Orthogonal circular polarization high-efficiency transmit-receive isolation radar system and design method

Abstract

The invention discloses an orthogonal circular polarization high-efficiency transmit-receive isolation radar system and a design method, and belongs to the technical field of radar systems. In the system, a transmitter module is used for performing power amplification on a signal to be transmitted and transmitting the signal to an antenna module through a transmission waveguide; the receiver module is used for amplifying the received signal and providing overload protection at the same time; the antenna module comprises a double-waveguide stepped diaphragm circular polarizer and a horn antenna which are connected in sequence, the double-waveguide stepped diaphragm circular polarizer is used for converting a linear polarization signal sent by the transmitter module into a circular polarization signal, and the horn antenna is used for radiating the circular polarization signal to a specified direction of a space. Meanwhile, target scattering signals are received and fed back to the receiver module. According to the invention, the loss and risk caused by the isolator are significantly reduced, the aliasing phenomenon of a dihedral angle and a trihedral angle in a common linear polarization image is improved, the over-bright spot effect is relieved, the image interpretation effect is improved, and the method can adapt to different polarization orientation angles.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar systems, and in particular relates to an orthogonal circular polarization high-efficiency transmit-receive isolation radar system and a design method thereof. Background Art

[0002] Radar is a remote sensing device that uses electromagnetic wave transmission and reception to detect targets. It is divided into imaging radar and non-imaging radar. In a radar system, the signal link can usually be divided into a transmitting link and a receiving link. The principle is as follows: Figure 1 As shown in the figure. In the transmit chain, the digital signal generated by the baseband digital signal processor passes through an IF amplifier and IF filter to obtain an IF signal. This signal is then input into a mixer for mixing with the local oscillator frequency to generate an RF signal. This signal passes through an RF filter and a power amplifier, then into a circulator and is fed into an antenna for radiation. In the receive chain, the signal received by the antenna is input into a circulator, then passes through a low-noise amplifier and an RF filter, and then into a mixer for downconversion to an IF signal. Finally, it passes through an IF filter and an IF amplifier and is output to a signal processor for processing. In a typical radar system, the transmit and receive signals typically use the same linear polarization, obtaining signals with HH or VV polarization.

[0003] In order to meet the high transmission power requirements and achieve efficient transmission and reception isolation, a high-power circulator is usually required as a key component. Figure 2 As shown in Figure 1, a signal entering the circulator's port 1 is output from port 2, but not from port 3. Similarly, a signal entering port 2 is directed to port 3, while a signal entering port 3 is directed to port 1. Traditional radar systems typically acquire signals using linear polarization.

[0004] To achieve high transmit power and efficient transmit / receive isolation, radar systems often use high-power circulators. Circulators utilize the gyromagnetic properties of ferrite materials to achieve non-reciprocal transmission, but their performance is limited by the ferrite's power handling capacity. Furthermore, high-frequency circulators require extremely high manufacturing processes, and insufficient process precision leads to high losses. While some research has attempted to increase power handling by creating longitudinal standing waves within ferrites, this technology remains immature and requires additional nitrogen gas flow for operation.

[0005] Therefore, how to design an efficient, low-loss radar system under high-power conditions without increasing system complexity and ensuring sensitivity is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] To address the above technical problems, the present invention provides a radar system and design method for orthogonal circular polarization with high-efficiency transmit-receive isolation. This system uses a dual-waveguide stepped diaphragm circular polarizer to replace traditional high-power isolators, utilizing left-handed circularly polarized transmit signals and right-handed circularly polarized receive signals to achieve a single horn for both transmission and reception. This configuration eliminates the need for a circulator and achieves over 25dB of transmit-receive isolation through polarization channel differences. This system offers significant advantages in increasing system power capacity, reducing system complexity, lowering system losses, improving system reliability, and mitigating the Faraday effect and the influence of polarization orientation angles.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A radar system with orthogonal circular polarization and high-efficiency transmission and reception isolation, comprising a transmitter module, a receiver module and an antenna module;

[0009] The transmitter module is used to amplify the power of the signal to be transmitted and transmit it to the antenna module through the transmission waveguide;

[0010] The receiver module is used to amplify the received signal and provide overload protection;

[0011] The antenna module includes a dual-waveguide stepped diaphragm circular polarizer and a high-gain horn antenna connected in sequence; the dual-waveguide stepped diaphragm circular polarizer is used to convert the linear polarization signal sent by the transmitter module into a circular polarization signal, and complete the transmission and reception isolation through orthogonal polarization; the high-gain horn antenna is used to radiate the circular polarization signal to a specified direction in space, while receiving the target scattered signal and feeding it back to the receiver module.

[0012] In another aspect, the present invention provides a method for designing a radar system with high-efficiency transmission and reception isolation using orthogonal circular polarization, which is applied to the aforementioned radar system with high-efficiency transmission and reception isolation using orthogonal circular polarization, comprising:

[0013] The transmitter module amplifies the power of the signal to be transmitted and transmits it to the antenna module through the transmission waveguide;

[0014] The antenna module's dual-waveguide stepped diaphragm circular polarizer converts the linearly polarized signal sent by the transmitter module into a circularly polarized signal and achieves transmit-receive isolation through orthogonal polarization. The horn antenna radiates the circularly polarized signal to a specified direction in space, while receiving the target scattered signal and feeding it back to the receiver module.

[0015] The receiver module amplifies the received signal and provides overload protection.

[0016] In a third aspect, the present invention provides an electronic device comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned orthogonal circular polarization high-efficiency transmit-receive isolation radar system design method.

[0017] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned method for designing a radar system with high-efficiency orthogonal circular polarization transmit and receive isolation.

[0018] The beneficial effects of the present invention are:

[0019] 1. The radar system of this invention utilizes a dual-waveguide stepped diaphragm circular polarizer to achieve orthogonal circularly polarized transmission and reception (transmitting left-handed circularly polarized waves and receiving right-handed circularly polarized waves), significantly improving transmit-receive isolation (better than 25 dB) and saving at least 1.0 dB of round-trip loss. Compared with traditional circulator solutions, this design significantly increases power capacity, effectively protects the receiver, and reduces risks during high-power transmission. The dual-waveguide stepped diaphragm circular polarizer is compact, easy to manufacture, and requires no complex tuning. This significantly improves system reliability and stability, while reducing the high losses and discharge risks associated with insufficient circulator process precision.

[0020] 2. The radar system of the present invention is not only applicable to a single horn antenna, but can also be extended to reflector antennas and phased array antenna systems. By adjusting the amplitude and phase of the T / R components, the antenna radiation pattern can be flexibly changed, thereby improving the adaptability and flexibility of the system.

[0021] 3. By analyzing the full-link loss, radar sensitivity, the relationship between circularly polarized and linearly polarized signals, the Faraday effect, and the influence of polarization orientation angle, the present invention significantly improves system stability. It can effectively improve the dihedral and trihedral angle aliasing phenomenon in ordinary linearly polarized images, alleviate the bright spot effect, improve image interpretation, and adapt to different polarization orientation angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a block diagram of a typical radar system;

[0023] Figure 2 This is a schematic diagram of a ferrite element circulator;

[0024] Figure 3 This is a schematic diagram of a radar system that achieves high-efficiency transmit-receive isolation based on orthogonal circular polarization according to the present invention;

[0025] Figure 4 Schematic diagram of a dual-waveguide stepped diaphragm circular polarization isolator;

[0026] Figure 5 The design diagram of the partition size of the double-waveguide stepped diaphragm circular polarization isolator;

[0027] Figure 6 is a schematic diagram of a horn antenna;

[0028] Figure 7 The schematic diagram of the reflector microwave system using a dual-waveguide stepped diaphragm circular polarizer to achieve isolation;

[0029] Figure 8 The schematic diagram of a phased array radar system using a dual-waveguide stepped diaphragm circular polarizer to achieve isolation.

[0030] Figure 9 This is a schematic diagram of the speaker unit of the phased array radar system;

[0031] Figure 10 is the performance curve of circular polarization isolator;

[0032] Figure 11 The received power curves of different polarization channels of dihedral targets are shown in Figure 2. (a) shows the co-polarization amplitude variation curve with the target orientation angle, and (b) shows the cross-polarization amplitude variation curve with the target orientation angle.

[0033] Figure 12 The received power curves of different polarization channels of a dipole target are shown in Figure 1. (a) shows the co-polarization amplitude variation curve with the target orientation angle, and (b) shows the cross-polarization amplitude variation curve with the target orientation angle.

[0034] Figure 13 The received power curves of different polarization channels of a cylindrical target are shown in Figure 2. (a) shows the co-polarization amplitude variation curve with the target orientation angle, and (b) shows the cross-polarization amplitude variation curve with the target orientation angle.

[0035] Figure 14 These are the orthogonal circular polarization and co-circular polarization images of the port area in an embodiment of the present invention, where (a) is the orthogonal circular polarization image and (b) is the co-circular polarization image;

[0036] Figure 15 These are orthogonal circular polarization and linear polarization images of the port area in an embodiment of the present invention, where (a) is an orthogonal circular polarization image and (b) is a linear polarization image;

[0037] Figure 16 These are images of different polarization channels of a cross-sea bridge in an embodiment of the present invention, where (a) is an HH linear polarization image, (b) is an HV linear polarization image, (c) is an LR circular polarization image, and (d) is an LL circular polarization image.

[0038] Figure 17These are magnified images of the cross-sea bridge in different polarization channels in an embodiment of the present invention, where (a) is the HH linear polarization image and (b) is the LR circular polarization image. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and examples.

[0040] like Figure 3 As shown in the figure, a schematic diagram of a radar system based on orthogonal circular polarization to achieve high-efficiency transmit-receive isolation in the present invention is also divided into a transmitting link and a receiving link. After the RF signal in the transmitting link is amplified by the power amplifier, the obtained high-power microwave signal enters the dual-waveguide stepped diaphragm circular polarizer through the transmission waveguide. The circularly polarized signal generated at the output port of the isolator is radiated out through the antenna.

[0041] In the receiving chain, circularly polarized electromagnetic waves, after passing through the dual-waveguide stepped diaphragm circular polarizer, are converted into linear polarizations with opposite polarization directions, depending on the direction of the electric field rotation, and are output from different ports. When a ground object receives circularly polarized electromagnetic radiation, the echo's primary energy is concentrated in the opposite polarization direction. For example, when a radar transmits left-hand circular polarization (LHCP), the received right-hand circular polarization (RHCP) energy is much greater than that of the left-hand circular polarization. The right-hand circularly polarized echo received by the receiving antenna passes through the dual-waveguide stepped diaphragm circular polarizer and enters the low-noise amplifier through the discharge tube. Simultaneously, a small amount of left-hand circularly polarized echo received by the receiving antenna passes through the dual-waveguide stepped diaphragm circular polarizer and is coupled to the power amplifier port, where it is attenuated by the isolator at the power amplifier port.

[0042] In one embodiment, the radar system is divided into three main modules: a transmitter module, a receiver module, and an antenna module shared by the two.

[0043] In one embodiment, the main function of the transmitter module is to amplify the power of the transmission signal and transmit it to the antenna through a transmission waveguide to achieve efficient signal radiation. It includes the following components electrically connected in sequence:

[0044] Power amplifier: used to achieve high-gain signal amplification.

[0045] Transmission waveguide: used to efficiently combine the output power and transmit it to the antenna module.

[0046] In one embodiment, the core function of the receiver module is to amplify and process the received signal while providing overload protection to ensure safe operation of the system. It includes the following layout:

[0047] Limiter (discharge tube): When the received signal energy is too high, it protects the low noise amplifier receiver from damage by discharging (i.e. Figure 3 limit protection).

[0048] Low noise amplifier (LNA): amplifies the received signal with low noise and high gain.

[0049] Receiver: Further processes or stores the amplified signal to provide data support for subsequent analysis or use.

[0050] In one embodiment, the combination of polarization isolation (25dB) and limiters provides multi-level overload protection, ensuring safe and stable system operation. Machining and welding eliminate the need for tuning, simplifying the manufacturing process and reducing the complexity of commissioning and maintenance.

[0051] In one embodiment, the antenna module uses an orthogonal dual circularly polarized transceiver horn solution instead of a circulator + linearly polarized horn solution. It is responsible for radiating the amplified signal toward the target and simultaneously receiving the scattered signal from the target and feeding it back to the receiver module. It includes the following components:

[0052] The dual-waveguide stepped diaphragm circular polarizer is compact, easy to process, lightweight, and small, capable of supporting high power and wide bandwidth. Its unique feature is that it combines the functions of an orthogonal mode coupler and a circular polarizer, enabling both polarization conversion and polarization separation, thus simplifying the system structure.

[0053] In one embodiment, the core of the dual-waveguide stepped diaphragm circular polarizer is Figure 4 The rectangular waveguide shown (i.e. Figure 4 rectangular waveguide section), partition (i.e. Figure 4 of the partition section) and the square waveguide (i.e. Figure 4 square waveguide section), where the first and second ports of the dual-waveguide stepped diaphragm circular polarizer are standard rectangular waveguide ports, and the third and fourth ports are square common ports, representing TE 01 Mould and TE 10 When the signal is transmitted, the TE excited from the first port (or the second port) 10 The mode line polarization signal is transmitted through the rectangular waveguide, and the TE signal is transmitted through the diaphragm with a specific size according to the center frequency. 10 Mould and TE 01 The amplitude of the mode signals is close, but the phase difference is 90 degrees, thus synthesizing the left-hand (or right-hand) circularly polarized signal, and performing energy synthesis and output through the square waveguide, so that the signal is converted into an output circularly polarized signal at the 3 / 4 port after passing through the circular polarization isolator. When the signal is received, the left-hand (or right-hand) circularly polarized signal input from the 3 / 4 port passes through the designed partition, and the energy is converted into TE 10 The mode line polarization signal is output from the first port (or the second port). If the center frequency of the electromagnetic wave is λ, the partition size design is as follows: Figure 5As shown, a horn antenna radiates immediately behind it during operation.

[0054] High-gain horn antennas, such as Figure 6 As shown, it is immediately behind the third port of the dual-waveguide stepped diaphragm circular polarizer and is integrated with the circular polarizer to further radiate the circularly polarized signal to a specified direction in space, while receiving the target scattered signal and transmitting it to the receiver.

[0055] In one embodiment, Figure 7 As shown in the figure, the high-gain horn antenna no longer radiates electromagnetic waves directly to the target, but acts as a feed element of the transmitting surface to transmit to the reflecting surface. Its working principle is the same as Figure 3 It is basically the same, except that the distribution of the electromagnetic wave beam in space is further changed through the reflecting surface.

[0056] In one embodiment, Figure 8 As shown, multiple orthogonal circularly polarized transceiver speakers form an array to radiate electromagnetic waves. The working principle of each orthogonal circularly polarized transceiver speaker is as follows: Figure 9 As shown, Figure 3 The difference is that the 1 / 2 ports of the orthogonal circular polarization transceiver horn are connected to a T / R component respectively. By adjusting the amplitude and phase of the T / R component, the antenna pattern of the entire array can be changed, thus Figure 3 The principle is expanded to form a circularly polarized transceiver phased array, which radiates electromagnetic waves into space through the phased array antenna.

[0057] Using orthogonal circular polarization design to replace the traditional circulator + linear polarization speaker solution can significantly improve the transmit and receive isolation performance, increase the transmitter power capacity, and be suitable for high-power applications; at the same time, it simplifies the system structure and improves reliability. Figure 10 As shown, the port polarization isolation is ≥25 dB. In the 8.2 GHz to 8.4 GHz frequency band, the S parameter (scattering parameter) S12 is always below -25 dB, effectively protecting the receive link and reducing signal interference. It receives most of the energy scattered by the target, reducing the effects of the Faraday effect and multipath, distinguishing between dihedral and trihedral scattered energy in high-resolution signals, and alleviating the bright spot effect.

[0058] The application effects of the present invention and the traditional solution are theoretically analyzed and compared by simulation.

[0059] For the conversion relationship between circular polarization and linear polarization, the scattering matrix S is transformed in different orthogonal coordinate bases. Suppose there are two sets of orthogonal polarization bases and polarization base , the unitary transformation matrix between two sets of orthogonal polarization bases is , transform the scattering matrix S from the polarization basis The scattering matrix Transform to polarization basis The scattering matrix .in, and are two mutually orthogonal unit vectors, representing two independent polarization directions. Represents vertical direction, Represents Vertical direction.

[0060] incident wave The transformation relationship between the two coordinate bases is:

[0061] (1)

[0062] in, Represents polarization basis The incident wave, Represents polarization basis of the incident wave.

[0063] scattered waves The transformation relationship between the two coordinate bases is:

[0064] (2)

[0065] in, Represents polarization basis The scattered waves, Represents polarization basis of scattered waves.

[0066] You can get:

[0067] (3)

[0068] in, , which is the common similarity transformation of the polarization scattering matrix, the superscript represents the complex conjugate, and the superscript T represents the transpose of the matrix.

[0069] Combined linear polarization base and circularly polarized basis The unitary transformation relationship between and can be obtained by converting the scattering matrix between the linear polarization basis and the circular polarization basis:

[0070] (4)

[0071] in, and Represent the horizontal polarization direction and the vertical polarization direction respectively. and represents the left-hand circular polarization direction and the right-hand circular polarization direction, j is an imaginary unit; 、 、 、 is the scattering parameter, L and R represent left-hand circular polarization and the equivalent right-hand circular polarization, respectively. 、 、 、 is the backscattering coefficient under linear polarization basis, H represents the horizontal direction, and V represents the vertical direction.

[0072] Generally, right-handed circular vector Represents the left-hand circular polarization vector (i.e. left-hand circular polarization direction) The orthogonal equivalent polarization basis, that is The total polarization power Span is rotationally invariant in the coordinate basis transformation and does not change with the change of the coordinate basis, that is:

[0073] (5)

[0074] Regarding the analysis of the influence of the Faraday effect, the Faraday effect describes the polarization rotation phenomenon of light waves when passing through a magnetic field. The rotation angle is related to factors such as the wavelength of light, the intensity of the magnetic field, the properties of the medium, and the distance the light propagates in the medium.

[0075] Assuming the magnetic induction intensity is B and the path length of light in the material is d, the angle of rotation of the vibration plane is:

[0076] (6)

[0077] Where V is the Verdet constant, which is related to the properties of the material, temperature, and the frequency (wavelength) of light. In a certain material, whether light propagates along the direction of the magnetic field or against the direction of the magnetic field, the direction of the vibration plane is the same and is determined only by the direction of the magnetic field. If the direction of the rotation forms a right-handed spiral relationship with the direction of the magnetic field, the V of the material is positive, that is, >0. Thus, after light travels the same distance back and forth, the rotation angle of its vibration plane is equal to twice the one-way rotation angle. This is the difference between magneto-optical rotation and natural optical rotation (in natural optical rotation, the vibration plane returns to its original orientation after traveling the same distance back and forth).

[0078] The effect of wavelength is primarily reflected in the Faraday rotation constant, as this constant is related to material properties, and materials respond differently to electromagnetic waves of different wavelengths. This means that under the same conditions, shorter wavelength light waves may produce smaller polarization rotations, while longer wavelength light waves may produce larger polarization rotations. Therefore, for high-frequency SAR systems, the Faraday effect causes linearly polarized waves to produce smaller vibration deflections. However, for circularly polarized waves, the vibration directions of H and V polarizations deflect by the same angle, and the combined wave remains circularly polarized, with only the overall phase shifted, resulting in a smaller effect.

[0079] For the comparison of scattered energy of different targets, according to the conversion relationship between linear polarization and circular polarization, we can obtain:

[0080] (7)

[0081] in, represents the electric field strength of the horizontal polarization component, represents the electric field strength of the vertical polarization component,

[0082] represents the electric field strength of the left-hand circularly polarized component, Represents the electric field strength of the right-hand circularly polarized component.

[0083] Considering the circular polarization axis ratio When the measurement matrix under the dual circular polarization basis is and linear polarization scattering matrix The relationship is as follows:

[0084] (8)

[0085] According to the research results of Cameron et al., complex target scattering in high-resolution SAR images can be decomposed into dihedral angles, trihedral angles (spheres, plates), dipoles (linear bodies), cylinders, narrow dihedral angles, left-handed helices, right-handed helices, The present invention focuses on analyzing the circularly polarized SAR scattering characteristics of simple structure scatterers such as wave oscillators, among which dihedral angles, trihedral angles (spheres, plates), dipoles (linear bodies), cylinders and other typical structural units.

[0086] In addition to being related to factors such as the target's shape, structure, and material, the target's polarization scattering characteristics are also related to the target's posture relative to the radar's line of sight. For a target that rotates around the incident direction of the radar wave in a plane perpendicular to the radar's line of sight, the rotation angle is called the orientation angle. Let the above formula be the orientation angle The target linear polarization scattering matrix at time , then the orientation angle is When , the linear polarization scattering matrix of the target is:

[0087] (9)

[0088] The rotation scattering matrices for different targets are shown below:

[0089] Trihedral angle:

[0090] (10)

[0091] Dihedral angle:

[0092] (11)

[0093] Dipole:

[0094] (12)

[0095] Cylinder:

[0096] (13)

[0097] The electric field vector of a linearly polarized wave changes with time in a fixed direction perpendicular to the radar's line of sight, while the electric field vector of a circularly polarized wave changes with time in a left-hand or right-handed manner around the radar's line of sight. Radar targets with linear and circular polarization will exhibit different polarization scattering characteristics. Substituting the linear polarization scattering matrices of targets such as trihedral angles, dihedral angles, dipoles, and cylinders into the above formula yields the elliptical polarization scattering matrix of the relevant target, as shown below:

[0098] Trihedral angle:

[0099] (14)

[0100] Dihedral angle:

[0101] (15)

[0102] Dipole:

[0103] (16)

[0104] Cylinder:

[0105] (17)

[0106] In circular polarization axial ratio When it is less than 1, the amplitude (absolute value) of each polarization complex scattering amplitude in the elliptical polarization scattering matrix of dihedral angle, dipole, cylinder and other targets changes with the target orientation angle and axis ratio. Figure 11-13 The curves of the amplitude (absolute value) of each polarization complex scattering amplitude in the elliptical polarization scattering matrix of dihedral, dipole, cylinder and other targets as a function of the target orientation angle and axis ratio are given respectively. Figure 11-13 (a) are the curves of the dihedral angle, dipole, and cylinder co-polarization amplitude changing with the target orientation angle, Figure 11-13(b) are the curves of the cross-polarization amplitude variation with the target orientation angle for dihedral, dipole and cylinder respectively. It can be seen from the curve that the maximum value of the amplitude (absolute value) of the complex scattering amplitude of each polarization in the elliptical polarization scattering matrix of the three targets as the target orientation angle changes occurs at a 45° orientation angle. When the axial ratio is greater than 0.7, the maximum value of the amplitude of the dihedral cross-polarization complex scattering amplitude as the target orientation angle changes is less than 0.26. The maximum value of the amplitude of the complex scattering amplitude of each polarization of other targets as the target orientation angle changes is less than 0.05 compared with the amplitude when the axial ratio is 1, and the impact is small.

[0107] The following conclusions are drawn from simulation analysis:

[0108] For plane, spherical, and trihedral targets, the energy received by the LR transceiver mode is comparable to that of the HH transceiver mode, and much greater than that of the LL transceiver mode;

[0109] For dihedral targets, the received energy of the LL transceiver mode is comparable to that of the HH transceiver mode, and much greater than that of the LR transceiver mode;

[0110] For dipole targets, the received power of the LR transceiver mode is greater than that of the HH transceiver mode when the polarization orientation angle is greater than 45°;

[0111] For cylindrical targets, when the polarization orientation angle is greater than 45°, the received power of the LR transceiver mode is greater than that of the HH transceiver mode, and the received power of the LR transceiver mode is greater than that of the LL transceiver mode.

[0112] Example:

[0113] In satellite-to-ground communications, circular polarization for both transmission and reception has been widely adopted due to its numerous advantages, including suppressing rain and fog interference, combating multipath reflections, minimizing the impact of ionospheric Faraday rotation, and eliminating polarization mismatches caused by slant angles between the satellite and Earth stations. In the radar field, the synthetic aperture radar (SAR) subfield has also seen widespread application in recent years. One advantage of circular polarization in SAR is that it offers higher target classification performance than linear polarization in dual-polarization mode. Furthermore, circularly polarized SAR is less susceptible to multipath interference and polarization mismatch losses caused by mismatched antenna polarization directions.

[0114] The following simulation verifies the circular polarization transmission and reception using the measured data of the Lutan-1 spaceborne SAR port and bridge areas.

[0115] Comparative analysis of L-band SAR images under different polarization transmission and reception modes is performed. Figure 14Figure 1 shows a comparison of the right-hand and left-hand received power for the radar's left-hand transmission mode, with (a) showing orthogonal circular polarization and (b) showing co-circular polarization. The figures first compare the right-hand and left-hand received power for left-hand transmission, corresponding to the LR and LL modes, respectively. Both figures use the same dynamic range, demonstrating comparable power in the LR and LL modes. The LL mode exhibits higher power in dihedral areas, while the LR mode exhibits higher power in planar areas.

[0116] Next Figure 15 A comparison chart of LR and HH transceiver modes is given, where Figure 15 (a) is the orthogonal circular polarization image, Figure 15 (b) is a linearly polarized image. In this figure, the received power in LR mode is slightly lower than that in HH mode. Compared with HH mode, LR mode can reduce the strong points of dihedral scattering to a certain extent and improve the sidelobes.

[0117] Compare the images near the cross-sea bridge. Figure 16 As shown, Figure 16 (a) is the HH linear polarization image, Figure 16 (b) is the HV linear polarization image, Figure 16 (c) is the LR circular polarization image, and (d) is the LL circular polarization image. It can be seen that there are many dense scattering points under HH linear polarization, making it difficult to distinguish the bridge structure. The HV linear polarization receiving power is relatively small, while the LR and LL transceiver modes can distinguish the scattering power corresponding to the dihedral angle and trihedral angle, which is more conducive to the discrimination of the target's fine structure.

[0118] Further zoom in on the part of the cross-sea bridge. Figure 17 As shown, Figure 17 (a) is the HH linear polarization image, Figure 17 (b) is the LR circular polarization image. Comparing the images of the HH polarization channel and the LR polarization channel, it can be seen that the HH channel has strong aliasing and it is difficult to distinguish the features, while the image of the LR polarization channel is relatively clear.

[0119] In summary, the present invention uses a dual-waveguide stepped diaphragm circular polarizer to replace the high-power isolator composed of microwave ferrite. Compared with a series of problems caused by ferrite absorption in traditional high-power isolators, the dual-waveguide stepped diaphragm circular polarizer is mainly implemented by waveguides, which has the advantages of compact structure, easy processing, light weight, and small size. The upper limit of its power capacity will be mainly determined by the micro-discharge effect of the waveguide. Compared with traditional isolators, the insertion loss is smaller, the transmit and receive isolation is improved, and the receiver is protected during high-power transmission. By eliminating the high-power circulator, the discharge risk caused by process accuracy is reduced, the system loss is reduced, the system heat dissipation requirements are reduced, and the system stability is improved. For application scenarios requiring high resolution and high signal-to-noise ratio, the present invention can make the electromagnetic wave power that actually reaches the antenna and radiates out more, so that the detection distance and detection accuracy of the radar system are improved. By separating the scattering energy of the dihedral angle and the trihedral angle through orthogonal circular polarization, the bright spot effect is alleviated and the signal interpretation effect is improved.

[0120] In another aspect, the present invention provides a radar system design method for achieving high-efficiency transmit / receive isolation based on orthogonal circular polarization, which is applied to the aforementioned radar system for achieving high-efficiency transmit / receive isolation based on orthogonal circular polarization, comprising:

[0121] The transmitter module amplifies the power of the signal to be transmitted and transmits it to the antenna module through the transmission waveguide;

[0122] The dual-waveguide stepped diaphragm circular polarizer of the antenna module converts the linear polarization signal sent by the transmitter module into a circular polarization signal. The horn antenna radiates the circular polarization signal to a specified direction in space, while receiving the target scattered signal and feeding it back to the receiver module.

[0123] The receiver module amplifies the received signal and provides overload protection.

[0124] In a third aspect, the present invention provides an electronic device comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned radar system design method for achieving high-efficiency transmit-receive isolation based on orthogonal circular polarization.

[0125] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned radar system design method for achieving high-efficiency transmit-receive isolation based on orthogonal circular polarization.

[0126] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk drives, CD-ROMs, optical storage devices, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0127] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0128] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0129] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0130] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0131] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A radar system with high efficiency transmit and receive isolation using orthogonal circular polarization, characterized in that: Including transmitter module, receiver module and antenna module; The transmitter module is used to amplify the power of the signal to be transmitted and transmit it to the antenna module through the transmission waveguide; The receiver module is used to amplify the received signal and provide overload protection; The antenna module includes a dual-waveguide stepped diaphragm circular polarizer and a high-gain horn antenna connected in sequence; the dual-waveguide stepped diaphragm circular polarizer is used to convert the linear polarization signal sent by the transmitter module into a circular polarization signal, and complete the transmission and reception isolation through orthogonal polarization; the high-gain horn antenna is used to radiate the circular polarization signal to a specified direction in space, while receiving the target scattered signal and feeding it back to the receiver module.

2. The orthogonal circular polarization high-efficiency transmit-receive isolation radar system according to claim 1, characterized in that: The transmitter module includes a power amplifier and a transmission waveguide electrically connected in sequence, wherein the power amplifier is used to amplify the signal to be transmitted, and the transmission waveguide is used to efficiently synthesize the output power of the amplified signal to be transmitted and transmit it to the antenna module.

3. The orthogonal circular polarization high-efficiency transmit-receive isolation radar system according to claim 1, characterized in that: The receiver module includes a limiter, a low-noise amplifier, and a receiver; the low-noise amplifier is used to amplify the received signal with low noise and high gain; the limiter is used to protect the low-noise amplifier receiver from damage by discharging; The receiver is used to process or store the amplified received signal.

4. The orthogonal circular polarization high-efficiency transmit-receive isolation radar system according to claim 1, characterized in that: The dual-waveguide stepped diaphragm circular polarizer includes a rectangular waveguide, a partition and a square waveguide. The rectangular waveguide includes a first port and a second port. The square waveguide includes a third common port and a fourth common port. When the signal is transmitted, the TE excited from the first port or the second port 10 The mode line polarization signal is transmitted through the rectangular waveguide. By designing a specific size of partition according to the center frequency, the TE after passing through the partition is 10 Mould and TE 01 The amplitudes of the mode signals are close, and the phases differ by 90 degrees, and a left-hand circularly polarized signal or a right-hand circularly polarized signal is synthesized and output through a square waveguide; the horn antenna is connected behind the third common port and the fourth common port of the circular polarizer.

5. The orthogonal circular polarization high-efficiency transmit-receive isolation radar system according to claim 1, characterized in that: It also includes a reflecting surface, and the high-gain horn antenna serves as a feed element of the emitting surface to emit light toward the reflecting surface.

6. The orthogonal circular polarization high-efficiency transmit-receive isolation radar system according to claim 1, characterized in that: The antenna module includes multiple horn antennas that radiate electromagnetic waves in an array form to form a circularly polarized transceiver phased array.

7. The orthogonal circular polarization high-efficiency transmit-receive isolation radar system according to claim 6, characterized in that: The first port and the second port of each of the multiple horn antennas are respectively connected to a T / R component, and the antenna pattern of the entire array is changed by adjusting the amplitude and phase of the T / R component.

8. A method for designing a radar system with orthogonal circular polarization and high-efficiency transmit / receive isolation, applied to the radar system with orthogonal circular polarization and high-efficiency transmit / receive isolation according to any one of claims 1 to 7, characterized in that: include: The transmitter module amplifies the power of the signal to be transmitted and transmits it to the antenna module through the transmission waveguide; The antenna module's dual-waveguide stepped diaphragm circular polarizer converts the linearly polarized signal sent by the transmitter module into a circularly polarized signal and achieves transmit-receive isolation through orthogonal polarization. The horn antenna radiates the circularly polarized signal to a specified direction in space, while receiving the target scattered signal and feeding it back to the receiver module. The receiver module amplifies the received signal and provides overload protection.

9. An electronic device, characterized in that: include: one or more processors; a memory for storing one or more programs; When one or more programs are executed by the one or more processors, the one or more processors implement the method for designing a radar system with high-efficiency transmit and receive isolation of orthogonal circular polarization as described in claim 8.

10. A computer-readable storage medium, characterized in that Executable instructions are stored thereon, and when the instructions are executed by the processor, the processor can implement the orthogonal circular polarization high-efficiency transmit-receive isolation radar system design method described in claim 8.

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