A cognitive polarization emission anti-interference method

Abstract

The present invention discloses a method for cognitive polarization transmission anti-interference, which is to use the radar transmitting end to transmit signals in a polarization mode orthogonal to the interference polarization, and obtain the polarization angle pattern in the process of suppressing forwarding interference; then, based on the mathematical relationship between the interception distance and the amplitude of the signal received by the jammer, the polarization angle pattern and the amplitude loss, the interception distance after the polarization optimization of the radar transmitting end is obtained. The present invention changes the polarization of the radar transmitting end through the polarization angle information of the polarization-aware forwarding interference, so that it is orthogonal to the interference polarization, reducing the energy of the radar signal received by the jammer, and the interception distance will be reduced. Because forwarding interference must detect the radar signal before it can be implemented, when the radar is in the optimal transmission polarization, the forwarding interference can be completely suppressed. The present invention can make full use of the radar's transmission polarization information and can significantly improve the radar's anti-interference performance.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and in particular relates to a cognitive polarization transmission anti-interference method suitable for adaptively suppressing forwarding interference. Background Art

[0002] In recent years, the electromagnetic environment facing radar has become increasingly complex and severe. Therefore, how to mine and utilize radar's electromagnetic information to improve its anti-interference performance and survivability in the face of various types of interference, enabling it to better adapt to complex and changing electromagnetic environments, has become a pressing issue facing radar technology. With the increasing understanding and utilization of polarization information, polarization anti-interference technology has gradually become a hot topic in radar technology development.

[0003] Traditional polarization-domain anti-interference technology primarily relies on polarization filtering at the radar receiver. Polarization filtering, in essence, suppresses interference by adaptively adjusting weights based on the cross-correlation between polarization channels. This approach doesn't utilize the polarization of the radar transmitter, resulting in only one interference source being suppressed, limiting the radar's anti-interference capabilities. Summary of the Invention

[0004] To address the shortcomings of the aforementioned prior art, the present invention develops a polarization-aware transmission anti-interference method suitable for adaptively suppressing repeater interference. Polarization countermeasure performance can be evaluated using interception range. A smaller interception range reduces the probability of intercept, improves LPI performance, and ultimately enhances the radar's anti-interference performance. Furthermore, by fully utilizing radar transmit polarization information, this method lays a solid foundation for successful multi-interference countermeasures for subsequent radars.

[0005] The present invention provides a method for cognitive polarization transmission anti-interference, comprising:

[0006] Step 1: The radar transmitter transmits a signal in a polarization mode orthogonal to the interference polarization, and obtains a polarization angle pattern used to describe the selectivity of the polarization filter to the incident signal polarization in the process of suppressing forwarding interference;

[0007] Step 2, determine the mathematical relationship between the interception range and the amplitude of the signal received by the jammer;

[0008] Step 3: Obtain null depths corresponding to different interference polarization angles according to the polarization angle pattern obtained in step 1, and transform the null depths to obtain the amplitude loss of the signal received by the jammer;

[0009] Step 4, obtaining the interception distance after polarization optimization at the radar transmitter according to the mathematical relationship between the interception distance and the amplitude of the signal received by the jammer and the amplitude loss;

[0010] Step 5: Based on the optimized interception distance, evaluate the interference suppression performance of the radar transmitter when transmitting a signal in a polarization mode orthogonal to the interference polarization.

[0011] Beneficial effects of the present invention:

[0012] The present invention provides a method for cognitive polarization transmission anti-interference, which effectively suppresses interference by adjusting the polarization mode of the radar transmitter to be orthogonal to the interference polarization. The interception distance can be used as an evaluation indicator of polarization countermeasure performance, so the present invention combines the error histogram of the polarization angle and the polarization direction diagram to obtain a corresponding histogram of the interception distance. Because forwarding interference must detect the radar signal before it can be implemented, when the radar is in the optimal transmission polarization, forwarding interference can be completely suppressed. This method can make full use of the radar's transmission polarization information, lay the foundation for the radar to successfully suppress two interferences, and can significantly improve the radar's anti-interference performance.

[0013] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a flow chart of a method for cognitive polarization transmission anti-interference according to the present invention;

[0015] Figure 2 The incident antenna polarization ellipse and the receiving antenna polarization ellipse form a polarization orthogonal state diagram;

[0016] Figure 3 is the polarization pattern of the radar at the best transmitting polarization;

[0017] Figure 4 This is the interception distance histogram when the interference to noise ratio is 50dB;

[0018] Figure 5 The histogram shows that the interception distance becomes a multiple of the original interception distance when the interference to noise ratio is 50dB;

[0019] Figure 6 The probability distribution diagram of the interception distance becoming a multiple of the original interception distance when the interference to noise ratio is 50dB;

[0020] Figure 7 The probability distribution diagram of the interception distance becoming a multiple of the original interception distance when the interference to noise ratio is 10dB;

[0021] Figure 8 This is the probability distribution diagram of the interception distance becoming a multiple of the original interception distance when the interference to noise ratio is 30dB. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0023] The basic idea of ​​this invention is to adjust the radar's transmit polarization to be orthogonal to the forwarding jammer's polarization. When the jammer's polarization angle sensing results are completely error-free, the jammer will essentially fail to intercept the radar's transmitted signal and, therefore, will not interfere. However, in practice, the jammer's polarization angle estimated by jammer polarization sensing will always have some error. In this case, the error histogram of the estimated polarization angle and the polarization pattern can be combined to produce a probability distribution of the interception distance becoming a multiple of the original interception distance, indicating the probability of the radar successfully countering the jammer.

[0024] Example 1

[0025] refer to Figure 1 As shown, the present invention provides a method for cognitive polarization transmission anti-interference, including:

[0026] Step 1: The radar transmitter transmits a signal in a polarization mode orthogonal to the interference polarization, and obtains a polarization angle pattern used to describe the selectivity of the polarization filter to the incident signal polarization in the process of suppressing forwarding interference;

[0027] Step 2, determine the mathematical relationship between the interception range and the amplitude of the signal received by the jammer;

[0028] Step 3: Obtain null depths corresponding to different interference polarization angles according to the polarization angle pattern obtained in step 1, and transform the null depths to obtain the amplitude loss of the signal received by the jammer;

[0029] Step 4, obtaining the interception distance after polarization optimization at the radar transmitter according to the mathematical relationship between the interception distance and the amplitude of the signal received by the jammer and the amplitude loss;

[0030] Step 5: Based on the optimized interception distance, evaluate the interference suppression performance of the radar transmitter when transmitting a signal in a polarization mode orthogonal to the interference polarization.

[0031] The present invention provides a method for cognitive polarization transmission anti-interference, which effectively suppresses interference by adjusting the polarization mode of the radar transmitter to be orthogonal to the interference polarization. The polarization angle pattern is obtained using the actual polarization angle of the interference. By combining the error histogram of the estimated polarization angle and the polarization pattern, a histogram of the corresponding interception distance can be obtained. Because forwarding interference must detect radar signals before it can be implemented, forwarding interference can be completely suppressed when the radar is in the optimal transmission polarization. This method can fully utilize the radar's transmission polarization information, laying the foundation for the radar to successfully suppress two interferences, and can significantly improve the radar's anti-interference performance.

[0032] Example 2

[0033] As an optional embodiment of the present invention, step 1 includes:

[0034] Step 1.1: The radar transmitter transmits signals in a polarization mode orthogonal to the interference polarization, thereby suppressing the forwarding interference and obtaining the true polarization angle of the interference during the forwarding interference suppression process.

[0035] The polarization pattern is used to describe the selectivity of a polarization filter to the polarization of the incident signal. Its concept is similar to the concept of an array antenna pattern in spatial domain processing.

[0036] Step 1.2, obtain the optimal transmit polarization state of the radar under the interference background according to the real polarization angle of the interference;

[0037] The actual polarization angle of the forwarding interference is θ J (0≤θ J ≤90), the polarization state is represented by the Jones vector H J , the radar's transmit polarization is set to H t , the power coefficient of the radar signal received by the jammer is H t T H J When the radar transmit polarization and the interference polarization are orthogonal to each other, the coefficient is equal to 0. The transmit polarization at this time is called the optimal transmit polarization of the radar under the interference background, which is recorded as H t,opt This is also called the polarization orthogonal state. This polarization orthogonal state can be described by the polarization ellipse of the incident antenna and the polarization ellipse of the receiving antenna. If the major and minor axes of these two polarization ellipses overlap and have the same rotation direction, this is the polarization orthogonal state, such as Figure 2 shown.

[0038] The optimal transmit polarization state of the radar is expressed by the Jones vector:

[0039]

[0040] in, Represent the polarization angles of the horizontal and vertical linear polarization receiving antennas respectively;

[0041] gather The polarization angle grid formed covers all possible polarization angle directions; let

[0042]

[0043] Step 1.3: Obtain the corresponding polarization angle pattern based on the radar's optimal transmit polarization state.

[0044] Then the polarization angle pattern described in step 1.3 can be expressed by the following formula:

[0045] p(θ)=|H t,opt ·A|.

[0046] This invention refers to p(θ) as a function of the polarization angle pattern, reflecting the polarization filter's selectivity for incoming wave polarization. From the polarization angle pattern expression p(θ), it can be seen that when the radar is in optimal transmit polarization, the polarization pattern will form a null at the polarization angle where the forwarding interference occurs. Therefore, if a linearly polarized antenna array is to have different effects on interference at different polarization angles in space, this can be achieved by changing the polarization state of the radar transmitter and, therefore, the array pattern.

[0047] By establishing the polarization angle pattern, the polarization angle pattern is transformed into the best transmitting polarization H of the radar. t,opt The parameters are expressed, laying the foundation for the subsequent evaluation of polarization countermeasure performance.

[0048] Example 3

[0049] As an optional embodiment of the present invention, step 2 includes:

[0050] Step 2.1: After determining the polarization state of the radar transmitter, the power relationship between the signal power that the jammer can receive and the interception distance from the radar to the jammer, the gain of the radar antenna in the direction of the jammer, and the gain of the jammer antenna;

[0051] Step 2.2, determine the peak power of the transmitted signal based on the power relationship, and determine the mathematical relationship between the interception distance and the amplitude of the signal received by the jammer based on the relationship between the amplitude of the signal received by the jammer and the total energy of the transmitted signal, and the total energy and the peak power.

[0052] When discussing the definition of intercept range, we should first understand the concept of radar low probability of intercept (LPI). Currently, there are two more formal definitions related to LPI radar: Definition (1): A radar that transmits a special waveform to prevent non-cooperative interception receivers from intercepting and detecting the radar's transmitted signal is also called a low probability of intercept (LPI) radar; Definition (2): A radar that transmits a special waveform to prevent non-cooperative interception receivers from intercepting and detecting the radar's transmitted signal. Even if there is a probability of interception, the parameters and modulation method of the radar's transmitted waveform are difficult to identify. This can be called a low probability of identification (LPID) radar.

[0053] From the two definitions above, it can be seen that the primary concern of LPI is that the radar transmission waveform is difficult to intercept. Therefore, the LPI radar transmission waveform should focus on minimizing the probability of the opponent's jamming equipment detecting the radar's own signal. In other words, the radar should have strong anti-interference performance.

[0054] Known technologies that can effectively improve LPI performance include pulse compression technology, selecting large time-bandwidth product signals for transmission, using low-gain transmitting antennas and high-gain receiving antennas, reducing the peak power of radar transmission signals and reducing the side lobes of antenna radiation patterns, etc. However, the core issue at present is the optimization design of radar transmission power.

[0055] The design of radar transmit waveforms and the development of modern jammers in implementing high-powered jamming are in a race to the bottom, mutually reinforcing and increasing their capabilities. Any improvement in jammer detection, interception, and parameter estimation of radar transmit signals will drive radar researchers to further refine radar transmit waveform design. To measure radar LPI performance, the maximum range at which a jammer can receive radar transmit signals, also known as the interception range, should be considered.

[0056] To measure interception range, one needs to understand the operating principle of radar. Radar is an electromagnetic system primarily used to detect and locate perceptible natural environments. Aircraft, ships, spacecraft, and vehicles are equipped with radar. Radar radiates electromagnetic energy through its antenna. When it detects the presence of a target, it uses a threshold to determine the echo of the received target signal. A monostatic radar uses a single antenna, which uses time-division multiplexing for both transmission and reception. A bistatic radar uses separate transmitting and receiving antennas. Monostatic radar is the most commonly used mode of modern radar. The operating principle of monostatic radar is as follows: After transmitting a pulse, the monostatic radar antenna switches from transmit mode to receive mode via a duplexer to receive the incoming reflected pulse.

[0057] The radar system primarily consists of a radar transmitter, a radar antenna, a radar receiver, a data processing unit for parameter extraction and target detection, and other auxiliary equipment. The radar transmitter generates a radar transmission signal waveform (RTSW) that meets certain requirements. This signal is then radiated from the transmitting antenna via a feeder and transceiver switch. Upon encountering a target, a portion of the electromagnetic wave is reflected back, then travels through the receiving antenna and transceiver switch to the radar receiver. The radar data processing unit then processes the echo signal to obtain relevant information. In short, radar can use electromagnetic waves to determine the presence, distance, and speed of a target.

[0058] Due to the presence of an enemy jammer, the radar will also receive interference through its receiving antenna. The jammer will then radiate electromagnetic waves to the radar, jamming it and obscuring the target signal. For repeater jammers, they must first detect the radar's transmitted signal before radiating the jamming signal. These jammers intercept radar signals using the most direct and common method: detecting the peak power of the radar signal. Therefore, minimizing the peak power of the radar signal received by the jammer is a key measure for achieving Low Power Precision Index (LPI). To achieve LPI, repeater jammers and the polarization information of the radar's transmitting antenna are used to reduce the signal energy received by the jammer. This reduces the probability of interception and the interception range, resulting in better LPI performance and significantly improving the radar's anti-interference capabilities. The following describes the derivation of the interception range.

[0059] After the radar transmits the signal, the power of the signal that the jammer can receive is:

[0060]

[0061] Among them, P t is the transmission power of the radar transmitter, R I is the distance from the radar to the jammer; G1 is the gain of the radar antenna in the direction of the jammer, G2 is the gain of the jammer antenna, and L I is the loss factor of the jammer, and λ is the wavelength used;

[0062] Let P I =δ I , we can get the maximum interception distance that the jammer can detect:

[0063]

[0064] Among them, the δ I is the sensitivity of the jammer, is the minimum input signal power that the jammer can detect;

[0065] In this paper, by studying the working principle of radar and the principle of jammer intercepting radar signals, a formula for the maximum interception distance that the jammer can detect is given. The interception distance can be used to evaluate the anti-interference performance of cognitive polarization transmission.

[0066] With the polarization angle pattern corresponding to the radar's optimal transmit polarization state, we can derive the null depths corresponding to different jamming polarization angles. Obviously, the smaller the polarization angle estimation error, the larger the corresponding null depth. Transforming the null depth using the formula yields the amplitude loss of the signal received by the jammer.

[0067] The expression of the peak power of the transmitted signal is:

[0068] P t =E / T;

[0069] Wherein, E is the total energy of the transmitted signal, T is the pulse width; the amplitude of the signal received by the jammer is A r ,

[0070] E∝P t

[0071]

[0072]

[0073] The mathematical relationship between the interception distance and the signal amplitude received by the jammer is expressed as: R I ∝A r , ∝ means proportional. Let the estimated polarization angle be θ est , due to 20log 10 2≈6dB, that is, 6dB means double, so the amplitude loss of the signal received by the jammer is A loss for:

[0074]

[0075] Among them, the estimated polarization angle value is θ est In practice, the polarization angle value obtained is θ, so the amplitude loss of the signal received by the jammer is A loss Expressed as:

[0076]

[0077] Obviously, for repeater jamming, the amplitude loss of the signal received by the jammer is A. loss The larger it is, the smaller the amplitude of the corresponding received signal is, the lower the probability of the jammer intercepting the radar signal is, and the better the radar's anti-interference performance is.

[0078] The mathematical relationship between the interception distance and the amplitude of the signal received by the jammer shows that the interception distance is directly proportional to the amplitude of the signal received by the jammer. That is, the smaller the amplitude of the signal received by the jammer, the smaller the interception distance, the lower the probability of interception, and the better the radar LPI performance. In this case, the jammer needs to be closer to the radar to have a jamming effect. It is easy to see that the amplitude of the signal received by the jammer is inversely proportional to the amplitude loss of the signal received by the jammer. Therefore, the interception distance is inversely proportional to the amplitude loss of the signal received by the jammer.

[0079] Assume the original interception distance is R pre, from the analysis of steps 3 and 4, we can get the relationship between the null depth (amplitude loss of the signal received by the jammer) and the interception distance obtained after the radar transmit polarization optimization:

[0080]

[0081] Among them, R pre It is the original interception distance when the transmitter does not transmit the signal in a polarization mode orthogonal to the interference polarization. now is the interception distance after the radar transmit polarization is optimized, and its size can be used as an effective evaluation of the anti-interference method of cognitive polarization transmission. Obviously, the interception distance R obtained after the radar transmit polarization is optimized is now The smaller it is, the better the effect of the cognitive polarization emission anti-interference method.

[0082] The following simulation test verifies the performance and effect of the cognitive polarization transmission anti-interference method of the present invention.

[0083] Experiment 1: Polarization pattern simulation experiment

[0084] Experimental conditions:

[0085] A linearly polarized forwarding interference signal is incident on the antenna array, with an interference-to-noise ratio of 50dB and a polarization angle of 90 degrees. The polarization state of the radar transmitter is set to be orthogonal to the polarization state of the forwarding interference, and the polarization pattern obtained is as follows: Figure 3 shown.

[0086] Software platform: MATLAB.

[0087] Experimental content:

[0088] Simulation 1 explores the polarization pattern when the radar is in the optimal transmit polarization state, that is, the selectivity of the incident signal polarization angle.

[0089] Experimental results and analysis:

[0090] The experimental results of simulation 1 are as follows Figure 3 shown.

[0091] from Figure 3 As can be seen in the figure, because the polarization state of the radar transmitter is orthogonal to that of the repeater jammer, a deep null is formed at the repeater jammer's polarization angle, i.e., 90 degrees. At this point, the jammer essentially cannot receive the radar's transmitted signal and therefore does not interfere, improving the radar's anti-jamming performance. Furthermore, near 90 degrees, it can be seen that the smaller the estimated polarization angle error, the deeper the null, the weaker the radar signal intercepted by the jammer, and the better the radar's anti-jamming performance.

[0092] Experiment 2: Interception distance simulation experiment

[0093] Experimental conditions:

[0094] A linearly polarized repeater jammer signal is incident on the antenna array. Four receiving antennas are configured: horizontal, 30-degree, 60-degree, and vertical. The interference-to-noise ratio (INR) varies between 10 and 50 dB, and the polarization angle is set to 90 degrees. The original interception range is set to 100 km. The estimated polarization angle error of the repeater jammer is averaged over 64 snapshots and combined with the polarization pattern obtained in simulation experiment 1 to generate the corresponding interception range results.

[0095] Software platform: MATLAB.

[0096] Experimental content:

[0097] In simulation 1, assuming the presence of one interferer and an interference-to-noise ratio of 50 dB in the polarization domain signal reception model, the estimated polarization angle error of the forwarding interference is averaged over 64 snapshots and combined with the polarization pattern obtained in simulation experiment 1 to obtain an intercept range histogram.

[0098] In simulation 2, assuming the presence of one interferer and an interference-to-noise ratio of 50 dB in the polarization domain signal reception model, the estimated polarization angle error of the forwarding interference is averaged over every 64 snapshots and combined with the polarization pattern obtained in simulation experiment 1 to obtain a histogram showing how the interception distance is converted to multiples of the original interception distance.

[0099] In simulation 3, assuming the presence of one interferer and an interference-to-noise ratio of 50 dB in the polarization domain signal reception model, the estimated polarization angle error of the forwarding interference is averaged over every 64 snapshots and combined with the polarization pattern obtained in simulation experiment 1 to obtain the probability distribution of the interception distance becoming a multiple of the original interception distance.

[0100] In simulation 4, assuming the presence of one interferer and an interference-to-noise ratio of 10 dB in the polarization domain signal reception model, the estimated polarization angle error of the forwarding interference is averaged over 64 snapshots and combined with the polarization pattern obtained in simulation experiment 1 to obtain the probability distribution of the interception distance becoming a multiple of the original interception distance.

[0101] In simulation 5, assuming the presence of one interferer and an interference-to-noise ratio of 30 dB in the polarization domain signal reception model, the estimated polarization angle error of the forwarding interference is averaged over 64 snapshots and combined with the polarization pattern obtained in simulation experiment 1 to obtain the probability distribution of the interception distance becoming a multiple of the original interception distance.

[0102] Experimental results and analysis:

[0103] The experimental results of simulation 1, simulation 2, simulation 3, simulation 4 and simulation 5 are as follows: Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 shown.

[0104] from Figures 4 to 6 It can be seen that as the intercept distance of the horizontal axis increases, the height of the histogram becomes shorter, that is, the probability density becomes lower, which is consistent with the theoretical curve. Figures 6 to 8 It can be seen that the larger the interference-to-noise ratio, the smaller the corresponding interception distance and the better the LPI performance. This is because a larger interference-to-noise ratio reduces the estimated polarization angle error, and the corresponding null depth on the polarization pattern becomes deeper, reducing the probability that the jammer will intercept the radar's transmitted signal and achieving a more significant interference suppression effect.

[0105] In summary, the simulation experiments have verified the correctness, effectiveness and reliability of the present invention.

[0106] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0107] Although the present application is described herein with reference to various embodiments, those skilled in the art will be able to understand and implement other variations of the disclosed embodiments in practicing the claimed application by reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality.

[0108] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for cognitive polarization transmission anti-interference, characterized in that: include: Step 1: The radar transmitter transmits a signal in a polarization mode orthogonal to the interference polarization, and obtains a polarization angle pattern used to describe the selectivity of the polarization filter to the incident signal polarization in the process of suppressing forwarding interference; Step 2, determine the mathematical relationship between the interception range and the amplitude of the signal received by the jammer; Step 3: Obtain null depths corresponding to different interference polarization angles according to the polarization angle pattern obtained in step 1, and transform the null depths to obtain the amplitude loss of the signal received by the jammer; Step 4, obtaining the interception distance after polarization optimization at the radar transmitter according to the mathematical relationship between the interception distance and the amplitude of the signal received by the jammer and the amplitude loss; Step 5: Based on the optimized interception distance, evaluate the interference suppression performance of the radar transmitter when transmitting a signal in a polarization mode orthogonal to the interference polarization.

2. The method for cognitive polarization transmission anti-interference according to claim 1, characterized in that: Step 1 includes: Step 1.1: The radar transmitter transmits signals in a polarization mode orthogonal to the interference polarization, thereby suppressing the forwarding interference and obtaining the true polarization angle of the interference during the forwarding interference suppression process. Step 1.2, obtain the optimal transmit polarization state of the radar under the interference background according to the real polarization angle of the interference; Step 1.3: Obtain the corresponding polarization angle pattern based on the radar's optimal transmit polarization state.

3. The method for cognitive polarization transmission anti-interference according to claim 2, characterized in that: The actual polarization angle of the repeater interference in step 1.1 is θ J , 0°≤θ J ≤90°, the polarization state is represented by the Jones vector H J , the radar's transmit polarization is set to H t , the power coefficient of the radar signal received by the jammer is When the radar transmit polarization and the interference polarization are orthogonal to each other, the coefficient is equal to 0. The transmit polarization at this time is called the optimal transmit polarization of the radar under the interference background, which is recorded as H. t,opt , the optimal transmit polarization state of the radar is expressed by the Jones vector: in, , Represent the polarization angles of the horizontal and vertical linear polarization receiving antennas respectively; gather The polarization angle grid formed covers all possible polarization angle directions; let Then the polarization angle pattern described in step 1.3 can be expressed by the following formula: p(θ)=|H t,opt ·A|.

4. The method for cognitive polarization transmission anti-interference according to claim 3, characterized in that: Step 2 includes: Step 2.1: After determining the polarization state of the radar transmitter, the power relationship between the signal power that the jammer can receive and the interception distance from the radar to the jammer, the gain of the radar antenna in the direction of the jammer, and the gain of the jammer antenna; Step 2.2, determine the peak power of the transmitted signal based on the power relationship, and determine the mathematical relationship between the interception distance and the amplitude of the signal received by the jammer based on the relationship between the amplitude of the signal received by the jammer and the total energy of the transmitted signal, and the total energy and the peak power.

5. The method for cognitive polarization transmission anti-interference according to claim 3, characterized in that: After the radar transmits the signal in step 2.1, the power of the signal that the jammer can receive is: Among them, P t is the transmission power of the radar transmitter, R I is the distance from the radar to the jammer; G1 is the gain of the radar antenna in the direction of the jammer, G2 is the gain of the jammer antenna, and L I is the loss factor of the jammer, and λ is the wavelength used; Let P I =δ I , we can get the maximum interception distance that the jammer can detect: Among them, the δ I is the sensitivity of the jammer, is the minimum input signal power that the jammer can detect; The expression of the peak power of the transmitted signal is: P t =E / T; Wherein, E is the total energy of the transmitted signal, T is the pulse width; the amplitude of the signal received by the jammer is A r , E∝P t The mathematical relationship between the interception distance and the signal amplitude received by the jammer is expressed as: R I ∝A r , ∝ means proportional.

6. The method for cognitive polarization transmission anti-interference according to claim 1, characterized in that: The amplitude loss in step 3 is expressed as: Wherein, θ is the polarization angle value obtained in practice.

7. The method for cognitive polarization transmission anti-interference according to claim 1, characterized in that: The intercept distance after optimization in step 4 is expressed as: Among them, R pre It is the original interception distance when the transmitter does not transmit the signal in a polarization mode that is orthogonal to the interference polarization.

Images