A radar error measurement method and system under composite electromagnetic interference

Abstract

The present invention provides a radar error measurement method and system under composite electromagnetic interference. Based on radar characteristic parameters and carrier-based aircraft characteristic parameters, a random number generator is used to generate random numbers that obey a normal distribution with specific parameters and random numbers that obey a Rayleigh distribution with specific scale parameters at all time points within a certain time period. A random number sequence is then formed to simulate Gaussian white noise and clutter interference signals within the time period, thereby obtaining the instantaneous amplitudes of the Gaussian white noise and clutter interference signals. A specific calculation method is then used to respectively calculate the instantaneous amplitudes of the noise amplitude modulation and frequency modulation interference signals, thereby calculating the instantaneous power of the composite electromagnetic interference signal. The radar signal-to-noise ratio is then calculated using a specific calculation method, thereby calculating the root mean square of the angle measurement error and the root mean square of the ranging error, and inputting them into the random number generator respectively. The angle measurement error and the ranging error are output to achieve accurate measurement of the radar error.

Description

Technical Field

[0001] The present invention relates to the technical field of radar signal processing, and in particular to a radar error measurement method and system under composite electromagnetic interference. Background Art

[0002] With the advancement of technology, ship-borne drones have become a vital component of aircraft carrier operations. However, maritime operations are not easy. Every takeoff and landing on an aircraft carrier is a delicate dance. First, the maritime environment is complex. During rainy weather, rain can reflect radar signals into clutter, affecting radar system measurements. Lightning strikes can also generate numerous narrow pulses with random amplitudes and phases due to multiple discharges, making radar systems highly susceptible to interference. Furthermore, the ocean is rife with electromagnetic interference, caused by interference signals from carrier-based aircraft radar electronics systems, aircraft carrier radar avionics systems, and enemy jammers. In this complex electromagnetic environment, drones' onboard equipment, such as radar and optoelectronics, is highly susceptible to these interferences, resulting in measurement signal errors and compromising the safety of their landings. Therefore, research on complex and complex electromagnetic interference is crucial in the maritime battlefield, as it directly impacts the landing of aircraft—a crucial combat force on aircraft carriers. Therefore, it is crucial to investigate the safety of radar-guided landings of ship-based drones under electromagnetic interference.

[0003] Radar-guided landing involves using the radar's range and angle measurement capabilities to determine the aircraft's relative position relative to the carrier's radar, thereby locating the specific position of the aircraft's tail hook relative to the ideal glide path. The specific process involves transforming the radar's measurement data, calculating the difference between the aircraft's tail hook and the ideal glide path, and applying deck motion compensation. The guided data is then fed into the command computer, generating throttle and elevator control signals. These signals are then transmitted to the aircraft's flight control system for corresponding operations, controlling the throttle and elevator movements, achieving corresponding flight parameter changes and ultimately implementing a fully automated landing system. During this process, radar measurement errors can potentially affect the final landing success. Radar operates on the principle of electromagnetic wave propagation. In a complex electromagnetic environment, the superposition of the original radar return waveform and interference waveforms can cause errors in the signal received by the radar receiver and the final processed result. Therefore, radar is susceptible to electromagnetic interference. Current research on the effects of electromagnetic interference on radar focuses primarily on anti-interference research, which necessarily presupposes an understanding of how radar is affected. In the large-scale environment of ocean warfare, the sea space is also full of electromagnetic interference due to the interference signals generated by the radar electronic systems of carrier-based aircraft, the radar avionics systems on aircraft carriers, and enemy jammers. These interferences will cause radar measurement errors to increase, seriously affecting the landing safety of ship-borne drones; at the same time, the artificial interference signals emitted by enemy jammers will also affect the accuracy of radar measurements.

[0004] While some technologies currently attempt to address specific types of electromagnetic interference, most existing technologies focus on suppressing a single interference source, such as designing specialized filtering algorithms to eliminate Gaussian white noise or using signal processing techniques to reduce the impact of clutter. However, these methods are ineffective when faced with complex electromagnetic interference because they typically focus on only one or a few types of interference and fail to fully consider the interactive effects of multiple interference sources. This means that in real-world scenarios where multiple interference sources coexist, the effectiveness of these technologies is significantly reduced, making it impossible to accurately predict and quantify radar performance in such complex environments. Summary of the Invention

[0005] The present invention addresses the current problem of radar error measurement focusing on only one or several interference forms while failing to fully consider the interactive effects of multiple interference sources. The present invention provides a radar error measurement method under composite electromagnetic interference. Based on radar characteristic parameters and carrier-based aircraft characteristic parameters, the method generates a composite electromagnetic interference signal containing Gaussian white noise, clutter, noise amplitude modulation, and noise frequency modulation through simulation and mathematical modeling. A specific calculation method is used to calculate the radar's signal-to-noise ratio, the root mean square of the angle measurement error, and the root mean square of the ranging error. Furthermore, a random number generator is used to generate the angle measurement error and ranging error. This method improves the accuracy of radar error measurement, enables more precise evaluation of radar performance in complex electromagnetic environments, and helps improve the landing safety of carrier-based unmanned aerial vehicles. The present invention also relates to a radar error measurement system under composite electromagnetic interference.

[0006] The technical solutions of the present invention are as follows:

[0007] A radar error measurement method under composite electromagnetic interference, characterized by comprising the following steps:

[0008] Parameter acquisition step: acquiring radar characteristic parameters and carrier-based aircraft characteristic parameters, wherein the radar characteristic parameters include the carrier voltage, wavelength, root mean square bandwidth, center frequency and amplitude of the carrier signal, radar transmit power, radar transmit antenna gain, radar receive antenna gain, and radar antenna aperture of the electromagnetic wave transmitted by the radar; and the carrier-based aircraft characteristic parameters include the scattering cross-sectional area of ​​the carrier-based aircraft and the distance between the carrier-based aircraft and the radar;

[0009] The instantaneous amplitude generation step of the Gaussian white noise interference signal comprises the following steps: using a random number generator to generate random numbers that obey a normal distribution with specific parameters at all time points within a certain time period, thereby forming a random number sequence to simulate the Gaussian white noise interference signal within the time period, and using the random number at each time point in the random number sequence as the instantaneous amplitude of the Gaussian white noise interference signal at the corresponding time point; and then performing band-limiting processing on each random number in the random number sequence that represents the Gaussian white noise interference signal to obtain Gaussian band-limited white noise;

[0010] The instantaneous amplitude generation step of the clutter interference signal is as follows: a random number generator is used to generate random numbers that obey a Rayleigh distribution with a specific scale parameter at all time points within a certain time period, thereby forming a random number sequence to simulate the clutter interference signal within the time period, and the random number at each time point in the random number sequence is used as the instantaneous amplitude of the clutter interference signal at the corresponding time point;

[0011] The instantaneous amplitude calculation steps of the noise AM and FM interference signals are as follows: the instantaneous amplitude of the noise AM interference signal is calculated based on the carrier voltage, the Gaussian band-limited white noise and the center frequency of the carrier signal; and the instantaneous amplitude of the noise FM interference signal is calculated based on the amplitude of the carrier signal, the Gaussian band-limited white noise and the center frequency of the carrier signal;

[0012] Instantaneous power calculation step: calculating the amplitude of the composite electromagnetic interference signal according to the instantaneous amplitude of the Gaussian white noise interference signal, the instantaneous amplitude of the clutter interference signal, the instantaneous amplitude of the noise amplitude modulation interference signal, and the instantaneous amplitude of the noise frequency modulation interference signal, and then calculating the instantaneous power of the composite electromagnetic interference signal according to the amplitude of the composite electromagnetic interference signal;

[0013] SNR calculation steps: Calculate the radar's received echo power based on the radar transmit power, radar transmit antenna gain, radar receive antenna gain, wavelength, scattering cross-section, and the distance between the carrier-based aircraft and the radar. Calculate the radar's SNR based on the received echo power and the instantaneous power of the composite electromagnetic interference signal.

[0014] Calculation steps for angle measurement and ranging error root mean square: Calculate the angle measurement error root mean square based on the signal-to-noise ratio, radar antenna aperture, and wavelength, and calculate the ranging error root mean square based on the signal-to-noise ratio and root mean square bandwidth;

[0015] Angle measurement and ranging error generation steps: The root mean square of the angle measurement error and the root mean square of the ranging error are input into the random number generator respectively, and the angle measurement error and the ranging error are output to realize the measurement of the radar error.

[0016] Preferably, in the signal-to-noise ratio calculation step, after calculating the received echo power of the radar, the received echo power is corrected using the loss factor to obtain the corrected received echo power to reflect the actual situation where the effective received power is reduced due to loss.

[0017] Preferably, in the step of generating the instantaneous amplitude of the Gaussian white noise interference signal, using a random number generator to generate random numbers that obey a normal distribution with specific parameters for all time points within a certain time period specifically includes:

[0018] A random time seed that obeys a normal distribution with a first specific parameter is generated by a random number generator in MATLAB software, and the random time seed is input into a SIMULINK model in MATLAB software. The SIMULINK model generates random numbers that obey a normal distribution with a second specific parameter for all time points within a certain time period.

[0019] Preferably, in the parameter acquisition step, the radar characteristic parameters also include the effective receiving area of ​​the radar receiving antenna and the transmitting antenna, the electromagnetic wave propagation speed, and the time delay of receiving the signal echo after the radar transmits a signal; the radar receiving antenna gain is calculated based on the effective receiving area and wavelength of the radar receiving antenna; and the radar transmitting antenna gain is calculated based on the effective receiving area and wavelength of the radar transmitting antenna.

[0020] Preferably, in the step of calculating the instantaneous amplitude of the noise amplitude modulation and frequency modulation interference signals, digital signal processing technology is also used to refine the instantaneous amplitude of the noise amplitude modulation and frequency modulation interference signals respectively to obtain instantaneous amplitudes with higher resolution; the digital signal processing technology includes wavelet transform or Fourier transform.

[0021] Preferably, the distance between the carrier-based aircraft and the radar is calculated based on the propagation speed of electromagnetic waves and the time delay of receiving the echo of a signal after the radar transmits the signal.

[0022] A radar error measurement system under composite electromagnetic interference is characterized by comprising a parameter acquisition module, a Gaussian white noise interference signal instantaneous amplitude generation module, a clutter interference signal instantaneous amplitude generation module, a noise amplitude modulation and frequency modulation interference signal instantaneous amplitude calculation module, an instantaneous power calculation module, a signal-to-noise ratio calculation module, an angle measurement and ranging error root mean square calculation module, and an angle measurement and ranging error generation module, which are connected in sequence.

[0023] The parameter acquisition module acquires radar characteristic parameters and carrier-based aircraft characteristic parameters. The radar characteristic parameters include the carrier voltage, wavelength, root mean square bandwidth, center frequency and amplitude of the carrier signal, radar transmit power, radar transmit antenna gain, radar receive antenna gain, and radar antenna aperture of the electromagnetic wave transmitted by the radar. The carrier-based aircraft characteristic parameters include the scattering cross-sectional area of ​​the carrier-based aircraft and the distance between the carrier-based aircraft and the radar.

[0024] The Gaussian white noise interference signal instantaneous amplitude generation module uses a random number generator to generate random numbers that obey a normal distribution with specific parameters at all time points within a certain time period, thereby forming a random number sequence to simulate the Gaussian white noise interference signal within the time period, and uses the random number at each time point in the random number sequence as the instantaneous amplitude of the Gaussian white noise interference signal at the corresponding time point; and then performs band-limiting processing on each random number representing the Gaussian white noise interference signal in the random number sequence to obtain Gaussian band-limited white noise;

[0025] The clutter interference signal instantaneous amplitude generation module uses a random number generator to generate random numbers that obey a Rayleigh distribution with a specific scale parameter at all time points within a certain time period, thereby forming a random number sequence to simulate the clutter interference signal within the time period, and uses the random number at each time point in the random number sequence as the instantaneous amplitude of the clutter interference signal at the corresponding time point;

[0026] The noise AM and FM interference signal instantaneous amplitude calculation module calculates the instantaneous amplitude of the noise AM interference signal based on the carrier voltage, Gaussian band-limited white noise and the center frequency of the carrier signal; and calculates the instantaneous amplitude of the noise FM interference signal based on the amplitude of the carrier signal, Gaussian band-limited white noise and the center frequency of the carrier signal;

[0027] The instantaneous power calculation module calculates the amplitude of the composite electromagnetic interference signal according to the instantaneous amplitude of the Gaussian white noise interference signal, the instantaneous amplitude of the clutter interference signal, the instantaneous amplitude of the noise amplitude modulation interference signal, and the instantaneous amplitude of the noise frequency modulation interference signal, and then calculates the instantaneous power of the composite electromagnetic interference signal according to the amplitude of the composite electromagnetic interference signal;

[0028] The signal-to-noise ratio calculation module calculates the radar's received echo power based on the radar's transmit power, the radar's transmit antenna gain, the radar's receive antenna gain, the wavelength, the scattering cross-section, and the distance between the carrier-based aircraft and the radar, and calculates the radar's signal-to-noise ratio based on the received echo power and the instantaneous power of the composite electromagnetic interference signal;

[0029] The angle measurement and ranging error root mean square calculation module calculates the angle measurement error root mean square according to the signal-to-noise ratio, radar antenna aperture and wavelength, and calculates the ranging error root mean square according to the signal-to-noise ratio and root mean square bandwidth;

[0030] The angle measurement and ranging error generation module inputs the angle measurement error root mean square and the ranging error root mean square into a random number generator respectively, and outputs the angle measurement error and the ranging error to achieve radar error measurement.

[0031] Preferably, in the signal-to-noise ratio calculation module, after calculating the received echo power of the radar, the received echo power is corrected using the loss factor to obtain the corrected received echo power to reflect the actual situation where the effective received power is reduced due to loss.

[0032] Preferably, in the Gaussian white noise interference signal instantaneous amplitude generation module, using a random number generator to generate random numbers that obey a normal distribution with specific parameters for all time points within a certain time period specifically includes:

[0033] A random time seed that obeys a normal distribution with a first specific parameter is generated by a random number generator in MATLAB software, and the random time seed is input into a SIMULINK model in MATLAB software. The SIMULINK model generates random numbers that obey a normal distribution with a second specific parameter for all time points within a certain time period.

[0034] Preferably, the radar characteristic parameters also include the effective receiving areas of the radar receiving antenna and the transmitting antenna, the electromagnetic wave propagation speed, and the time delay of receiving the signal echo after the radar transmits a certain signal; the radar receiving antenna gain is calculated based on the effective receiving area and wavelength of the radar receiving antenna; the radar transmitting antenna gain is calculated based on the effective receiving area and wavelength of the radar transmitting antenna; and the distance between the carrier-based aircraft and the radar is calculated based on the electromagnetic wave propagation speed and the time delay of receiving the signal echo after the radar transmits a certain signal.

[0035] The beneficial effects of the present invention are:

[0036] The present invention provides a radar error measurement method under composite electromagnetic interference. The method is based on radar characteristic parameters and carrier-based aircraft characteristic parameters, and uses a random number generator to generate random numbers that obey a normal distribution with specific parameters and a Rayleigh distribution with specific scale parameters at all time points within a certain time period. This method then forms a random number sequence to simulate Gaussian white noise interference signals and clutter interference signals that are more consistent with actual conditions within the time period. The random number at each time point in the random number sequence is used as the instantaneous amplitude of the Gaussian white noise interference signal and the clutter interference signal at the corresponding time point. A specific calculation method is then used to calculate the instantaneous amplitudes of the noise amplitude modulation and frequency modulation interference signals, respectively, and then the amplitude and instantaneous power of the composite electromagnetic interference signal are calculated. By comprehensively considering the impact of a complex electromagnetic interference environment composed of multiple interference signals on the radar, the method can more accurately evaluate the operating performance of the radar in a complex electromagnetic environment with higher accuracy, thereby helping to improve the landing safety of carrier-based unmanned aerial vehicles. Then, a specific calculation method is used to calculate the received echo power of the radar, and the signal-to-noise ratio of the radar is calculated based on the received echo power and the instantaneous power of the composite electromagnetic interference signal. By combining the physical characteristics of the radar and the influence of the composite electromagnetic interference, the error performance of the radar in different environments can be more accurately estimated, so that it can still maintain high performance in complex electromagnetic environments; then the root mean square of the angle measurement error and the root mean square of the ranging error are calculated based on the signal-to-noise ratio, and finally the root mean square of the angle measurement error and the root mean square of the ranging error are input into the random number generator respectively, and the angle measurement error and the ranging error are output to achieve accurate measurement of the radar error. Since the signal-to-noise ratio corresponding to different moments is different, the radar error generation that meets different conditions (i.e., mean and root mean square) is generated at each moment. By analyzing the radar error change trend under different signal-to-noise ratio conditions, R&D personnel can identify which factors have a greater impact on radar accuracy, and adjust the radar parameter settings accordingly to improve overall performance, better calibrate and compensate for radar measurement errors, thereby improving the accuracy of target tracking and positioning. The present invention helps to formulate effective anti-interference strategies and enhance the survivability and combat effectiveness of radar systems by understanding the response characteristics of radars under different interference conditions.

[0037] The present invention also relates to a radar error measurement system under composite electromagnetic interference. This system corresponds to the above-mentioned radar error measurement method under composite electromagnetic interference and can be understood as a system for implementing the above-mentioned radar error measurement method under composite electromagnetic interference. The system includes a parameter acquisition module, a Gaussian white noise interference signal instantaneous amplitude generation module, a clutter interference signal instantaneous amplitude generation module, a noise amplitude modulation and frequency modulation interference signal instantaneous amplitude calculation module, an instantaneous power calculation module, a signal-to-noise ratio calculation module, an angle measurement and ranging error root mean square calculation module, and an angle measurement and ranging error generation module, which are connected in sequence. The modules cooperate with each other to generate a composite electromagnetic interference signal containing Gaussian white noise, clutter, noise amplitude modulation, and noise frequency modulation based on radar characteristic parameters and carrier-based aircraft characteristic parameters through simulation and mathematical modeling. The radar's signal-to-noise ratio, angle measurement error root mean square, and ranging error root mean square are calculated using a specific calculation method. The angle measurement error and ranging error are then generated using a random number generator. The system has higher accuracy and can more accurately evaluate the radar's operating performance in complex electromagnetic environments, thereby helping to improve the landing safety of carrier-based unmanned aerial vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The figure is a flow chart of the radar error measurement method under composite electromagnetic interference of the present invention.

[0039] Figure 2 This is a flow chart of converting pseudo-random numbers into true random numbers in the present invention. DETAILED DESCRIPTION

[0040] The present invention will be described below with reference to the accompanying drawings.

[0041] The present invention relates to a radar error measurement method under composite electromagnetic interference. The flow chart of the method is as follows: Figure 1 As shown, the following steps are included in sequence:

[0042] Parameter acquisition step: Acquire radar characteristic parameters and carrier-based aircraft characteristic parameters. Radar characteristic parameters include the carrier voltage, wavelength, root mean square bandwidth, center frequency and amplitude of the carrier signal, radar transmission power, radar transmission antenna gain, radar receiving antenna gain, and radar antenna aperture of the electromagnetic wave emitted by the radar; carrier-based aircraft characteristic parameters include the scattering cross-sectional area of ​​the carrier-based aircraft and the distance between the carrier-based aircraft and the radar. Preferably, the radar characteristic parameters also include the effective receiving area of ​​the radar receiving antenna, the effective receiving area of ​​the transmitting antenna, the electromagnetic wave propagation speed, and the time delay of receiving the signal echo after the radar transmits a certain signal; according to the effective receiving area A of the radar receiving antenna r The radar receiving antenna gain is calculated by the following formula:

[0043]

[0044] Among them, A r is the effective receiving area of ​​the radar receiving antenna, and λ is the wavelength of the electromagnetic wave emitted by the radar.

[0045] And according to the effective receiving area A of the radar transmitting antenna t The radar transmitting antenna gain is calculated by the following formula:

[0046]

[0047] Among them, A t is the effective receiving area of ​​the radar transmitting antenna, and λ is the wavelength of the electromagnetic wave emitted by the radar.

[0048] In addition, when the radar is working, it transmits a series of periodic high-frequency pulses into space. Assume that the time delay of receiving the echo of the signal after the signal is transmitted is t r , the electromagnetic wave propagation speed is c, then the straight-line distance between the target and the antenna, that is, the distance R between the carrier-based aircraft and the radar, is calculated according to the following formula:

[0049]

[0050] The instantaneous amplitude generation step of the Gaussian white noise interference signal is as follows: a random number generator is used to generate random numbers that obey a normal distribution with specific parameters for all time points within a certain time period, thereby forming a random number sequence to simulate the Gaussian white noise interference signal within the time period, and the random number at each time point in the random number sequence is used as the instantaneous amplitude of the Gaussian white noise interference signal at the corresponding time point; and each random number representing the Gaussian white noise interference signal in the random number sequence is band-limited to obtain Gaussian band-limited white noise.

[0051] Specifically, in naval warfare environments, due to the presence of various types of interference, the waveform, phase, and power of electromagnetic signals are often highly random, creating a complex electromagnetic interference environment. This directly affects the accuracy and stability of electronic equipment, and is particularly detrimental to radar. This is because in a complex electromagnetic interference environment, the receiver will receive interference waves, resulting in measurement errors. Therefore, a full understanding of the complex electromagnetic interference environment is of great significance for the safety analysis of radar-guided landing missions of carrier-based aircraft in such environments. Interference types are mainly divided into natural electromagnetic interference and man-made interference. Natural electromagnetic interference includes noise interference (i.e., noise interference signals) and clutter interference (i.e., clutter interference signals).

[0052] Assuming that the aircraft carrier is far away from the land, the interference signals received by its radar detection are classified into the three categories mentioned above, specifically:

[0053] 1) Noise interference: electronic noise from equipment on board ships, such as radar receiver noise;

[0054] 2) Clutter interference: There is no need to detect the reflected echo generated by the object and the scattering effect of the medium on the electromagnetic wave, such as rain clutter and sea clutter;

[0055] 3) Human interference: interference signals emitted by enemy jammers, such as noise FM interference, noise AM interference, etc.

[0056] Noise interference signals are primarily composed of two components: the noise present in the natural environment and the noise generated by co-frequency equipment on both sides. This noise signal is similar to white noise, so Gaussian white noise is selected as the simulation model. Its description formula is as follows:

[0057] J(t)=U n (t)cos[w j t+φ(t)]

[0058] Among them, U n (t) and φ(t) are both independent functions, functions of time t, and can be random variables. j is the carrier frequency constant.

[0059] However, due to the fact that pseudo-random numbers are mostly used in the simulation process of Gaussian white noise, pseudo-random numbers are random numbers generated for each time node in sequence starting from the initial time point within a certain time period, that is, there is a random sequence, but the time of appearance is progressive from the initial time to the end time, which is not random. Therefore, each simulation will generate the same random number sequence, resulting in repeatability of the simulation results, and cannot truly reflect the random behavior of the aircraft landing process and cannot simulate the real random interference environment. At the same time, since the simulation cannot cover all possible interference situations, it will lead to deviations in the simulation results, and it is impossible to fully evaluate the performance of the system under different interference conditions. Therefore, Figure 2 As shown, first, a random time seed 'Seed' that obeys the normal distribution of the first specific parameter is generated by the random number generator in the MATLAB software. The value of the random time seed parameter variable adopts the normal distribution that satisfies the first specific parameter N (mean is 0, variance is 10000), and the random time seed 'Seed' parameter is composed of random variables. Therefore, when generating the 'Seed' variable, a reset time seed statement is used to make the 'Seed' variable a true random number; then the random time seed is input into the SIMULINK model in the MATLAB software, and the SIMULINK model generates a random number that obeys the second specific parameter (i.e., the mean is 0, the variance is σ) for all time points within a certain time period. 2) are randomly distributed random numbers (i.e., true random numbers) with a given value, and then a random number sequence is formed to simulate the Gaussian white noise interference signal within the simulation time period. This ensures that the initial time seed of the Gaussian white noise maintains random characteristics in each simulation, that is, the Gaussian white noise random number sequence is different in each simulation, which can ensure the diversity and authenticity of the simulation results, more accurately simulate the random interference environment, help improve the accuracy of the simulation, make the simulation results closer to the actual situation, and more comprehensively evaluate the success rate of radar-guided landing of aircraft under different interference conditions.

[0060] Then the random number at each time point in the random number sequence is used as the instantaneous amplitude U1 of the Gaussian white noise interference signal at the corresponding time point; and each random number representing the Gaussian white noise interference signal in the random number sequence is band-limited to obtain a mean of 0 and a variance of σ 2 Gaussian band-limited white noise u A (t). The probability density formula satisfied by the instantaneous amplitude of the Gaussian white noise interference signal is:

[0061]

[0062] Where, u is the instantaneous amplitude of the Gaussian white noise interference signal, σ 2 is the interference signal power.

[0063] The instantaneous amplitude generation step of the clutter interference signal is as follows: a random number generator is used to generate random numbers that obey the Rayleigh distribution with a specific scale parameter for all time points within a certain time period, thereby forming a random number sequence to simulate the clutter interference signal within the time period, and the random number at each time point in the random number sequence is used as the instantaneous amplitude of the clutter interference signal at the corresponding time point.

[0064] Specifically, clutter signals refer to the echo components of received radar echo signals caused by surface or volume scattering. They typically originate from the ground, buildings, the ocean, rain and snow, flocks of birds, and insects. Essentially, clutter signals are interference signals received by radars during operation. These signals are identical to the echo signals from target objects, but possess more complex characteristics. Essentially, clutter scattering is a random distribution process based on the morphological characteristics of the ground and sea surfaces. Commonly used clutter amplitude statistical models and clutter correlation analysis models can fully describe the clutter distribution structure. Clutter models recognized in academia include the Rayleigh, Log Normal, Weibull, and K distributions. Therefore, the Rayleigh distribution model, which primarily describes meteorological clutter signals, low-resolution radar clutter signals, and chaff interference signals, was used for simulation. Therefore, a random number generator is first used to generate random numbers that obey the Rayleigh distribution with a specific scale parameter (that is, the scale parameter is σ) for all time points within a certain time period, and then a random number sequence is formed to simulate the clutter interference signal within the time period. The random number at each time point in the random number sequence is then used as the instantaneous amplitude U2 of the clutter interference signal at the corresponding time point.

[0065] Among them, the probability distribution density function of the Rayleigh distribution model is:

[0066]

[0067] Here, we simulate Rayleigh-distributed clutter with a scale parameter of 5. The scale parameter, defined as the value σ in the function, determines the overall signal amplitude. As σ increases, the overall amplitude increases, although the signal amplitude can vary due to random distribution. The reverse is also true. It should be noted that the scale parameter is not unique; its value varies with time and random factors. Different scale parameters can be selected based on actual needs.

[0068] The instantaneous amplitude calculation step of the noise AM and FM interference signals includes the following steps: calculating the instantaneous amplitude of the noise AM interference signal based on the carrier voltage, the Gaussian band-limited white noise, and the center frequency of the carrier signal; and calculating the instantaneous amplitude of the noise FM interference signal based on the amplitude of the carrier signal, the Gaussian band-limited white noise, and the center frequency of the carrier signal. Preferably, after calculating the instantaneous amplitudes of the noise AM and FM interference signals, digital signal processing technology (such as wavelet transform or Fourier transform) is further used to refine the instantaneous amplitudes of the noise AM and FM interference signals to obtain instantaneous amplitudes with higher resolution.

[0069] Specifically, man-made electromagnetic interference is mainly generated by interference signals emitted by enemy jammers, such as noise amplitude modulation interference and noise frequency modulation interference. Among them, interference that uses noise to modulate the amplitude of the RF signal is called noise amplitude modulation interference, and the noise amplitude modulation interference signal is expressed as follows:

[0070] J(t)=[U0+u A (t)]cos(w j t)

[0071] In the above formula, U0 is the carrier voltage; u A (t) has zero mean and variance σ 2 Gaussian band-limited white noise is a random variable whose value changes with time and random factors. Taking the absolute value of J(t) (i.e., calculating |J(t)|) yields the instantaneous amplitude U3 of the noise amplitude modulation interference signal at time t.

[0072] Noise FM interference refers to an interference signal formed by frequency modulating the carrier signal with a random baseband signal waveform. j , the center frequency is w j The carrier signal is frequency modulated to generate a noise frequency modulation interference signal J(t), as shown in the following formula:

[0073]

[0074] In the above formula, U j is the amplitude of the carrier signal, w j is the center frequency of the carrier signal, K FM is the frequency modulation slope, u(t) modulation noise is a zero-mean, wide-sense stationary random process, which can be expressed as zero mean and variance σ 2 The instantaneous amplitude U4 of the noise FM interference signal at time t can be obtained by taking the absolute value of J(t) (i.e., calculating |J(t)|).

[0075] Instantaneous power calculation steps: The amplitude of the composite electromagnetic interference signal is calculated based on the instantaneous amplitude of the Gaussian white noise interference signal, the instantaneous amplitude of the clutter interference signal, the instantaneous amplitude of the noise amplitude modulation interference signal, and the instantaneous amplitude of the noise frequency modulation interference signal, and then the instantaneous power of the composite electromagnetic interference signal is calculated based on the amplitude of the composite electromagnetic interference signal.

[0076] Specifically, the amplitude U of the composite electromagnetic interference signal is first calculated based on the instantaneous amplitude U1 of the Gaussian white noise interference signal, the instantaneous amplitude U2 of the clutter interference signal, the instantaneous amplitude U3 of the noise amplitude modulation interference signal, and the instantaneous amplitude U4 of the noise frequency modulation interference signal, and is calculated according to the following formula:

[0077] U=U1+U2+U3+U4

[0078] When noise interference, clutter interference and jammer interference act at the same time, the receiver will receive the composite electromagnetic interference, which is called composite electromagnetic interference. Therefore, the instantaneous power P of the composite electromagnetic interference signal is calculated based on the amplitude of the composite electromagnetic interference signal. n , calculated according to the following formula:

[0079] P n =U 2

[0080] The signal-to-noise ratio calculation step includes calculating the radar's received echo power based on the radar transmit power, radar transmit antenna gain, radar receive antenna gain, wavelength, scattering cross-section, and the distance between the carrier-based aircraft and the radar. The radar's signal-to-noise ratio is then calculated based on the received echo power and the instantaneous power of the composite electromagnetic interference signal. Preferably, before calculating the signal-to-noise ratio, the radar's received echo power and the instantaneous power of the composite electromagnetic interference signal are normalized to obtain the normalized received echo power and the instantaneous power of the composite electromagnetic interference signal, to ensure that the calculation result is not affected by the absolute power level.

[0081] Specifically, the radar received echo power is first calculated based on the radar transmit power, radar transmit antenna gain, radar receive antenna gain, wavelength, scattering cross-section, and the distance between the carrier-based aircraft and the radar, using the following formula:

[0082]

[0083] In the above formula, P t is the radar transmission power, G t is the radar transmitting antenna gain, G r is the radar receiving antenna gain, λ is the wavelength of the electromagnetic wave emitted by the radar, σ is the scattering cross-section of the carrier-based aircraft, and R is the distance between the carrier-based aircraft and the radar.

[0084] The actual loss of the equipment and environmental factors are taken into account, and the received echo power equation taking into account the two influencing factors is given to obtain the impact of electromagnetic interference on the radar effect, and then simulation is used to obtain the impact of the radar effect on the UAV landing.

[0085] Since radar systems in actual operation always have various losses, a correction factor of loss should be introduced, and the loss factor L should be used to correct the received echo power to obtain the corrected received echo power to reflect the reduction in effective received power due to loss in actual situations. By considering actual losses and environmental factors, a received echo power equation that takes into account both factors is given to obtain the impact of electromagnetic interference on the radar effect, and then simulate the impact of the radar effect on the landing of UAVs. L is used to represent the loss factor added to the denominator of the received echo power. L is a value greater than 1 and is expressed in positive decibels. The corrected received echo power is expressed as:

[0086]

[0087] Then, the radar signal-to-noise ratio (SNR) is calculated based on the corrected received echo power and the instantaneous power of the composite electromagnetic interference signal, as shown in the following formula:

[0088]

[0089] Steps for calculating the RMS error of angle measurement and ranging: Calculate the RMS error of angle measurement based on the signal-to-noise ratio, radar antenna aperture, and wavelength, and use the following formula:

[0090]

[0091] In the above formula, SNR is the signal-to-noise ratio of the radar, D is the radar antenna aperture, and λ is the wavelength.

[0092] The RMS of the ranging error is calculated based on the signal-to-noise ratio and the RMS bandwidth, and is calculated according to the following formula:

[0093]

[0094] In the above formula, B c represents the RMS bandwidth of the radar transmit signal, SNR is the radar’s signal-to-noise ratio, and c is the speed of light.

[0095] Angle measurement and ranging error generation steps: The root mean square of the angle measurement error and the root mean square of the ranging error are input into the random number generator respectively, and the angle measurement error and the ranging error are output to realize the measurement of the radar error.

[0096] Specifically, a random number generator is used to generate, at each moment, an angular error that follows a normal distribution with a mean of 0 and a standard deviation equal to the root mean square of the angular error. A random number generator is also used to generate, at each moment, a ranging error that follows a normal distribution with a mean of 0 and a standard deviation equal to the root mean square of the ranging error. Because the signal-to-noise ratio (SNR) varies at different moments, radar errors (angular and ranging) that meet different conditions (i.e., zero mean and zero root mean square) are generated at each moment.

[0097] The present invention also relates to a radar error measurement system under composite electromagnetic interference. The system corresponds to the above-mentioned radar error measurement method under composite electromagnetic interference and can be understood as a system for implementing the above-mentioned method. The system includes a parameter acquisition module, a Gaussian white noise interference signal instantaneous amplitude generation module, a clutter interference signal instantaneous amplitude generation module, a noise amplitude modulation and frequency modulation interference signal instantaneous amplitude calculation module, an instantaneous power calculation module, a signal-to-noise ratio calculation module, an angle measurement and ranging error root mean square calculation module, and an angle measurement and ranging error generation module, which are connected in sequence. Specifically,

[0098] The parameter acquisition module acquires radar characteristic parameters and carrier-based aircraft characteristic parameters. The radar characteristic parameters include the carrier voltage, wavelength, root mean square bandwidth, center frequency and amplitude of the carrier signal, radar transmit power, radar transmit antenna gain, radar receive antenna gain, and radar antenna aperture of the electromagnetic wave transmitted by the radar. The carrier-based aircraft characteristic parameters include the scattering cross-sectional area of ​​the carrier-based aircraft and the distance between the carrier-based aircraft and the radar.

[0099] The Gaussian white noise interference signal instantaneous amplitude generation module uses a random number generator to generate random numbers that obey a normal distribution with specific parameters at all time points within a certain time period, thereby forming a random number sequence to simulate the Gaussian white noise interference signal within the time period, and uses the random number at each time point in the random number sequence as the instantaneous amplitude of the Gaussian white noise interference signal at the corresponding time point; and then performs band-limiting processing on each random number representing the Gaussian white noise interference signal in the random number sequence to obtain Gaussian band-limited white noise;

[0100] The clutter interference signal instantaneous amplitude generation module uses a random number generator to generate random numbers that obey a Rayleigh distribution with a specific scale parameter at all time points within a certain time period, thereby forming a random number sequence to simulate the clutter interference signal within the time period, and uses the random number at each time point in the random number sequence as the instantaneous amplitude of the clutter interference signal at the corresponding time point;

[0101] The noise AM and FM interference signal instantaneous amplitude calculation module calculates the instantaneous amplitude of the noise AM interference signal based on the carrier voltage, Gaussian band-limited white noise and the center frequency of the carrier signal; and calculates the instantaneous amplitude of the noise FM interference signal based on the amplitude of the carrier signal, Gaussian band-limited white noise and the center frequency of the carrier signal;

[0102] The instantaneous power calculation module calculates the amplitude of the composite electromagnetic interference signal according to the instantaneous amplitude of the Gaussian white noise interference signal, the instantaneous amplitude of the clutter interference signal, the instantaneous amplitude of the noise amplitude modulation interference signal, and the instantaneous amplitude of the noise frequency modulation interference signal, and then calculates the instantaneous power of the composite electromagnetic interference signal according to the amplitude of the composite electromagnetic interference signal;

[0103] The signal-to-noise ratio calculation module calculates the radar's received echo power based on the radar's transmit power, the radar's transmit antenna gain, the radar's receive antenna gain, the wavelength, the scattering cross-section, and the distance between the carrier-based aircraft and the radar, and calculates the radar's signal-to-noise ratio based on the received echo power and the instantaneous power of the composite electromagnetic interference signal;

[0104] The angle measurement and ranging error root mean square calculation module calculates the angle measurement error root mean square according to the signal-to-noise ratio, radar antenna aperture and wavelength, and calculates the ranging error root mean square according to the signal-to-noise ratio and root mean square bandwidth;

[0105] The angle measurement and ranging error generation module inputs the angle measurement error root mean square and the ranging error root mean square into a random number generator respectively, and outputs the angle measurement error and the ranging error to achieve radar error measurement.

[0106] Preferably, in the signal-to-noise ratio calculation module, after calculating the received echo power of the radar, the received echo power is corrected using the loss factor to obtain the corrected received echo power to reflect the actual situation where the effective received power is reduced due to loss.

[0107] Preferably, in the noise amplitude modulation and frequency modulation interference signal instantaneous amplitude calculation module, digital signal processing technology is also used to refine the instantaneous amplitude of the noise amplitude modulation and frequency modulation interference signals respectively to obtain instantaneous amplitudes with higher resolution; the digital signal processing technology includes wavelet transform or Fourier transform.

[0108] Preferably, the radar characteristic parameters also include the effective receiving areas of the radar receiving antenna and the transmitting antenna, the electromagnetic wave propagation speed, and the time delay of receiving the signal echo after the radar transmits a certain signal; the radar receiving antenna gain is calculated based on the effective receiving area and wavelength of the radar receiving antenna; the radar transmitting antenna gain is calculated based on the effective receiving area and wavelength of the radar transmitting antenna; and the distance between the carrier-based aircraft and the radar is calculated based on the electromagnetic wave propagation speed and the time delay of receiving the signal echo after the radar transmits a certain signal.

[0109] The present invention provides an objective and scientific radar error measurement method and system under composite electromagnetic interference. Based on radar characteristic parameters and carrier-based aircraft characteristic parameters, a composite electromagnetic interference signal including Gaussian white noise, clutter, noise amplitude modulation, and noise frequency modulation is generated through simulation and mathematical modeling. A specific calculation method is then used to calculate the radar's signal-to-noise ratio, the root mean square of the angle measurement error, and the root mean square of the ranging error. The angle measurement error and ranging error are then generated through a random number generator. This method makes the radar error measurement more accurate, enables more precise evaluation of the radar's operating performance in complex electromagnetic environments, and helps improve the landing safety of carrier-based unmanned aerial vehicles.

[0110] It should be noted that the specific embodiments described above can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Therefore, although this specification has described the present invention in detail with reference to the drawings and embodiments, those skilled in the art should understand that the present invention can still be modified or replaced with equivalents. In short, all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of protection of the patent for the present invention.

Claims

1. A radar error measurement method under composite electromagnetic interference, characterized in that: The following steps are involved: Parameter acquisition step: acquiring radar characteristic parameters and carrier-based aircraft characteristic parameters, wherein the radar characteristic parameters include the carrier voltage, wavelength, root mean square bandwidth, center frequency and amplitude of the carrier signal, radar transmit power, radar transmit antenna gain, radar receive antenna gain, and radar antenna aperture of the electromagnetic wave transmitted by the radar; and the carrier-based aircraft characteristic parameters include the scattering cross-sectional area of ​​the carrier-based aircraft and the distance between the carrier-based aircraft and the radar; The instantaneous amplitude generation step of the Gaussian white noise interference signal comprises the following steps: using a random number generator to generate random numbers that obey a normal distribution with specific parameters at all time points within a certain time period, thereby forming a random number sequence to simulate the Gaussian white noise interference signal within the time period, and using the random number at each time point in the random number sequence as the instantaneous amplitude of the Gaussian white noise interference signal at the corresponding time point; and then performing band-limiting processing on each random number in the random number sequence that represents the Gaussian white noise interference signal to obtain Gaussian band-limited white noise; The instantaneous amplitude generation step of the clutter interference signal is as follows: a random number generator is used to generate random numbers that obey a Rayleigh distribution with a specific scale parameter at all time points within a certain time period, thereby forming a random number sequence to simulate the clutter interference signal within the time period, and the random number at each time point in the random number sequence is used as the instantaneous amplitude of the clutter interference signal at the corresponding time point; The instantaneous amplitude calculation steps of the noise AM and FM interference signals are as follows: the instantaneous amplitude of the noise AM interference signal is calculated based on the carrier voltage, the Gaussian band-limited white noise and the center frequency of the carrier signal; and the instantaneous amplitude of the noise FM interference signal is calculated based on the amplitude of the carrier signal, the Gaussian band-limited white noise and the center frequency of the carrier signal; Instantaneous power calculation step: calculating the amplitude of the composite electromagnetic interference signal according to the instantaneous amplitude of the Gaussian white noise interference signal, the instantaneous amplitude of the clutter interference signal, the instantaneous amplitude of the noise amplitude modulation interference signal, and the instantaneous amplitude of the noise frequency modulation interference signal, and then calculating the instantaneous power of the composite electromagnetic interference signal according to the amplitude of the composite electromagnetic interference signal; SNR calculation steps: Calculate the radar's received echo power based on the radar transmit power, radar transmit antenna gain, radar receive antenna gain, wavelength, scattering cross-section, and the distance between the carrier-based aircraft and the radar. Calculate the radar's SNR based on the received echo power and the instantaneous power of the composite electromagnetic interference signal. Calculation steps for angle measurement and ranging error root mean square: Calculate the angle measurement error root mean square based on the signal-to-noise ratio, radar antenna aperture, and wavelength, and calculate the ranging error root mean square based on the signal-to-noise ratio and root mean square bandwidth; Angle measurement and ranging error generation steps: The root mean square of the angle measurement error and the root mean square of the ranging error are input into the random number generator respectively, and the angle measurement error and the ranging error are output to realize the measurement of the radar error.

2. The radar error measurement method under composite electromagnetic interference according to claim 1, characterized in that: In the signal-to-noise ratio calculation step, after calculating the radar's received echo power, the received echo power is corrected using the loss factor to obtain the corrected received echo power to reflect the actual reduction in effective received power due to loss.

3. The radar error measurement method under composite electromagnetic interference according to claim 1, characterized in that: In the instantaneous amplitude generation step of the Gaussian white noise interference signal, using a random number generator to generate random numbers that obey a normal distribution with specific parameters for all time points within a certain time period specifically includes: A random time seed that obeys a normal distribution with a first specific parameter is generated by a random number generator in MATLAB software, and the random time seed is input into a SIMULINK model in MATLAB software. The SIMULINK model generates random numbers that obey a normal distribution with a second specific parameter for all time points within a certain time period.

4. The radar error measurement method under composite electromagnetic interference according to claim 1, characterized in that: In the parameter acquisition step, the radar characteristic parameters also include the effective receiving area of ​​the radar receiving antenna and the transmitting antenna, the electromagnetic wave propagation speed, and the time delay of receiving the signal echo after the radar transmits a signal; the radar receiving antenna gain is calculated based on the effective receiving area and wavelength of the radar receiving antenna; and the radar transmitting antenna gain is calculated based on the effective receiving area and wavelength of the radar transmitting antenna.

5. The radar error measurement method under composite electromagnetic interference according to claim 1, characterized in that: In the step of calculating the instantaneous amplitude of the noise AM and FM interference signals, digital signal processing technology is also used to refine the instantaneous amplitudes of the noise AM and FM interference signals respectively to obtain instantaneous amplitudes with higher resolution; the digital signal processing technology includes wavelet transform or Fourier transform.

6. The radar error measurement method under composite electromagnetic interference according to claim 4, characterized in that: The distance between the carrier-based aircraft and the radar is calculated based on the propagation speed of electromagnetic waves and the time delay of receiving the echo of a signal after the radar transmits a signal.

7. A radar error measurement system under composite electromagnetic interference, characterized in that: It includes a parameter acquisition module, a Gaussian white noise interference signal instantaneous amplitude generation module, a clutter interference signal instantaneous amplitude generation module, a noise amplitude modulation and frequency modulation interference signal instantaneous amplitude calculation module, an instantaneous power calculation module, a signal-to-noise ratio calculation module, an angle measurement and ranging error root mean square calculation module, and an angle measurement and ranging error generation module, which are connected in sequence. The parameter acquisition module acquires radar characteristic parameters and carrier-based aircraft characteristic parameters. The radar characteristic parameters include the carrier voltage, wavelength, root mean square bandwidth, center frequency and amplitude of the carrier signal, radar transmit power, radar transmit antenna gain, radar receive antenna gain, and radar antenna aperture of the electromagnetic wave transmitted by the radar. The carrier-based aircraft characteristic parameters include the scattering cross-sectional area of ​​the carrier-based aircraft and the distance between the carrier-based aircraft and the radar. The Gaussian white noise interference signal instantaneous amplitude generation module uses a random number generator to generate random numbers that obey a normal distribution with specific parameters at all time points within a certain time period, thereby forming a random number sequence to simulate the Gaussian white noise interference signal within the time period, and uses the random number at each time point in the random number sequence as the instantaneous amplitude of the Gaussian white noise interference signal at the corresponding time point; and then performs band-limiting processing on each random number representing the Gaussian white noise interference signal in the random number sequence to obtain Gaussian band-limited white noise; The clutter interference signal instantaneous amplitude generation module uses a random number generator to generate random numbers that obey a Rayleigh distribution with a specific scale parameter at all time points within a certain time period, thereby forming a random number sequence to simulate the clutter interference signal within the time period, and uses the random number at each time point in the random number sequence as the instantaneous amplitude of the clutter interference signal at the corresponding time point; The noise AM and FM interference signal instantaneous amplitude calculation module calculates the instantaneous amplitude of the noise AM interference signal based on the carrier voltage, Gaussian band-limited white noise and the center frequency of the carrier signal; and calculates the instantaneous amplitude of the noise FM interference signal based on the amplitude of the carrier signal, Gaussian band-limited white noise and the center frequency of the carrier signal; The instantaneous power calculation module calculates the amplitude of the composite electromagnetic interference signal according to the instantaneous amplitude of the Gaussian white noise interference signal, the instantaneous amplitude of the clutter interference signal, the instantaneous amplitude of the noise amplitude modulation interference signal, and the instantaneous amplitude of the noise frequency modulation interference signal, and then calculates the instantaneous power of the composite electromagnetic interference signal according to the amplitude of the composite electromagnetic interference signal; The signal-to-noise ratio calculation module calculates the radar's received echo power based on the radar's transmit power, the radar's transmit antenna gain, the radar's receive antenna gain, the wavelength, the scattering cross-section, and the distance between the carrier-based aircraft and the radar, and calculates the radar's signal-to-noise ratio based on the received echo power and the instantaneous power of the composite electromagnetic interference signal; The angle measurement and ranging error root mean square calculation module calculates the angle measurement error root mean square according to the signal-to-noise ratio, radar antenna aperture and wavelength, and calculates the ranging error root mean square according to the signal-to-noise ratio and root mean square bandwidth; The angle measurement and ranging error generation module inputs the angle measurement error root mean square and the ranging error root mean square into a random number generator respectively, and outputs the angle measurement error and the ranging error to achieve radar error measurement.

8. The radar error measurement system under composite electromagnetic interference according to claim 7, characterized in that: In the signal-to-noise ratio calculation module, after calculating the radar's received echo power, the received echo power is corrected using the loss factor to obtain the corrected received echo power to reflect the actual reduction in effective received power due to loss.

9. The radar error measurement system under composite electromagnetic interference according to claim 7, characterized in that: In the instantaneous amplitude generation module of the Gaussian white noise interference signal, the random number generator is used to generate random numbers that obey the normal distribution of specific parameters at all time points within a certain time period, specifically including: A random time seed that obeys a normal distribution with a first specific parameter is generated by a random number generator in MATLAB software, and the random time seed is input into a SIMULINK model in MATLAB software. The SIMULINK model generates random numbers that obey a normal distribution with a second specific parameter for all time points within a certain time period.

10. The radar error measurement system under composite electromagnetic interference according to claim 7, characterized in that: The radar characteristic parameters also include the effective receiving areas of the radar receiving antenna and transmitting antenna, the electromagnetic wave propagation speed, and the time delay of receiving the signal echo after the radar transmits a signal; the radar receiving antenna gain is calculated based on the effective receiving area and wavelength of the radar receiving antenna; the radar transmitting antenna gain is calculated based on the effective receiving area and wavelength of the radar transmitting antenna; and the distance between the carrier-based aircraft and the radar is calculated based on the electromagnetic wave propagation speed and the time delay of receiving the signal echo after the radar transmits a signal.

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