A high-precision RCS measurement method and device based on navigation radar intermediate frequency signals
By modifying the intermediate frequency signal interface of the navigation radar and deploying a high-precision AD acquisition board, combined with improved radar equations and environmental corrections, low-cost, miniaturized, and high-precision RCS measurement was achieved. This solved the problems of expensive equipment, limited deployment, and low measurement accuracy in existing technologies, and is suitable for maritime target identification and surveillance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINESE PEOPLES LIBERATION ARMY UNIT 91977
- Filing Date
- 2025-12-26
- Publication Date
- 2026-07-21
AI Technical Summary
Existing marine navigation radars cannot achieve low-cost, miniaturized, and high-precision RCS measurement. Furthermore, existing technologies are expensive, have limited deployment, and low measurement accuracy, failing to meet the real-time and accurate measurement requirements for the RCS of maritime targets.
By modifying the intermediate frequency signal interface of the navigation radar and deploying a high-precision AD acquisition board, synchronous acquisition of intermediate frequency signals and radar pulses is achieved. The RCS is calculated by combining the improved radar equations, and corrections are made considering marine environmental factors. A standardized interface mechanism and timing synchronization architecture are established.
It achieves accurate (relative error ≤10%) and real-time (delay ≤200ms) measurement of the RCS of maritime targets. The modification cost is only 1/200 to 1/100 of that of dedicated equipment, solving the problems of expensive equipment, difficult deployment, and low accuracy. It is suitable for maritime target identification and surveillance.
Smart Images
Figure CN121899772B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of radar target characteristic measurement and marine surveillance technology, specifically to a high-precision RCS measurement method and device based on intermediate frequency signals from navigation radar. Background Technology
[0002] Marine navigation radar, as a core piece of equipment for ship navigation, is widely deployed on various civilian vessels (such as cargo ships, passenger ships, and fishing boats). Its core functions are to achieve collision avoidance, route surveillance, and maritime target detection, thus ensuring the safety of ship navigation. In existing technologies, traditional marine navigation radars only output basic navigation parameters such as the target's position (longitude, latitude), azimuth, and range to the user. The raw echo signals processed internally, especially the intermediate frequency (IF) signals containing complete electromagnetic characteristic information of the target, are usually processed in a closed mode without external interfaces. This means that the IF signals cannot be used for target electromagnetic characteristic analysis, resulting in a waste of radar hardware resources.
[0003] Currently, RCS measurement of maritime targets mainly relies on two types of technical solutions: one is a dedicated measurement radar system, which requires high-gain antennas, high-power transmitters and high-precision signal processing units. The equipment is expensive (the cost of a single system usually exceeds one million yuan), and the system is bulky and heavy, making it difficult to deploy on small and medium-sized ships; the other is a shore-based calibration system, which can only carry out measurements in fixed shoreline areas and cannot move with the ship, making it difficult to achieve real-time RCS measurement of targets in the open sea.
[0004] In existing technologies, although some studies have attempted to estimate target strength using video signals output by navigation radar, these video signals undergo nonlinear compression processing (such as logarithmic compression) during generation and are affected by the automatic gain control (AGC) mechanism of radar. This disrupts the linear relationship between the signal amplitude and the target's true scattering characteristics, failing to meet the linearity (requiring linear error ≤5%) and dynamic range (requiring dynamic range ≥60dB) requirements for quantitative RCS inversion. Consequently, the measurement results have extremely large errors (relative errors typically exceeding 30%), making them unsuitable for accurate characterization of the target's RCS.
[0005] A search revealed that there is currently no mature technical solution for converting ordinary marine navigation radar into an RCS measurement platform, particularly in the following three key technical areas: (1) There is a lack of standardized open mechanism for the intermediate frequency signal interface of marine navigation radar. Most of the existing radar intermediate frequency signals are transmitted internally, without unified interface definition, signal level standard and transmission protocol, which makes it impossible for external devices to obtain intermediate frequency signals stably and reliably. (2) The lack of a high-fidelity intermediate frequency signal acquisition architecture that is synchronized in real time with radar operating parameters (such as transmit power, pulse repetition frequency, antenna pointing angle, etc.) makes it difficult for existing acquisition equipment to achieve accurate alignment of acquisition timing with radar pulses (requiring time synchronization error ≤10ns), which can easily lead to loss of target echo signal or clutter. (3) There is a lack of mathematical models for RCS inversion that integrate radar system parameters and original intermediate frequency echoes. Existing models do not consider the impact of offshore platform sway (such as roll and pitch) on signal propagation paths, nor do they establish a dynamic correction mechanism for system gain drift, resulting in poor stability and low accuracy of RCS calculation results.
[0006] Therefore, there is an urgent need for a low-cost, miniaturized, and high-precision RCS measurement method that can be embedded in existing navigation radar systems to solve the problems of expensive equipment, limited deployment, and low measurement accuracy in existing technologies, and to meet the needs of real-time and accurate RCS measurement of maritime targets. Summary of the Invention
[0007] This invention primarily addresses how to achieve a low-cost, miniaturized, and embeddable high-precision RCS measurement method for existing navigation radar systems. This method solves the problems of expensive equipment, limited deployment, and low measurement accuracy in existing technologies, and meets the need for real-time and accurate RCS measurement of maritime targets. This invention discloses a high-precision RCS measurement method and device based on intermediate frequency signals from navigation radar.
[0008] In a first aspect, this invention discloses a high-precision RCS measurement method based on intermediate frequency signals from navigation radar, comprising: S1, acquire the set of operating parameter information and intermediate frequency analog signal output port information of the navigation radar; S2, Based on the set of working parameter information and the intermediate frequency analog signal output port information, the digital intermediate frequency signal is acquired; S3, process the digital intermediate frequency signal to obtain the target RCS value.
[0009] The set of operating parameter information includes the navigation radar's peak transmit power Pt, antenna gain G, and operating wavelength. Pulse width Distance cell resolution The parameters include: antenna real-time pointing angle, receiver noise figure Fn, total system loss Ls, parameter output frequency, and radar pulse repetition frequency PRF; the antenna real-time pointing angle includes azimuth angle. With pitch angle The output frequency of the parameter is consistent with the radar pulse repetition frequency (PRF). The intermediate frequency analog signal output port information includes the output impedance, signal level range, and signal bandwidth of the intermediate frequency analog signal output port of the navigation radar.
[0010] The process of acquiring a digital intermediate frequency (IF) signal based on the set of operating parameter information and the IF analog signal output port information includes: S21, acquire target trajectory information output by navigation radar, the target trajectory information including target distance R and target distance gate number; S22, calculate the acquisition parameters based on the target trajectory information; S23, based on the acquisition parameters and intermediate frequency analog signal output port information, digital sampling is performed on the intermediate frequency analog signal output port of the navigation radar to obtain a digital intermediate frequency signal.
[0011] The parameters to be collected, calculated based on the target trajectory information, include: Based on the target distance R, the arrival time t of the target echo is calculated, and its calculation expression is t=2R / c, where c is the speed of light; The time window in which the target echo is located is calculated based on the arrival time of the target echo. ,in This is for time redundancy; Determine the corresponding target distance unit based on the target distance gate number; Based on the sampling rate of AD sampling The range of sampling points was calculated. Its calculation expression is: , floor and ceil represent rounding up and rounding down, respectively; The acquisition parameters are constructed using the target echo arrival time t, time window, target distance unit, and sampling point range.
[0012] The process of processing the digital intermediate frequency signal to obtain the target RCS value includes: S31, The digital intermediate frequency signal is processed to obtain the target RCS value; S32, according to a preset time interval, acquire clutter signals in a calm sea area, and calibrate the target RCS value based on the clutter signals.
[0013] The step of calculating and processing the digital intermediate frequency signal to obtain the target RCS value includes: S311, Perform digital down-conversion processing on the digital intermediate frequency signal to obtain a baseband signal; perform quadrature demodulation processing on the baseband signal to obtain I / Q baseband signals; perform matched filtering processing on the I / Q baseband signals to obtain an output signal; S312, extract the complex envelope of the output signal within the target distance cell; S313, the target complex envelope peak value is obtained by using a peak detection algorithm to detect the complex envelope. ; S314: Extract a portion of the output signal within the adjacent non-target region of the target range cell. Use this extracted portion as the background sample signal and calculate the root mean square noise voltage of the background sample signal. ,Will As a system reference response ; S315, substituting the aforementioned set of operating parameter information, the target complex envelope peak value, and the system reference response into the improved radar equation, the target RCS value is calculated; the improved radar equation is: , in, For the target RCS value, This is the system total loss correction factor. This is the receiver noise figure correction factor. This indicates exponential operation, where k is a preset marine environmental correction factor.
[0014] The process of acquiring clutter signals from calm sea areas at preset time intervals and calibrating the target RCS value based on the clutter signals includes: S321, select clutter in a calm sea area as the calibration source; S322, according to a preset time interval, acquire clutter signals in the calm sea area; S323, calculate the root mean square voltage of the clutter signal in the calm sea area. Determine whether the root mean square voltage satisfies If the first discrimination result is satisfied, the antenna gain is corrected to obtain the corrected antenna gain; if the first discrimination result is not satisfied, the antenna gain is not processed. S324 substitutes the corrected antenna gain into the improved radar equation to complete the calibration of the target RCS value.
[0015] A second aspect of this invention discloses a high-precision RCS measurement device based on intermediate frequency signals from navigation radar, the device comprising: Memory containing executable program code; A processor coupled to the memory; The processor calls the executable program code stored in the memory to execute the high-precision RCS measurement method based on the intermediate frequency signal of navigation radar.
[0016] In a third aspect of this invention, a computer-readable storage medium is disclosed, wherein the computer-readable storage medium stores computer instructions, which, when invoked by a computer, are used to execute the high-precision RCS measurement method based on navigation radar intermediate frequency signals.
[0017] In a fourth aspect of this invention, an information data processing terminal is disclosed, which is used to implement the high-precision RCS measurement method based on the intermediate frequency signal of navigation radar.
[0018] The beneficial effects of this invention are as follows: This invention discloses a high-precision RCS measurement method for targets based on linear acquisition and processing of intermediate frequency (IF) signals from navigation radar. This method modifies a shipboard navigation radar, opens a standardized interface between the IF signal and system parameters, and deploys a high-precision AD acquisition board to achieve IF signal acquisition synchronized with radar pulses. The acquired signal undergoes digital down-conversion and matched filtering to extract target features. The target RCS is calculated using an improved radar equation (including marine environment correction), and online calibration ensures measurement stability. The four main innovations of this invention are a standardized interface mechanism, a timing synchronization architecture, an environmental fusion model, and a low-cost modification scheme. It can achieve accurate (relative error ≤10%) and real-time (delay ≤200ms) measurement of the RCS of maritime targets. The modification cost is only 1 / 200 to 1 / 100 of that of dedicated equipment, solving the problems of expensive equipment, difficult deployment, and low accuracy in existing technologies. This method can be widely applied in the fields of maritime target identification and surveillance.
[0019] This invention breaks through the limitations of closed processing of intermediate frequency signals in existing navigation radars. For the first time, it defines the hardware standard (interface type, impedance, level) and system parameter transmission protocol for intermediate frequency signal interfaces, realizing stable and reliable output of intermediate frequency signals and radar parameters. It provides a standardized interface foundation for the transformation of ordinary navigation radars into RCS measurement platforms and solves the problems of inconsistent interfaces and difficulty in signal acquisition in existing technologies.
[0020] This invention designs an intermediate frequency signal acquisition architecture based on radar transmitted pulse triggering. By matching the target range-time window with external trigger synchronization (time synchronization error ≤10ns), the acquisition timing is accurately aligned with the radar pulse and target echo, avoiding invalid signal acquisition and ensuring no loss of target echo signal. This solves the problems of timing asynchrony and low signal fidelity in existing acquisition equipment. The linearity error of the acquired signal is ≤3%, and the dynamic range is ≥84dB.
[0021] This invention establishes an RCS inversion mathematical model that includes platform attitude correction, environmental propagation loss correction, and dynamic system gain correction. For the first time, it incorporates factors such as offshore platform sway (roll and pitch) and sea surface environment (wind speed and wave height) into RCS calculation. The corrected model improves the physical consistency with the actual offshore scene by ≥20%, and the relative measurement error is ≤10%, solving the problems of existing models not considering the offshore environment and having low calculation accuracy.
[0022] This invention proposes an embedded retrofit scheme based on existing navigation radar. It only requires the addition of a high-precision AD acquisition board (cost ≤ 50,000 RMB) and a signal processing unit, without replacing the radar host. The retrofit cost is only 1 / 200 to 1 / 100 of that of a dedicated measurement radar. Moreover, the equipment is small in size (AD acquisition board size ≤ 200mm × 150mm × 50mm) and light in weight (≤ 1kg), which can be flexibly deployed on small and medium-sized ships, solving the problems of expensive equipment and limited deployment in the prior art. Attached Figure Description
[0023] Figure 1 This is a flowchart illustrating the implementation of the method of the present invention. Detailed Implementation
[0024] To better understand the content of this invention, three embodiments are given here.
[0025] Figure 1 This is a flowchart illustrating the implementation of the method of the present invention.
[0026] Example 1: In a first aspect, this invention discloses a high-precision RCS measurement method based on intermediate frequency signals from navigation radar, comprising: S1, acquire the set of operating parameter information and intermediate frequency analog signal output port information of the navigation radar; S2, Based on the set of working parameter information and the intermediate frequency analog signal output port information, the digital intermediate frequency signal is acquired; S3, process the digital intermediate frequency signal to obtain the target RCS value.
[0027] The set of operating parameter information includes the navigation radar's peak transmit power Pt, antenna gain G, and operating wavelength. Pulse width Distance cell resolution The parameters include: antenna real-time pointing angle, receiver noise figure Fn, total system loss Ls, parameter output frequency, and radar pulse repetition frequency PRF; the antenna real-time pointing angle includes azimuth angle. With pitch angle The output frequency of the parameter is consistent with the radar pulse repetition frequency (PRF). The intermediate frequency analog signal output port information includes the output impedance, signal level range, and signal bandwidth of the intermediate frequency analog signal output port of the navigation radar; The process of acquiring a digital intermediate frequency (IF) signal based on the set of operating parameter information and the IF analog signal output port information includes: S21, acquire target trajectory information output by navigation radar, the target trajectory information including target distance R and target distance gate number; S22, calculate the acquisition parameters based on the target trajectory information; S23, Based on the acquisition parameters and the intermediate frequency analog signal output port information, the intermediate frequency analog signal output port of the navigation radar is digitally sampled to obtain a digital intermediate frequency signal; The parameters to be collected, calculated based on the target trajectory information, include: Based on the target distance R, the arrival time t of the target echo is calculated. The formula is t = 2R / c, where c is the speed of light. m / s; The time window in which the target echo occurs is calculated based on the pulse width and the arrival time of the target echo. ,in For time redundancy, The value is the pulse width. 5-10 times larger, to ensure the target echo is completely contained within the acquisition window; Determine the corresponding target distance unit based on the target distance gate number; Based on the sampling rate of AD sampling The range of sampling points was calculated. Its calculation expression is: , floor and ceil represent rounding up and rounding down, respectively; The acquisition parameters are constructed using the target echo arrival time t, time window, target distance unit, and sampling point range.
[0028] The step of determining the corresponding target range unit based on the target range gate number is based on the correspondence between the target range gate number and the target range unit stored internally by the navigation radar. This correspondence is used for target detection and display.
[0029] Based on the acquired parameters and the intermediate frequency analog signal output port information, the intermediate frequency analog signal output port of the navigation radar is digitally sampled to obtain a digital intermediate frequency signal. Based on the sampling point range in the acquisition parameters, and according to the intermediate frequency analog signal output port information, the intermediate frequency analog signal output port of the navigation radar is digitally sampled using an AD acquisition board to obtain a digital intermediate frequency signal.
[0030] The process of processing the digital intermediate frequency signal to obtain the target RCS value includes: S31, The digital intermediate frequency signal is processed to obtain the target RCS value; S32, according to a preset time interval, acquire clutter signals in a calm sea area, and calibrate the target RCS value based on the clutter signals.
[0031] The step of calculating and processing the digital intermediate frequency signal to obtain the target RCS value includes: S311, the digital intermediate frequency signal is subjected to digital down-conversion (DDC) processing to obtain a baseband signal; the baseband signal is subjected to quadrature demodulation processing to obtain I / Q baseband signals; the I / Q baseband signals are subjected to matched filtering processing to obtain an output signal; the impulse response of the matched filter is conjugate with the time-domain waveform of the radar transmitted pulse to improve the range resolution and signal-to-noise ratio (SNR); the SNR improvement of the filtered signal is ≥10dB. S312, extract the complex envelope of the output signal within the target distance cell; S313, For the complex envelope, a peak detection algorithm (such as the maximum amplitude method) is used to obtain the target complex envelope peak value. (Unit: V); S314: Extract a portion of the output signal within the adjacent non-target region of the target range cell. Use this extracted portion as the background sample signal and calculate the root mean square noise voltage of the background sample signal. (Unit: V) As a system reference response This is used for calibration in subsequent RCS calculations; S315, Substitute the aforementioned set of operating parameter information, the target complex envelope peak value, and the system reference response into the improved radar equation to calculate the target RCS value. The improved radar equation is as follows: , in, Target RCS value (unit: ), This is the system total loss correction factor, which converts losses in decibels (dB) to a linear factor. This is the receiver noise figure correction factor, used to compensate for the impact of noise on signal detection. k is a preset marine environment correction factor, with a value range of 1.0-1.2, which is dynamically adjusted according to the complexity of the marine environment. The process of acquiring clutter signals from calm sea areas at preset time intervals and calibrating the target RCS value based on the clutter signals includes: S321, select clutter in a calm sea area as the calibration source; S322, according to a preset time interval, acquire clutter signals in the calm sea area; S323, calculate the root mean square voltage of the clutter signal in the calm sea area. Determine whether the root mean square voltage satisfies If the first discrimination result is satisfied, the antenna gain is corrected to obtain the corrected antenna gain; if the first discrimination result is not satisfied, the antenna gain is not processed. S324 substitutes the corrected antenna gain into the improved radar equation to complete the calibration of the target RCS value.
[0032] The formula for calculating the corrected antenna gain is as follows: , in, This is the corrected antenna gain.
[0033] The acquisition of clutter signals in the calm sea area is achieved by pointing the navigation radar beam at the calm sea area to obtain echo signals, which are then used as clutter signals in the calm sea area.
[0034] The step of acquiring clutter signals from calm sea areas at preset time intervals and calibrating the target RCS value based on the clutter signals may further include: S3201, select clutter in a calm sea area as the calibration source; S3202, according to a preset set of time intervals, acquire clutter signals of the calm sea surface area in each time interval; the set of time intervals includes several time intervals; S3203, Discretely sample the clutter signal of the calm sea area acquired in each time interval to obtain the corresponding sampling sequence; S3204, using the sampling sequences of all time intervals, a sampling matrix is constructed; S3205, Perform singular value calculation on the sampling matrix to obtain a set of singular values; the set of singular values includes singular values; S3206, Perform fusion fluctuation calculation on the singular value set to obtain a fusion fluctuation value; determine whether the fusion fluctuation value is greater than a preset fluctuation threshold; if it is greater, correct the antenna gain to obtain a corrected antenna gain; the calculation expression for the corrected antenna gain is: , in, This is the corrected antenna gain.
[0035] S3207 substitutes the corrected antenna gain into the improved radar equation to complete the calibration of the target RCS value.
[0036] The expression for calculating the fusion fluctuation is: ， Where r is the fusion fluctuation value, and Let represent the maximum singular value and the average of all singular values in the set of singular values, respectively.
[0037] In all embodiments of the present invention, the variables involved in all computational expressions or mathematical functions have been dimensionlessized before computation.
[0038] In all embodiments of the present invention, the values of the independent variables in the input of all computational expressions or mathematical functions meet the reasonable requirements of the input range of the computational expressions or mathematical functions, and can ensure that the computational expressions or mathematical functions can be calculated smoothly without violating physical laws or mathematical rules.
[0039] A second aspect of this invention discloses a high-precision RCS measurement device based on intermediate frequency signals from navigation radar, the device comprising: Memory containing executable program code; A processor coupled to the memory; The processor calls the executable program code stored in the memory to execute the high-precision RCS measurement method based on the intermediate frequency signal of navigation radar.
[0040] In a third aspect of this invention, a computer-readable storage medium is disclosed, wherein the computer-readable storage medium stores computer instructions, which, when invoked by a computer, are used to execute the high-precision RCS measurement method based on navigation radar intermediate frequency signals.
[0041] In a fourth aspect of this invention, an information data processing terminal is disclosed, which is used to implement the high-precision RCS measurement method based on the intermediate frequency signal of navigation radar.
[0042] Example 2: This invention provides a high-precision target RCS measurement method based on linear acquisition and processing of intermediate frequency signals from navigation radar, characterized by the following steps: Step S1: Standardization and Opening of the Interface Between Navigation Radar Intermediate Frequency Signal and System Parameters Hardware or firmware modifications to shipboard maritime navigation radars (including X-band and S-band navigation radars) specifically include: 1.1 Open the radar's internal intermediate frequency (IF) analog signal output port, defining the interface standard: adopting an SMA type coaxial interface, output impedance... The signal level range is 0-2Vpp, the bandwidth covers the intermediate frequency operating range of navigation radar (10-60MHz), and it is equipped with an anti-interference shielding layer to reduce the impact of external electromagnetic interference on the signal. 1.2 An open digital interface for radar system parameters is provided, employing Ethernet or RS422 communication protocols to output key radar operating parameters in real time. These parameters include: peak transmit power Pt (unit: W), antenna gain G (unit: dBi, including horizontal and vertical gain), and operating wavelength. (Unit: m, calculated from radar center frequency), Pulse width (Unit: ns), Distance cell resolution (Unit: m), Real-time antenna pointing angle (including azimuth) With pitch angle ,unit: The receiver noise figure Fn (in dB) and total system loss Ls (in dB, including transmission line loss, antenna feed loss, etc.) are set. The output frequency of the parameters is consistent with the radar pulse repetition frequency (PRF) to ensure that the parameters are synchronized with the timing of the signal.
[0043] Step S2: Design and Deployment of High-Precision Intermediate Frequency Signal Acquisition System Develop a dedicated high-precision analog-to-digital (ADI) acquisition board, whose key technical indicators meet the following requirements: 2.1 The sampling rate is ≥200MSPS to ensure that the Nyquist sampling theorem is satisfied for the intermediate frequency signal with a maximum frequency of 60MHz, and to avoid signal aliasing; 2.2 Resolution ≥ 14 bits, ensuring the dynamic range of the acquired signal ≥ 84dB, covering the amplitude difference between the target echo and background clutter; 2.3 Analog bandwidth ≥ 100MHz, ensuring flatness of signal amplitude-frequency response in the 10-60MHz intermediate frequency range. dB, with no significant attenuation; 2.4 It has an external trigger synchronization function. The trigger signal adopts TTL level (3.3V), rising edge trigger, trigger delay ≤10ns, and can start the acquisition synchronously with the radar transmission pulse to achieve precise alignment of the acquisition timing with the radar pulse; 2.5 Integrate a Field Programmable Gate Array (FPGA) chip to perform real-time buffering (buffer depth ≥ 16MB) and preprocessing (such as signal filtering and downsampling) of the acquired digital signals, thereby reducing the computing power pressure on subsequent processing units; The AD acquisition board is connected to the navigation radar through a standardized intermediate frequency signal interface to form a closed-loop connection of "radar-acquisition board". This ensures that the original intermediate frequency echo signal is digitized without distortion. The acquired data is transmitted to the subsequent signal processing unit through a PCIe 3.0 or Gigabit Ethernet interface.
[0044] Step S3: Precise acquisition and triggering of intermediate frequency signal based on target parameters 3.1 The signal processing unit receives target trajectory information output by the navigation radar in real time. The trajectory information includes target distance R (unit: m) and azimuth angle. (unit: Speed v (unit: m / s) and distance gate number; 3.2 Calculate the arrival time t of the target echo based on the target distance R: t = 2R / c (where c is the speed of light, and its value is...) (m / s), combined with the radar pulse repetition period T, to determine the time window in which the target echo occurs. ,in This is the time redundancy, and its value is the pulse width. 5-10 times larger, to ensure the target echo is completely contained within the acquisition window; 3.3 Determine the corresponding distance unit based on the target distance gate number, and combine this with the sampling rate of the AD acquisition board. Calculate the range of sampling points corresponding to this distance cell: , ; 3.4 The signal processing unit generates a acquisition trigger signal to control the AD acquisition board to acquire intermediate frequency signals within the above sampling point range, thereby achieving accurate acquisition of the target echo signal and avoiding invalid signals (such as clutter from non-target distance units) from occupying storage resources and processing power.
[0045] Step S4: RCS inversion signal processing and calculation based on marine environment 4.1 Intermediate Frequency Signal Preprocessing: The acquired digital intermediate frequency signal is processed by digital downconversion (DDC) to shift the intermediate frequency signal to the baseband. Orthogonal demodulation technology is used to obtain I / Q baseband signals. The baseband signal is then subjected to matched filtering. The impulse response of the matched filter is conjugate with the time-domain waveform of the radar transmitted pulse to improve the range resolution and signal-to-noise ratio (SNR). The SNR improvement of the filtered signal is ≥10dB. 4.2 Target Echo Extraction: Based on the range cell determined in step S3, extract the complex envelope of the baseband signal within that cell, and use a peak detection algorithm (such as the maximum amplitude method) to obtain the peak value of the target complex envelope. (Unit: V); 4.3 Background Noise and Clutter Calibration: Select background samples in the adjacent non-target areas of the target range cell (usually 5-10 range cells before and after the target), and calculate the root mean square noise voltage of the background samples. (Unit: V) As a system reference response This is used for calibration in subsequent RCS calculations; 4.4 Correction for marine environmental factors: This includes corrections for the rolling and pitching motion of offshore platforms (typically...). The platform's real-time attitude angles are obtained through ship attitude sensors (such as inertial measurement units, IMUs), and the radar antenna pointing angle is corrected to ensure that the deviation between the antenna pointing angle and the actual target azimuth is corrected. Meanwhile, the propagation loss of electromagnetic waves at the air-sea interface is corrected based on environmental parameters such as sea surface wind speed and humidity (correction amount ≤ 2dB). 4.5 RCS Calculation: Based on the corrected radar system parameters and preprocessed signal data, the target RCS is calculated by substituting them into the improved radar equation. The improved radar equation is as follows: in: For target RCS (unit: ); This is the total system loss correction factor, which converts losses in decibels (dB) to linear factors. This is the receiver noise figure correction factor, used to compensate for the impact of noise on signal detection; k is the marine environment correction coefficient, with a value ranging from 1.0 to 1.2, which is dynamically adjusted according to the complexity of the marine environment; Step S5: Online dynamic calibration (preferred step) To further improve measurement accuracy, the present invention also includes an online dynamic calibration step: 5.1 Select clutter from a calm sea area (wind speed ≤ 3 m / s, wave height ≤ 0.5 m) as the calibration source. There are no obvious targets in this area, and the clutter characteristics are stable. 5.2 Acquire clutter signals in the area every 30-60 minutes and calculate the root mean square voltage of the clutter. and the initial calibration value Compare; 5.3 If 5%, then according to The system gain is dynamically corrected using the following formula: This ensures that the system gain drift is ≤2%, guaranteeing the stability of long-term measurements; 5.4 If radar system parameters (such as transmit power and antenna gain) change (the change is ≥5%), the RCS calculation in step S4 will be automatically re-executed to avoid measurement errors caused by parameter changes.
[0046] Example 3: This embodiment uses a bulk carrier (target A) as the measurement object and conducts a sea trial in an open sea area to verify the measurement accuracy and stability of the method of the present invention.
[0047] 1.1 Experimental Equipment and Parameter Configuration Navigation Radar: The Furuno FAR-2218 X-band navigation radar is used, and its key parameters are as follows: Center frequency: 9.4 GHz (corresponding to operating wavelength). =3.21cm); Peak transmit power Pt: 25kW; Antenna gain G: 32dBi (horizontal), 18dBi (vertical); Pulse width 80ns; Pulse repetition frequency (PRF): 2kHz; Range cell resolution 1.5m; Receiver noise figure Fn: 4dB; Total system loss Ls: 6dB; 1.2 Experimental Procedure 1.2.1 Interface Modification and Connection: According to step S1 of this invention, the firmware of the Furuno FAR-2218 radar is upgraded to open the intermediate frequency signal interface (SMA interface, 30MHz center frequency, 20MHz bandwidth) and the system parameter interface (Ethernet protocol, output frequency 2kHz); the AD acquisition board is connected to the radar through the intermediate frequency interface, the trigger signal terminal is connected to the radar transmit pulse trigger signal, and the IMU, AIS receiver, and weather station are all connected to the signal processing unit (embedded industrial computer, CPU model Intel Core i7-12700H) through Ethernet; 1.2.2 Target Detection and Parameter Acquisition: After the radar was powered on, target A was detected at a distance of 8.5 km. The AIS receiver acquired information about target A: ship length 225m, ship width 32m, speed 12 knots, and heading... The signal processing unit receives the target parameters output by the radar: range R = 8500m, azimuth angle. 170 meters from gate number; 1.2.3 Intermediate Frequency Signal Acquisition: Calculate the target echo arrival time according to step S3. Set time redundancy =800ns (10 times the pulse width of 80ns), the acquisition time window is determined to be (56.67). -0.8 56.67 +0.8 Combined with an AD sampling rate of 200MSPS, the sampling point range is calculated as follows: N_start=floor((56.67e-6-0.8e-6)×200e6)=11134, N_end =ceil((56.67e-6+0.8e-6)×200e6)=11534; The signal processing unit generates a trigger signal to control the AD acquisition board to acquire the intermediate frequency signal within this range, continuously acquiring 10 coherent pulses; 1.2.4 Signal Processing and RCS Calculation: Following step S4, the acquired intermediate frequency signal is processed as follows: Digital downconversion: The 30MHz intermediate frequency signal is shifted to the baseband to obtain I / Q signals; Matched filtering: A matched filter based on LFM pulses is used, which improves the signal-to-noise ratio by 12dB after filtering; Target peak extraction: Extract the complex envelope peak value at a distance of 170 from the gate. =1.82V; Background calibration: Select distances of 160-165 and 175-180 from the gate as the background area, and calculate... =0.042V (i.e.) =0.042V). Environmental correction: IMU measured platform roll , swaying Corrected antenna azimuth angle The environmental correction factor k = 1.05; RCS calculation: Substituting into the improved radar equation: Calculated ; 1.2.5 Online Calibration: Following step S5, a calm sea surface area at a distance of 10 km was selected as the calibration source. Clutter signals were collected every 30 minutes, and calculations were performed. =0.041V, compared to the initial calibration value =0.042V comparison, deviation 2.38% (<5%), no system gain correction required; 1.3 Verification of Experimental Results 1.3.1 Comparison of Theoretical Values: According to the "Ship RCS Estimation Manual", a fully loaded bulk carrier with a length of 225m in the transverse direction (azimuth angle) The theoretical RCS range for near-positive transverse is 2000-3000. The measured value in this embodiment is 2520. Within the theoretical range, the relative error is ≤8%; 1.3.2 Repeated Measurement Stability: Target A was measured 10 times consecutively, and the RCS measurement results were 2520, 2512, 2535, 2508, 2525, 2518, 2530, 2505, 2522, and 2515, respectively. The average value is 2519. Standard deviation ±9.8 Excellent stability; 1.3.3 Comparison with traditional methods: When measuring the same target using the traditional video signal method (based on radar ARPA output intensity levels), the estimated RCS value is 1800-3400. The average value is 2600. Standard deviation ±520 The measurement accuracy and stability of the method of the present invention are significantly better than those of traditional methods.
[0048] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.
Claims
1. A high-precision RCS measurement method based on intermediate frequency signals of navigation radar, characterized in that, include: S1, acquire the set of operating parameter information and intermediate frequency analog signal output port information of the navigation radar; The set of operating parameter information includes the navigation radar's peak transmit power Pt, antenna gain G, and operating wavelength. Pulse width Distance cell resolution The parameters include: antenna real-time pointing angle, receiver noise figure Fn, total system loss Ls, parameter output frequency, and radar pulse repetition frequency PRF; the antenna real-time pointing angle includes azimuth angle. With pitch angle The output frequency of the parameter is consistent with the radar pulse repetition frequency (PRF). The intermediate frequency analog signal output port information includes the output impedance, signal level range, and signal bandwidth of the intermediate frequency analog signal output port of the navigation radar; S2, Based on the set of working parameter information and the intermediate frequency analog signal output port information, the digital intermediate frequency signal is acquired; S3, Process the digital intermediate frequency signal to obtain the target RCS value, including: S31, perform calculations on the digital intermediate frequency signal to obtain the target RCS value, including: S311, Perform digital down-conversion processing on the digital intermediate frequency signal to obtain a baseband signal; perform quadrature demodulation processing on the baseband signal to obtain I / Q baseband signals; perform matched filtering processing on the I / Q baseband signals to obtain an output signal; S312, extract the complex envelope of the output signal within the target distance cell; S313, the target complex envelope peak value is obtained by using a peak detection algorithm to detect the complex envelope. ; S314: Extract a portion of the output signal within the adjacent non-target region of the target range cell. Use this extracted portion as the background sample signal and calculate the root mean square noise voltage of the background sample signal. ,Will As a system reference response ; S315, substituting the aforementioned set of operating parameter information, the target complex envelope peak value, and the system reference response into the improved radar equation, the target RCS value is calculated; the improved radar equation is: ， in, For the target RCS value, This is the system total loss correction factor. This is the receiver noise figure correction factor. This indicates exponential operation, where k is a preset marine environmental correction coefficient; S32, according to a preset time interval, acquire clutter signals in a calm sea area, and perform calibration processing on the target RCS value based on the clutter signals, including: S321, select clutter in a calm sea area as the calibration source; S322, according to a preset time interval, acquire clutter signals in the calm sea area; S323, calculate the root mean square voltage of the clutter signal in the calm sea area. Determine whether the root mean square voltage satisfies If the first discrimination result is satisfied, the antenna gain is corrected to obtain the corrected antenna gain; if the first discrimination result is not satisfied, the antenna gain is not processed. S324 substitutes the corrected antenna gain into the improved radar equation to complete the calibration of the target RCS value. As another feasible implementation, the step of acquiring clutter signals from calm sea areas at preset time intervals and calibrating the target RCS value based on the clutter signals further includes: S3201, select clutter in a calm sea area as the calibration source; S3202, according to a preset set of time intervals, acquire clutter signals of the calm sea surface area in each time interval; the set of time intervals includes several time intervals; S3203, Discretely sample the clutter signal of the calm sea area acquired in each time interval to obtain the corresponding sampling sequence; S3204, using the sampling sequences of all time intervals, a sampling matrix is constructed; S3205, Perform singular value calculation on the sampling matrix to obtain a set of singular values; the set of singular values includes singular values; S3206, Perform fusion fluctuation calculation on the singular value set to obtain a fusion fluctuation value; determine whether the fusion fluctuation value is greater than a preset fluctuation threshold; if it is greater, correct the antenna gain to obtain a corrected antenna gain; the calculation expression for the corrected antenna gain is: ， in, For the corrected antenna gain; S3207 substitutes the corrected antenna gain into the improved radar equation to complete the calibration of the target RCS value. The expression for calculating the fusion fluctuation is: ， Where r is the fusion fluctuation value, and Let represent the maximum singular value and the average of all singular values in the set of singular values, respectively.
2. The high-precision RCS measurement method based on intermediate frequency signals of navigation radar as described in claim 1, characterized in that, The process of acquiring a digital intermediate frequency (IF) signal based on the set of operating parameter information and the IF analog signal output port information includes: S21, acquire target trajectory information output by navigation radar, the target trajectory information including target distance R and target distance gate number; S22, calculate the acquisition parameters based on the target trajectory information; S23, based on the acquisition parameters and intermediate frequency analog signal output port information, digital sampling is performed on the intermediate frequency analog signal output port of the navigation radar to obtain a digital intermediate frequency signal.
3. The high-precision RCS measurement method based on intermediate frequency signals of navigation radar as described in claim 2, characterized in that, The parameters to be collected, calculated based on the target trajectory information, include: Based on the target distance R, the arrival time t of the target echo is calculated, and its calculation expression is t=2R / c, where c is the speed of light; The time window in which the target echo is located is calculated based on the arrival time of the target echo. ,in This is for time redundancy; Determine the corresponding target distance unit based on the target distance gate number; Based on the sampling rate of AD sampling The range of sampling points was calculated. Its calculation expression is: , floor and ceil represent rounding up and rounding down, respectively; The acquisition parameters are constructed using the target echo arrival time t, time window, target distance unit, and sampling point range.
4. A high-precision RCS measurement device based on intermediate frequency signals of navigation radar, characterized in that, The device includes: Memory containing executable program code; A processor coupled to the memory; The processor calls the executable program code stored in the memory to execute the high-precision RCS measurement method based on the intermediate frequency signal of navigation radar as described in any one of claims 1 to 3.
5. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions, which, when invoked by a computer, are used to execute the high-precision RCS measurement method based on the intermediate frequency signal of navigation radar as described in any one of claims 1 to 3.
6. An information data processing terminal, characterized in that, The information data processing terminal is used to implement the high-precision RCS measurement method based on the intermediate frequency signal of navigation radar as described in any one of claims 1 to 3.