A radar out-of-band third-order intermodulation false alarm effect test prediction method and system

Abstract

The application discloses a radar out-of-band third-order intermodulation false alarm effect test prediction method and system, relates to the field of complex electromagnetic environment adaptability test evaluation, and comprises the following steps: acquiring electromagnetic radiation interference spectrum of a working environment of a subject radar; determining a single-frequency interference signal according to the interference spectrum and a third-order intermodulation false alarm sensitive frequency offset range; determining a double-frequency and triple-frequency third-order intermodulation false alarm interference frequency combination according to the single-frequency interference signal and a single-frequency false alarm sensitive frequency band range of the subject radar; determining a third-order intermodulation false alarm interference effect index according to the double-frequency and triple-frequency third-order intermodulation false alarm interference frequency combination by using a universal third-order intermodulation false alarm effect model; and determining a third-order intermodulation false alarm interference prediction result of the subject radar according to the third-order intermodulation false alarm interference effect index. The application can realize accurate evaluation of the third-order intermodulation false alarm effect of the subject radar in a complex electromagnetic environment.

Description

Technical Field

[0001] This invention relates to the field of adaptability testing and evaluation in complex electromagnetic environments, and in particular to a method and system for testing and predicting the false alarm effect of third-order intermodulation in radar out-of-band. Background Technology

[0002] During operation, frequency-using equipment inevitably generates harmonics and noise electromagnetic radiation. When various high-power frequency-using devices operate simultaneously, the superposition of electromagnetic radiation leads to a denser and more intense electromagnetic spectrum, which in turn significantly impacts the performance of the frequency-using equipment. Electromagnetic radiation not only reduces useful signals and causes blocking effects, but if treated as useful signals, it can also cause false alarms and interference to radar and other detection equipment. To better understand the electromagnetic interference resistance of frequency-using equipment, comprehensive electromagnetic environment effect testing and evaluation are necessary to provide technical support for equipment application and electromagnetic protection hardening.

[0003] For the assessment of electromagnetic environment effects on equipment, some methods use statistical analysis to establish a survival probability model for electronic systems; others combine the analytic hierarchy process (AHP) and a comprehensive fuzzy evaluation method to construct an electromagnetic damage effect assessment model for electronic equipment; still others use a weighted assessment method based on the adaptability of complex electromagnetic environments to single technical indicators to assess the effects of the tested equipment. However, these methods usually require obtaining the performance indicators of the tested equipment, which not only involves complex calculations and poor accuracy, but also has certain limitations in their application. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for testing and predicting the third-order intermodulation false alarm effect of radar out-of-band, so as to achieve accurate evaluation of the third-order intermodulation false alarm effect of the radar under test in the complex electromagnetic environment.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A method for testing and predicting the false alarm effect of third-order intermodulation in radar out-of-band includes:

[0007] Obtain the electromagnetic interference spectrum of the operating environment of the tested radar;

[0008] The single-frequency interference signal is determined based on the interference spectrum and the third-order intermodulation false alarm sensitive frequency offset range; the single-frequency interference signal is a single-frequency interference signal that is within the third-order intermodulation false alarm sensitive frequency offset range.

[0009] The frequency combinations of dual-frequency and tri-frequency third-order intermodulation false alarm interference are determined based on the single-frequency interference signal and the single-frequency false alarm sensitive frequency band of the tested radar.

[0010] The third-order intermodulation false alarm interference effect index is determined using a universal third-order intermodulation false alarm effect model based on the frequency combination of dual-frequency and tri-frequency third-order intermodulation false alarm interference.

[0011] The third-order intermodulation false alarm interference prediction result of the tested radar is determined based on the third-order intermodulation false alarm interference effect index; the third-order intermodulation false alarm interference prediction result of the tested radar is either the electromagnetic radiation frequency combination in which third-order intermodulation false alarm interference occurs or the tested radar will not experience third-order intermodulation false alarm interference.

[0012] Optionally, the process of determining the sensitive frequency offset range for third-order intermodulation false alarms includes:

[0013] A single-frequency electromagnetic radiation false alarm effect test was conducted on the tested radar to determine the false alarm sensitivity level;

[0014] Based on the false alarm sensitivity level, a single-frequency electromagnetic radiation critical false alarm effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation false alarm sensitivity frequency offset range.

[0015] Based on the blocking sensitivity criterion, a single-frequency electromagnetic radiation critical blocking effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation blocking sensitive frequency offset range.

[0016] Outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, select frequency points to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range.

[0017] Optionally, frequency points outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range are selected to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range, specifically including:

[0018] Multiple fundamental frequency points are selected at equal frequency intervals outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range;

[0019] Dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests were conducted on multiple fundamental frequency points to determine the third-order intermodulation false alarm interference factor corresponding to each fundamental frequency point.

[0020] The variation law of the third-order intermodulation false alarm interference factor with radiation frequency offset is determined based on the third-order intermodulation false alarm interference factor.

[0021] The range of sensitive frequency offset for false alarms of the third-order intermodulation is determined based on the aforementioned variation pattern.

[0022] Optionally, the process of determining the universal third-order intermodulation false alarm effect model includes:

[0023] The initial false alarm effect model is determined based on the third-order intermodulation false alarm interference mechanism.

[0024] The initial false alarm effect model is universally modified to obtain a universal third-order intermodulation false alarm effect model.

[0025] This invention also provides a radar out-of-band third-order intermodulation false alarm effect testing and prediction system, comprising:

[0026] The acquisition module is used to acquire the electromagnetic interference spectrum of the operating environment of the radar under test;

[0027] A single-frequency interference signal determination module is used to determine a single-frequency interference signal based on the interference spectrum and the third-order intermodulation false alarm sensitive frequency offset range; the single-frequency interference signal is a single-frequency interference signal that is within the third-order intermodulation false alarm sensitive frequency offset range.

[0028] A dual-frequency and tri-frequency third-order intermodulation false alarm interference frequency combination determination module is used to determine the dual-frequency and tri-frequency third-order intermodulation false alarm interference frequency combination based on the single-frequency interference signal and the single-frequency false alarm sensitive frequency band range of the tested radar.

[0029] The module for determining the third-order intermodulation false alarm interference effect index is used to determine the third-order intermodulation false alarm interference effect index based on the combination of dual-frequency and three-frequency third-order intermodulation false alarm interference frequencies using a universal third-order intermodulation false alarm effect model.

[0030] The module for determining the prediction result of third-order intermodulation false alarm interference is used to determine the prediction result of third-order intermodulation false alarm interference of the tested radar based on the third-order intermodulation false alarm interference effect index; the prediction result of third-order intermodulation false alarm interference of the tested radar is either the electromagnetic radiation frequency combination in which third-order intermodulation false alarm interference occurs or the tested radar will not experience third-order intermodulation false alarm interference.

[0031] Optionally, the process of determining the sensitive frequency offset range for third-order intermodulation false alarms includes:

[0032] A single-frequency electromagnetic radiation false alarm effect test was conducted on the tested radar to determine the false alarm sensitivity level;

[0033] Based on the false alarm sensitivity level, a single-frequency electromagnetic radiation critical false alarm effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation false alarm sensitivity frequency offset range.

[0034] Based on the blocking sensitivity criterion, a single-frequency electromagnetic radiation critical blocking effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation blocking sensitivity frequency offset range.

[0035] Outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, select frequency points to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range.

[0036] Optionally, frequency points outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range are selected to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range, specifically including:

[0037] Multiple fundamental frequency points are selected at equal frequency intervals outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range;

[0038] Dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests were conducted on multiple fundamental frequency points to determine the third-order intermodulation false alarm interference factor corresponding to each fundamental frequency point.

[0039] The variation law of the third-order intermodulation false alarm interference factor with radiation frequency offset is determined based on the third-order intermodulation false alarm interference factor.

[0040] The range of sensitive frequency offset for false alarms of the third-order intermodulation is determined based on the aforementioned variation pattern.

[0041] Optionally, the process of determining the universal third-order intermodulation false alarm effect model includes:

[0042] The initial false alarm effect model is determined based on the third-order intermodulation false alarm interference mechanism.

[0043] The initial false alarm effect model is universally modified to obtain a universal third-order intermodulation false alarm effect model.

[0044] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0045] This invention acquires the electromagnetic radiation interference spectrum of the operating environment of the tested radar; determines a single-frequency interference signal based on the interference spectrum and the sensitive frequency offset range of the third-order intermodulation false alarm; the single-frequency interference signal is a single-frequency interference signal within the sensitive radiation frequency offset range of the third-order intermodulation false alarm of the tested radar; determines the frequency combinations of dual-frequency and triple-frequency third-order intermodulation false alarm interference based on the single-frequency interference signal and the sensitive frequency band range of the single-frequency false alarm of the tested radar; determines the third-order intermodulation false alarm interference effect index using a universal third-order intermodulation false alarm effect model based on the frequency combinations of dual-frequency and triple-frequency third-order intermodulation false alarm interference; determines the third-order intermodulation false alarm interference prediction result of the tested radar based on the third-order intermodulation false alarm interference effect index; the predicted third-order intermodulation false alarm interference result of the tested radar is either the electromagnetic radiation interference frequency combination in which third-order intermodulation false alarm interference occurs or the tested radar will not experience third-order intermodulation false alarm interference, thereby achieving an accurate assessment of the third-order intermodulation false alarm effect in the complex electromagnetic environment of the tested radar. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 Schematic diagram of the configuration for a radar third-order intermodulation false alarm effect test;

[0048] Figure 2 This is an image of radar third-order intermodulation false alarm interference.

[0049] Figure 3 This diagram illustrates the relationship between the false alarm level and the interference field strength for single-frequency radar interference.

[0050] Figure 4 The graph shows the variation of the false alarm level of dual-frequency third-order intermodulation with the strength of a single interference field.

[0051] Figure 5 A schematic diagram of the false alarm level of third-order intermodulation when the field strength of dual-frequency interference changes proportionally.

[0052] Figure 6 A schematic diagram of the critical false alarm interference field strength of single-frequency electromagnetic radiation of the tested radar.

[0053] Figure 7 A schematic diagram of the critical blocking interference field strength of the single-frequency electromagnetic radiation of the tested radar.

[0054] Figure 8 A schematic diagram of the false alarm interference factor of the third-order intermodulation of the tested radar;

[0055] Figure 9 A schematic diagram of the overall method for testing and predicting the false alarm effect of third-order intermodulation outside the radar band;

[0056] Figure 10 The flowchart shows the method for testing and predicting the false alarm effect of third-order intermodulation outside the radar band. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] The purpose of this invention is to provide a method and system for testing and predicting the third-order intermodulation false alarm effect of radar out-of-band, so as to achieve accurate evaluation of the third-order intermodulation false alarm effect of the radar under test in the complex electromagnetic environment.

[0059] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0060] like Figure 10 As shown, the present invention provides a method for testing and predicting the false alarm effect of third-order intermodulation in radar out-of-band, comprising:

[0061] Step 101: Obtain the electromagnetic interference spectrum of the operating environment of the radar under test.

[0062] Step 102: Determine the single-frequency interference signal based on the interference spectrum and the third-order intermodulation false alarm sensitive frequency offset range; the single-frequency interference signal is a single-frequency interference signal within the third-order intermodulation false alarm sensitive frequency offset range.

[0063] Step 103: Determine the frequency combinations of dual-frequency and tri-frequency third-order intermodulation false alarm interference based on the single-frequency interference signal and the single-frequency false alarm sensitive frequency band range of the tested radar.

[0064] Step 104: Determine the third-order intermodulation false alarm interference effect index using a universal third-order intermodulation false alarm effect model based on the frequency combination of the dual-frequency and tri-frequency third-order intermodulation false alarm interference.

[0065] Step 105: Determine the third-order intermodulation false alarm interference prediction result of the tested radar based on the third-order intermodulation false alarm interference effect index; the third-order intermodulation false alarm interference prediction result of the tested radar is either the electromagnetic radiation frequency combination that causes third-order intermodulation false alarm interference or the tested radar will not cause third-order intermodulation false alarm interference.

[0066] As an optional implementation, the process for determining the sensitive frequency offset range of third-order intermodulation false alarm includes:

[0067] A single-frequency electromagnetic radiation false alarm effect test was conducted on the tested radar to determine the false alarm sensitivity level.

[0068] Based on the false alarm sensitivity level, a single-frequency electromagnetic radiation critical false alarm effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation false alarm sensitivity frequency offset range.

[0069] Based on the blocking sensitivity criterion, a single-frequency electromagnetic radiation critical blocking effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation blocking sensitivity frequency offset range.

[0070] Outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, select frequency points to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range.

[0071] Specifically, outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, frequency points are selected to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range, including:

[0072] Multiple fundamental frequency points are selected at equal frequency intervals outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range.

[0073] Dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests were conducted on multiple fundamental frequency points to determine the third-order intermodulation false alarm interference factor corresponding to each fundamental frequency point. In this invention, four fundamental frequency points were initially selected.

[0074] Four new base frequencies are selected, and the third-order intermodulation false alarm interference factor of the corresponding frequencies is determined using the method described above. Alternatively, the frequency to be tested is combined with the frequency of the determined third-order intermodulation false alarm interference factor. A third-order intermodulation critical false alarm interference effect test is conducted to determine the third-order intermodulation false alarm interference factor of the frequency to be tested. This process is repeated.

[0075] The variation law of the third-order intermodulation false alarm interference factor with radiation frequency offset is determined based on the third-order intermodulation false alarm interference factor.

[0076] The range of sensitive frequency offset for false alarms of the third-order intermodulation is determined based on the aforementioned variation pattern.

[0077] The process of determining the universal third-order intermodulation false alarm effect model includes: determining the initial false alarm effect model based on the third-order intermodulation false alarm interference mechanism; and performing universal modification on the initial false alarm effect model to obtain the universal third-order intermodulation false alarm effect model.

[0078] This invention conducts research on experimental and modeling evaluation methods for complex electromagnetic environment effects, combining mechanism modeling and effect testing. Regarding the false alarm effect of the tested radar, previous research clarified the laws and mechanisms of the false alarm effect of single-frequency electromagnetic radiation on radar, concluding that multi-frequency electromagnetic radiation has almost no impact on the non-intermodulation false alarm signal of the radar. However, third-order intermodulation signals from out-of-band electromagnetic radiation easily enter the false alarm sensitive frequency band of the tested radar's single-frequency electromagnetic radiation, and like single-frequency interference signals, can also cause false alarm interference. Therefore, it is necessary to establish a third-order intermodulation false alarm effect model and propose an effect testing and prediction method.

[0079] The modeling and evaluation process for the third-order intermodulation false alarm effect of radar equipment is as follows: Figure 9 As shown:

[0080] (1) Conduct a single-frequency electromagnetic radiation false alarm effect test and give the curve of the false alarm level changing with the interference field strength. Select a specific false alarm level in the lower part of the linear change range as the false alarm sensitive level F0 when testing the third-order intermodulation false alarm interference factor.

[0081] Model parameter determination was conducted using a Ku-band stepped-frequency ranging radar as the research object. A differential-mode injection method was used to replace electromagnetic radiation to conduct out-of-band third-order intermodulation critical false alarm interference effect tests on the tested radar. The third-order intermodulation false alarm interference factor was measured, and the accuracy of the effect model was verified. To eliminate the influence of intermodulation components generated by the nonlinearity of the microwave power amplifier on the experimental results, two independent electromagnetic interference systems were used. These systems were directly injected into the RF front-end of the tested radar via a combiner and injection coupling module. The injected signal power was measured using a spectrum analyzer and converted into radiated field strength. The experimental configuration was as follows: Figure 1 As shown, the out-of-band electromagnetic radiation third-order intermodulation false alarm interference imaging of the tested radar is as follows: Figure 2 As shown.

[0082] Determination of false alarm sensitivity level during parameter measurement

[0083] Previous studies have elucidated the laws and mechanisms of the false alarm effect of single-frequency electromagnetic radiation on radar. The false alarm signal level changes monotonically with the interference field strength (signal level), such as... Figure 3 As shown, due to the blocking effect, the signal initially increases linearly, then the rate of increase decreases until it reaches a stable value. The third-order intermodulation signal is essentially still a single-frequency signal, but its variation with the radiation field strength is more complex: With a fixed field strength of one interfering signal in dual-frequency electromagnetic radiation, the false alarm level of the third-order intermodulation signal exhibits a maximum value as the field strength of the other interfering signal changes; if the field strengths of the two interfering signals change proportionally, the change in the false alarm level with the interfering field strength is the same as that of single-frequency interference, such as... Figure 4 and Figure 5 As shown.

[0084] Theoretically, the false alarm level of third-order intermodulation is more severely affected by blocking effects than that of single-frequency false alarms, and its maximum false alarm level is generally lower than that of single-frequency electromagnetic radiation. Different combinations of third-order intermodulation frequencies, even with the same third-order intermodulation frequency, can result in significant differences in the maximum false alarm level. However, the variation of the third-order intermodulation false alarm level with the cube of the interference field strength is similar to that of the single-frequency false alarm level, exhibiting a linear relationship for small signals, but with a greater tendency for the rate of increase to decrease or reach a peak. Therefore, when measuring the third-order intermodulation false alarm interference factor, it is not advisable to select an excessively high false alarm sensitivity level. Figures 3 to 5 Based on the test results, 5dBmV was selected as the false alarm level for model parameter determination in the linear region.

[0085] (2) Conduct a single-frequency electromagnetic radiation critical false alarm effect test, give the curve of the critical interference field strength with the radiation frequency deviation, and determine the sensitive frequency deviation range of the single-frequency electromagnetic radiation false alarm of the tested radar.

[0086] Single-frequency electromagnetic radiation false alarm effect sensitive frequency deviation test

[0087] The false alarm mechanism of third-order intermodulation interference is the same as that of single-frequency electromagnetic radiation interference. Considering that the third-order intermodulation signal in the false alarm sensitive band of single-frequency electromagnetic radiation is generally much smaller than the intensity of its single-frequency electromagnetic radiation signal, third-order intermodulation false alarm interference can be disregarded in the false alarm sensitive band of single-frequency electromagnetic radiation. To determine the approximate range of the sensitive frequency offset of third-order intermodulation false alarm interference, it is first necessary to test and determine the sensitive frequency offset range of single-frequency electromagnetic radiation false alarm interference for the tested radar.

[0088] Using a radar third-order intermodulation false alarm effect test setup, the output of one of the microwave power amplifiers was directly connected to the injection coupling module via a combiner. The operating frequency of the signal generator was set to be the same as that of the radar under test. The output power of the signal generator was adjusted using a variable step-size ramping method to make the false alarm level U of the radar under test close to the false alarm sensitivity level U. c (5dBmV), correction amount ΔU=U c -U, based on the forward power P measured by the spectrum analyzer, the radiation field strength E is calculated. According to the principle that the false alarm level U is proportional to the radiation field strength E, the critical false alarm interference field strength E corresponding to the false alarm sensitivity level is calculated. c The specific method is as follows:

[0089] Will Figure 1 The target under test is replaced by a horn antenna, which is fed by a microwave power amplifier. The power of the signal generator is adjusted so that the radiated field strength E0 in the test space is 10V / m. The RF output of the signal generator is turned off. The radar under test is placed in the test space with its receiving antenna in the original field strength test position. After the radar is working normally, the RF output of the signal generator is turned on, and the forward power P0 received by the radar antenna is tested using a spectrum analyzer. If the forward power P, radiated field strength E, and false alarm level U are in dBm, dBV / m, and dBmV respectively, then the radiated field strength is:

[0090] E = E0 + P - P0 (1)

[0091] The critical interference field strength ΔE, forward power ΔP, and false alarm level correction ΔU are the same:

[0092] ΔE=ΔP=ΔU (2)

[0093] Critical interference field strength E c :

[0094] E c =E0+P-P0+ΔU (3)

[0095] The test was conducted by changing the radiated frequency offset to determine the variation of the critical false alarm interference field strength with the radiated frequency offset. The experimental results are as follows: Figure 6 As shown. When the radiation frequency offset is greater than 70MHz, even if the radiation field strength increases to 200V / m, the tested radar no longer experiences false alarm interference. To improve data resolution, Figure 6 The maximum field strength was only calibrated to 20 dBV / m. The false alarm sensitive frequency offset range of the tested radar was approximately -70 MHz to 70 MHz. The critical false alarm interference field strengths fitted at different radiation frequency offsets are listed in Table 1. * False alarms will not occur at frequency points outside the sensitive band where the frequency offset is larger.

[0096] Table 1 Critical False Alarm Interference Field Strength of the Tested Radar

[0097] <![CDATA[E Fi / (dBV / m)]]> -8.3 -8.1 -7.8 -7.2 -5.6 -3.1 1.7 13.1 <![CDATA[40 * ]]> <![CDATA[Δf i / MHz]]> -10 -20 -30 -40 -50 -60 -70 -73 <![CDATA[E Fi / (dBV / m)]]> -8.3 -8.2 -7.8 -7.2 -5.3 -2.1 5.5 <![CDATA[40 * ]]>

[0098] (3) Conduct a single-frequency electromagnetic radiation critical blocking effect test, give the curve of the critical blocking interference field strength with the radiation frequency deviation, and determine the sensitive frequency deviation range of single-frequency electromagnetic radiation blocking.

[0099] Single-frequency electromagnetic radiation critical blocking sensitive frequency deviation test

[0100] Using a useful signal compression of 6 dB as the single-frequency blocking sensitivity criterion, the critical blocking interference field strength of the single-frequency electromagnetic radiation of the tested radar was determined as a function of the radiation frequency deviation (Δf) using the above method. i =f i The curve of the change of -f0), Δf i For radiation frequency offset, f i Given a given interference frequency and f0 as the operating frequency of the radar under test, provide the electromagnetic radiation sensitivity bandwidth of the radar under test. The test results are as follows: Figure 7 As shown, the sensitive frequency deviation range of 10dB is approximately (-170 to 172)MHz, and the critical blocking interference field strength basically no longer increases beyond the frequency deviation range of (-180, 180)MHz.

[0101] (4) Take four fundamental frequency points at equal frequency intervals outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests, and determine the third-order intermodulation false alarm interference factor of the four fundamental frequency points (deviation); for the first test, it is advisable to select one frequency point close to the working frequency of the radar under test outside the blocking sensitive frequency band as interference frequency 1, and select frequency 2 far away from the working frequency so that the third-order intermodulation frequency of the two falls on the working frequency of the radar under test. Based on the difference Δ between frequency 2 and frequency 1, select frequency 3 and frequency 4.

[0102] Combined Determination Method of Dual-Frequency and Tri-Frequency Critical False Alarm Interference Effect Test

[0103] Four out-of-band fundamental frequencies are selected at equal intervals: f1 = f0 ± Δ, f2 = f0 ± 2Δ, f3 = f0 ± 3Δ, and f4 = f0 ± 4Δ. Taking both "+" and "-" signs in the equations, we get: 2f1 - f2 = f0, 2f2 - f4 = f0, f1 + f2 - f3 = f0, and f1 + f3 - f4 = f0. Through the critical false alarm interference effect experiment of the above four frequency combinations, the third-order intermodulation false alarm interference factor corresponding to the radiated frequency offset of the four fundamental frequencies is simultaneously determined.

[0104] To simplify the calculation, the logarithm of both sides of equations (23) and (24) is taken. Considering the critical false alarm interference, the third-order intermodulation false alarm interference effect exponent R is... F3 =1, then:

[0105]

[0106]

[0107] Where, α F1 α F2 and α F3 These are the third-order intermodulation false alarm interference factors corresponding to interference frequencies F1, F2, and F3, respectively, E Ff E F0 E F1 E F2 and E F3 E1, E2, and E3 are the single-frequency false alarm critical interference field strengths corresponding to the third-order intermodulation frequency point, the operating frequency point f0 of the tested radar, and the interference frequencies F1, F2, and F3, respectively. E1, E2, and E3 are the interference signal field strengths corresponding to the interference frequencies F1, F2, and F3, respectively. If all physical quantities in equations (4) and (5) are in dB, and the third-order intermodulation false alarm interference factor α F (dB)=20lgα F ,but:

[0108]

[0109]

[0110] If the combination of frequency points i and j corresponds to the dual-frequency third-order intermodulation false alarm critical interference field strength and its respective single-frequency false alarm critical interference field strength, then the combination of... Abbreviation is The combination of the ratio of the critical false alarm interference field strength of the three-frequency third-order intermodulation interference field strength corresponding to the i, j, and k frequency points to the critical false alarm interference field strength of each single-frequency interference field strength Abbreviation is For the four sets of critical false alarm interference effect tests constructed at the above four basic frequency points, the third-order intermodulation frequency was the same as the operating frequency of the tested radar. From equations (6) and (7), we can obtain:

[0111]

[0112]

[0113]

[0114]

[0115] Where E F4 E1 and E2 are the single-frequency false alarm threshold interference field strength and interference signal field strength corresponding to the 4th fundamental frequency point, respectively. Solving by combining equations (8) to (11) yields:

[0116]

[0117]

[0118]

[0119]

[0120] After the third-order intermodulation false alarm interference factor corresponding to the radiation frequency offset of the four basic frequency points is determined, the four basic frequency points can be reselected according to the above method to conduct a critical false alarm interference effect test to determine its third-order intermodulation false alarm interference factor. Alternatively, the out-of-band frequency point to be tested can be selected in combination with the basic frequency points so that the third-order intermodulation frequency falls within the single-frequency false alarm sensitive frequency band of the radar under test. The third-order intermodulation false alarm interference factor of the out-of-band frequency point to be tested can be calculated according to formula (6) based on the critical false alarm interference effect test data until the variation law of the third-order intermodulation false alarm interference factor of the radar under test with the radiation frequency offset can be fully described.

[0121] Measurement of the false alarm interference factor of the third-order intermodulation at the fundamental frequency

[0122] The curve showing the critical blocking interference field strength of single-frequency electromagnetic radiation as a function of radiation frequency offset basically reflects the frequency selectivity characteristics of the tested radar's radio frequency front-end. Within its sensitive frequency offset range, the nonlinearity of the circuit response is not significant, while the third-order intermodulation false alarm interference has the same effect mechanism as the single-frequency electromagnetic radiation false alarm interference. Therefore, significant third-order intermodulation false alarm interference can only occur outside the blocking sensitive frequency offset range.

[0123] According to the aforementioned method for determining the third-order intermodulation false alarm interference factor, four frequency points with equal frequency intervals outside the blocking sensitive frequency offset range were selected for critical false alarm interference effect tests. The results are shown in Table 2, which also provides two sets of test results.

[0124] Table 2 Combination of Fundamental Frequency and Critical False Alarm Interference Field Strength for Third-Order Intermodulation

[0125]

[0126]

[0127] Based on the test data listed in Table 1, the third-order intermodulation false alarm interference factor at the fundamental frequency was calculated according to equations (12) to (15), and the results are shown in Table 3. Since single-frequency electromagnetic radiation cannot generate effective false alarm interference for the tested radar outside the false alarm and blocking sensitive frequency bands, the critical false alarm interference field strength E at all frequency points is used to calculate the third-order intermodulation false alarm interference factor. Fi All calculations are based on 40 dBV / m.

[0128] Table 3. Calculation results of the false alarm interference factor of the fundamental frequency and third-order intermodulation.

[0129]

[0130] (5) The third-order intermodulation critical false alarm interference factor is determined by using the method of determining the third-order intermodulation critical false alarm interference factor at the basic frequency or by combining the frequency point of the determined third-order intermodulation false alarm interference factor with the extrapolated frequency point to conduct a third-order intermodulation critical false alarm effect test, so that the third-order intermodulation frequency point falls within the false alarm sensitive frequency band of the tested radar, the third-order intermodulation false alarm interference factor corresponding to the extrapolated frequency point is determined, the variation law of the third-order intermodulation critical false alarm interference factor with the radiation frequency offset is accurately described, and the sensitive frequency offset range is determined.

[0131] Measurement of extrapolated frequency point third-order intermodulation false alarm interference factor

[0132] For ease of calculation and comparison, the extrapolated interference frequency is selected so that the third-order intermodulation false alarm interference frequency generated by the combined effect of dual-frequency or tri-frequency electromagnetic radiation falls at the operating frequency of the tested radar, i.e., the third-order intermodulation false alarm interference frequency offset is 0. There are two methods for selecting the test frequency: one is to select different combinations of fundamental frequencies according to the above method, conduct four sets of multi-frequency third-order intermodulation critical false alarm effect experiments, and simultaneously determine the third-order intermodulation false alarm interference factor corresponding to four different frequency offsets; the other is to combine the frequency point with the determined third-order intermodulation false alarm interference factor with the extrapolated frequency point to conduct a third-order intermodulation critical false alarm effect experiment, and determine the third-order intermodulation false alarm interference factor corresponding to the extrapolated frequency point.

[0133] The combined test results of the critical false alarm interference field strength of the third-order intermodulation at the extrapolated frequency point are shown in Table 4. The table also lists the extrapolated frequency point third-order intermodulation false alarm interference factor calculated according to Equation (6) and Equation (7). During the calculation process, the third-order intermodulation false alarm interference factor of the known frequency point is taken as the average of the two test calculation results.

[0134] Table 4. Test results of the field strength of the third-order intermodulation critical false alarm interference at the positive frequency offset extrapolation point.

[0135]

[0136] For the extrapolated frequency points with negative frequency offset, a set of third-order intermodulation critical false alarm effect experiments were first conducted based on the third-order intermodulation false alarm interference factor of the base frequency point. Then, four third-order intermodulation critical false alarm effect experiments were conducted by combining the frequency points with the determined third-order intermodulation false alarm interference factor with the four extrapolated frequency points. The test results of the frequency point combination and the critical false alarm interference field strength combination are shown in Table 5. The calculation results of the third-order intermodulation false alarm interference factor of the extrapolated frequency points with negative frequency offset are shown in Table 6.

[0137] Table 5. Combination of Field Strengths for Third-Order Intermodulation Critical False Alarm Interference at Negative Frequency Offset Extrapolation Frequency Point

[0138]

[0139]

[0140] Table 6. Calculation results of the false alarm interference factor of the third-order intermodulation at the negative frequency offset extrapolation point.

[0141]

[0142] Based on the calculation results listed in Tables 3, 4, and 6, the curves showing the variation of the third-order intermodulation false alarm factor of the tested radar with the radiated frequency offset are plotted as follows: Figure 8 As shown in the figure, the two measurement data and their fitted curves are marked at the same time. The error is within 1dB. The fitting results are listed in Table 7.

[0143] Table 7. Fitting results of the third-order intermodulation false alarm interference factor of the tested radar.

[0144]

[0145] Model accuracy verification experiments

[0146] The relationship between the third-order intermodulation false alarm interference factor and the radiated frequency offset reflects the third-order intermodulation false alarm sensitivity characteristics of the tested radar, and the effect model has universality. If the third-order intermodulation false alarm interference factor remains constant, and the interference field strength combinations obtained from different third-order intermodulation critical false alarm effect tests are substituted into the effect model, the effect exponent, expressed in dB, represents the model error. The accuracy of the model is then verified by changing the interference rating, field strength combinations, and sensitivity level.

[0147] (1) Keep the false alarm sensitivity level unchanged at 5dBmV. The verification results are shown in Table 8, with a maximum error of 1.4dB.

[0148] Table 8. Model error verification when the sensitivity level remains unchanged.

[0149]

[0150]

[0151] (2) The false alarm sensitivity level was changed to 3dBmV and 8dBmV. The verification results are shown in Table 9. The maximum error is 1.9dB.

[0152] Table 9. Model error verification at different sensitivity levels.

[0153]

[0154] In summary, the third-order intermodulation false alarm effect model has an accuracy better than 2 dB, which meets the accuracy requirements for experimental evaluation.

[0155] (6) Universal model revision to prepare for evaluation.

[0156] Theoretical Modeling of Third-Order Intermodulation False Alarm Effect

[0157] Third-order intermodulation originates from the nonlinear response of the signal processing circuit of the frequency-using equipment to multi-frequency signals. When a new third-order intermodulation frequency of a dual-frequency or tri-frequency signal enters the single-frequency false alarm sensitive band of the radar under test, this signal, like the in-band single-frequency signal, can cause false alarm interference to the radar under test. By comparing the third-order intermodulation signal level with the critical single-frequency false alarm interference level at the corresponding frequency, and introducing relevant parameters describing the nonlinear characteristics of the radar under test, a model of the third-order intermodulation false alarm interference effect of the radar under test can be established.

[0158] Theoretical derivation of the model

[0159] Let the electromagnetic radiation field strengths at different frequencies in space be E i (f i The transfer function of the signal field coupling and signal processing circuit is A. i (f i If the signal level S is... i (f i )for:

[0160] S i (f i ) = A i (f i E i (f i (16)

[0161] Where: i = 0 represents a signal with the same operating frequency as the radar under test (for frequency-sweeping radars such as step-frequency radar, it is its center operating frequency, the same below), and other values ​​of i represent in-band and out-of-band interference signals, respectively. Because the signal frequencies differ, the antenna gain and circuit gain of the radar under test change accordingly, and the circuit gain may also be related to the operating frequency of the radar under test. Therefore, A i (f i It is related not only to the signal frequency, but also to the operating frequency f0 of the radar under test.

[0162] Considering the strong frequency selectivity and limited sensitive operating bandwidth of the tested radar, the third-order intermodulation signals generated by out-of-band interference signals at frequencies f1 and f2 falling into the operating band of the tested radar and causing false alarm interference effects can mainly be in two combinations: 2f1-f2 or 2f2-f1. The probability of 2f1+f2, 2f2+f1, or 3f1 and 3f2 falling into the operating band of the tested radar and causing false alarm interference effects is very low and will not be considered.

[0163] Without loss of generality, assume that the third-order intermodulation frequency f = 2f1 - f2 falls within the operating frequency band of the radar under test, and the third-order intermodulation signal level generated by out-of-band interference signals at frequencies f1 and f2 is... It can be represented as:

[0164]

[0165] Where D is the third-order intermodulation nonlinear coefficient related to the transfer function of the tested radar.

[0166] Similar to in-band single-frequency interference signals, third-order intermodulation (TMI) interference signals can cause false alarms in the tested radar if their amplitude is sufficiently large and they are treated as useful signals. Generally, the ratio of the TMI false alarm signal level to the critical false alarm interference level F0 is defined as the TMI false alarm interference effect exponent R. F3 When R F3 Third-order intermodulation false alarm interference occurs when the value is ≥1. If the interference frequency is f i The false alarm sensitivity coefficient of the tested radar is B. Fi (f i Then, the level value of the third-order intermodulation false alarm signal can be expressed as:

[0167]

[0168] If the critical false alarm interference field strength of the single-frequency electromagnetic radiation of the tested radar is E Fi (f i The single-frequency critical false alarm level F0 is only related to the resolution of the tested radar, and the variation factors related to the interference frequency f are all included in the sensitivity coefficient B. Fi (f i In ), then:

[0169] A1B F1 E F1 =A2B F2 E F2 =…=A0B F0 E F0 =F0 (19)

[0170] Among them, A i To be compatible with the interference frequency f i The corresponding transfer function Ai (f i By taking the value of (16) to (19) and solving them simultaneously, we can obtain:

[0171]

[0172] Considering that the false alarm sensitive bandwidth of the tested radar is relatively narrow (generally narrower than its operating bandwidth), the signal transfer function A within the false alarm sensitive bandwidth is ignored. i (f i As the frequency changes, we can obtain the following from equation (19):

[0173] B F0 E F0 =B Ff E Ff (twenty one)

[0174] Among them B F0 B Ff and E F0 E Ff These are the false alarm sensitivity coefficient and critical false alarm interference field strength corresponding to the operating frequency f0 and the third-order intermodulation frequency f of the tested radar, respectively.

[0175] Introducing a third-order intermodulation false alarm interference factor α F The nonlinearity and false alarm sensitivity of the tested radar signal processing circuit are comprehensively described, α F The larger the value, the more severe the nonlinear distortion generated by the tested radar at the corresponding frequency, and the greater the probability of generating a third-order intermodulation false alarm interference effect in conjunction with other frequencies. Let:

[0176] α Fi (f i )=(F0 2 B F0 D) 1 / 3 / B Fi (f i ) (twenty two)

[0177] Substituting equations (21) and (22) into equation (20), the third-order intermodulation false alarm interference effect exponent R is obtained. F3 It can be represented as:

[0178]

[0179] If the frequencies of the third-order intermodulation signals generated by the three out-of-band interference signals with frequencies f1, f2, and f3 fall within the false alarm sensitive frequency band of the tested radar, the exponent R of the third-order intermodulation false alarm interference effect can be obtained similarly. F3 The expression for is:

[0180]

[0181] Equations (23) and (24) are respectively called the out-of-band dual-frequency and tri-frequency electromagnetic radiation third-order intermodulation false alarm interference effect models. From the derivation process, it can be seen that the third-order intermodulation false alarm interference factor α... Fi The operating frequency f0 of the tested radar and the frequency f of the jamming signal i This is relevant. Since the radar input signal is frequency-shifted to the intermediate frequency after local oscillator mixing for signal processing, as an engineering approximation, the third-order intermodulation false alarm interference factor α can be considered as... Fi Only with radiation frequency deviation Δf i =f i -f0 changes.

[0182] Improvement of model universality

[0183] Third-order intermodulation false alarm interference factor α Fi It is a fundamental property of the tested radar. Theoretical calculations or simulation analyses require the use of nonlinear parameters of relevant components and electromagnetic radiation false alarm sensitivity parameters of the tested radar, which is objectively difficult to achieve. However, based on the test data of the electromagnetic radiation critical false alarm interference effect of the tested radar, and according to the third-order intermodulation false alarm interference effect model (23) and (24), α can be calculated and determined through the critical false alarm effect test data. Fi .

[0184] Considering that the superposition of third-order intermodulation false alarm interference signals and single-frequency false alarm interference signals when they are close together may introduce significant errors to the false alarm interference level test, in order to improve the accuracy of the third-order intermodulation false alarm interference factor test, a higher critical false alarm interference level value F0 can be selected in the "linear region" where the false alarm interference level changes with the radiation field strength to conduct the critical false alarm interference effect test, and the third-order intermodulation false alarm interference factor α can be calculated. Fi At this point, the third-order intermodulation false alarm interference effect index is inversely proportional to the critical false alarm interference level. From equation (18), it can be seen that if the critical interference false alarm level is F during actual evaluation... S Therefore, the third-order intermodulation false alarm interference effect model of out-of-band dual-frequency and tri-frequency electromagnetic radiation should be modified to Equation (25) and Equation (26) to become a universal third-order intermodulation false alarm interference effect model:

[0185]

[0186]

[0187] (7) Based on the electromagnetic radiation interference spectrum of the working environment of the radar under test and the sensitive frequency offset range of the third-order intermodulation false alarm, select a single-frequency interference signal that is within the sensitive radiation frequency offset range of the third-order intermodulation - an interference signal that may generate a third-order intermodulation false alarm.

[0188] (8) In accordance with the principle that the third-order intermodulation frequency is within the single-frequency false alarm sensitive frequency band of the tested radar, select the combination of dual-frequency and three-frequency third-order intermodulation false alarm interference frequencies from the interference signals that may generate third-order intermodulation false alarms.

[0189] (9) Using the field strength and relevant model parameters of each dual-frequency and tri-frequency third-order intermodulation false alarm interference frequency combination, calculate R according to the universal third-order intermodulation false alarm effect model. FS3 R FS3 When ≥1, the tested radar exhibits third-order intermodulation false alarm interference under the combined jamming signal. FS3 When the value is less than 1, the tested radar will not experience third-order intermodulation false alarm interference.

[0190] (10) Based on the calculation results of the third-order intermodulation false alarm effect index of all interference frequency combinations, give the evaluation conclusion that the electromagnetic radiation combination that produces third-order intermodulation false alarm interference or the tested radar will not produce third-order intermodulation false alarm interference.

[0191] This invention also provides a radar out-of-band third-order intermodulation false alarm effect testing and prediction system, comprising:

[0192] The acquisition module is used to acquire the electromagnetic interference spectrum of the operating environment of the radar under test.

[0193] A single-frequency interference signal determination module is used to determine a single-frequency interference signal based on the interference spectrum and the third-order intermodulation false alarm sensitive frequency offset range; the single-frequency interference signal is a single-frequency interference signal that is within the third-order intermodulation false alarm sensitive frequency offset range.

[0194] The dual-frequency and tri-frequency third-order intermodulation false alarm interference frequency combination determination module is used to determine the dual-frequency and tri-frequency third-order intermodulation false alarm interference frequency combination based on the single-frequency interference signal and the single-frequency false alarm sensitive frequency band range of the tested radar.

[0195] The module for determining the third-order intermodulation false alarm interference effect index is used to determine the third-order intermodulation false alarm interference effect index based on the combination of dual-frequency and three-frequency third-order intermodulation false alarm interference frequencies using a universal third-order intermodulation false alarm effect model.

[0196] The module for determining the prediction result of third-order intermodulation false alarm interference is used to determine the prediction result of third-order intermodulation false alarm interference of the tested radar based on the third-order intermodulation false alarm interference effect index; the prediction result of third-order intermodulation false alarm interference of the tested radar is either the electromagnetic radiation frequency combination in which third-order intermodulation false alarm interference occurs or the tested radar will not experience third-order intermodulation false alarm interference.

[0197] As an optional implementation, the process for determining the sensitive frequency offset range of third-order intermodulation false alarm includes:

[0198] A single-frequency electromagnetic radiation false alarm effect test was conducted on the tested radar to determine the false alarm sensitivity level.

[0199] Based on the false alarm sensitivity level, a single-frequency electromagnetic radiation critical false alarm effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation false alarm sensitivity frequency offset range.

[0200] Based on the blocking sensitivity criterion, a single-frequency electromagnetic radiation critical blocking effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation blocking sensitivity frequency offset range.

[0201] Outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, select frequency points to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range.

[0202] As an optional implementation, frequency points outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range are selected to conduct dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range, specifically including:

[0203] Multiple fundamental frequency points are selected at equal frequency intervals outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range.

[0204] Dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests were conducted on multiple fundamental frequency points to determine the third-order intermodulation false alarm interference factor corresponding to each fundamental frequency point.

[0205] The variation law of the third-order intermodulation false alarm interference factor with radiation frequency offset is determined based on the third-order intermodulation false alarm interference factor.

[0206] The range of sensitive frequency offset for false alarms of the third-order intermodulation is determined based on the aforementioned variation pattern.

[0207] As an optional implementation, the process of determining the universal third-order intermodulation false alarm effect model includes:

[0208] The initial false alarm effect model is determined based on the third-order intermodulation false alarm interference mechanism.

[0209] The initial false alarm effect model is universally modified to obtain a universal third-order intermodulation false alarm effect model.

[0210] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0211] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for testing and predicting the false alarm effect of third-order intermodulation in radar out-of-band, characterized in that, include: Obtain the electromagnetic interference spectrum of the operating environment of the tested radar; The single-frequency interference signal is determined based on the interference spectrum and the third-order intermodulation false alarm sensitive frequency offset range; the single-frequency interference signal is a single-frequency interference signal that is within the third-order intermodulation false alarm sensitive frequency offset range. The frequency combinations of dual-frequency and tri-frequency third-order intermodulation false alarm interference are determined based on the single-frequency interference signal and the single-frequency false alarm sensitive frequency band of the tested radar. The third-order intermodulation false alarm interference effect index is determined using a universal third-order intermodulation false alarm effect model based on the frequency combination of dual-frequency and tri-frequency third-order intermodulation false alarm interference. The third-order intermodulation false alarm interference prediction result of the tested radar is determined based on the third-order intermodulation false alarm interference effect index; the third-order intermodulation false alarm interference prediction result of the tested radar is the electromagnetic radiation frequency combination that produces third-order intermodulation false alarm interference or the tested radar will not produce third-order intermodulation false alarm interference. The process of determining the sensitive frequency offset range for third-order intermodulation false alarms includes: A single-frequency electromagnetic radiation false alarm effect test was conducted on the tested radar to determine the false alarm sensitivity level; Based on the false alarm sensitivity level, a single-frequency electromagnetic radiation critical false alarm effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation false alarm sensitivity frequency offset range. Based on the blocking sensitivity criterion, a single-frequency electromagnetic radiation critical blocking effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation blocking sensitive frequency offset range. Outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, select frequency points to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range.

2. The method for testing and predicting the false alarm effect of third-order intermodulation in radar out-of-band according to claim 1, characterized in that, Outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, frequency points were selected to conduct dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range, specifically including: Multiple fundamental frequency points are selected at equal frequency intervals outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range; Dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests were conducted on multiple fundamental frequency points to determine the third-order intermodulation false alarm interference factor corresponding to each fundamental frequency point. The variation law of the third-order intermodulation false alarm interference factor with radiation frequency offset is determined based on the third-order intermodulation false alarm interference factor. The range of sensitive frequency offset for false alarms of the third-order intermodulation is determined based on the aforementioned variation pattern.

3. The method for testing and predicting the false alarm effect of third-order intermodulation in radar out-of-band according to claim 1, characterized in that, The process of determining a universal third-order intermodulation false alarm effect model includes: The initial false alarm effect model is determined based on the third-order intermodulation false alarm interference mechanism. The initial false alarm effect model is universally modified to obtain a universal third-order intermodulation false alarm effect model.

4. A radar out-of-band third-order intermodulation false alarm effect testing and prediction system, characterized in that, include: The acquisition module is used to acquire the electromagnetic interference spectrum of the operating environment of the radar under test; A single-frequency interference signal determination module is used to determine a single-frequency interference signal based on the interference spectrum and the third-order intermodulation false alarm sensitive frequency offset range; the single-frequency interference signal is a single-frequency interference signal that is within the third-order intermodulation false alarm sensitive frequency offset range. A dual-frequency and tri-frequency third-order intermodulation false alarm interference frequency combination determination module is used to determine the dual-frequency and tri-frequency third-order intermodulation false alarm interference frequency combination based on the single-frequency interference signal and the single-frequency false alarm sensitive frequency band range of the tested radar. The module for determining the third-order intermodulation false alarm interference effect index is used to determine the third-order intermodulation false alarm interference effect index based on the combination of dual-frequency and three-frequency third-order intermodulation false alarm interference frequencies using a universal third-order intermodulation false alarm effect model. The module for determining the prediction result of third-order intermodulation false alarm interference is used to determine the prediction result of third-order intermodulation false alarm interference of the tested radar based on the third-order intermodulation false alarm interference effect index; the prediction result of third-order intermodulation false alarm interference of the tested radar is either the electromagnetic radiation frequency combination in which third-order intermodulation false alarm interference occurs or the tested radar will not experience third-order intermodulation false alarm interference. The process of determining the sensitive frequency offset range for third-order intermodulation false alarms includes: A single-frequency electromagnetic radiation false alarm effect test was conducted on the tested radar to determine the false alarm sensitivity level; Based on the false alarm sensitivity level, a single-frequency electromagnetic radiation critical false alarm effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation false alarm sensitivity frequency offset range. Based on the blocking sensitivity criterion, a single-frequency electromagnetic radiation critical blocking effect test was conducted on the tested radar to determine the single-frequency electromagnetic radiation blocking sensitive frequency offset range. Outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, select frequency points to conduct dual-frequency and three-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range.

5. The radar out-of-band third-order intermodulation false alarm effect testing and prediction system according to claim 4, characterized in that, Outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range, frequency points were selected to conduct dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests to determine the third-order intermodulation false alarm sensitive frequency deviation range, specifically including: Multiple fundamental frequency points are selected at equal frequency intervals outside the single-frequency electromagnetic radiation blocking sensitive frequency deviation range; Dual-frequency and tri-frequency third-order intermodulation critical false alarm interference effect tests were conducted on multiple fundamental frequency points to determine the third-order intermodulation false alarm interference factor corresponding to each fundamental frequency point. The variation law of the third-order intermodulation false alarm interference factor with radiation frequency offset is determined based on the third-order intermodulation false alarm interference factor. The range of sensitive frequency offset for false alarms of the third-order intermodulation is determined based on the aforementioned variation pattern.

6. The radar out-of-band third-order intermodulation false alarm effect testing and prediction system according to claim 4, characterized in that, The process of determining a universal third-order intermodulation false alarm effect model includes: The initial false alarm effect model is determined based on the third-order intermodulation false alarm interference mechanism. The initial false alarm effect model is universally modified to obtain a universal third-order intermodulation false alarm effect model.

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