, and the antenna A2, A3, and A4 channels are switched to the receiving state, and the calibration signal is received simultaneously. The calibration signal is down-converted to form an intermediate frequency signal after passing through the receiving channel, and is output for digital processing after being sampled by the ADC. In the digital processing, amplitude difference calculation and phase discrimination processing are performed to complete the amplitude and phase difference calculation between any two of the antenna A2, A3, and A4 channels;

[0020] The calibration signal is fed into the antenna A2 port, and the antenna A3, A4, and A1 channels are switched to the receiving state, and the calibration signal is received simultaneously. The calibration signal is down-converted to form an intermediate frequency signal after passing through the receiving channel, and is output for digital processing after being sampled by the ADC. In the digital processing, amplitude difference calculation and phase discrimination processing are performed to complete the amplitude and phase difference calculation between any two of the antenna A3, A4, and A1 channels;

[0021] The calibration signal is fed into the port of antenna A3. The channels of antennas A4, A1, and A2 are switched to the receiving state to receive the calibration signal simultaneously. After passing through the receiving channels, the calibration signal is down-converted to form an intermediate-frequency signal, which is sampled by the ADC and then output for digital processing. In the digital processing, amplitude difference calculation and phase discrimination processing are performed to complete the calculation of the amplitude-phase differences between any two of the channels of antennas A4, A1, and A2.

[0022] The calibration signal is fed into the port of antenna A4. The channels of antennas A1, A2, and A3 are switched to the receiving state to receive the calibration signal simultaneously. After passing through the receiving channels, the calibration signal is down-converted to form an intermediate-frequency signal, which is sampled by the ADC and then output for digital processing. In the digital processing, amplitude difference calculation and phase discrimination processing are performed to complete the calculation of the amplitude-phase differences between any two of the channels of antennas A1, A2, and A3.

[0023] The amplitude differences and phase differences calculated in the above steps are weighted to obtain the amplitude differences and phase differences of the channels of antennas A1, A2, A3, and A4, which are the channel amplitude compensation data and channel phase compensation data.

[0024] 4. A method for direction finding of an airborne collision avoidance system according to claim 1, wherein the steps of performing channel amplitude and phase compensation on the signals received by the directional antenna using the channel compensation data specifically include:

[0025] The target signal enters 4 receiving channels through the directional antenna. After being processed by the receiving channels, 4 original intermediate-frequency signals are output. The 4 original intermediate-frequency signals are sampled digitally by the ADC and then output for digital processing.

[0026] The corresponding channel compensation data is used to complete channel amplitude and phase compensation for the received signal.

[0027] Preferably, the digital shaping processing of the present invention specifically includes amplitude monopulse system beam shaping processing and phase monopulse system beam shaping processing;

[0028] The three groups of signals output in parallel after digital shaping processing of the compensated channel data are: 4-channel data of the amplitude monopulse system, 4-channel data of the phase monopulse system, and 1 weighted composite signal.

[0029] Preferably, the amplitude monopulse system beam shaping processing of the present invention specifically performs weighted combination processing on the signals received by 4 channels according to the digital beam synthesis rule to form 4 received signals, which is equivalent to the pattern characteristics of the original amplitude monopulse system antenna.

[0030] Preferably, the phase monopulse system beam shaping of the present invention specifically performs pairwise phase discrimination processing on the signals received by 4 channels according to the interferometer direction finding rule to form 4 received signals.

[0031] Preferably, the present invention performs amplitude weighted combination processing on the signals received by the four channels to form one weighted composite signal.

[0032] Preferably, the target azimuth signal of the present invention is specifically obtained by weighted fusion based on the azimuth information in the amplitude monopulse system and the azimuth signal in the phase monopulse system, in combination with the target historical information.

[0033] On the other hand, the present invention provides a direction finding system for an airborne collision avoidance system, including a directional antenna module, an amplitude-phase real-time calibration module, a channel signal shaping module, and a target azimuth decision module;

[0034] The directional antenna module uses two directional antennas, and each directional antenna is composed of four antenna elements. The four antenna elements are arranged at the four vertices of a square, and the layout length meets the standing wave requirement, 50-ohm characteristic impedance matching requirement at typical application frequency points of 1030 MHz and 1090 MHz, and has a DC impedance different from that of traditional amplitude system / phase system directional antennas;

[0035] The amplitude-phase real-time calibration module is used to obtain the corresponding channel compensation data according to the type of the selected directional antenna, and perform channel amplitude and phase compensation on the signals received by the directional antenna using the channel compensation data;

[0036] The channel signal shaping module is used to perform digital shaping processing on the signals after channel amplitude and phase compensation, and output three groups of signals in parallel: the received signals in the amplitude monopulse system, the received signals in the phase monopulse system, and the weighted combined signal;

[0037] The target azimuth decision module processes the three groups of signals output by the channel signal shaping module in parallel, obtains the azimuth information in the amplitude monopulse system and the azimuth information in the phase monopulse system, and makes a decision on the azimuth information of the two systems to determine the target azimuth information.

[0038] The present invention has the following advantages and beneficial effects:

[0039] The present invention equivalently provides two direction finding data sources in a set of TCAS devices. After effective arbitration, it can improve the target direction finding accuracy, improve the anti-interference performance of TCAS direction finding, and improve the direction finding precision.

[0040] The present invention achieves the purpose of increasing the target measurement distance range through beam synthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0042] Figure 1 Schematic flowchart of the direction finding method according to an embodiment of the present invention.

[0043] Figure 2 Principle block diagram of the direction finding system according to an embodiment of the present invention.

[0044] Figure 3 Principle block diagram of the amplitude-phase real-time calibration module according to an embodiment of the present invention. Detailed implementation manners

[0045] Hereinafter, the term "comprising" or "may comprise" used in various embodiments of the present invention indicates the presence of the functions, operations or elements of the present invention, and does not limit the addition of one or more functions, operations or elements. Further, as used in various embodiments of the present invention, the terms "comprising", "having" and their cognates are only intended to indicate the presence of specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be construed as precluding the presence or addition of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items first.

[0046] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the listed words. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0047] Expressions (such as "first", "second", etc.) used in various embodiments of the present invention may modify various components in various embodiments, but do not limit the corresponding components. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of various embodiments of the present invention, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0048] It should be noted that: if it is described that one component is "connected" to another component, the first component may be directly connected to the second component, and a third component may be "connected" between the first component and the second component. Conversely, when one component is "directly connected" to another component, it can be understood that there is no third component between the first component and the second component.

[0049] The terms used in various embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the various embodiments of the present invention. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the present invention pertain. The terms (such as those defined in a commonly used dictionary) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning unless clearly defined in the various embodiments of the present invention.

[0050] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the embodiments and the accompanying drawings. The illustrative embodiments and descriptions thereof of the present invention are only for the purpose of explaining the present invention and do not serve as a limitation to the present invention.

[0051] Embodiment 1

[0052] The existing direction-finding technologies for anti-collision systems mainly include: direction-finding based on amplitude monopulse system and direction-finding based on phase monopulse system; the direction-finding technology based on amplitude monopulse system has high requirements for the design and processing accuracy of the directional antenna, and it is difficult to guarantee the direction-finding accuracy, while the direction-finding technology based on phase monopulse system is sensitive to phase and has weak anti-interference ability. Therefore, this embodiment provides a direction-finding method for an airborne anti-collision system that takes both direction-finding systems into account, realizes both direction-finding mechanisms in the backend digital processing, forms the channel signals required for the corresponding systems through digital weighted combination, and then adopts the direction-finding processing methods of the original two systems, thereby realizing the complementary advantages of the two direction-finding systems and improving the anti-interference performance and reliability of the direction-finding of the airborne anti-collision system.

[0053] As Figure 1 shown, the direction-finding method of this embodiment mainly includes the following steps:

[0054] Step 1: Obtain the corresponding channel compensation data according to the type of the selected directional antenna.

[0055] In this embodiment, during the idle time slot, the amplitude and phase of the receiving channel are calibrated in real time to obtain the channel amplitude and phase compensation data, which is used to update the channel amplitude and phase difference information in the backend digital processing.

[0056] Step 2: Use the channel amplitude and phase compensation data to perform channel amplitude and phase compensation on the signals received by the directional antenna.

[0057] Step 3: Perform digital shaping processing on the compensated channel data and output three groups of signals in parallel: the received signals of the amplitude monopulse system, the received signals of the phase monopulse system, and the weighted combined signals.

[0058] Step 4: Process the three groups of signals output after shaping in parallel to obtain the azimuth information in the amplitude monopulse system and the azimuth information in the phase monopulse system, and make a decision on the azimuth information of the two systems to determine the target azimuth information.

[0059] The directional antenna in this embodiment adopts a passive design composed of 4 antenna elements. The 4 antenna elements are arranged at the four vertices of a square, and meet the standing wave requirements, 50-ohm characteristic impedance matching requirements, and have a DC impedance different from that of traditional amplitude system / phase system directional antennas near the typical application frequency points of 1030 MHz and 1090 MHz, and support antenna connection status detection. Two directional antennas are used in this embodiment. The specific method for obtaining the directional antenna channel compensation data in step 1 of this embodiment is as follows:

[0060] Step 11: Feed the calibration signal into the antenna A1 port, switch the antenna A2, A3, and A4 channels to the receiving state, and receive the calibration signal at the same time. The calibration signal is down-converted to form an intermediate frequency signal after passing through the receiving channel, and is output for digital processing after being sampled by the ADC. In the digital processing, perform amplitude difference calculation (subtract the amplitude sampling values of the A2, A3, and A4 channels pairwise), and phase discrimination processing (using the intermediate frequency frequency source as a reference, first perform phase discrimination on the A2, A3, and A4 channels to obtain phase information, and subtract the phase information of the A2, A3, and A4 channels pairwise) to complete the calculation of the amplitude and phase differences between the A2, A3, and A4 channels pairwise.

[0061] Step 12: Feed the calibration signal into the antenna A2 port, switch the antenna A3, A4, and A1 channels to the receiving state, and receive the calibration signal at the same time. The calibration signal is down-converted to form an intermediate frequency signal after passing through the receiving channel, and is output for digital processing after being sampled by the ADC. In the digital processing, perform amplitude difference calculation (subtract the amplitude sampling values of the A3, A4, and A1 channels pairwise), and phase discrimination processing (using the intermediate frequency frequency source as a reference, first perform phase discrimination on the A3, A4, and A1 channels to obtain phase information, and subtract the phase information of the A3, A4, and A1 channels pairwise) to complete the calculation of the amplitude and phase differences between the A3, A4, and A1 channels pairwise.

[0062] Step 13: Feed the calibration signal into the antenna A3 port, switch the antenna A4, A1, and A2 channels to the receiving state, and receive the calibration signal at the same time. The calibration signal is down-converted to form an intermediate frequency signal after passing through the receiving channel, and is output for digital processing after being sampled by the ADC. In the digital processing, perform amplitude difference calculation (subtract the amplitude sampling values of the A4, A1, and A2 channels pairwise), and phase discrimination processing (using the intermediate frequency frequency source as a reference, first perform phase discrimination on the A4, A1, and A2 channels to obtain phase information, and subtract the phase information of the A4, A1, and A2 channels pairwise) to complete the calculation of the amplitude and phase differences between the A4, A1, and A2 channels pairwise.

[0063] Step 14: Feed the calibration signal into the A4 port of the antenna. Switch the channels of antennas A1, A2, and A3 to the receiving state to simultaneously receive the calibration signal. After passing through the receiving channels, the calibration signal is down-converted to form an intermediate-frequency signal, which is sampled by the ADC and then output for digital processing. In the digital processing, calculate the amplitude differences (subtract the amplitude sampling values of the A1, A2, and A3 channels pairwise) and perform phase discrimination processing (using the intermediate-frequency frequency source as a reference, first perform phase discrimination on the phases of the A1, A2, and A3 channels to obtain phase information, and then subtract the phase information of the A1, A2, and A3 channels pairwise), thus completing the calculation of the amplitude and phase differences between any two of the A1, A2, and A3 channels of the antenna.

[0064] Step 15: Perform weighted processing on the amplitude differences and phase differences obtained in Step 11, Step 12, Step 13, and Step 14 to obtain the amplitude differences and phase differences of the A1, A2, A3, and A4 channels of the antenna.

[0065] Step 16: Switch the channels of antennas A1, A2, A3, and A4 to channels B1, B2, B3, and B4. According to Steps 11 - 15, obtain the amplitude differences and phase differences of the B1, B2, B3, and B4 channels of the antenna.

[0066] The specific steps of Step 2 in this embodiment include the following sub-steps:

[0067] Step 21: The target signal enters 4 receiving channels through the directional antenna. After being processed by the receiving channels, 4 original intermediate-frequency signals are output, which are digitally sampled by the ADC and then output for digital processing.

[0068] Step 22: Use the corresponding channel compensation data to complete the channel amplitude and phase compensation for the received signal.

[0069] In Step 3 of this embodiment, 3 groups of signals are output in parallel after digital shaping processing of the compensated channel data, which are: the channel data of the 4-channel amplitude monopulse system, the channel data of the 4-channel phase monopulse system, and 1 weighted combined signal.

[0070] Among them, for the amplitude monopulse system beamforming, specifically, according to the digital beam synthesis rule, the signals received by 4 antenna elements are weighted and combined to form 4 received signals, which is equivalent to the pattern characteristics of the original amplitude monopulse system antenna. The amplitude and phase weighted distribution between the formed beam and each RF channel is shown in the following table.

[0071]

[0072]

[0073] Phase monopulse beamforming is to perform phase detection on the signals received by the four antenna elements in pairs according to the rules of interferometer direction finding.

[0074] The signals received by the four antenna elements are weighted and combined to form a weighted composite signal. The amplitude of the composite signal is as follows:

[0075] A combination=k1*A1+k2*A2+k3*A3+k4*A4

[0076] (where, ki(i=1~4)∈[0,1])

[0077] In step 4 of this embodiment, in a microwave darkroom, the amplitude difference and phase difference of each channel are measured according to the real azimuth determined by calibration (with the forward beam 0 degrees as the reference, clockwise), and a "azimuth-amplitude difference-phase difference" correspondence table is obtained. The data in this table is stored inside the device, and the original azimuth information of the target is obtained by looking up the table based on the amplitude difference and phase difference obtained by measuring the amplitude single pulse and the phase single pulse. Weighted processing is performed in combination with the azimuth information maintained by the target track to obtain the current azimuth information of the target. At the same time, based on the weighted synthetic signal and in accordance with the principle of secondary radar ranging, the time difference between the interrogation pulse and the response pulse is calculated, and the distance is calculated based on the electromagnetic wave propagation speed to obtain the target measurement distance.

[0078] Example 2

[0079] This embodiment also proposes an airborne collision avoidance system direction finding system, such as Figure 2 As shown, the direction finding system of this embodiment mainly includes a directional antenna module, a real-time amplitude and phase calibration module, a channel signal shaping module, and a target direction determination module.

[0080] The directional antenna module of this embodiment adopts two directional antennas, which are a passive design consisting of four antenna elements. The four antenna elements are arranged at the four vertices of a square, and meet the standing wave requirements and 50 ohm characteristic impedance matching requirements near the typical application frequencies of 1030 MHz and 1090 MHz. It has a DC impedance that is different from that of traditional amplitude / phase directional antennas, supports antenna connection status detection, and is used to achieve matching and identification of different antenna types.

[0081] The real-time amplitude and phase calibration module of this embodiment is used to obtain the corresponding channel compensation data according to the type of the selected directional antenna, and use the channel amplitude and phase compensation data to perform channel amplitude and phase compensation on the signal received by the directional antenna.

[0082] The amplitude and phase real-time calibration module of this embodiment is also used to implement:

[0083] Receive the calibration signal initiated by the anti-collision host periodically, and perform amplitude-phase real-time calibration on the receiving channel by simultaneous reception in the receiving channel to obtain the amplitude-phase compensation data of the channel for amplitude-phase compensation of the target signal.

[0084] The channel signal shaping module of this embodiment is used to parallelly output three types of direction-finding data in the backend digital processing, namely: 4-channel receiving signals equivalent to the original amplitude monopulse system, 4-channel phase signals equivalent to the original phase monopulse system, and 1 weighted synthesis signal after weighted synthesis.

[0085] The target azimuth decision module of this embodiment is used to parallelly perform direction-finding based on the amplitude monopulse system and direction-finding based on the phase monopulse system in the backend digital processing, and make a decision on the two types of data to determine the final target azimuth information.

[0086] As Figure 3 shown, the amplitude-phase real-time calibration module of this embodiment further includes an ADC, an amplitude difference calculation unit, a phase discriminator unit, a weighting unit, and a compensation unit ( Figure 3 Principle block diagram of the amplitude-phase real-time calibration module).

[0087] Among them, the ADC is used to convert the intermediate-frequency signal output by the channel of the directional antenna module into a digital signal;

[0088] The amplitude difference calculation unit is used to calculate the amplitude differences between every two of the 4 channels, the phase discriminator unit is used to calculate the phase differences between every two of the 4 antenna channels, and the weighting unit is used to perform weighting processing according to the output results of the amplitude difference calculation unit and the phase discriminator unit to obtain the amplitude difference and phase difference compensation data of the 4 channels.

[0089] The specific implementation manners described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A direction finding method for an airborne collision avoidance system, characterized in that, it includes: Obtain the corresponding channel compensation data according to the type of the selected directional antenna; Use the channel compensation data to perform channel amplitude and phase compensation on the signals received by the directional antenna; Perform digital shaping processing on the signals after amplitude and phase compensation, and parallel output three groups of signals: the received signals in amplitude monopulse system, the received signals in phase monopulse system, and the weighted combined signal; Parallel process the three groups of signals output after the shaping processing to obtain the azimuth information in the amplitude monopulse system and the azimuth information in the phase monopulse system, and make a decision on the azimuth information of the two systems to determine the target azimuth information; The directional antenna is composed of 4 antenna elements; The 4 antenna elements are arranged at the four vertices of a square, and meet the standing wave requirements, 50-ohm characteristic impedance matching requirements at the typical application frequency points of 1030 MHz and 1090 MHz, have a DC main impedance different from the traditional amplitude system / phase system directional antenna, and support antenna connection state detection; The digital shaping processing specifically includes amplitude monopulse system beam shaping processing and phase monopulse system beam shaping processing; The three groups of signals parallel output after digital shaping processing of the compensated channel data are respectively: the channel data of 4 channels in the amplitude monopulse system, the channel data of 4 channels in the phase monopulse system, and 1 weighted synthesis signal; The amplitude monopulse system beam shaping processing is specifically to perform weighted combination processing on the signals received by 4 channels according to the digital beam synthesis rule to form 4 received signals, which is equivalent to the pattern characteristics of the original amplitude monopulse system antenna; The phase monopulse system beam shaping is specifically to perform pairwise phase discrimination processing on the signals received by 4 channels according to the interferometer direction finding rule to form 4 received signals.

2. The direction finding method for an airborne collision avoidance system according to claim 1, characterized in that, the channel compensation data is obtained through the following steps: The calibration signal is fed into the antenna A1 channel, and the antenna A2, A3, and A4 channels are switched to the receiving state to receive the calibration signal at the same time. The calibration signal is down-converted to form an intermediate frequency signal after passing through the receiving channel, and is output for digital processing after being sampled by the ADC. In the digital processing, amplitude difference calculation and phase discrimination processing are performed to complete the amplitude and phase difference calculation between any two of the antenna A2, A3, and A4 channels; The calibration signal is fed into the antenna A2 port, and the antenna A3, A4, and A1 channels are switched to the receiving state to receive the calibration signal at the same time. The calibration signal is down-converted to form an intermediate frequency signal after passing through the receiving channel, and is output for digital processing after being sampled by the ADC. In the digital processing, amplitude difference calculation and phase discrimination processing are performed to complete the amplitude and phase difference calculation between any two of the antenna A3, A4, and A1 channels; The calibration signal is fed into the port of antenna A3. The channels of antennas A4, A1, and A2 are switched to the receiving state to receive the calibration signal simultaneously. After passing through the receiving channels, the calibration signal is down-converted to form an intermediate-frequency signal, which is sampled by the ADC and then output for digital processing. In the digital processing, amplitude difference calculation and phase discrimination processing are performed to complete the calculation of the amplitude-phase differences between any two of the channels of antennas A4, A1, and A2. The calibration signal is fed into the port of antenna A4. The channels of antennas A1, A2, and A3 are switched to the receiving state to receive the calibration signal simultaneously. After passing through the receiving channels, the calibration signal is down-converted to form an intermediate-frequency signal, which is sampled by the ADC and then output for digital processing. In the digital processing, amplitude difference calculation and phase discrimination processing are performed to complete the calculation of the amplitude-phase differences between any two of the channels of antennas A1, A2, and A3. The amplitude differences and phase differences obtained by the above steps are weighted to obtain the amplitude differences and phase differences of the channels of antennas A1, A2, A3, and A4, which are the channel amplitude compensation data and channel phase compensation data.

3. A method for direction finding of an airborne collision avoidance system according to claim 1, characterized in that, The steps of performing channel amplitude and phase compensation on the signal received by the directional antenna using the channel compensation data specifically include: The target signal enters 4 receiving channels through the directional antenna. After being processed by the receiving channels, 4 original intermediate-frequency signals are output. The 4 original intermediate-frequency signals are digitally sampled by the ADC and then output for digital processing; The corresponding channel compensation data is used to complete the channel amplitude and phase compensation for the received signal.

4. A method for direction finding of an airborne collision avoidance system according to claim 1, characterized in that, The signals received by the 4 channels are subjected to amplitude weighted combination processing to form 1 weighted combined signal.

5. A method for direction finding of an airborne collision avoidance system according to claim 1, characterized in that, The target azimuth signal is specifically obtained by weighted fusion of the azimuth information under the amplitude monopulse system and the azimuth signal under the phase monopulse system, combined with the target historical information.

6. An airborne collision avoidance system direction finding system, characterized in that, It includes a directional antenna module, an amplitude-phase real-time calibration module, a channel signal shaping module, and a target azimuth decision module; The directional antenna module uses 2 directional antennas. The directional antenna is composed of 4 antenna elements, and the 4 antenna elements are arranged at the four vertices of a square. The layout length meets the standing wave requirements, 50-ohm characteristic impedance matching requirements, and has a DC impedance different from that of traditional amplitude system / phase system directional antennas at typical application frequency points of 1030 MHz and 1090 MHz; The amplitude-phase real-time calibration module is used to obtain the corresponding channel compensation data according to the type of the selected directional antenna, and perform channel amplitude and phase compensation on the signal received by the directional antenna using the channel compensation data; The channel signal shaping module is used to perform digital shaping processing on the signal after channel amplitude and phase compensation, and output three groups of signals in parallel: the received signal under the amplitude monopulse system, the received signal under the phase monopulse system, and the weighted combined signal; The target azimuth decision module processes the three groups of signals output by the channel signal shaping module in parallel, obtains the azimuth information in the amplitude monopulse system and the azimuth information in the phase monopulse system, and decides on the azimuth information of the two systems to determine the target azimuth information; The digital shaping process specifically includes amplitude monopulse system beam shaping processing and phase monopulse system beam shaping processing; The three groups of signals output in parallel after digital shaping processing of the compensated channel data are: 4-channel data of the amplitude monopulse system, 4-channel data of the phase monopulse system, and 1 weighted composite signal; The amplitude monopulse system beam shaping processing specifically weights and combines the signals received by 4 channels according to the digital beam synthesis rule to form 4 received signals, which is equivalent to the pattern characteristics of the original amplitude monopulse system antenna; The phase monopulse system beam shaping specifically performs pairwise phase discrimination processing on the signals received by 4 channels according to the interferometer direction finding rule to form 4 received signals.

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