Reverse cross-eye jamming method of four-source non-uniform linear array based on flying carrier

Abstract

The present invention belongs to the field of radar electronic countermeasure technology, and discloses a four-source non-uniform linear array reverse cross-eye jamming method based on a flying carrier, which uses four non-uniformly distributed Archimedean spiral antennas to form a linear array antenna. The linear array antenna adopts a reverse structure to generate cross-eye interference in the narrow space of the flying carrier. The first step is to use the Archimedean spiral antenna as the cross-eye jammer antenna; the second step is to use a two-source reverse cross-eye jammer structure with a single antenna for transmitting and receiving in a single jamming loop; the third step is to determine the interference baseline ratio of the two jamming loops; the fourth step is to perform cross-eye interference on a single pulse radar in the normal direction. The present invention can effectively interfere with a single pulse angle measuring radar, provide effective protection for the penetration of small aircraft such as flying bodies and unmanned aerial vehicles, and provide support for the practical application of cross-eye jamming technology. Effective protection is formed for aircraft using accompanying interference, and the penetration capability of the aircraft is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of radar electronic countermeasures. Based on the narrow space available on a flying body, a four-source non-uniform linear array reverse cross-eye jamming method based on a flying carrier is proposed, which is mainly used for jamming the direction-finding performance of a single-pulse radar during penetration. Background Art

[0002] Precision-guided weapons have become the most important hard-kill weapons on the battlefield, and have huge advantages in penetrating aerial vehicles and attacking large surface facilities. In order to ensure the tracking and attack capabilities of aerial vehicles, it is necessary to effectively interfere with detection and tracking radars.

[0003] At present, single-pulse angle measurement technology has the advantages of high angle measurement accuracy and strong anti-interference ability, and is widely used in target tracking and other fields. Advanced tracking and guidance radars generally use single-pulse technology. Interference with single-pulse radar once became a research hotspot and difficulty in the field of electronic warfare. The main interference styles of single-pulse radar include towed decoy interference, cross-polarization interference and cross-eye interference. Among them, cross-eye interference is considered to be the most effective interference style for interfering with single-pulse radar. Cross-eye interference is an interference style that can effectively counter single-pulse angle measurement radar. It belongs to the coherent interference system and has the advantages of high reliability, short system response time, long effective interference time, and low life cycle cost. In recent years, it has received extensive attention from scholars at home and abroad.

[0004] Cross-eye jamming is to transmit two or more jamming signals with approximately equal amplitudes and a phase difference of 180°, which can cause the monopulse radar to deviate from the target or even cause the monopulse radar to lose tracking lock. Cross-eye jamming was first proposed in 1958. After more than half a century of development, it currently mainly includes two-source reverse cross-eye jamming and multi-source reverse cross-eye jamming. With the introduction of digital RF memory and reverse antenna arrays with self-phasing characteristics, cross-eye jamming technology has been realized in engineering applications.

[0005] At present, cross-eye jamming technology has been applied to the fields of ground-based radar anti-radiation flying body strike, aircraft target anti-monopulse radar detection, etc., and has played an effective role in protecting ground radars and aircraft. This is because ground-based radars and aircraft can provide an installation baseline length greater than 10m when used as carriers, which can meet the space requirements for the effective implementation of two-source cross-eye jamming. However, limited by the stringent parameter tolerance of traditional two-source cross-eye jamming technology, flying bodies such as drones, small aircraft, missiles and other small space carriers cannot achieve limited cross-eye jamming, which limits the application of cross-eye jamming technology. For example, when an aircraft is penetrating a monopulse detection radar, the cross-sectional diameter that can be used to arrange the cross-eye jamming equipment generally does not exceed 1m, which is far from meeting the use requirements of traditional two-source cross-eye jamming equipment. In view of the urgent needs of small flying body penetration applications, it is urgent to carry out research on cross-eye jamming technology with characteristics such as multi-source, short baseline, and non-uniform linear array distribution. The use of array antenna structure to increase the number of antenna pairs and improve the degree of freedom of cross-eye jamming can obtain greater gain than traditional two-source cross-eye jamming and reduce the demand for parameter tolerance. Non-uniform linear array distribution can obtain a larger cross-eye gain than uniform distribution when the number of sources is constant, thereby enhancing the interference effect. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention proposes a four-source non-uniform linear array reverse cross-eye jamming method for a single-pulse angle measuring radar based on a flying carrier.

[0007] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0008] A four-source non-uniform linear array reverse cross-eye jamming method based on a flying carrier is a four-source non-uniform linear array reverse cross-eye jamming method based on a flying carrier for a single pulse angle measurement radar. Four non-uniformly distributed Archimedean spiral antennas are used to form a linear array antenna. The linear array antenna adopts a reverse structure to generate cross-eye interference in the narrow space of the flying carrier. The steps are as follows:

[0009] Step 1: Use Archimedean spiral antenna as cross-eye jammer antenna;

[0010] The main problem faced in implementing cross-eye jamming in the narrow space of an aircraft platform is the layout of the cross-eye jammer antenna. The isolation requirements between antennas must be met to reduce mutual interference, and a larger interference loop baseline ratio must be achieved to obtain a large cross-eye jammer gain. The cross-eye jammer antenna uses an Archimedean spiral antenna in the 100MHz to 50GHz frequency band. It has wide bandwidth, circular polarization, small size, and is easy to install. It has a stable radiation pattern, axial ratio, and input impedance in the frequency band.

[0011] Step 2: A single jamming loop uses a two-source reverse cross-eye jammer structure with a single transmitting and receiving antenna;

[0012] Reverse cross-eye jammer refers to a cross-eye jammer with a reverse antenna structure. The reverse antenna array is composed of a number of paired antennas, and the signal is transmitted in two directions. The reverse antenna has a self-phasing characteristic, with two interference signals with approximately equal amplitudes and opposite phases, which can interfere with single-pulse radars.

[0013] The reverse antenna has the function of self-compensating the phase difference in the jamming loop that exceeds the system parameter tolerance. The use of a reverse antenna array is a necessary condition for the cross-eye jammer.

[0014] The four-source non-uniform linear array reverse cross-eye jammer has two jamming loops. A single jamming loop adopts a two-source reverse cross-eye jammer structure with a single transmitting and receiving antenna. The two jamming signals pass through the same transmitting and receiving antenna, circulator, and feeder. The power attenuation and phase delay introduced by the components and feeder do not affect the parameter matching between the two jamming signals. Therefore, the feeder length can be selected arbitrarily.

[0015] Step 3: Determine the interference baseline ratio of the two interference loops;

[0016] The interference loop baseline ratio refers to the ratio of the length of the interference loop 2 baseline to the interference loop 1 baseline, and the ratio is not greater than 1; the interference loop baseline ratio reflects the nonlinear distribution of the array elements in the linear array, and the four-source reverse cross-eye gain is:

[0017]

[0018] Among them, F2 is the interference loop baseline ratio; from the expression of cross-eye gain, the factor that affects the gain size is the interference loop baseline ratio; the baseline length of interference loop 2 can be arbitrarily selected within the total baseline length; for a two-source reverse cross-eye jammer, under the premise that other parameters remain unchanged, the longer the jammer antenna array baseline, the greater the angle measurement error of the single-pulse radar caused by the cross-eye interference, and the antenna of the jammer system is arranged on both sides of the wing or ship's side to maximize the antenna array baseline length; according to the cross-eye gain formula, under the condition of a certain signal amplitude-phase relationship, the larger the interference loop baseline ratio, the larger the cross-eye gain, and the two are in a linear relationship, and at this time the parameter tolerance of the jammer is looser;

[0019] For the Archimedean spiral antenna, the relationship between the antenna aperture and the operating frequency band is taken as d p =2.5λ, when kd>>1 is satisfied, the spacing requirement between the two antennas with sufficient isolation is obtained:

[0020]

[0021] Since the Archimedean spiral antenna is a circular antenna, the requirement of the above formula is understood as the distance between the edges of two adjacent antennas is greater than 10 times λ / (2π), so the minimum setting distance between the center points of adjacent antennas is:

[0022]

[0023] In order to reduce the mutual interference between antennas, take d min =3λ; Based on the obtained minimum antenna setting distance, three important conclusions are obtained:

[0024] The first is a flying carrier four-source non-uniform linear array reverse cross-eye jammer using Archimedean spiral antennas, with the minimum setting distance between adjacent antennas being three times the wavelength;

[0025] Second, the minimum application platform diameter of the flying carrier four-source linear array reverse cross-eye jammer using Archimedean spiral antenna is 9λ;

[0026] Third, the maximum interference baseline ratio used by the jammer is:

[0027]

[0028] Among them, d 2max is the longest baseline value used by interference loop 2, d c is the baseline length of the jammer antenna array, i.e. the baseline value of jammer loop 1;

[0029] Step 4: Perform cross-eye interference on the monopulse radar in the normal direction;

[0030] During the penetration phase of the aircraft, when it is illuminated by the single-pulse detection and tracking radar in the normal direction, the cross-eye jammer will interfere with it;

[0031] The four-source non-uniform linear array reverse cross-eye jammer requires that the two jamming signals have approximately equal amplitudes and opposite phases to effectively interfere with the single-pulse radar; controlling the amplitude ratio of the two jamming signals in the two jamming loops within the range of (0.8, 1.2) and the phase difference within the range of (170°, 190°) will cause errors in the phase sum and difference single-pulse radar angle measurement, and even lose lock on the target, making it impossible to provide accurate aircraft angle information and unable to effectively defend against incoming aircraft.

[0032] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0033] The present invention proposes a four-source non-uniform linear array reverse cross-eye jamming method for monopulse angle-measuring radar. By adopting a linear array antenna composed of four non-uniformly distributed Archimedean spiral antennas, the antenna adopts a reverse structure, and effective cross-eye jamming is achieved in a small space. The present invention can effectively interfere with monopulse angle-measuring radar, provide effective protection for small aircraft such as flying objects and drones, and provide support for the practical application of cross-eye jamming technology.

[0034] From the simulation results, it can be concluded that the four-source non-uniform linear array reverse cross-eye jammer of the flying vehicle can effectively interfere with the single-pulse angle-measuring radar and provide effective protection for the aircraft using accompanying jammers, which effectively improves the penetration capability of the aircraft and has important engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the aircraft structure.

[0036] Figure 2 It is a schematic diagram of a four-source non-uniform linear array reverse cross-eye jammer installed on the front cross section of an aircraft.

[0037] Figure 3 It is a schematic diagram of the single-antenna structure of a two-source reverse cross-eye jammer for transmission and reception.

[0038] Figure 4 The applicable scenario of the present invention is given, that is, a schematic diagram of a scenario in which an aircraft cross-eye jammer interferes with a single-pulse radar.

[0039] Figure 5 This is a graph showing the relationship between the cross-eye gain of a four-source reverse cross-eye jammer and the amplitude ratio of interference loop 2 when the parameters of interference loop 1 are typical values.

[0040] Figure 6 This is a graph showing the relationship between the cross-eye gain of a four-source reverse cross-eye jammer and the phase difference of interference loop 2 when the parameters of interference loop 1 are typical values.

[0041] Figure 7 This is a graph showing the relationship between the cross-eye gain of the missile-borne four-source non-uniform linear array reverse cross-eye jammer and the amplitude ratio of the interference loop 2 when the interference baseline ratio is 0.775 and the parameters of the interference loop 1 are typical values.

[0042] Figure 8 This is the relationship between the cross-eye gain of the missile-borne four-source non-uniform linear array reverse cross-eye jammer and the phase difference of interference loop 2 when the interference baseline ratio is 0.775 and the parameters of interference loop 1 are typical values.

[0043] Fig. 9This is a relationship diagram between the single-pulse radar angle measurement error, decoy distance and the amplitude ratio of interference loop 2 caused by the missile-borne four-source non-uniform linear array reverse cross-eye interference when the interference baseline ratio is 0.775 and the interference loop 1 parameters are typical values.

[0044] Fig.10 This is a graph showing the relationship between the single-pulse radar angle measurement error, decoy distance and the phase difference of interference loop 2 caused by the missile-borne four-source non-uniform linear array reverse cross-eye interference when the interference baseline ratio is 0.775 and the interference loop 1 parameters are typical values. DETAILED DESCRIPTION

[0045] The present invention will be further described below in conjunction with the accompanying drawings.

[0046] like Figures 1 to 10 As shown, a four-source non-uniform linear array reverse cross-eye jamming method based on a flying vehicle is a four-source non-uniform linear array reverse cross-eye jamming method for a single pulse angle measuring radar. Four non-uniformly distributed Archimedean spiral antennas are used to form a linear array antenna. The linear array antenna adopts a reverse structure to generate cross-eye interference in the narrow space of the aircraft. The steps are as follows:

[0047] Step 1: Use Archimedean spiral antenna as the cross-eye jammer antenna.

[0048] The main problem faced in realizing cross-eye interference in the narrow space of the aircraft penetration platform is the layout of the cross-eye jammer antenna. It is necessary to ensure the isolation requirements between antennas, reduce mutual interference, and ensure as large an interference loop baseline ratio as possible to obtain a large cross-eye interference gain. The Archimedean spiral antenna has the advantages of wide bandwidth, circular polarization, small size, and can be embedded in the frequency band of 100MHz to 50GHz. It has a stable radiation pattern, axial ratio and input impedance over a very wide frequency band. Therefore, the present invention adopts the Archimedean spiral antenna as the cross-eye jammer antenna of the flight carrier.

[0049] Step 2: A single jamming loop uses a two-source reverse cross-eye jammer structure with a single transmitting and receiving antenna.

[0050] A reverse cross-eye jammer refers to a cross-eye jammer that uses a reverse antenna structure. The reverse antenna array is composed of a number of paired antennas, and the signal can be transmitted in two directions. The reverse antenna has a self-phasing characteristic. It does not need to consider the phase difference in the interference signal propagation loop, nor does it need to obtain the radar position in advance. It only needs to ensure that the amplitudes of the two interference signals are approximately equal and the phases are inverted to effectively interfere with the single-pulse radar. Since the cross-eye jammer has very strict requirements on the amplitude ratio and phase difference tolerance of the system parameters, the reverse antenna can perfectly self-compensate for the phase difference in the interference loop that exceeds the system parameter tolerance. Therefore, the use of a reverse antenna array is a necessary condition for the cross-eye jammer to become practical.

[0051] The four-source non-uniform linear array reverse cross-eye jammer has two jamming loops, and a single jamming loop adopts a two-source reverse cross-eye jammer structure with a single transmitting and receiving antenna. The two jamming signals pass through the same transmitting and receiving antennas, circulators, and feeders. The power attenuation and phase delay introduced by the components and feeders do not affect the parameter matching between the two jamming signals, so the feeder length can be selected arbitrarily. This type of jammer has high requirements for the transmit and receive isolation of the circulator, but it is more suitable for practical applications due to its superior consistency characteristics.

[0052] Step 3: Determine the interference baseline ratio of the two interference loops.

[0053] The interference loop baseline ratio refers to the ratio of the length of the interference loop 2 baseline to the interference loop 1 baseline, and the ratio is not greater than 1. The interference loop baseline ratio reflects the nonlinear distribution of the array elements in the linear array, which will affect the interference performance of the cross-eye jammer. The four-source reverse cross-eye gain is:

[0054]

[0055] Among them, F2 is the interference loop baseline ratio. It can be seen from the expression of the cross-eye gain that the main factor affecting the gain size is the interference loop baseline ratio. The baseline length of the interference loop 2 can be arbitrarily set within the total baseline length. For a two-source reverse cross-eye jammer, under the premise that other parameters remain unchanged, the longer the baseline of the jammer antenna array, the greater the angle measurement error of the single-pulse radar caused by the cross-eye interference. This is also the reason why the jammer system usually arranges the antenna on both sides of the wing or ship's side to maximize the antenna array baseline length. According to the cross-eye gain formula, under the condition of a certain signal amplitude-phase relationship, the larger the interference loop baseline ratio, the larger the cross-eye gain, and the two are linearly related. At this time, the parameter tolerance of the jammer is looser.

[0056] For the Archimedean spiral antenna, the relationship between the antenna aperture and the operating frequency band is taken as d p =2.5λ, when kd>>1 is satisfied, the spacing requirement between the two antennas with sufficient isolation is obtained:

[0057]

[0058] Since the Archimedean spiral antenna is a circular antenna, in general, the requirement of the above formula can be understood as the distance between the edges of two adjacent antennas is greater than 10 times λ / (2π), so the minimum setting distance between the center points of adjacent antennas is:

[0059]

[0060] In order to facilitate theoretical analysis and practical application, and to fully reduce the mutual interference between antennas, d min=3λ. According to the obtained minimum antenna setting distance, three important conclusions can be drawn. First, the minimum setting distance between adjacent antennas of the missile-borne four-source non-uniform linear array reverse cross-eye jammer using Archimedean spiral antenna is 3 times the wavelength; second, the minimum application platform diameter of the missile-borne four-source linear array reverse cross-eye jammer using Archimedean spiral antenna is 9λ; third, the maximum interference baseline ratio that can be used by the jammer is:

[0061]

[0062] Among them, d 2max is the longest baseline value that can be used by interference loop 2, d c is the baseline length of the jammer antenna array, that is, the baseline value of interference loop 1.

[0063] Step 4: Perform cross-eye interference on the single-pulse radar in the normal direction.

[0064] During the penetration phase of the flying body, when it is illuminated by the single-pulse detection and tracking radar in the forward direction, the cross-eye jammer will interfere with it.

[0065] The four-source non-uniform linear array reverse cross-eye jammer designed by the present invention does not need to consider the phase difference in the jamming signal propagation loop, nor does it need to obtain the radar position in advance. It only needs to ensure that the amplitudes of the two jamming signals are approximately equal and the phases are inverted to effectively interfere with the monopulse radar. The amplitude ratio of the two jamming signals in the two jamming loops is controlled within the range of (0.8, 1.2), and the phase difference is controlled within the range of (170°, 190°), which will cause errors in the phase sum difference monopulse radar angle measurement, and even lose the target lock, and cannot provide accurate angle information of the flying object, and cannot effectively defend the flying object.

[0066] The electronic jamming equipment carried by this flying object has the ability of cross-eye jamming, which can effectively interfere with the opponent's detection radar, making it impossible for it to accurately detect the flying position or even lock onto the flying target.

[0067] like Figure 1 As shown, a schematic diagram of the structure of the flying body. The length of the flying body is generally about 4m, the wing width is 1 to 2m, and the diameter is generally within 1m. The cross-eye jammer can be set in two locations, one is the forward circular cross-section of the flying body, generally in the head antenna cover of the flying body, used to interfere with the radar in the front-facing direction; the other is the side of the flying body, used to interfere with the detection radar in the side-looking direction and the interceptor attacking from the side. For the first case, the present invention performs cross-eye interference on the single-pulse detection radar in the front-looking direction.

[0068] Figure 2Schematic diagram of a four-source non-uniform linear array reverse cross-eye jammer. The jammer includes two jamming loops with a total of four sources, and the feeder lengths of the two jamming loops are the same. The Archimedean spiral antenna is used as a single-receive and single-transmit antenna, and the four jammer antennas are distributed on the diameter of the cross-section of the flying body to obtain the maximum baseline length of the jamming loop 1.

[0069] Figure 3 This is a schematic diagram of the structure of a two-source reverse cross-eye jammer with a single antenna for transmission and reception. The single loop of the four-source non-uniform linear array reverse cross-eye jammer adopts the structure of a two-source reverse cross-eye jammer with a single antenna for transmission and reception. The two interference signals pass through the same transceiver antenna, circulator, and feeder. The power attenuation and phase delay introduced by the components and feeder will not affect the parameter matching between the two interference signals, so the feeder length can be selected arbitrarily. This type of structured jammer has high requirements for the transceiver isolation of the circulator, but it is more suitable for practical applications due to its superior consistency characteristics.

[0070] Figure 4 The scenario of a four-source non-uniform linear array reverse cross-eye jammer interfering with a phase-comparison monopulse radar is given. The jammer consists of four array elements. Antenna elements 1 and 4 form a pair of transmit and receive antennas, called interference loop 1, and antenna elements 2 and 3 form interference loop 2. The signal flow of interference loop 1 is as follows: the radar signal received by antenna element 1 is modulated and sent out by antenna element 4; the radar signal received by antenna element 4 is modulated and sent out by antenna element 1. The signal flow of interference loop 2 is the same. r is the distance from the center of the radar antenna to the center of the jammer, that is, the interference distance; d p is the phase comparison monopulse radar antenna aperture; θ r is the rotation angle of the radar axis relative to the center of the jammer, that is, the radar rotation angle; θ c is the rotation angle of the jammer relative to the center of the radar, that is, the jammer rotation angle; θ e is the half angle of the jammer antenna array relative to the radar line of sight; θ2 is the half angle of the jammer loop 2 relative to the radar line of sight; d c is the baseline length of the jammer antenna array; d2 is the element spacing of the jammer loop 2. To ensure the reverse structure of the antenna array, the feeder length of each loop is equal. Existing literature is basically based on the equal spacing of the array elements. However, it is difficult to ensure the equal spacing of the array elements in actual use. The non-uniformly distributed linear array has more practical application value. The single pulse radar adopts the sum and difference angle measurement system. The sum channel is used to transmit and receive signals, and the difference channel echo is normalized, while the difference channel is used to receive echoes and generate error signals.

[0071] The half angle θ of the antenna array relative to the radar line of sight e Given by the geometric relation:

[0072]

[0073] Considering that the cross-eye jammer is in the far field of the single pulse radar antenna, that is, r>>d c For cross-eye jammers, r≥1km,d c ≤5m, so the approximation in the above formula is reasonable. The half angles θ1 and θ2 of interference loops 1 and 2 relative to the radar line of sight are:

[0074]

[0075] Define the factor F2 = d2 / d c , is the interference loop baseline ratio, and its physical meaning is the ratio of the interference loop 2 baseline to the total baseline length of the antenna array, and F2≤1. The interference loop baseline ratio reflects the nonlinear distribution of the array elements in the linear array, which will affect the interference performance of the cross-eye jammer.

[0076] according to Figure 4 In the interference scenario shown in the figure, the angles between the radar line of sight and the two array elements 1 and 4 of the interference loop 1 are θ r ±θ1, then the phase monopulse radar sum channel and difference channel are at θ r The normalized gains in the ±θ1 directions are:

[0077]

[0078] Where P r is the radar antenna beam, P r (θ r ±θ1) is the radar beam at θ r The gain in the ±θ1 direction, β is the free space phase constant, β = 2π / λ, λ is the wavelength.

[0079] According to the trigonometric addition formula, we get:

[0080]

[0081] where k s1 With k c1 They are:

[0082]

[0083] Then the normalized sum channel and difference channel gains can be simplified to:

[0084]

[0085] Assuming that the amplitude ratio of the two direction signals in the interference loop 1 is a1 and the phase difference is φ1, the single pulse radar sum channel and difference channel echoes are:

[0086]

[0087] Where P c is the jammer antenna beam, at θ c The beam gain in the ±θ1 direction is P c (θ c ±θ1).

[0088] definition Substituting formula (14) into formula (15), we get:

[0089]

[0090] Where P1 = P r (θ r -θ1)P c (θ c -θ1)P r (θ r +θ1)P c (θ c +θ1).

[0091] When the two interference loops work simultaneously, the sum channel echo is:

[0092]

[0093] The total difference channel echo is:

[0094]

[0095] The single pulse processor uses the sum channel echo to normalize the difference channel echo, and the derived single pulse ratio is:

[0096]

[0097] in To calculate the imaginary part, This is the real part operation.

[0098] Single pulse indication angle θ i It can be obtained from the following relationship:

[0099]

[0100] When the monopulse radar tracks the target θ i =θ r ; When there is cross-eye interference θ i ≠θ r .

[0101] The cross-eye gain is an important indicator for measuring the angle measurement error. According to the trigonometric approximation in the literature, equation (19) can be simplified as follows:

[0102] cos(2kc1 )=cos[βd p cos(θ r )sin(θ e )]≈1 (21)

[0103] When θ e <<βd p When , the above approximation holds. At the same time, due to θ n ≤θ e 、r>>d c , the following approximation can also be made:

[0104]

[0105] Substituting equations (21) and (22) into equation (19), the single pulse ratio can be simplified as:

[0106]

[0107] in:

[0108]

[0109] The four-source reverse cross-eye gain is defined as:

[0110]

[0111] Because four array elements correspond to two interference loops, the gain is G c2 . Then the single pulse ratio can be expressed as:

[0112]

[0113] The first term of the single pulse ratio formula represents the beacon, indicating the true angle of the target, and the second term is the single pulse angle measurement error introduced by the cross-eye interference. It can be seen from formula (26) that the angle measurement error is proportional to the cross-eye gain G c2 and the interference antenna half angle θ e Related. e It is determined by the baseline length of the jammer antenna. After the baseline length is determined according to the use requirements, θ e is a fixed value. Therefore, the angle measurement error depends on the cross-eye gain. When the number of array elements is 2, the cross-eye gain is the same as that of the two-source reverse cross-eye interference, and the famous traditional cross-eye interference usage conditions are obtained: the amplitudes of the two interference signals are approximately equal and the phases are opposite.

[0114] Figure 5 This is the relationship between the cross-eye gain of the four-source reverse cross-eye jammer and the amplitude ratio of the interference loop 2 when the parameters of the interference loop 1 are typical values. Figure 6This is a graph showing the relationship between the cross-eye gain of a four-source reverse cross-eye jammer and the phase difference of interference loop 2 when the parameters of interference loop 1 are typical values. Figure 5 and Figure 6 The variation law of the gain of the uniformly distributed four-source linear array reverse cross-eye jammer with the two sets of amplitude ratio phase differences (a1, φ1) and (a2, φ2) of the two jamming loops is given, and compared with the gain of the traditional two-source cross-eye jammer under the same conditions. Figure 5 This is a partial enlargement. Because the maximum value of the cross-eye gain corresponding to the (1,185°) curve is too large, the other curves are too small to be observed. For the convenience of calculation and representation, the signal amplitude ratio and cross-eye gain in the figure are both multiple values, and the dB form is not used. Two important conclusions can be drawn from the figure. First, the cross-eye gain of the four-source cross-eye jammer is significantly greater than that of the traditional two-source cross-eye jammer, indicating that the interference intensity of the four-source cross-eye jammer is greater than that of the two-source cross-eye jammer; second, the parameter tolerance of the four-source cross-eye jammer is better than that of the traditional two-source cross-eye jammer, and the interference parameters can be set in a wider range, and the amplitude-phase relationship requirements of the interference antenna signal are no longer as harsh as before. The above two characteristics make the four-source cross-eye jammer more suitable for practical applications than the traditional two-source cross-eye jammer, and the interference effect on single-pulse radar is better.

[0115] Figure 5 , Figure 6 The paper adopts a uniformly distributed four-source linear array reverse cross-eye jammer. The simulation results show that its jamming effect is better than the traditional two-source cross-eye jammer, and the parameter configuration is more flexible and convenient, indicating that the four-source cross-eye jammer has important practical application value. However, the uniform distribution condition is relatively harsh for the carrier platform, especially the flying body, and it is difficult to strictly guarantee it in the actual design. At the same time, the uniformly distributed linear antenna structure is not the best antenna structure for the multi-source linear cross-eye jammer. Therefore, it is necessary to deeply analyze the influence of the antenna distribution structure of the four-source linear cross-eye jammer on the jammer's jamming characteristics, that is, the influence of the jamming loop baseline ratio on the cross-eye jamming characteristics.

[0116] Figure 7 This is the relationship between the cross-eye gain of the four-source non-uniform linear array reverse cross-eye jammer and the amplitude ratio of the interference loop 2 when the interference baseline ratio is 0.775 and the parameters of the interference loop 1 are typical values. Figure 8This is the relationship between the cross-eye gain of the four-source non-uniform linear array reverse cross-eye jammer and the phase difference of the interference loop 2 when the interference baseline ratio is 0.775 and the parameters of the interference loop 1 are typical values. It can be seen from the expression of the cross-eye gain that the main factor affecting the gain size is the interference loop baseline ratio. The baseline length of the interference loop 2 can be arbitrarily set within the total baseline length. For a two-source reverse cross-eye jammer, under the premise that other parameters remain unchanged, the longer the jammer antenna array baseline, the greater the angle measurement error of the single pulse radar caused by the cross-eye interference. This is also the reason why the jammer system usually arranges the antenna on both sides of the wing or ship's side to maximize the antenna array baseline length. According to the cross-eye gain formula, under the condition of a certain signal amplitude-phase relationship, the larger the interference loop baseline ratio, the larger the cross-eye gain, and the two are linearly related. At this time, the parameter tolerance of the jammer is looser.

[0117] The main problem faced in realizing cross-eye interference in the narrow space of the aircraft platform is the layout of the cross-eye antenna. It is necessary to ensure the isolation requirements between antennas, reduce mutual interference, and ensure the largest possible interference loop baseline ratio to obtain a large cross-eye interference gain. Assuming that the distance between the two antennas is d, when kd>>1 is satisfied, it can be considered that the two antennas have sufficient isolation, where k=2π / λ is the wave number. Taking the Archimedean spiral antenna as an example for analysis, it has the advantages of wide bandwidth, circular polarization, small size, and can be embedded in the frequency band of 100MHz to 50GHz. It has a stable radiation pattern, axial ratio and input impedance over a very wide frequency band.

[0118] The relationship between the antenna aperture and the operating frequency band is taken as d p =2.5λ, when kd>>1 is satisfied, the spacing requirement between the two antennas with sufficient isolation is obtained:

[0119]

[0120] Since the Archimedean spiral antenna is a circular antenna, in general, the requirement of formula (27) can be understood as the distance between the edges of two adjacent antennas is greater than 10 times λ / (2π), so the minimum setting distance between the center points of adjacent antennas is:

[0121]

[0122] In order to facilitate theoretical analysis and practical application, and to fully reduce the mutual interference between antennas, d min =3λ. According to the obtained minimum antenna setting distance, three important conclusions can be drawn. First, the minimum setting distance between adjacent antennas of the four-source non-uniform linear array reverse cross-eye jammer using Archimedean spiral antennas is 3 times the wavelength; second, the minimum application platform diameter of the four-source linear array reverse cross-eye jammer using Archimedean spiral antennas is 9λ; third, the maximum interference baseline ratio that can be used by the jammer is:

[0123]

[0124] Among them, d 2max is the longest baseline value that can be used by interference loop 2, d c is the baseline length of the jammer antenna array, that is, the baseline value of interference loop 1.

[0125] The length of the aircraft is about 4m, the wing width is 1-2m, and the diameter is within 1m. The baseline length d of the jammer antenna array is set in the simulation c The working wavelength of the jammer is λ = 0.03m. The distance between the cross-eye jammer and the single-pulse radar is 1km. The jammer and the radar are facing each other. r =θ c =0°. Under this condition, the maximum interference baseline ratio F of the jammer can be calculated. 2max =(d c -6λ) / d c =0.775.

[0126] Figure 7 and Figure 8 The relationship curve between the cross-eye gain and the interference loop 2 parameters (a2, φ2) is given under 15 typical interference loop 1 parameters (a1, φ1) when the interference baseline ratio is 0.775. It can be seen from the figure that near the ideal parameter conditions of equal amplitude and reverse direction, the cross-eye gain is large and the cross-eye interference effect is obvious. In the wide parameter range of amplitude ratio (0.8, 1.2) and phase difference (170°, 190°), the cross-eye gain is basically more than 10 times, indicating that the parameter tolerance of the four-source non-uniform linear array reverse cross-eye jammer is relatively loose, which is convenient for practical engineering applications. Figure 5 , Figure 6 Comparing the cross-eye gain performance curves of the uniformly distributed cross-eye jammer, it can be seen that when the baseline ratio is 0.775, under the same amplitude ratio and phase difference conditions, the value of the cross-eye gain becomes larger and the cross-eye jamming effect is enhanced.

[0127] Fig. 9 This is the relationship between the single pulse radar angle measurement error, decoy distance and the amplitude ratio of interference loop 2 caused by the four-source non-uniform linear array reverse cross-eye interference when the interference baseline ratio is 0.775 and the interference loop 1 parameters are typical values. Fig.10 This is a relationship diagram between the single-pulse radar angle measurement error, decoy distance and the phase difference of interference loop 2 caused by the four-source non-uniform linear array reverse cross-eye interference when the interference baseline ratio is 0.775 and the parameters of interference loop 1 are typical values. Fig. 9 and Fig.10The single pulse radar angle measurement error and decoy distance caused by the four-source non-uniform linear array reverse cross-eye jammer of the present invention are given. It can be seen from the figure that within the larger parameter tolerance range of amplitude ratio (0.8, 1.2) and phase difference (170°, 190°), cross-eye interference can cause the single pulse radar angle measurement error to reach more than 0.5° and the decoy distance to reach more than 8.7m. For a flying object with a diameter generally within 1m, the protection effect brought by cross-eye interference is very significant.

Claims

1. A four-source non-uniform linear array reverse cross-eye jamming method based on a flying carrier, characterized by: Based on the four-source non-uniform linear array reverse cross-eye jamming method for single-pulse angle-measuring radar of the flying carrier, four non-uniformly distributed Archimedean spiral antennas are used to form a linear array antenna. The linear array antenna adopts a reverse structure to generate cross-eye jamming in the narrow space of the flying carrier. The steps are as follows: Step 1: Use Archimedean spiral antenna as cross-eye jammer antenna; The main problem faced in implementing cross-eye jamming in the narrow space of an aircraft platform is the layout of the cross-eye jammer antenna. The isolation requirements between antennas must be met to reduce mutual interference, and a larger interference loop baseline ratio must be achieved to obtain a large cross-eye jammer gain. The cross-eye jammer antenna uses an Archimedean spiral antenna in the 100MHz to 50GHz frequency band. It has wide bandwidth, circular polarization, small size, and is easy to install. It has a stable radiation pattern, axial ratio, and input impedance in the frequency band. Step 2: A single jamming loop uses a two-source reverse cross-eye jammer structure with a single transmitting and receiving antenna; Reverse cross-eye jammer refers to a cross-eye jammer with a reverse antenna structure. The reverse antenna array is composed of a number of paired antennas, and the signal is transmitted in two directions. The reverse antenna has a self-phasing characteristic, with two interference signals with approximately equal amplitudes and opposite phases, which can interfere with single-pulse radars. The reverse antenna has the function of self-compensating the phase difference in the jamming loop that exceeds the system parameter tolerance. The use of a reverse antenna array is a necessary condition for the cross-eye jammer. The four-source non-uniform linear array reverse cross-eye jammer has two jamming loops. A single jamming loop adopts a two-source reverse cross-eye jammer structure with a single transmitting and receiving antenna. The two jamming signals pass through the same transmitting and receiving antenna, circulator, and feeder. The power attenuation and phase delay introduced by the components and feeder do not affect the parameter matching between the two jamming signals. Therefore, the feeder length can be selected arbitrarily. Step 3: Determine the interference baseline ratio of the two interference loops; The interference loop baseline ratio refers to the ratio of the length of the interference loop 2 baseline to the interference loop 1 baseline, and the ratio is not greater than 1; the interference loop baseline ratio reflects the nonlinear distribution of the array elements in the linear array, and the four-source reverse cross-eye gain is: Where, F2 is the interference loop baseline ratio; is the real part operation; the amplitude ratio of the two direction signals in the interference loop 1 is a1, and the phase difference is φ1; definition A2 is defined as follows: the amplitude ratio of the two direction signals in interference loop 2 is a2, and the phase difference is From the expression of cross-eye gain, the factor that affects the gain size is the interference loop baseline ratio; the baseline length of interference loop 2 can be arbitrarily set within the total baseline length; for a two-source reverse cross-eye jammer, under the premise that other parameters remain unchanged, the longer the jammer antenna array baseline, the greater the angle measurement error of the single-pulse radar caused by the cross-eye interference, and the antenna of the jammer system is arranged on both sides of the wing or ship's side to maximize the antenna array baseline length; according to the cross-eye gain formula, under the condition of a certain signal amplitude-phase relationship, the larger the interference loop baseline ratio, the larger the cross-eye gain, and the two are in a linear relationship, and at this time the parameter tolerance of the jammer is looser; For the Archimedean spiral antenna, the relationship between the antenna aperture and the operating frequency band is taken as d p =2.5λ, when kd>>1 is satisfied, the spacing requirement between the two antennas with sufficient isolation is obtained: The parameter k = 2π / λ is the wave number; λ is the wavelength; Since the Archimedean spiral antenna is a circular antenna, the requirement of the above formula is understood as the distance between the edges of two adjacent antennas is greater than 10 times λ / (2π), so the minimum setting distance between the center points of adjacent antennas is: In order to reduce the mutual interference between antennas, take d min =3λ; Based on the obtained minimum antenna setting distance, three important conclusions are obtained: The first is a flying carrier four-source non-uniform linear array reverse cross-eye jammer using Archimedean spiral antennas, with the minimum setting distance between adjacent antennas being three times the wavelength; Second, the minimum application platform diameter of the flying carrier four-source linear array reverse cross-eye jammer using Archimedean spiral antenna is 9λ; Third, the maximum interference baseline ratio used by the jammer is: Among them, d 2max is the longest baseline value used by interference loop 2, d c is the baseline length of the jammer antenna array, i.e. the baseline value of jammer loop 1; Step 4: Perform cross-eye interference on the monopulse radar in the normal direction; During the penetration phase of the aircraft, when it is illuminated by the single-pulse detection and tracking radar in the normal direction, the cross-eye jammer will interfere with it; The four-source non-uniform linear array reverse cross-eye jammer requires that the two jamming signals have approximately equal amplitudes and opposite phases to effectively interfere with the single-pulse radar; controlling the amplitude ratio of the two jamming signals in the two jamming loops within the range of (0.8, 1.2) and the phase difference within the range of (170°, 190°) will cause errors in the phase sum and difference single-pulse radar angle measurement, and even lose lock on the target, making it impossible to provide accurate aircraft angle information and unable to effectively defend against incoming aircraft.

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