Spacecraft non-cooperative target approaching detection system and method based on antenna port impedance abrupt change effect

Abstract

The invention discloses a spacecraft non-cooperative target approach detection system and method based on an antenna port impedance abrupt change effect, and the method comprises the steps: connecting a reflection wave monitoring module in parallel on a transmitting link, and transmitting an output signal of the reflection wave monitoring module to a platform control system; the transmitting link comprises a transmitter, a directional coupler and a monitoring antenna; the directional coupler is connected in parallel between the output end of the transmitter and the monitoring antenna, and a coupling port of the directional coupler is connected with the input end of the reflected wave monitoring module; the directional coupler is used for directionally separating signals, so that most of transmitted radio-frequency signals smoothly pass through the monitoring antenna, and meanwhile, a small part of reflected radio-frequency signals which are reversely propagated are coupled to the reflected wave monitoring module; a special reflected wave monitoring module and built-in threshold judgment logic are additionally arranged by utilizing an existing launching system of a spacecraft, and near-field target detection is realized by measuring and analyzing the reflection coefficient change of an antenna port.

Description

Technical Field

[0001] This invention relates to spacecraft on-orbit safety and collision avoidance technology, antenna self-monitoring and fault diagnosis technology, space target detection and identification, and electromagnetic near-field scattering theory, specifically to a spacecraft non-cooperative target approach detection system and method based on the antenna port impedance abrupt change effect.

[0002] This invention is mainly applied to the autonomous safety protection of spacecraft during on-orbit operation, specifically including the following scenarios:

[0003] 1. Spacecraft Collision Avoidance Warning: Used to detect the approach of non-cooperative targets (such as space debris, defunct satellites, and other spacecraft). These targets are often unpredictable using cooperative beacons or predefined orbital data and may approach at high relative velocities, posing a collision risk. This invention achieves real-time detection at distances ranging from meters to sub-meters by monitoring abrupt changes in antenna port impedance and voltage standing wave ratio, making it particularly suitable for debris-dense regions such as Low Earth Orbit (LEO) and Geosynchronous Orbit (GEO).

[0004] 2. Self-monitoring and health management of large space antennas: For large-aperture antennas (such as parabolic antennas and phased array antennas) carried by communication satellites, remote sensing satellites, and deep space probes, this invention can be integrated into the antenna system to monitor near-field disturbances in real time. For example:

[0005] 1) When an external object (such as a detached thermal control material or a micrometeoroid) enters the near-field region of the antenna, the system can trigger an early warning to prevent the antenna performance from deteriorating or being physically damaged.

[0006] 2) It can be extended for fault diagnosis during the antenna deployment phase, such as detecting whether the antenna deployment mechanism is blocked by foreign objects.

[0007] 3. Expandable application areas:

[0008] 1) Ground-based large antenna array protection: Used for ground facilities such as radio telescopes and radar stations to prevent birds, drones or foreign objects from approaching the antenna aperture, causing signal distortion or equipment damage.

[0009] 2) Close-range collision avoidance between UAVs and vehicle-mounted radar antennas: In complex environments (such as urban canyons and forests), existing communication antennas can be used to monitor surrounding obstacles, reducing reliance on dedicated sensors. Background Technology

[0010] Current spacecraft collision avoidance technologies mainly rely on the following three types of solutions, but all of them have shortcomings:

[0011] 1. External measurement methods (such as far-field radar, optical telescopes, laser ranging):

[0012] 1) Poor real-time performance: Relying on data transmission and processing from ground stations or space surveillance networks, the early warning delay can reach the minute level, making it unable to cope with sudden approach events (such as rapid debris approach).

[0013] 2) Large blind zone: Optical and radar systems have detection blind zones for targets at specific angles or distances, especially when the target size is small or the surface reflectivity is low, resulting in a high rate of missed detection.

[0014] 3) Insufficient autonomy: The spacecraft relies entirely on external information and cannot make independent decisions in the event of communication interruption or untimely data updates.

[0015] 4) High complexity: Achieving far-field radar detection requires independent transmit and receive channels and complex signal processing algorithms to extract weak echoes from noise, resulting in a complex system with high power consumption and cost.

[0016] 2. Airborne active sensors (such as miniature radar, laser rangefinders, and optical cameras):

[0017] 1) High hardware complexity: Additional sensor modules need to be installed, increasing the mass, size and power consumption of the spacecraft (the power consumption of a typical radar system can reach 10-100W).

[0018] 2) Cost and reliability issues: Dedicated sensors require aerospace-grade certification, which is costly in terms of research and development and deployment; and electronic components are prone to failure in the space radiation environment, making maintenance difficult.

[0019] 3) Limited coverage: Active sensors are usually designed for far-field (>10m) targets, and have insufficient sensitivity to near-field (<1m) targets, and may be affected by the antenna's own radiation interference.

[0020] 3. Flight dynamics prediction (based on orbital database and numerical simulation):

[0021] 1) Inability to deal with non-cooperative targets: It relies on pre-compiled target orbit data, but the amount of space debris is huge and the trajectory is uncertain. The database updates are lagging and it is difficult to cover all potential threats.

[0022] 2) Computationally intensive: High-precision orbit prediction requires a large amount of onboard computing power, which is not suitable for spacecraft with limited resources.

[0023] 3) Ignoring near-field effects: Pure mechanical models cannot handle scenarios at very close distances, resulting in a lack of warnings at sub-meter distances.

[0024] The existing solutions are generally inadequate in terms of real-time performance, autonomy, cost, and near-field detection capabilities, and cannot meet the spacecraft's requirements for lightweight, low-power, and high-reliability protection. Summary of the Invention

[0025] This invention aims to solve the problems existing in current collision avoidance technologies:

[0026] 1. Near-field detection blind zone problem: Traditional sensors have low sensitivity to non-cooperative targets (such as small debris) at sub-meter distances. However, this invention is based on electromagnetic principles and directly senses near-field disturbances through changes in antenna port impedance. The detection distance depends on the target size and antenna type, and can be as low as meters or as high as several meters to tens of meters.

[0027] 2. System complexity and cost issues: By utilizing the existing antennas on the spacecraft, a new standard reflection coefficient (S11 / VSWR) monitoring module is added to achieve low-cost integration.

[0028] 3. Real-time performance and autonomy: Measurements can be completed in milliseconds without the need for external data input, enabling spacecraft to have fully autonomous early warning capabilities, which is particularly suitable for emergency maneuver scenarios.

[0029] A spacecraft non-cooperative target proximity detection system and method based on the antenna port impedance abrupt change effect is provided.

[0030] The technical solution of the present invention is: a spacecraft non-cooperative target proximity detection system based on antenna port impedance abrupt change effect, characterized in that: it includes a transmitter, a directional coupler, a monitoring antenna, a reflected wave monitoring module, and a platform control system;

[0031] The transmitter generates high-frequency radio frequency signals for communication, telemetry, or radar functions.

[0032] The directional coupler is connected in parallel between the transmitter output and the monitoring antenna, and the coupling port (reflection port) of the directional coupler is connected to the input of the reflected wave monitoring module. The directional coupler is used to directionally separate the signal: allowing most of the transmitted radio frequency signal to pass smoothly to the monitoring antenna, while coupling out a small portion of the reverse-propagating reflected radio frequency signal to the reflected wave monitoring module.

[0033] The reflected wave monitoring module includes a radio frequency detection circuit module, a digital circuit module, and a processing and threshold judgment logic module.

[0034] The radio frequency detection circuit module receives the reflected radio frequency signal from the directional coupler and converts it into a DC or intermediate frequency voltage signal containing amplitude and phase information.

[0035] The digital circuit module converts the analog voltage signal output by the radio frequency detection circuit into a digital signal, which is then used by the subsequent processor for mathematical operations and logical judgments.

[0036] The processing and threshold judgment logic module receives the reflection coefficient data processed by the digital circuit module and executes the threshold judgment logic.

[0037] The threshold determination logic is as follows:

[0038] Step 1: Calculate the change: Calculate the real-time voltage standing wave ratio. Compared with baseline Compare them and calculate the absolute value of their changes. in The known quantity represents the baseline value of the voltage standing wave ratio of the antenna in a near-normal state without a target, or a set of reference values ​​related to slowly varying parameters such as temperature and attitude, which are obtained through prior ground calibration.

[0039] Step 2, Basic Judgment Logic: If If the value exceeds the set threshold, it is immediately determined that a target has entered the antenna's near field, triggering an early warning; otherwise, the system determines it to be in a normal state and continues to monitor in a loop.

[0040] The platform control system is used to initiate subsequent actions after receiving an early warning signal.

[0041] Furthermore, the threshold determination logic also includes:

[0042] Step 3, Intelligent Threshold Decision: The processing unit will calculate the absolute value of the voltage standing wave ratio change in real time. and its rate of change The comparison is made with a preset dynamic decision threshold; the dynamic decision threshold can be baseline-calibrated based on the spacecraft's current operating conditions (such as temperature and attitude); when Significantly exceeding the threshold in an extremely short time (e.g., on the order of seconds), and When the value exceeds a set threshold, it is determined to be a valid target approach event. Since the voltage standing wave ratio change caused by target approach is rapid and abrupt, while the drift caused by environmental factors is slow, false alarms can be effectively suppressed by setting a dual threshold that combines amplitude and rate of change.

[0043] Furthermore, the subsequent actions described in the platform control system include issuing alarms and performing evasive maneuvers to avoid collision risks.

[0044] This invention also provides a spacecraft non-cooperative target proximity detection method based on antenna port impedance abrupt change effect, wherein a reflected wave monitoring module is connected in parallel on the transmission link and the output signal of the reflected wave monitoring module is transmitted to the platform control system;

[0045] The transmission link includes a transmitter, a directional coupler, and a monitoring antenna;

[0046] The transmitter generates high-frequency radio frequency signals for communication, telemetry, or radar functions.

[0047] The directional coupler is connected in parallel between the transmitter output and the monitoring antenna, and the coupling port (reflection port) of the directional coupler is connected to the input of the reflected wave monitoring module. The directional coupler is used to directionally separate the signal: allowing most of the transmitted radio frequency signal to pass smoothly to the monitoring antenna, while coupling out a small portion of the reverse-propagating reflected radio frequency signal to the reflected wave monitoring module.

[0048] The reflected wave monitoring module includes a radio frequency detection circuit module, a digital circuit module, and a processing and threshold judgment logic module.

[0049] The radio frequency detection circuit module receives the reflected radio frequency signal from the directional coupler and converts it into a DC or intermediate frequency voltage signal containing amplitude and phase information.

[0050] The digital circuit module converts the analog voltage signal output by the radio frequency detection circuit into a digital signal, which is then used by the subsequent processor for mathematical operations and logical judgments.

[0051] The processing and threshold judgment logic module receives the reflection coefficient data processed by the digital circuit module and executes the threshold judgment logic.

[0052] The threshold determination logic is as follows:

[0053] Step 1: Calculate the change: Calculate the real-time voltage standing wave ratio. Compared with baseline Compare them and calculate the absolute value of their changes. ;in The known quantity represents the baseline value of the voltage standing wave ratio of the antenna in a near-normal state without a target, or a set of reference values ​​related to slowly varying parameters such as temperature and attitude, which are obtained through prior ground calibration.

[0054] Step 2, Basic Judgment Logic: If If the value exceeds the set threshold, it is immediately determined that a target has entered the antenna's near field, triggering an early warning; otherwise, the system determines it to be in a normal state and continues to monitor in a loop.

[0055] The platform control system is used to initiate subsequent actions after receiving an early warning signal.

[0056] Furthermore, the threshold determination logic also includes:

[0057] Step 3, Intelligent Threshold Decision: The processing unit will calculate the absolute value of the voltage standing wave ratio change in real time. and its rate of change The comparison is made with a preset dynamic decision threshold; the dynamic decision threshold can be baseline-calibrated based on the spacecraft's current operating conditions (such as temperature and attitude); when Significantly exceeding the threshold in an extremely short time (e.g., on the order of seconds), and When the value exceeds a set threshold, it is determined to be a valid target approach event. Since the voltage standing wave ratio change caused by target approach is rapid and abrupt, while the drift caused by environmental factors is slow, false alarms can be effectively suppressed by setting a dual threshold that combines amplitude and rate of change.

[0058] Furthermore, the subsequent actions described in the platform control system include issuing alarms and performing evasive maneuvers to avoid collision risks.

[0059] The beneficial effects of this invention are: it provides a spacecraft non-cooperative target proximity detection system and method based on the antenna port impedance abrupt change effect. Based on electromagnetic derivation and engineering quantitative analysis, it has the following advantages:

[0060] 1. Reliable physical mechanism: From Starting from the equations and two-port network theory, the impedance change can be derived. Parsing expressions (such as) For passive small targets, this ensures the reliability of the detection mechanism. For example, for large targets (size ≥ wavelength). Significant variations are observed over distances in the meter range.

[0061] 2. High sensitivity and adaptability:

[0062] 1) Sensitive to changes in reactivity (imaginary part): Near-field coupling mainly produces changes in reactance, which are relatively small. (e.g., tens of euros) can cause Significant increase (e.g.) It is easier to detect than changes in pure resistance.

[0063] 2) Compatible with multiple antenna types: from small patch antennas to large parabolic antennas, only the detection threshold needs to be adjusted (e.g., the Fresnel zone of a large-aperture antenna extends to several meters, allowing for a longer detection distance).

[0064] 3. The project is easy to implement:

[0065] 1) Low hardware modification: Directly utilize existing antennas and add... Upgrades to the monitoring module and software algorithms.

[0066] 2) Low power consumption: The power consumption of the impedance measurement circuit is negligible. It is suitable for long-term on-orbit operation.

[0067] 3) Scalability: Supports multi-port joint monitoring (such as phased array antennas), and improves detection accuracy by comparing the ΔZ of each unit to estimate the target direction.

[0068] 4) Instead of actively emitting electromagnetic waves for detection, it utilizes existing communication signals and their reflections.

[0069] 5) By monitoring the intrinsic parameters of the antenna port The system can detect changes by directly utilizing the spacecraft's existing transmission signal and reflection power monitoring circuits, eliminating the need for an additional independent radio frequency transceiver system and simplifying the system.

[0070] 4. Significant economic benefits:

[0071] 1) Save on sensor procurement and installation costs.

[0072] 2) Reduce the risk of on-orbit failure due to collisions and extend mission life.

[0073] 5. Enhanced safety redundancy: Complementing radar, optics, and other methods, it constructs a multi-layered protection system that conforms to the high reliability design principles of spacecraft. Attached Figure Description

[0074] Figure 1 This is a system block diagram and signal flow diagram. Detailed Implementation

[0075] The present invention will now be further described with reference to the accompanying drawings.

[0076] The core of this invention lies in utilizing the existing launch system of spacecraft, adding a dedicated reflected wave monitoring module and built-in threshold judgment logic, and measuring and analyzing the reflection coefficient of the antenna port. The system enables near-field target detection through variations. It consists of several key components connected according to a specific signal flow.

[0077] like Figure 1 As shown, the technical names and functions of each component / part are as follows:

[0078] 1. Transmitter

[0079] 1) Professional names: Radio frequency signal source, communication transmitter, radar transmitter.

[0080] 2) Function: Generates high-frequency radio frequency signals for communication, measurement and control, or radar functions. It is the energy source for the entire system, and its continuous emission characteristic provides a continuous detection signal for this invention.

[0081] 2. Directional Coupler

[0082] 1) Function: This is a newly added key radio frequency component. It is connected in parallel between the transmitter output and the monitoring antenna. Its core function is to directionally separate the signal: allowing most of the transmitted power to pass smoothly to the monitoring antenna, while coupling out a small portion of the reflected power signal propagating in the opposite direction. This is for extracting the reflected wave (impedance value). or voltage standing wave ratio The physical basis of ).

[0083] 3. Monitoring antenna

[0084] 1) Professional names: Communication antenna, radar antenna, inter-satellite link antenna.

[0085] 2) Function: It performs the original radiation emission function and also serves as the near-field sensor of this invention. Its port impedance changes due to the presence of scatterers in the near field, thereby altering the reflection coefficient.

[0086] 4. Reflected wave monitoring module (the core new module of this invention)

[0087] This module is a standalone signal processing unit, containing three cascaded sub-components:

[0088] 1) Radio frequency detection circuit

[0089] a) Professional name: Detector, amplitude and phase detection circuit.

[0090] b) Function: Receives reflected wave signals from the directional coupler and converts them into DC or intermediate frequency voltage signals containing amplitude and phase information. It converts high-frequency radio frequency parameters into measurable low-frequency electrical quantities.

[0091] 2) Digital circuits

[0092] a) Professional name: Analog-to-digital converter (ADC).

[0093] b) Function: Converts the analog voltage signal output by the radio frequency detection circuit into a digital signal for subsequent processors to perform mathematical operations and logical judgments.

[0094] 3) Processing and threshold judgment logic

[0095] a) Professional name: Embedded processor, Field Programmable Gate Array (FPGA).

[0096] b) Function: This is the core decision-making unit for implementing the detection algorithm. It receives the digitized reflectance coefficient data and executes the following threshold judgment logic.

[0097] 5. Threshold determination logic (a new algorithm module in this invention)

[0098] 1) This logic runs in the reflected wave monitoring module.

[0099] 2) Calculate the change: Calculate the voltage standing wave ratio (VSWR) collected in real time. Compared with baseline Compare them and calculate the absolute value of their changes. .in The known quantity represents the baseline value of the voltage standing wave ratio of the antenna under the normal state of "no target approach", or a set of reference values ​​related to slowly varying parameters such as temperature and attitude, which are obtained through prior ground calibration.

[0100] 3) Basic judgment logic: If If the value exceeds the set threshold, it is immediately determined that a target has entered the antenna's near field, triggering an early warning. Otherwise, the system is considered to be in a normal state and continues to monitor in a loop.

[0101] 4) Intelligent threshold decision (optional): The processing unit will calculate the absolute value of the voltage standing wave ratio change in real time. and its rate of change The result is compared with a preset dynamic decision threshold. This dynamic decision threshold can be baseline-calibrated based on the spacecraft's current operating conditions (such as temperature and attitude). Significantly exceeding the threshold in an extremely short time (e.g., on the order of seconds), and When the value exceeds a set threshold, it is determined to be a valid target approach event. Since the voltage standing wave ratio change caused by target approach is rapid and abrupt, while the drift caused by environmental factors is slow, false alarms can be effectively suppressed by setting a dual threshold that combines amplitude and rate of change.

[0102] 5) The detection distance of this system and the electromagnetic scattering cross-section of the target Directly related. Therefore, the detection threshold can be adaptively adjusted according to the required protection level of the spacecraft. For high-value areas, a lower threshold can be set to achieve sensitive detection of smaller targets; for general areas, a higher threshold can be set to ensure a low false alarm rate.

[0103] 6. Platform Control System

[0104] 1) Professional name: Attitude and orbit control system Or a star management system.

[0105] 2) Function: Once the threshold judgment module outputs a warning signal, the platform control system can choose to initiate subsequent actions, such as issuing an alarm or performing evasive maneuvers, to avoid the risk of collision.

[0106] The entire system can be divided into three clearly defined and interconnected links, whose physical connection methods and logical relationships are as follows: Figure 1 As shown, this constitutes a complete chain structure from signal transmission and information extraction to decision execution. The connection relationships of each component are as follows:

[0107] 1. Signal transmission link (existing system foundation):

[0108] 1) Transmitter → Directional Coupler → Monitoring Antenna.

[0109] 2) This is the inherent communication or radar signal transmission path of a spacecraft. The transmitter generates radio frequency signals, which are transmitted through the main path of the directional coupler and finally radiated out by the monitoring antenna.

[0110] 2. Reflected wave monitoring link (a core new structure in this invention):

[0111] 1) The signal flow is: reflected signal from the monitoring antenna → directional coupler → reflected wave monitoring module.

[0112] 2) Connection relationship: The coupling port (reflection port) of the directional coupler is connected to the input terminal of the newly added reflected wave monitoring module. This module converts the reflected radio frequency signal into an analog voltage signal characterizing the reflected power or impedance, which is then digitized by an ADC analog-to-digital converter and sent to the processing unit for real-time processing and decision-making.

[0113] 3) Structural innovation: This monitoring link is connected to the main transmission link in parallel or as a bypass. It does not interfere with the transmission of the main signal, but only samples the reflected signal of the main signal through a directional coupler, achieving minimal intrusive modification to the existing system.

[0114] 3. Control and execution chain (interface and feedback):

[0115] 1) Reflected wave monitoring module → Platform control system → Actuator.

[0116] 2) Connection: The reflected wave monitoring module communicates with the platform control system via the spacecraft's standard data bus (such as CAN bus or 422 serial port). When a threat is detected, the reflected wave monitoring module issues a digital warning signal. After receiving the signal, the platform control system (such as the attitude and orbit control system AOCS) generates control commands to drive the actuators (such as thrusters to perform evasive maneuvers or trigger alarms).

[0117] Structural advantages:

[0118] 1. Modular integration: The entire innovative function is encapsulated in the new module, with clear boundaries from the original system, which facilitates independent design, testing and installation.

[0119] 2. Functional isolation and high reliability: Failure of the monitoring system will not affect the normal operation of the main communication link because the two are physically connected in parallel. This conforms to the design principle of high reliability for spacecraft.

[0120] 3. Resource efficiency: The newly added reflected wave monitoring module (RF detection, ADC, processing unit) can be implemented using low-power, small-size aerospace-grade chips, which has minimal impact on the mass, power consumption and space budget of the spacecraft.

[0121] The principle behind the improvement achieved through core steps:

[0122] The working principle of this invention can be summarized as follows: transforming the spacecraft antenna and its constantly transmitted radio frequency signals into an active, continuously operating near-field radar sensor. The core of this invention lies in adding a dedicated monitoring branch in parallel with the existing transmission link, i.e., adding a new high-sensitivity reflected wave monitoring system, and structurally integrating it with the spacecraft's transmitter system. Through a threshold judgment logic, unprecedented near-field target detection capabilities are achieved.

[0123] 1. Traditionally, spacecraft antennas have been primarily considered as radiating elements with a high reflectivity. This is usually only considered during ground testing or occasional antenna health checks.

[0124] 2. This invention innovatively utilizes the characteristic that communication or radar antennas are in a continuous transmitting state. Through the addition of a reflected wave monitoring module, the measurement of reflected power is transformed from an offline diagnostic method into an online real-time sensing method. Any conductor entering the antenna's near field will scatter an electromagnetic field. This scattered field, combined with the antenna's own reflected field, instantly changes the total voltage standing wave ratio (VSWR) at the port. By monitoring The sudden change can detect when a target is approaching at extremely close range, posing a risk of collision.

[0125] System working principle: Near-field coupling theory and early warning distance estimation

[0126] The physical basis of this invention is the principle of electromagnetism: any conductor entering the near-field region of an antenna will change its boundary conditions, thereby disturbing the electromagnetic field distribution at the antenna port, which manifests as a change in input impedance. The following is a derivation of a typical "small passive target" model.

[0127] 1.1 Incident field generated by the transmitting antenna at the target

[0128] Assume the monitoring antenna can be equivalent to a length of A short dipole carrying an electric current angular frequency is Its near-field area

[0129] The main term of the electric field is:

[0130]

[0131] Incident electric field intensity at the target location ;

[0132] : Equivalent length of the transmitting antenna ;

[0133] Port current of the transmitting antenna ;

[0134] Vacuum permittivity ;

[0135] Angular frequency ;

[0136] Distance between the target and the antenna .

[0137] Conclusion 1: Incident field strength With distance It is inversely proportional to the cube of the power.

[0138] 1.2 Target's Induced Dipole Moment

[0139] Let the target be the radius. Ideal conductive spheres (electric bodies) Its polarizability The induced dipole moment generated under the action of an external electric field is:

[0140]

[0141] The equivalent electric dipole moment generated by the target excitation

[0142] Target equivalent radius

[0143] However, the principles of this invention are universal and not limited to electrically small targets. For electrically large targets (such as non-cooperative spacecraft larger than the wavelength), which are more common in practice, their scattering capabilities are stronger, and their coupling characteristics with the antenna may lie between the far-field and induced near-field. In engineering, the impedance change introduced can be approximated by a more general relationship: ,in The characteristic scattering area of ​​the target, the exponent The value is typically between 2 and 4. This indicates that the larger the target size, the greater the target's induced dipole moment, and the farther its detection range. For ease of derivation, this paper still assumes an electrically small target, which does not affect the conclusions.

[0144] Conclusion 2: The induced dipole moment of the target Similarly with Inversely proportional.

[0145] 1.3 Voltage induced at the antenna port by the target scattered field

[0146] The induced dipole A scattered field will be generated at the original transmitting antenna. The scattered field also follows the same pattern in the near-field region. law:

[0147]

[0148] This scattered field has a length of The open-circuit voltage induced on the antenna is:

[0149]

[0150] Will Substitute the expression:

[0151]

[0152] 1.4 Equivalent impedance variation at the antenna port

[0153] Impedance change Defined as the ratio of scattering induced voltage to emission current:

[0154]

[0155] Its amplitude is:

[0156]

[0157] Change in antenna input impedance

[0158] Conclusion 3: For electrically small passive targets, the amplitude of antenna impedance change With distance It is inversely proportional to the sixth power. This is the "excitation-scattering" dual near-field effect (both are...). The result of superposition.

[0159] 1.5 Voltage Standing Wave Ratio change

[0160] In engineering, the system's measured quantity is the voltage standing wave ratio (VSWR). or reflection coefficient ( These are related to the antenna input impedance. and system characteristic impedance ( , usually There is a definite relationship.

[0161]

[0162] When no target is approaching, the antenna's inherent impedance is The corresponding reflection coefficient is When the target approaches, it causes a change in impedance. After that, the new input impedance is The new reflection coefficient is .

[0163] Relationship with reflection coefficient:

[0164] 1.6 Derivation of the Threshold for Change

[0165] Assume the antenna is initially well-matched: = 1.2. This corresponds to a reflection coefficient. .

[0166] Setting a meaningful detection threshold: We believe that when An alert is triggered when a clearly identifiable change occurs. For example, an alert threshold can be set as follows: (This is a widely accepted threshold value in engineering that indicates the matching state begins to deteriorate significantly.) This corresponds to .

[0167] Therefore, the threshold for detectable change in reflectance is:

[0168]

[0169] To simplify and remain conservative, we take .

[0170] To simplify the analysis, we consider the most sensitive case, namely It is a pure reactance (a typical case of near-field coupling), and (Perfectly matched reference). At this point, the change in reflection coefficient caused by the impedance change is approximately:

[0171]

[0172] : The change in the amplitude of the reflection coefficient;

[0173] System characteristic impedance ( ).

[0174] From this, we can deduce the minimum impedance change required to reach the detection threshold:

[0175]

[0176] Conclusion 4: Under this assumption (original VSWR=1.2, warning threshold VSWR=1.5), the system needs to be able to detect an impedance change of approximately 11Ω.

[0177] 1.7 Early Warning Distance Estimation

[0178] We will detect thresholds Substitute into the formula and recalculate the warning distance. :

[0179]

[0180] Equivalent length of transmitting antenna Assume two typical cases: 0.5m and 1.0m.

[0181] Target equivalent radius Assume two scenarios: 1m and 5m, to simulate large debris, a failed satellite, or other spacecraft, respectively.

[0182] The table below shows the estimated distance for warning purposes:

[0183]

[0184] 1.8 Feasibility Analysis:

[0185] 1) Proof of validity: The table above clearly shows that for dimensions not less than The goal is to , and The theoretical warning distance for both bands is approximately 1 meter. This demonstrates that the detection capability of this invention against typical threats such as space debris is physically feasible.

[0186] 2) Trend Analysis:

[0187] a) The lower the frequency, the farther the warning distance: due to antenna size In proportion to wavelength, low-frequency antennas have larger physical dimensions and stronger coupling with the target.

[0188] b) The larger the target, the farther the warning distance: target radius Effect to the sixth power It is the most sensitive factor affecting the detection range.

[0189] 3) Conservative Explanation: This estimate is based on the simplest model of a conductive sphere. The equivalent scattering cross-section of actual spacecraft components (such as supports, plate structures) is usually much larger than that of a sphere of the same size, so the actual detectable distance is usually better than the values ​​listed in the table.

[0190] 4) Scope of application: For At higher frequencies or when the target size is comparable to the wavelength, the electrically small model may no longer be accurate, requiring full-wave electromagnetic simulation for more precise predictions. However, this estimation is sufficient to demonstrate that the present invention has an effective engineering application basis in major aerospace frequency bands.

[0191] The main advantage of this invention lies in the fact that it achieves new functionality through a structural improvement.

[0192] Advantage 1: Functional integration can be achieved with minimal structural modifications.

[0193] The core modification of this invention lies solely in inserting a directional coupler into the transmission channel, thereby leading to a new reflected wave monitoring module. This module operates independently of the main communication / radar functions, performing only signal sensing and judgment. This bypass structure minimizes the impact on the original system. The benefits include:

[0194] Easy to install and modify: For spacecraft in orbit or platforms that have already been designed, there is no need to change the antenna body or core processor. It can be modularly installed at the radio frequency back end, which is easy to implement and has low risk.

[0195] High reliability: Failure of the monitoring module will not affect the normal operation of the main communication link, realizing the isolation between the sensing function and the core task function, and improving the overall reliability of the system.

[0196] Low resource consumption: This module can be designed as a low-power, small-volume dedicated unit, which consumes very little of the spacecraft's precious weight, power consumption and space resources.

[0197] Advantage 2: It created near-field perception capabilities.

[0198] Transforming antennas from simple radiating elements into sensors with sensing capabilities enables real-time detection of non-cooperative targets within meter-level range. This provides a crucial safety distance defense for spacecraft, especially in response to sudden, rapid debris approaches.

[0199] Advantage 3: It achieves autonomous, real-time early warning.

[0200] The entire perception and judgment process is completed on-board, without relying on any ground stations or external data, and the decision time can be as low as milliseconds. The benefits include:

[0201] Autonomy: It is free from dependence on ground support and can operate independently even when communication is interrupted.

[0202] Real-time performance: The response speed far exceeds that of trajectory prediction-based methods, enabling it to cope with unpredictable collision risks.

[0203] Advantage 4: Zero marginal cost and multi-functional reuse.

[0204] It fully utilizes the radio frequency signals commonly emitted by spacecraft as a detection source, eliminating the need for a separate transmitter for the detection function. The advantages include:

[0205] Economic efficiency: It saves costs and achieves distance sensing without additional radiation power costs.

[0206] Functionality: This voltage standing wave ratio (VSWR) monitoring module can also be used for antenna health monitoring (such as detecting whether the antenna is properly deployed or whether the feeder is damaged), making it a multi-purpose device.

[0207] This invention achieves its best results in the following typical scenarios:

[0208] Example 1: Geosynchronous Orbit Equipped with a Large-Aperture High-Gain Antenna Communication satellite

[0209] 1. Scene Description: The threat of orbital space debris is growing, and satellites are highly valuable. These satellites typically carry parabolic antennas with apertures several meters in diameter and operate in... Band.

[0210] 2. Optimal usage condition:

[0211] 1) Monitoring targets: large space debris (size > 0.5 meters) or defunct satellites.

[0212] 2) Working principle: The near-field region (Fresnel region) of a large-aperture antenna is very large. For a 2-meter aperture, 10GHz signal, the near-field region can extend to tens of meters. Within this region, large targets will produce strong scattering, leading to significant [scattering / dispersion]. .

[0213] 3) Effect: The system can generate an effective early warning when the target is still several meters to ten meters away from the antenna, allowing sufficient time for the satellite to perform evasive maneuvers. At this time, The changes can reach several ohms or even tens of ohms, making the detection very reliable.

[0214] Example 2: Spacecraft performing close rendezvous, docking, or formation flying

[0215] 1. Scenario Description: Spacecraft need to approach each other during missions such as on-orbit servicing, space station resupply, and constellation formation flight.

[0216] 2. Optimal usage condition:

[0217] 1) Monitoring targets: Cooperative or non-cooperative docking targets, formation members.

[0218] 2) Working principle: Utilizing a communication link antenna (such as...) band or The inter-satellite link antenna (band-based) continuously transmits signals to monitor impedance changes caused by other spacecraft entering the near field in real time. Even with cooperative targets, this system can serve as an additional, non-cooperative proximity sensor independent of cooperative beacons.

[0219] 3) Working principle: Utilizing a communication link antenna (such as...) band or The inter-satellite link antenna (band-based) continuously transmits signals to monitor impedance changes caused by other spacecraft entering the near field in real time. Even with cooperative targets, this system can serve as an additional, non-cooperative proximity sensor independent of cooperative beacons.

[0220] Example 3: Spacecraft equipped with multi-port antennas (such as phased arrays)

[0221] 1. Scenario Description: The next generation of spacecraft may use phased array antennas for communication or remote sensing.

[0222] 2. Optimal usage condition:

[0223] 1) Monitoring target: Small debris approaching from any direction.

[0224] 2) Working principle: Each of the multiple radiating elements or subarrays of the phased array is equipped with a reflection monitoring module. By comparing the relative magnitude and timing of ΔZ of different elements, it is possible not only to detect the approach of a target, but also to roughly determine the direction from which the target originates.

[0225] 3) Upgrade the detection capability from simple presence detection to directional detection, providing directional information for evasive maneuvers.

[0226] In summary, the benefits of this invention become more significant when the spacecraft platform is larger, the antenna aperture is larger, and the launch frequency is more frequent, providing an autonomous security barrier for on-orbit assets at low cost.

[0227] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A spacecraft non-cooperative target proximity detection system based on the effect of antenna port impedance discontinuity, characterized in that: Includes a transmitter, directional coupler, monitoring antenna, reflected wave monitoring module, and platform control system; The transmitter generates high-frequency radio frequency signals for communication, telemetry, or radar functions. The directional coupler is connected in parallel between the transmitter output and the monitoring antenna, and the coupling port of the directional coupler is connected to the input of the reflected wave monitoring module. The directional coupler is used for directional signal separation: allowing most of the transmitted radio frequency signal to pass smoothly to the monitoring antenna, while coupling out a small portion of the reverse-propagating reflected radio frequency signal to the reflected wave monitoring module. The reflected wave monitoring module includes a radio frequency detection circuit module, a digital circuit module, and a processing and threshold judgment logic module. The radio frequency detection circuit module receives the reflected radio frequency signal from the directional coupler and converts it into a DC or intermediate frequency voltage signal containing amplitude and phase information. The digital circuit module converts the analog voltage signal output by the radio frequency detection circuit into a digital signal, which is then used by the subsequent processor for mathematical operations and logical judgments. The processing and threshold judgment logic module receives the reflection coefficient data processed by the digital circuit module and executes the threshold judgment logic. The threshold determination logic is as follows: Step 1: Calculate the change: Calculate the real-time voltage standing wave ratio. Compared with baseline Compare them and calculate the absolute value of their changes. ;in The known quantity represents the baseline value of the voltage standing wave ratio of the antenna in a near-normal state without a target, or a set of reference values ​​related to slowly changing parameters such as temperature and attitude, which are obtained through prior ground calibration. Step 2, Basic Judgment Logic: If If the value exceeds the set threshold, it is immediately determined that a target has entered the antenna's near field, triggering an early warning. Otherwise, the system determines it to be in a normal state and continues to monitor in a loop; The platform control system is used to initiate subsequent actions after receiving an early warning signal.

2. The spacecraft non-cooperative target proximity detection system based on antenna port impedance abrupt change effect according to claim 1, characterized in that, The threshold determination logic also includes: Step 3, Intelligent Threshold Decision: The processing unit will calculate the absolute value of the voltage standing wave ratio change in real time. and its rate of change The comparison is made with a preset dynamic decision threshold; the dynamic decision threshold can be baseline-calibrated according to the current operating conditions of the spacecraft; when It significantly exceeded the threshold in a very short period of time, and When the value exceeds the set threshold, it is determined as a valid target approach event.

3. The spacecraft non-cooperative target proximity detection system based on antenna port impedance discontinuity effect of claim 1, wherein: The subsequent actions described in the platform control system include issuing an alarm and performing evasive maneuvers.

4. A method for proximity detection of a non-cooperative target spacecraft based on the effect of the abrupt change of the antenna port impedance, characterized in that: A reflected wave monitoring module is connected in parallel on the transmission link, and the output signal of the reflected wave monitoring module is transmitted to the platform control system. The transmission link includes a transmitter, a directional coupler, and a monitoring antenna; The transmitter generates high-frequency radio frequency signals for communication, telemetry, or radar functions. The directional coupler is connected in parallel between the transmitter output and the monitoring antenna, and the coupling port of the directional coupler is connected to the input of the reflected wave monitoring module. The directional coupler is used for directional signal separation: allowing most of the transmitted radio frequency signal to pass smoothly to the monitoring antenna, while coupling out a small portion of the reverse-propagating reflected radio frequency signal to the reflected wave monitoring module. The reflected wave monitoring module includes a radio frequency detection circuit module, a digital circuit module, and a processing and threshold judgment logic module. The radio frequency detection circuit module receives the reflected radio frequency signal from the directional coupler and converts it into a DC or intermediate frequency voltage signal containing amplitude and phase information. The digital circuit module converts the analog voltage signal output by the radio frequency detection circuit into a digital signal, which is then used by the subsequent processor for mathematical operations and logical judgments. The processing and threshold judgment logic module receives the reflection coefficient data processed by the digital circuit module and executes the threshold judgment logic. The threshold determination logic is as follows: Step one, calculate the change: compare the real-time collected voltage standing wave ratio with the baseline , calculate the absolute value of the change ; wherein is a known quantity, indicating the baseline value of the voltage standing wave ratio of the antenna in the target-free near-normal state, or a set of reference values related to temperature and attitude slow-changing parameters, which are obtained through prior calibration on the ground; Step 2, Basic Judgment Logic: If If the value exceeds the set threshold, it is immediately determined that a target has entered the antenna's near field, triggering an early warning. Otherwise, the system determines it to be in a normal state and continues to monitor in a loop; The platform control system is used to initiate subsequent actions after receiving an early warning signal.

5. The spacecraft non-cooperative target proximity detection method based on antenna port impedance abrupt change effect according to claim 4, characterized in that, The threshold determination logic also includes: Step 3, Intelligent Threshold Decision: The processing unit will calculate the absolute value of the voltage standing wave ratio change in real time. and its rate of change The comparison is made with a preset dynamic decision threshold; the dynamic decision threshold can be baseline-calibrated according to the current operating conditions of the spacecraft; when It significantly exceeded the threshold in a very short period of time, and When the value exceeds the set threshold, it is determined as a valid target approach event.

6. The spacecraft non-cooperative target proximity detection method based on antenna port impedance abrupt change effect according to claim 4, characterized in that: The subsequent actions described in the platform control system include issuing an alarm and performing evasive maneuvers.

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