Two-dimensional adjustable radar cross section enhanced surface

Abstract

The invention discloses a two-dimensional adjustable radar cross section enhanced surface. The enhanced surface is formed by adding a one-dimensional Van atta array of a phase shifter into a feeder line and copying the one-dimensional Van atta array on the other dimension. The one-dimensional Van atta array has a low profile, and under the condition that the incoming wave direction is known, electromagnetic waves are made to backtrack along the incoming wave direction by regulating and controlling the phase of a phase shifter in the array. The unit structure of the one-dimensional Van atta array is composed of an antenna and a phase shifter. The antenna is a slot-coupled feed microstrip antenna, the radiation patch is rectangular, the dielectric substrate is arranged below the radiation patch, the antenna grounding plane with a slot is arranged below the dielectric substrate, the slot is I-shaped, the second dielectric substrate is arranged, and the T-shaped antenna feed microstrip line is arranged below the second dielectric substrate. The antenna feed microstrip line is connected with the phase shifter, and the units of the array at equal intervals are connected in pairs through microstrip lines with the same length to form a one-dimensional Van atta array.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar cross section, and particularly relates to a two-dimensional adjustable radar cross section enhanced surface. Background Art

[0002] The radar cross section (RCS) is an electromagnetic surface that reversely reflects electromagnetic waves along the incident wave direction. Such a surface has application value in fields such as radar deception, automotive autonomous driving, wireless communication, and wireless energy transmission. For example, as a decoy bomb to interfere with the enemy's radar's judgment of the target type; increasing the RCS of road facilities or pedestrians is beneficial for on-vehicle radar detection, etc.

[0003] RCS enhanced surfaces can be divided into active and passive types. The active enhanced surface realizes enhancement by amplifying microwave signals. This method has good enhancement effect but high power consumption. The passive enhanced surface does not amplify microwave signals and realizes RCS enhancement by reflecting electromagnetic waves back to the incident wave direction. Traditional passive RCS enhancement structures mainly include corner reflectors, Luneburg lenses, etc. Such enhancement structures have a single RCS characteristic, no intelligent variable ability, and are difficult to conform. The Van atta array can also realize RCS enhancement, but for a planar Van atta array, as the array surface increases, the feeder will become more and more complex. The phase gradient surface can also realize RCS enhancement, but each unit requires a control unit to control the reflection phase of the electromagnetic surface unit, so the cost is relatively high.

[0004] In order to develop new equipment with wideband dynamically variable RCS, by changing the target characteristics in real time to interfere with the enemy's detection, analysis, and judgment, the effectiveness of radar deception and penetration can be achieved, giving birth to new tactical methods. Based on this, it is necessary to develop a new RCS enhanced surface to achieve broadband RCS enhancement adjustable and maintain a low profile as much as possible. Summary of the Invention

[0005] The purpose of the present invention is to provide a two-dimensional adjustable radar cross section enhanced surface, which realizes RCS enhancement on the surface in two dimensions by controlling the phase of the phase shifters in the enhanced surface. The design of this enhanced surface combines the Van atta electromagnetic backtracking principle and the phase gradient principle. In the Phi = 0° plane, the electromagnetic waves are backtracked by the Van atta array. In the Phi = 90° plane, based on the phase gradient principle, by controlling the phase shifters in the array, the electromagnetic waves are reflected back to the incident direction to achieve RCS enhancement. In other planes, the Van atta principle and the phase gradient principle work together.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a two-dimensional adjustable radar cross-section enhancement surface, which includes a microstrip antenna unit, a 0-180° phase shifter, and a feeder line; the microstrip antenna unit adopts a slot coupling feeding method; the microstrip antenna unit successively includes a square radiation patch, a dielectric substrate, a ground plane with a coupling slot, and a second dielectric substrate from top to bottom, and a feeding layer is arranged below the second dielectric substrate; the feeding layer includes an antenna feeding microstrip line, a 0-180° phase shifter, and a one-dimensional Van atta microstrip line.

[0008] In practical applications, by adjusting the phase of the phase shifter in the surface, the surface realizes RCS enhancement in two dimensions. The design of this surface combines the Van atta electromagnetic backtracking principle with the phase gradient principle. In the Phi = 0° plane, the electromagnetic wave is backtracked by the Vanatta array. In the Phi = 90° plane, based on the phase gradient principle, by adjusting the phase shifters in the array, the electromagnetic wave is reflected in the incident direction to achieve RCS enhancement. In other planes, the Van atta principle and the phase gradient principle work together.

[0009] For the two-dimensional Van atta array provided by the prior art, as the array surface increases, the feeder line layout becomes more and more complex. However, the present invention overcomes this problem to a certain extent, that is, a one-dimensional Van atta array is adopted, and the wiring is simple, which is beneficial to the design of a large array surface. Since one control channel controls a whole column of units (a column of Van atta arrays), compared with the surface designed purely based on the phase gradient principle (for a two-dimensional RCS enhancement surface designed based on the phase gradient principle, each unit requires a control channel), a large number of control channels can be reduced, saving costs. And when this surface works, it can achieve RCS enhancement in a certain direction while not enhancing in other directions. This surface needs to know the incoming wave direction when working.

[0010] As a possible implementation, each of the 0-180° phase shifters includes three varactor diodes, and the reverse bias voltage of the varactor diodes ranges from 0 to 14V, corresponding to a capacitance value of 1.15 pF to 0.15 pF and a corresponding phase of 0 to 180°.

[0011] As a possible implementation, the ground plane with a coupling slot is square, and the coupling slot is in the shape of an I.

[0012] As a possible implementation, the length and width of the narrow part of the slot are 4.55 mm and 0.88 mm respectively, and the length and width of the extended parts on both sides are 1.14 mm and 0.88 mm respectively.

[0013] As a possible implementation, the antenna feeding microstrip line is in the shape of a T.

[0014] As a possible implementation, Ψ of the 0-180° phase shifter p h ase and the relationship with the incident wave direction satisfies:

[0015]

[0016] where ψ0 is the initial phase of the phase shifter; K0 is the wave number; d y is the array pitch of the antenna element along the y-axis.

[0017] As a possible implementation, an external DAC controller is used to apply a bias voltage to the varactor diode. At this time, the structure has fan-shaped branches for conducting DC and isolating AC.

[0018] As a possible implementation, the fan angle of the fan-shaped branch is 88°, the fan radius is 2.84 mm, and the fan-shaped branch is 4.9 mm away from the antenna feed microstrip line.

[0019] Compared with the prior art, the present invention has the following effects: The two-dimensional adjustable radar cross-section enhancement surface provided by the present invention can achieve an RCS enhancement greater than 10 dB in the range of Phi = 0-360°, Theta = ±60°. Compared with the two-dimensional phase gradient array, the present invention saves a large number of control units, and only one control unit is required for each column of units. Compared with the two-dimensional Vanatta array, the present invention has the characteristics of simple feeder wiring and easy implementation of large arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0021] Figure 1 is the overall framework diagram (schematic diagram) of the two-dimensional adjustable radar cross-section enhancement surface of the present invention;

[0022] Figure 2 is the overall structure diagram of the unit of the two-dimensional adjustable radar cross-section enhancement surface of the present invention;

[0023] Figure 3 is the structure diagram of each layer of the unit of the two-dimensional adjustable radar cross-section enhancement surface of the present invention;

[0024] Figure 4 is the input return loss diagram of the unit of the two-dimensional adjustable radar cross-section enhancement surface of the present invention;

[0025] Figure 5 is the phase control diagram of the unit of the two-dimensional adjustable radar cross-section enhancement surface of the present invention;

[0026] Figure 6 Pattern of the two - dimensional adjustable radar cross - section enhancement surface unit of the present invention;

[0027] Figure 7 Overall structure diagram of the two - dimensional adjustable radar cross - section enhancement surface of the present invention;

[0028] Figure 8 Enhancement situation diagram of the two - dimensional adjustable radar cross - section enhancement surface of the present invention in the Phi = 0° plane;

[0029] Figure 9 Enhancement situation diagram of the two - dimensional adjustable radar cross - section enhancement surface of the present invention in the Phi = 90° plane;

[0030] Figure 10 Enhancement situation diagram of the two - dimensional adjustable radar cross - section enhancement surface of the present invention in the y = tan15°z plane;

[0031] Figure 11 Enhancement situation diagram of the two - dimensional adjustable radar cross - section enhancement surface of the present invention in the y = tan30°z plane.

[0032] Wherein, 1 - radiation patch, 2 - dielectric substrate, 3 - antenna ground plane with coupling slot, 4 - second - layer dielectric substrate, 5 - phase shifter and feeder. Detailed implementation manners

[0033] For the convenience of clearly describing the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, terms such as "first" and "second" are used to distinguish identical or similar items with basically the same functions and roles. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and do not limit their sequence. Those skilled in the art can understand that terms such as "first" and "second" do not limit the quantity and execution order, and "first", "second", etc. do not necessarily mean different.

[0034] It should be noted that in the present invention, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the present invention should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Exactly, using words such as "exemplary" or "for example" aims to present relevant concepts in a specific manner.

[0035] In the present invention, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the relationship between associated objects and indicates that three relationships may exist. For example, A and / or B may represent the cases of A existing alone, A and B existing simultaneously, and B existing alone, where A and B may be singular or plural. The character " / " generally indicates an "or" relationship between the associated objects before and after. "At least one (item)" or a similar expression refers to any combination of these items, including any combination of single items or plural items. For example, at least one (item) of a, b, or c may represent: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b, and c, where a, b, and c may be single or multiple.

[0036] See Figure 1 , the microstrip antenna elements are arranged at equal intervals in I rows and J columns. Each column is a one-dimensional Van Atta array with a phase shifter in the feeder. The electromagnetic wave received by the (0,0) element will be emitted from the (I,0) element after passing through the microstrip line and the phase shifter. The (1,0) element corresponds to the (I - 1) element. When the electromagnetic wave is incident from the Phi = 0° plane, due to the phase conjugate property, the electromagnetic wave will trace back along the incident direction. By adjusting the phase of the phase shifter, the phase of the emitted electromagnetic wave can be controlled. After derivation, as long as the phase Ψ of the phase shifter p h ase and the direction of the incoming wave satisfy the relationship:

[0037]

[0038] where ψ0 is the initial phase of the phase shifter; K0 is the wave number; d y is the column array pitch of the antenna element along the y-axis. Then the electromagnetic wave will trace back along the incident direction.

[0039] It should be further explained that a 0 - 180° phase shifter is added under each antenna element of the one-dimensional Van Atta array. In a pair of antennas, the antenna receives the electromagnetic wave and emits it from the other antenna, which can just reach a 0 - 360° phase shift range. Changing the phase of the phase shifter can change the phase of the electromagnetic wave traced back by the Van Atta array, and the phase changes of each phase shifter in the one-dimensional Van Atta array are the same. Therefore, this change in phase does not destroy the phase conjugate property of the array. The above one-dimensional array is replicated and arranged in another dimension to form a two-dimensional array. That is, the two-dimensional adjustable RCS enhancement surface designed by us is formed.

[0040] The two-dimensional adjustable radar cross-section enhancement surface includes a microstrip antenna element, a 0-180° phase shifter, and a feeder; the microstrip antenna element adopts a slot-coupled feeding method; the microstrip antenna element from top to bottom is a square radiation patch, a dielectric substrate, a ground plane with a coupling slot, and a second dielectric substrate, and the second dielectric substrate is followed by a feeding layer; the feeding layer includes an antenna feeding microstrip line, a 0-180° phase shifter, and a one-dimensional Van atta array.

[0041] The 0-180° phase shifter is an analog phase shifter that changes the phase by adjusting the bias voltage of the varactor diode to change the capacitance value of the varactor diode. Each phase shifter contains three varactor diodes, and the bias voltage of the varactor diode is reverse-biased from 0 to 14V, corresponding to a capacitance value of 1.15 pF to 0.15 pF, corresponding to a phase of 0 to 180°.

[0042] In addition, a bias voltage is applied to the varactor diode through an external DAC controller, so there are also fan-shaped branches in the structure for conducting direct current and isolating alternating current.

[0043] Furthermore, the size of the radiation patch of the microstrip antenna element is 6.8 mm × 7.3 mm; the dielectric substrate is made of Rogers 4350B material with a dielectric constant of 3.66 and a loss tangent value of 0.004, and its thickness is 1.524 mm, and the length and width are both 15 mm. The ground plane of the antenna element is square with a side length of 15 mm, the coupling slot is in an "I" shape, the length and width of the narrow part of the slot are 4.55 mm and 0.88 mm respectively, and the length and width of the extended parts on both sides are 1.14 mm and 0.88 mm respectively.

[0044] The second dielectric substrate is made of Rogers 4350B material, with a length and width of 15 mm and a thickness of 0.508 mm. The second dielectric substrate is followed by a feeding layer, which includes an antenna feeding microstrip line, a 0-180° phase shifter, and a Van atta microstrip line layer. The width of the microstrip line is 1.12 mm and the impedance is 50 ohms; the 0-180° phase shifter is mainly composed of varactor diodes and microstrip coupling lines. The varactor diodes are in a reverse-biased state during operation, so the anodes of the varactor diodes are grounded through vias, and the cathodes are connected to the microstrip coupling lines and a bias voltage is applied by an external DAC chip. The odd-mode impedance of the coupling line is 45.6 ohms and the even-mode impedance is 80.1 ohms. The length of the coupling line is close to one-eighth of the wavelength of the operating frequency. After optimization design, the determined length of the coupling line in this design is 4.7 mm.

[0045] Furthermore, the fan-shaped angle of the fan-shaped branch for conducting direct current and isolating alternating current is 88°, the fan-shaped radius is 2.84 mm, and the fan-shaped branch is 4.9 mm away from the microstrip line.

[0046] As an example, Figure 2 is the overall structure diagram of the unit. The unit mainly consists of a microstrip antenna fed by slot coupling, a 0 - 180° phase shifter, and a fan-shaped stub for passing DC and blocking AC. The dimensions of each part are as Figure 3 shown, and the key dimension parameters are as follows in the table:

[0047] Table 1 Key Dimensions of the Unit Structure (unit: mm)

[0048]

[0049]

[0050] The input return loss and phase regulation characteristics of the radiation unit provided by the present invention are as Figure 4 and Figure 5 shown. By changing the bias voltage of the varactor diode, the capacitance value of the varactor diode can be changed, thereby changing the phase of the phase shifter. Figure 5 As shown in, the phase shift range of the unit is about 180°. The radiation pattern of the unit is as Figure 6 shown, and the beam width of the unit is about ±45°.

[0051] Figure 7 is the overall structure diagram of the designed two-dimensional adjustable RCS enhancement surface. This surface is composed of replicating 8 1×4 Van atta arrays arranged along the x-axis in the y-axis direction. Each column of the Van atta array is obtained by connecting the aforementioned units with equal-length microstrip lines. When connecting, unit 1 and unit 4 form a pair, and unit 2 and unit 3 form a pair. A fan-shaped stub is led out on each pair of microstrip lines, and the two fan-shaped stubs finally converge to a pin, and a bias voltage is applied through this pin to control the phase of the phase shifter.

[0052] Figure 8 is the RCS situation of the designed RCS enhancement surface in the Phi = 0° plane. The Van atta curve is the monostatic RCS of the designed surface, and the PEC curve is the monostatic RCS of an ideal conductor plane (PEC) of the same size. It can be seen that in the range of Theta = ±60°, the RCS enhancement effect is greater than 10 dB. The RCS enhancement situation in the Phi = 90° plane is as Figure 9 shown. The PEC curve is the monostatic RCS of PEC, and the others are the monostatic RCS enhancement situations when enhanced by 0°, 15°, 30°, 45°, and 60° respectively. It can be seen that in the range of Theta = ±60°, the RCS enhancement effect is greater than 10 dB.

[0053] Figure 10This is the enhancement diagram of the two-dimensional tunable RCS enhancement surface of the present invention in the plane of y = tan15°z. The abscissa α is the angle between the incident wave and the yoz plane. The PEC curve in the figure is still the monostatic RCS of PEC. The curves are the enhancement cases when α = 0°, 42.9°, and 58.8° respectively. In the plane of y = tan15°, when α = 42.9°, the angle between the incident wave and the z-axis is 45°, and when α = 58.8°, the angle between the incident wave and the z-axis is 60°. Figure 11 This is the enhancement diagram of the two-dimensional tunable RCS enhancement surface of the present invention in the plane of y = tan30°z. The PEC curve in the figure is still the monostatic RCS of PEC. The enhancement cases when α = 0°, 35.3°, and 54.7° are shown. In the plane of y = tan30°, when α = 35.3°, the angle between the incident wave and the z-axis is 45°, and when α = 54.7°, the angle between the incident wave and the z-axis is 60°. In summary, it can be seen that compared with PEC, in the range of Phi = 0 to 360° and Theta = ±60°, the enhancement amplitude of the designed surface is greater than 10 dB.

[0054] Although the present invention has been described in connection with various embodiments, however, in the process of implementing the claimed invention, those skilled in the art can understand and achieve other variations of the disclosed embodiments by viewing the drawings, the disclosure content, and the like. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude the case of multiple. A single processor or other unit can implement several functions listed in the specification. Certain measures are described in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0055] Although the present invention has been described in connection with specific features and their embodiments, obviously, various modifications and combinations can be made without departing from the spirit and scope of the present invention. Accordingly, this specification and the drawings are only exemplary descriptions of the present invention and are considered to have covered any and all modifications, variations, combinations, or equivalents within the scope of the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and its equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A two-dimensional adjustable radar cross-section enhancement surface, characterized in that: The invention comprises a microstrip antenna unit, a 0-180° phase shifter and a feed line; the microstrip antenna unit adopts a slot coupling feeding mode; the microstrip antenna unit comprises a square radiation patch, a dielectric substrate, a ground plane with a coupling slot, and a second dielectric substrate from top to bottom, and a feed layer is provided below the second dielectric substrate; the feed layer comprises an antenna feeding microstrip line, a 0-180° phase shifter and a one-dimensional Vanatta microstrip line.

2. The two-dimensional adjustable radar cross-section enhancement surface according to claim 1, characterized in that: Each of the 0-180° phase shifters includes three varactor diodes, and the varactor diode bias voltage is reverse biased from 0 to 14V, corresponding to a capacitance value of 1.15pF to 0.15pF, corresponding to a phase of 0 to 180°.

3. The two-dimensional adjustable radar cross-section enhancement surface according to claim 1, characterized in that: The ground plane with the coupling slot is square, and the coupling slot is I-shaped.

4. The two-dimensional adjustable radar cross-section enhancement surface according to claim 3, characterized in that: The length and width of the narrow part of the gap are 4.55mm and 0.88mm respectively, and the length and width of the extended parts on both sides are 1.14mm and 0.88mm respectively.

5. The two-dimensional adjustable radar cross section enhancement surface according to claim 1, characterized in that: The antenna feeding microstrip line is T-shaped.

6. The two-dimensional adjustable radar cross-section enhancement surface according to claim 1, characterized in that: Ψ of 0~180° phase shifter p h ase With the direction of the wave The relationship satisfies: Where ψ0 is the initial phase of the phase shifter; K0 is the wave number; d y is the array spacing of the antenna elements along the y-axis.

7. The two-dimensional adjustable radar cross-section enhancement surface according to claim 2, characterized in that: An external DAC controller is used to apply a bias voltage to the varactor diode. At this time, the structure has fan-shaped branches for conducting DC isolation AC.

8. The two-dimensional adjustable radar cross-section enhancement surface according to claim 7, characterized in that: The fan angle of the fan-shaped branch is 88°, the fan radius is 2.84 mm, and the fan-shaped branch is 4.9 mm away from the antenna feeding microstrip line.

9. A design method for a two-dimensional adjustable radar cross-section enhancement surface, characterized in that: The steps include: A 0-180° phase shifter is added under each antenna element of the one-dimensional Van atta array; In a pair of antennas, one antenna receives electromagnetic waves and transmits them from the other antenna, achieving a phase shift range of 0 to 360 degrees; changing the phase of the phase shifter can change the phase of the electromagnetic wave traced back by the one-dimensional Van atta array, and the phase change of each phase shifter in the one-dimensional Van atta array is the same, and the above phase change does not destroy the phase conjugation characteristics of the array; The one-dimensional Van atta array is replicated and arranged in another dimension to form a two-dimensional array, forming a two-dimensional adjustable radar scattering cross-section enhancement surface.

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