Self-adaptive reconfigurable intelligent radar radome system

Abstract

The invention provides a self-adaptive reconfigurable intelligent radar radome system, which can realize self-adaptive bidirectional band-pass high transmission for any radar signal when a radar works, and can realize full-band shielding when the radar does not work, thereby realizing electromagnetic protection and electromagnetic stealth of the radar to the greatest extent. According to the generalized Fresnel law principle, active feed is added on the electromagnetic metasurface, and the surface current density of the electromagnetic structure can be adaptively changed according to passing radar signals, so that the band-pass characteristic without a transition frequency band at any frequency point and any bandwidth can be realized. The problems that a traditional frequency selective surface cannot achieve full-band shielding when a radar does not work and cannot achieve band pass with the same frequency as a radar signal in a self-adaptive mode when the radar works are solved, and the frequency selective surface can be applied to the field of intelligent stealth of radar radomes.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic technology, and specifically relates to an adaptive reconfigurable intelligent radar radome system. Background Art

[0002] Advanced radar systems are the core equipment of electronic warfare. The stealth ability of the radar itself is one of the important directions for the development of modern electronic countermeasure technology. It can not only improve the survival ability and combat effectiveness of the radar itself, but also is one of the core elements for seizing the electromagnetic dominance in the modern joint combat system. The radome is the main coupling window of electromagnetic energy and is a key component determining the radar's stealth ability. With the increasingly fierce modern electronic warfare, higher and higher requirements are put forward for the electromagnetic characteristics of the radome. The intelligent stealth radome with the ability of adaptive real-time dynamic selection of spectral transmission is an important trend and core ability for its future development. To ensure the normal operation of the radar and avoid interference from the enemy's electromagnetic weapons, it is necessary to allow the radar signals of one's own side to pass through the radome bidirectionally to complete signal transmission and reception. Currently, the radome cannot achieve electromagnetic shielding in the full frequency band, and its electromagnetic stealth and protection performance are greatly limited. The most advanced current method can only implement a frequency selective surface on the radome through electromagnetic metasurfaces. Its passband bandwidth must be very large to meet various actual combat requirements such as frequency hopping and broadband of the radar signals of one's own side passing through. Even with the currently most advanced reconfigurable electromagnetic metasurface scheme, it can only achieve frequency selective transmission within a fixed frequency band, and it is impossible to avoid a relatively wide transition frequency band between the passband and the stopband, and electromagnetic protection and stealth functions cannot be achieved within these frequency bands.

[0003] Conventional electromagnetic metasurfaces are generally band-pass filters based on frequency selective surfaces, which are difficult to achieve shielding / band-pass switching, and even more impossible to achieve a band-pass with the same frequency as the radar signal, especially for the broadband adaptive requirements with an instantaneous bandwidth up to GHz. Summary of the Invention

[0004] The present invention proposes an adaptive reconfigurable intelligent radar radome system.

[0005] The technical solution for achieving the object of the present invention is as follows:

[0006] An adaptive reconfigurable intelligent radar radome system, comprising an intelligent radar radome, a signal source, an electromagnetic metasurface, a radar transmitting antenna, a radar receiving antenna, a power divider, a phase shifter, and a signal processing device. Among them, the intelligent radar radome is conformal to the electromagnetic metasurface. The signal source is connected to the main port of the power divider. The power divider divides the signal power emitted by the signal source into two paths. One path of the signal passes through the radar transmitting antenna and passes through the radar radome to be transmitted to detect the detection target. The other path of the signal is fed to the electromagnetic metasurface through the phase shifter. The signal processing device is used to divide the reflected power received by the receiving antenna by the power emitted by the transmitting antenna to obtain the real-time reflection coefficient or radar cross section. By controlling whether the other path of the signal of the power divider passes through the phase shifter to feed the electromagnetic metasurface, a co-frequency band-pass high-transparency mode or a full-band shielding mode is realized.

[0007] Preferably, when the output signal of the signal source is directly connected to the power divider and the signal is transmitted through the transmitting antenna, and the electromagnetic metasurface is not fed, the electromagnetic metasurface has a total reflection effect and is in the full-band shielding mode.

[0008] Preferably, when the output signal of the signal source is connected to the power divider and the signal is divided into two paths, one path is transmitted through the transmitting antenna, and the other path is connected to the phase shifter to feed the electromagnetic metasurface, the electromagnetic metasurface becomes an adaptive band-pass filter. By adjusting the power distribution ratio of the power divider and the phase of the phase shifter, the electromagnetic metasurface realizes the band-pass characteristic of the same frequency and the same bandwidth as the signal source, that is, it is in the co-frequency band-pass high-transparency mode.

[0009] Preferably, the electromagnetic metasurface is a square periodic metal grid.

[0010] Preferably, the electromagnetic metasurface is an aperiodic metal grid.

[0011] Preferably, the signal source is any one of a single-frequency narrowband, multi-frequency narrowband, broadband, or frequency-hopping signal.

[0012] Compared with the prior art, the significant advantages of the present invention are:

[0013] (1) The present invention can be applied to any fixed electromagnetic structure, and realizes real-time switchable full-band electromagnetic shielding / radar signal co-frequency band-pass high transparency through reasonable feeding.

[0014] (2) In the full-band electromagnetic shielding mode: the electromagnetic shielding effectiveness SE≥20dB in the frequency band of (1-18)GHz; in the radar signal co-frequency band-pass high-transparency mode: the band is passed in the frequency band with the same frequency as the radar signal, the transmittance≥80%, the out-of-band shielding effectiveness remains unchanged, and the instantaneous passband bandwidth≥1GHz.

[0015] (3) In the co - frequency band - pass mode, the present invention can achieve bidirectional high - transmission only in the radar operating signal frequency band, and can adaptively adjust the frequency points and bandwidth of the pass - band according to the incident radar signal. It remains highly shielded in other frequency bands and has no transition frequency band.

[0016] (4) The present invention can load an adjustable feed to the metasurface structure to achieve high - transparency reconstruction switching in any single - frequency point, any combination of multiple frequency points, any broadband or frequency - hopping cases.

[0017] The following further describes the present invention in detail with reference to the accompanying drawings. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of an adaptive reconfigurable intelligent radar radome system.

[0019] Figure 2 It is the curve spectrum of two modes of the simulation method and implementation.

[0020] Figure 3 It is the radar detection curve spectrum of the metasurface without feed in the embodiment.

[0021] Figure 4 It is the radar detection curve spectrum of the metasurface with feed in the embodiment.

[0022] Figure 5 It is a schematic diagram of two modes of full - band electromagnetic shielding / co - frequency band - pass high - transmission of radar signals. Detailed Embodiment

[0023] The following will further explain and illustrate the present invention with specific embodiments.

[0024] An adaptive reconfigurable intelligent radar radome system includes an intelligent radar radome (3), a signal source (4), a radar transmitting antenna (5), a radar receiving antenna (6), a power splitter (7), a phase shifter (8), and a signal processing device (9). Among them, the intelligent radar radome (3) is an electromagnetic metasurface conformal to the detection window. The signal source (4) is connected to the main port of the power splitter (7). The power splitter (7) divides the signal power emitted by the signal source into two paths. One path of the signal passes through the radar transmitting antenna (5) and passes through the radar radome (3) to be transmitted to detect the detection target (1). The other path of the signal feeds the electromagnetic metasurface through the phase shifter (8). The signal processing device (9) is used to control the output signal of the radar signal source (4), and divides the reflected power received by the receiving antenna (6) by the power emitted by the transmitting antenna (5) to obtain the real - time reflection coefficient or radar cross - section. By controlling whether the other path of the signal of the power splitter passes through the phase shifter (8) to feed the electromagnetic metasurface, the co - frequency band - pass high - transmission mode or the full - band shielding mode is realized.

[0025] In a further embodiment, when the output signal of the signal source (4) is directly connected to the power divider (7) and the signal is transmitted through the transmitting antenna (5), and the electromagnetic metasurface is not fed, the electromagnetic metasurface has a total reflection effect and is in the full-band shielding mode.

[0026] In a further embodiment, when the output signal of the signal source (4) is connected to the power divider (7) and the signal is divided into two paths, one path is transmitted through the transmitting antenna (5), and the other path is connected to the phase shifter (8) to feed the electromagnetic metasurface, the electromagnetic metasurface becomes an adaptive band-pass filter. By adjusting the power distribution ratio of the power divider (7) and the phase of the phase shifter (8), the electromagnetic metasurface realizes the band-pass characteristic of the same frequency and the same bandwidth as the signal source (4), that is, it is in the same-frequency band-pass high-transmission mode.

[0027] Taking the incident wave as x-polarized as an example, the working principle of the present invention is introduced in detail: rxx is the co-polarized electromagnetic reflection coefficient, txx is the co-polarized electromagnetic transmission coefficient. Signals are transmitted and received through the radar transmitter (4) and the receiving antenna (5), and the detection results are displayed on the detection result display device (8) (it can also be not displayed or other signal processing methods can be adopted according to needs). The specific calibration and use steps are as follows:

[0028] (1) First, perform system calibration (if the system does not change after calibration, theoretically there is no need to recalibrate): When the radar is working, the metasurface receives power through the power divider and the phase shifter. At this time, manually adjust the power divider (6) and the phase shifter (7) until the modulus of rxx at the radar communication frequency point is minimized (close to 0), and the modulus of txx is maximized (close to 1).

[0029] (2) When the output signal of the signal source (4) is directly connected to the power divider (7) and the signal is transmitted through the transmitting antenna (5), the electromagnetic metasurface is not fed. At this time, the electromagnetic metasurface has a total reflection effect, that is, the modulus of rxx is maximized (close to 1), and the modulus of txx is minimized (close to 0). The electromagnetic metasurface is in the full-band shielding mode.

[0030] (3) When the output signal of the signal source (4) is connected to the power splitter (7) and the signal power is divided into two paths, one path transmits the signal through the transmitting antenna (5), and the other path is connected to the phase shifter (8) to feed the metasurface. At this time, according to the principle of the generalized Fresnel's law, the electromagnetic metasurface becomes an adaptive band-pass filter. By adjusting the power distribution ratio of the power splitter (7) and the phase of the phase shifter (8), the electromagnetic metasurface realizes the band-pass characteristic with the same frequency and bandwidth as the signal source (4), that is, the modulus of rxx is minimized (close to 0) at the radar signal frequency band, and the modulus of txx is maximized (close to 1), while at other frequency points, it still maintains a high shielding state, that is, the modulus of rxx is maximized (close to 1), and the modulus of txx is minimized (close to 0), so as to ensure the normal operation of the radar. At this time, the electromagnetic metasurface is in the same-frequency band-pass and highly transparent mode of the radar signal.

[0031] According to the principle of the generalized Fresnel's law, the above two working modes of full-band electromagnetic shielding / same-frequency band-pass and highly transparent radar signals can be adaptively and reconfigurably switched in real time according to whether the output signal of the signal source (4) is connected to the power splitter (7), one path transmits the signal through the transmitting antenna (5), and the other path is connected to the phase shifter (8) to feed the metasurface.

[0032] When the incident wave is of other polarizations, similar methods can still be used for calculation and regulation.

[0033] In a further embodiment, the electromagnetic metasurface is a square periodic metal grid. Specifically, the electromagnetic metasurface is composed of a square periodic metal grid with a line width of 10 μm, a period of 100 μm, and a sheet resistance of 0.01 Ω / sq. Its performance can meet: in the full-band electromagnetic shielding mode: the electromagnetic shielding effectiveness SE ≥ 20 dB in the frequency band of (1 - 18) GHz; in the same-frequency band-pass and highly transparent mode of the radar signal: band-pass in the frequency band with the same frequency as the radar signal, the transmittance ≥ 80%, the out-of-band shielding effectiveness remains unchanged, and the instantaneous passband bandwidth ≥ 1 GHz.

[0034] In a further embodiment, the electromagnetic metasurface includes, but is not limited to, periodic and aperiodic grids of different shapes and other electromagnetic metasurface structures that can achieve broadband shielding, and can be designed for conformal or non-conformal installation on the radar surface according to needs.

[0035] In a further embodiment, for the conductive structure of the electromagnetic metasurface (2), there may or may not be a supporting dielectric layer below it. If there is a supporting dielectric layer, it includes isotropic and anisotropic dielectrics, where the dielectric constant and conductivity of the anisotropic dielectric are anisotropic, and the magnetic permeability is isotropic.

[0036] In a further embodiment, the signal source (4) is any one of single-frequency narrowband, multi-frequency narrowband, broadband, or frequency-hopping signals.

[0037] Embodiment 1

[0038] The simulation is carried out by CST full-wave simulation software. The metasurface is a metal grid, as Figure 2 shown in the left simulation schematic diagram. The total size of the grid is 300*300mm, the grid material is set as Perfect Electric Conductor (PEC), the grid line width is 2mm, the period is 10mm, and the periphery of the grid is PEC that surrounds and is electrically connected, with a total size of 1200*1200mm. An SMA connector is set at the center of the grid edge for feeding. The radar incident signal is set as a broadband pulse signal with an instantaneous bandwidth of 1.1GHz. A far-field probe is placed at the receiving end to detect the electric field values at different frequency points. The transmitted electric field amplitudes when not fed and when fed are as Figure 2 shown in the right curve graph. The simulation results show that when not fed, the detected transmitted electric field amplitude is basically 0, and broadband shielding effect can be achieved. When feeding is applied, broadband transmission effect with the same frequency as the radar detection signal can be achieved, and shielding is still maintained outside the band.

[0039] Example 2

[0040] An adaptive reconfigurable intelligent radar radome system. Adopt a feeding grid structure as Figure 2 shown. Among them, ① is a square-period metal grid structure, ② is the dielectric layer FR4 below it, and ③ is an SMA connector with a 2.92mm side feed at the feeding port. The grid is made of copper material, with a line width of 1mm, a period of 5mm, a substrate FR4, a size of 250mm*250mm*1mm, a dielectric constant of 4.4, and a circle of aluminum foil is pasted around it, with a total size of 640mm*550mm.

[0041] The specific system process is as follows:

[0042] (1) Taking the incident wave as x-polarized as an example, rxx is the co-polarized electromagnetic reflection coefficient, and txx is the co-polarized electromagnetic transmission coefficient. According to the derived generalized Fresnel's law: and calculate the surface current density J of the metasurface ② sx , the co-polarized reflection coefficient r in the x direction xx , where: ε 1 is the dielectric constant of air, μ 1 is the magnetic permeability of air, ε 2 is the dielectric constant of the medium in the metasurface (if there is no dielectric layer, it is air), μ 2 is the magnetic permeability of the medium in the metasurface (if there is no dielectric layer, it is air), σ sx is the conductivity in the x direction, E x0 is the incident electric field value in the x direction at the position of the metasurface ②, J sxis the surface current density in the x - direction of the metasurface ②. The radar transmits (4) and receives signals through the receiving antenna (5), and the detection results are displayed on the detection result display device (8).

[0043] (2) Connect the radar's transmitted signal to a power divider. The transmitted signal is divided into two paths. One path is connected to the radar's transmitting end, and the other path is not connected, and the metal grid is not fed. Place the metal grid 40 cm away from the radar's transmitting end. The center of the metal grid is on the same horizontal line as the center of the radar's transmitting end. Control the radar's transmission and reception through the test program. No peak appears at the detection target position. This shows that when the metal grid is not fed, the metal grid has a shielding effect and shields the radar's transmitted signal. The test results are as Figure 3 shown by the gray curve.

[0044] (3) Connect the radar's transmitted signal to a power divider. The transmitted signal is divided into two paths. One path is connected to the radar's transmitting end, and the other path is connected to the metal grid's feeding port after passing through an adjustable phase shifter to feed the metal grid. Place the radar at the same position as in (1) from the window sill, and the height of the radar center from the ground is 83 cm. Place the metal grid 40 cm away from the radar's transmitting end. The center of the metal grid is on the same horizontal line as the center of the radar's transmitting end. Control the radar's transmission and reception through the test program. A peak appears at the detection target distance. This shows that when the metal grid is fed, the window sill can be detected. The test results are as Figure 3 shown by the black curve.

[0045] (4) By controlling the signal processing device (9) to change the output signal source of the radar signal source (4), it can be a single - frequency point, any combination of multiple frequency points, any broadband or frequency hopping, etc. The output signal of the signal source (4) is connected to the power divider (7) and the signal power is divided into two paths. One path transmits the signal through the transmitting antenna (5), and the other path is connected to the phase shifter (8) to feed the metasurface. By adjusting the power distribution ratio of the power divider (7) and the phase of the phase shifter (8), the electromagnetic metasurface realizes the band - pass characteristic with the same frequency and bandwidth as the signal source (4).

[0046] In summary, the present invention has verified the performance of the designed radar radome system through simulation and actual measurement respectively, as Figure 5 shown. In the shielding mode, electromagnetic waves are blocked from entering the entire frequency band; in the band - pass mode, broadband transmission of the same frequency as the radar detection signal is achieved, and at the same time, high shielding effect is still maintained outside the band.

Claims

1. An adaptive reconfigurable intelligent radar radome system, characterized in that: The invention comprises an intelligent radar antenna cover (3), a signal source (4), an electromagnetic metasurface, a radar transmitting antenna (5), a radar receiving antenna (6), a power divider (7), a phase shifter (8), and a signal processing device (9), wherein the intelligent radar antenna cover (3) is conformal to the electromagnetic metasurface of the detection window, the signal source (4) is connected to the main port of the power divider (7), the power divider (7) divides the signal power emitted by the signal source into two paths, one signal passes through the radar transmitting antenna (5) and the radar antenna cover (3) to be emitted to detect the detection target (1), and the other signal feeds the electromagnetic metasurface through the phase shifter (8); the signal processing device (9) is used to control the output signal of the radar signal source (4), and divide the reflected power received by the receiving antenna (6) by the power emitted by the transmitting antenna (5) to obtain a real-time reflection coefficient or a radar scattering cross section; by controlling whether the other signal of the power divider is fed to the electromagnetic metasurface through the phase shifter (8), a same-band pass high-transmittance mode or a full-band shielding mode is realized.

2. The adaptive reconfigurable smart radar radome system according to claim 1, characterized in that: When the output signal of the signal source (4) is directly connected to the power divider (7) and the signal is transmitted through the transmitting antenna (5), and the electromagnetic metasurface is not fed, the electromagnetic metasurface has a total reflection effect and is in a full-band shielding mode.

3. The adaptive reconfigurable smart radar radome system according to claim 1, characterized in that: When the output signal of the signal source (4) is connected to the power divider (7) and the signal is divided into two paths, one path is transmitted through the transmitting antenna (5), and the other path is connected to the phase shifter (8) to feed the electromagnetic metasurface, the electromagnetic metasurface becomes an adaptive bandpass filter. By adjusting the power distribution ratio of the power divider (7) and the phase of the phase shifter (8), the electromagnetic metasurface achieves the same frequency and bandwidth bandpass characteristics as the signal source (4), that is, it is in the same frequency bandpass high-transmittance mode.

4. The adaptive reconfigurable smart radar radome system according to claim 1, characterized in that: The electromagnetic supersurface is a square periodic metal grid.

5. The adaptive reconfigurable smart radar radome system according to claim 1, characterized in that: The electromagnetic supersurface is a non-periodic metal grid.

6. The adaptive reconfigurable smart radar radome system according to claim 1, characterized in that: The signal source (4) is any one of a single-frequency narrowband, multi-frequency narrowband, broadband or frequency hopping signal.

Images