Multi-beam amplitude comparison direction finding method based on broadband guided wave type metasurface

Abstract

The invention discloses a multi-beam amplitude comparison direction finding method based on a broadband guided wave type metasurface, and the method comprises the steps: designing a broadband guided wave type metasurface, generating a plurality of scannable beams through a plurality of feed sources on the broadband guided wave type metasurface, and receiving the multiple beams at the same time; the broadband guided wave type metasurface receives an incident signal, it is set that the incident signal intersects with two adjacent wave beams in multiple wave beams received at the same time at a point c and a point d, the outer side direction of the incident signal is taken, and it is determined that the two wave beams, intersecting with the incident signal, of the outer side direction intersect at a point e and a point f; the vertex of the wave beam which is firstly intersected with the incident signal is a point, and a vertical line is drawn from the point a, so that another wave beam which is intersected with the incident signal is intersected at a point b; the point a, the point b and the point e form a triangle, the point b, the point f and the point e are connected to form a triangle, and the incoming wave direction of the incident signal is finally obtained according to a side beam trapezoidal approximation algorithm and a triangle approximation principle.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of radiation array synthesis, and particularly relates to a multi-beam amplitude comparison direction finding method based on a broadband guided-wave type metasurface. BACKGROUND

[0002] The demand for super-range wide-area high-precision passive direction finding technology is very urgent in the field of passive monitoring, and is also a hot topic and bottleneck in the field. The commonly used passive direction finding methods at present include amplitude comparison direction finding method, interferometer direction finding method and amplitude and phase comparison direction finding method. The interferometer direction finding method has the advantages of high direction finding accuracy, small volume and mass and low cost, but requires spatial co-visibility between the antennas arranged. The amplitude and phase comparison direction finding method has the advantages of high direction finding accuracy, small volume and low cost, but similar to the interferometer direction finding, it requires spatial co-visibility between the antennas arranged, which highlights the contradiction between the antenna gain and the coverage space. Compared with the interferometer direction finding and the amplitude and phase comparison direction finding, the amplitude comparison direction finding method has the characteristics of simple structure, stable performance and strong adaptability to complex environments under the same spatial coverage conditions, and can greatly improve the antenna gain, thereby improving the detection distance and having the super-range reconnaissance capability, and has strong anti-interference ability and multi-beam simultaneous processing capability. The current amplitude comparison direction finding system generally adopts a multi-beam array antenna scheme to simultaneously realize high gain and wide coverage, which can be generally divided into fixed multi-beam and phased array multi-beam. The fixed multi-beam has poor flexibility and cannot effectively cope with various interference threats in complex electromagnetic environments. The phased array multi-beam needs multiple parallel receiving and processing channels whether it is an analog phased array or a digital phased array, which leads to a sharp rise in equipment quantity, power consumption and price, thereby limiting its large-scale application.

[0003] The broadband guided-wave type metasurface is a two-dimensional artificial surface designed in sub-wavelength scale and arranged in combination to realize the control of the amplitude, phase, polarization and frequency of electromagnetic waves. By applying a control signal to the adjustable element on the electromagnetic unit, the broadband guided-wave type metasurface can dynamically control the electromagnetic properties of the electromagnetic unit, and then realize the active intelligent control of the spatial electromagnetic wave in a programmable manner to form an electromagnetic field with controllable phase, amplitude, polarization and frequency. As a two-dimensional implementation of metamaterial, the broadband guided-wave type metasurface naturally has the characteristics of low cost, low complexity, high gain and easy deployment. These characteristics of the broadband guided-wave type metasurface make it possible to replace the large number of parallel processing devices required by the traditional phased array multi-beam with the multi-electromagnetic parameter flexible control capability of the broadband guided-wave type metasurface, which is expected to improve the cost-effectiveness in the field of passive monitoring. Therefore, considering the demand for low-cost, low-power and high-performance passive direction finding technology in the current passive monitoring field, based on the broadband guided-wave type metasurface antenna system with independently adjustable amplitude, phase and frequency, a high-precision amplitude comparison direction finding algorithm is researched to realize the super-range wide-area high-precision passive direction finding with controllable cost and power consumption. SUMMARY

[0004] The application provides a multi-beam amplitude comparison direction finding method based on a broadband guided wave type metasurface.

[0005] The technical solution of the application is as follows: a multi-beam amplitude comparison direction finding method based on a broadband guided wave type metasurface comprises the following steps:

[0006] Step 1: a broadband guided wave type metasurface is designed, and a plurality of feed sources on the broadband guided wave type metasurface are used to generate a plurality of simultaneously received multi-beams that can be scanned, and step 2 is entered.

[0007] Step 2: the broadband guided wave type metasurface receives an incident signal, and the incident signal intersects with two adjacent beams in the plurality of simultaneously received multi-beams at two points, namely points c and d, the outside direction of the incident signal is determined, and the two beams intersecting with the incident signal at the outside direction intersect at two other points, namely points e and f, and step 3 is entered.

[0008] Step 3: the vertex of the beam first intersecting with the incident signal is point a, a perpendicular line is drawn from point a, and the perpendicular line intersects with another beam intersecting with the incident signal at point b, and step 4 is entered.

[0009] Step 4: a first triangle is formed by connecting points a, b and e, a second triangle is formed by connecting points b, f and e, and the direction of the incident signal is finally obtained according to the side beam trapezoidal approximation algorithm and the triangle approximation principle.

[0010] Compared with the prior art, the application has the following advantages:

[0011] (1) Compared with the interferometer direction finding and the amplitude comparison phase comparison direction finding, under the same space domain coverage condition, the amplitude comparison direction finding method used in the application has the characteristics of simple structure, stable performance, strong adaptability to complex environments, etc., and the amplitude comparison direction finding method can greatly improve the antenna gain, thereby improving the detection distance, and has strong anti-interference ability and multi-beam simultaneous processing ability.

[0012] (2) The broadband guided wave type metasurface used in the application has the characteristics of low cost, low complexity, high gain and easy deployment. Therefore, it is possible to replace a large number of parallel processing devices required by a traditional phased array multi-beam with the multi-electromagnetic parameter flexible control capability of the broadband guided wave type metasurface, and based on the broadband guided wave type metasurface, a high-precision amplitude comparison direction finding algorithm is researched, so that a cost- and power-conrollable over-the-horizon wide-area high-precision passive direction finding can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The accompanying drawings are a general flowchart of the embodiments of the application.

[0014] Figure 2 A schematic diagram of a wideband guided-wave type metasurface unit model.

[0015] Figure 3 A schematic diagram of a circuit for implementing a true-time delay phase control technology based on a microstrip line.

[0016] Figure 4 A schematic diagram of a radio frequency single-pole four-throw switch integrated with a phase control layer.

[0017] Figure 5 A multi-beam one-dimensional pattern based on a wideband guided-wave type metasurface; wherein (a) is a schematic diagram of a feed source and a lens, (b) is an antenna radiation pattern when the beam is directed at 0 degrees, (c) is an antenna radiation pattern when the beam is directed at 20 degrees and 40 degrees, and (d) is an antenna radiation pattern when the beam is directed at 40 degrees.

[0018] Figure 6 A schematic diagram of a side beam trapezoidal approximation algorithm. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.

[0021] In addition, the description of "first", "second", etc. in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0022] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; "connection" can mean a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible to those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0024] The following section will further introduce the specific implementation method, as well as the technical difficulties and inventive points of this invention, using this design example as an example.

[0025] like Figure 1 As shown, the multi-beam amplitude ratio direction finding method based on a broadband guided metasurface according to the present invention includes the following steps:

[0026] Step 1: Design a broadband waveguide metasurface and use multiple feeds on the broadband waveguide metasurface to generate scannable and simultaneously receive multiple beams.

[0027] In specific implementation, the method for simultaneously receiving multi-beam generation is as follows:

[0028] like Figure 2 As shown, the broadband radiating layer of the broadband waveguide metasurface structure receives incident electromagnetic waves and transmits radio frequency (RF) current to the phase modulation layer at the bottom of the metasurface structure through interlayer three-dimensional interconnects. The phase modulation layer contains multiple microstrip transmission lines of varying electrical lengths, all converging to an RF switch chip. The broadband phase response of the phase modulation layer employs true-time-delay phase modulation technology based on microstrip lines and reconfigurable phase response technology based on RF switches. By selecting different microstrip line paths through the RF switch, a true-time-delay phase response is achieved between the electromagnetic wave and the metasurface. Figure 3 A circuit diagram for implementing true time-delay phase modulation technology based on microstrip lines. Figure 4 This diagram illustrates a radio frequency (RF) single-pole four-throw (SPFT) switch integrated into the phase modulation layer. By configuring the bias current at the external port, it can select and switch between four paths. The RF switch chip receives control signals from the control signal layer, selects the path, and causes the RF current to pass through paths of different electrical lengths and be reflected back to the broadband radiation layer, generating secondary radiation. Based on the beam control signals from the control signal layer, different phase distributions are generated on the metasurface aperture surface, enabling beamforming and electrically controlled beam scanning.

[0029] For the case that the adjacent beams of the broadband guided wave type metasurface multi-beam exist coverage blind area, leading to the incident signal in the edge beam, the trapezoidal approximation principle based on the edge beam is used for optimization, and the angle estimation is carried out for the signal incident from the edge beam, so as to realize the super-range wide-area high-precision multi-beam amplitude comparison direction finding.

[0030] Go to step 2.

[0031] Step 2: A broadband guided wave type metasurface receives an incident signal, which intersects with the adjacent two beams in the simultaneously received multi-beam at two points, i.e. c point and d point. The outside direction of the incident signal (the side of the incident signal away from the central beam is the outside direction of the incident signal) is determined, and the two beams intersecting at another two points, i.e. e point and f point.

[0032] In specific implementation, the central beam in the simultaneously received multi-beam is denoted as the Mth beam, and the edge beam is denoted as the M+6th beam. The intersection point determination method is specifically:

[0033] Step 2.1: Let the azimuth angle of the incident signal be θ, and the incident signal intersect with the M+6th and M+5th beams at points c and d respectively. A c and A d are the amplitude values at points c and d.

[0034] Step 2.2: Take the outside direction θ1 of θ to intersect with the M+6th and M+5th beams at points e and f, A e and A f are the amplitude values at points e and f.

[0035] Go to step 3.

[0036] Step 3: The vertex of the beam first intersecting with the incident signal is point a, and a perpendicular line is drawn from point a, which intersects with another beam intersecting with the incident signal at point b.

[0037] In specific implementation, the intersection point determination method is specifically:

[0038] From the vertex a of the M+6th beam, a perpendicular line intersects with the M+5th beam at point b. The line connecting points e and b intersects with the line connecting points c and d at point g.

[0039] Go to step 4.

[0040] Step 4: The line connecting points a, b and e forms a triangle, and the line connecting points b, f and e forms a second triangle. According to the trapezoidal approximation algorithm of the edge beam, the direction of arrival of the incident signal is finally obtained according to the triangle approximation principle.

[0041] In specific implementation, the direction of arrival of the incident signal is calculated as follows:

[0042] Step 4.1: Let θa Let θ1 be the azimuth angle at vertex a, let θ and θ1 be subtracted respectively, and the ratio of the difference value is obtained, that is, the first difference ratio. a

[0043] Step 4.2: Let A c and A g , A b be subtracted respectively, and the second difference ratio is obtained.

[0044] Step 4.3: According to the principle of triangle approximation, the equation composed of the first difference ratio and the second difference ratio is obtained, that is, the first equation.

[0045] Step 4.4: Let θ and θ1 be subtracted respectively, and the third difference ratio is obtained. a

[0046] Step 4.5: Let A g and A d , A e and A f be subtracted respectively, and the fourth difference ratio is obtained.

[0047] Step 4.6: According to the principle of triangle approximation, the equation composed of the third difference ratio and the fourth difference ratio is obtained, that is, the second equation.

[0048] Step 4.7: The equation group is composed of the first equation and the second equation, and finally the azimuth angle of the incident signal is calculated as θ, that is, the direction of arrival of the incident signal is determined.

[0049] The multi-beam amplitude direction finding method based on the multi-layer guided wave configuration of the wideband metasurface structure as shown in Figure 2 , which is composed of a wideband radiation layer, an interlayer three-dimensional interconnection, a control signal layer and a phase control layer. The architecture is conducive to the independent function and decoupling of each layer, avoiding the performance changes caused by functional coupling in traditional metasurface design. Similar to traditional passive air-fed multi-beam antennas, multiple feeds on the wideband guided wave metasurface are used to generate a scannable multi-beam. The multi-beam pattern generated by the wideband guided wave metasurface antenna under multi-feed excitation is shown in Figure 5 .

[0050] For the case that the adjacent beams of the wideband guided wave metasurface multi-beam exist a coverage blind area, resulting in the incident signal being in the edge beam, the embodiment optimizes the traditional algorithm such as the three-beam approximation algorithm based on the edge beam trapezoidal approximation principle, which can estimate the angle of the signal incident from the edge beam and realize the super-range wide-area high-precision multi-beam amplitude direction finding. The principle of the edge beam trapezoidal approximation algorithm is as shown in Figure 6 ​​As shown in the embodiment, the center beam is denoted as the Mth beam, the side beams are denoted as the (M+6)th beam, the azimuth angle of the incident signal is θ, and the incident signal intersects with the (M+6)th and (M+5)th beams at points c and d respectively. The amplitude values ​​at points c and d are denoted as A. c and A d Take the outer azimuth θ1 and intersect the (M+6)th and (M+5)th beams at points e and f, respectively. The amplitude values ​​at points e and f are A. e and A f Draw a perpendicular line from the vertex a of the (M+6)th beam to intersect the (M+5)th beam at point b. The lines connecting points e and b to points c and d intersect at point g.

[0051] Let θ1 and θ be subtracted to obtain the difference in their orientations, θ1 - θ. Let θ a Let θ1 and θ be the azimuth angle at vertex a. a By subtracting the two, we obtain the difference in their orientations: θ1 - θ a Then, the difference in orientation between θ1 and θ is compared with the difference between θ1 and θ. a By comparing the differences in azimuth, we obtain the ratio of the azimuth difference values. Let the amplitude values ​​at points c and g be subtracted to obtain the amplitude difference A at points c and g. c -A g Then, subtract the amplitude values ​​at points a and b to obtain the amplitude difference A between points a and b. a -A b Then, compare the amplitude difference between points c and g with the amplitude difference between points a and b to obtain the ratio of amplitude differences. According to the principle of triangle approximation, θ1 and θ, θ a The ratio of the azimuth differences is equal to the ratio of the amplitude differences between points c and g to those between points a and b, which satisfies the following formula:

[0052]

[0053] Let θ and θ a By subtracting the two, we obtain the difference in their orientations, θ-θ. a Let θ1 and θ a By subtracting the two, we obtain the difference in their orientations: θ1 - θ a Then θ and θ a The difference in orientation with respect to θ1 and θ a By comparing the differences in azimuth, we obtain the ratio of the azimuth difference values. Let the amplitude values ​​at points g and d be subtracted to obtain the amplitude difference A at points g and d. g -A d Then, subtract the amplitude values ​​at points e and f to obtain the difference A between points e and f. e -A fThe difference between the amplitudes at points g and d is compared with the difference between the amplitudes at points e and f, and the ratio of the amplitude difference values is obtained According to the triangle approximation principle, the ratio of the direction difference between theta and theta a , theta1 and theta a is equal to the ratio of the amplitude difference between points g and d and points e and f, that is, the following formula is satisfied:

[0054]

[0055] The equation is combined with the equation to obtain the value of the incident angle theta, which is the ratio of the amplitude difference of the intersection point minus 1, and then multiplied by the direction difference between theta1 and theta a . The ratio of the amplitude difference of the intersection point is the difference between the amplitude values at points c and d in the numerator part, and the difference between the amplitude values at points a and b minus the difference between the amplitude values at points e and f in the denominator part, that is, the incident angle theta satisfies the following formula:

[0056]

[0057] The present application is based on the amplitude comparison of the multi-beam of the broadband guided wave type metasurface, has the advantages of low cost, low complexity, high gain and easy deployment, can guarantee high passive direction finding precision while considering the cost and controllable power consumption.

[0058] The above is only the preferred embodiment of the present application, the protection scope of the present application is not limited to the above-mentioned examples only, any technical scheme under the idea of the present application belongs to the protection scope of the present application. It should be pointed out that, for ordinary skilled in the art, some improvements and decorations without departing from the principle of the present application should be regarded as the protection scope of the present application.

Claims

1. A multi-beam amplitude ratio direction finding method based on a broadband guided metasurface, characterized in that, Includes the following steps: Step 1: Design a broadband waveguide metasurface, and use multiple feeds on the broadband waveguide metasurface to generate scannable and simultaneously receive multiple beams. Proceed to Step 2. Step 2: The broadband waveguide metasurface receives an incident signal. Suppose that the incident signal intersects with two adjacent beams in the multi-beam receiving process at two points, namely points c and d. Take the outer azimuth of the incident signal and determine that the two beams intersecting with the incident signal at the outer azimuth intersect at another two points, namely points e and f. Proceed to step 3. Step 3: The vertex of the beam that first intersects the incident signal is point a. Draw a perpendicular line from point a so that the other beam that intersects the incident signal intersects at point b. Proceed to step 4. Step 4: Connect points a, b, and e to form the first triangle, and connect points b, f, and e to form the second triangle. Based on the side-beam trapezoidal approximation algorithm, the direction of the incident signal is finally obtained by the triangle approximation principle.

2. The multi-beam amplitude ratio direction finding method based on a broadband guided metasurface according to claim 1, characterized in that, In step 1, a broadband waveguide metasurface is designed, and multiple feeds on the broadband waveguide metasurface are used to generate scannable, simultaneously receiving multi-beams, as detailed below: Step 1.1: Design a broadband waveguide metasurface: The broadband waveguide metasurface includes a broadband radiation layer, interlayer three-dimensional interconnection, control signal layer and phase modulation layer arranged sequentially from top to bottom; the broadband radiation layer serves as a feed to receive incident electromagnetic waves and transmits radio frequency current to the phase modulation layer at the bottom of the metasurface structure through the interlayer three-dimensional interconnection. The phase modulation layer contains multiple microstrip transmission lines of varying electrical lengths, all of which converge into a single radio frequency switch chip. The radio frequency switch chip receives control signals from the control signal layer, selects the path, and makes the radio frequency current pass through paths of different electrical lengths and reflect it back to the broadband radiation layer, generating secondary radiation. Step 1.2: Based on the wave control signal from the control signal layer, different phase distributions are generated on the aperture surface of the broadband waveguide metasurface to achieve beamforming and electronically controlled beam scanning, generating scannable and simultaneously receiving multiple beams.

3. The multi-beam amplitude ratio direction finding method based on a broadband waveguide metasurface according to claim 2, characterized in that, In the simultaneous reception of multiple beams, the center beam is denoted as the Mth beam, and the side beams are denoted as the (M+n)th beam, where M = 2, 3, ..., ∞, and n = 1, 2, ..., ∞.

4. The multi-beam amplitude ratio direction finding method based on a broadband guided metasurface according to claim 3, characterized in that, Step 2, determining the intersection point, includes the following steps: Step 2.1: Let the azimuth angle of the incident signal be θ. The incident signal intersects the M+n and M+n-1-th beams at points c and d, respectively. c and A d The amplitude values ​​at points c and d; Step 2.2: Take the outer azimuth θ1 of θ and intersect the M+n and M+n-1-th beams at points e and f, A e and A f Let f be the amplitude values ​​at points e and f.

5. The multi-beam amplitude ratio direction finding method based on a broadband guided metasurface according to claim 4, characterized in that, In step 3, a perpendicular line is drawn from the vertex a of the (M+n)th beam to intersect the (M+n-1)th beam at point b; the lines connecting points e and b with points c and d intersect at point g.

6. The multi-beam amplitude ratio direction finding method based on a broadband waveguide metasurface according to claim 1, characterized in that, In step 4, based on the sidebeam trapezoidal approximation algorithm, the direction of the incident signal is finally obtained using the triangle approximation principle. This specifically includes the following steps: Step 4.1: Let θ a Let θ1 be the azimuth angle at vertex a, and let θ1 be the azimuth angle of θ and θ2 respectively. a Take the difference to get the ratio of the differences between the two, which is the first difference ratio; Step 4.2: Let A c and A respectively g A b Take the difference to obtain the ratio of the second difference; Step 4.3: Using the principle of triangle approximation, we obtain the equation formed by the ratio of the first difference and the ratio of the second difference, which is the first equation; Step 4.4: Let θ and θ1 be related to θ respectively. a Subtract the differences to obtain the ratio of the third difference; Step 4.5: Let A g and A d A e and A f Subtract the values ​​to obtain the ratio of the fourth difference; Step 4.6: Using the principle of triangle approximation, we obtain the equation formed by the ratio of the third difference and the ratio of the fourth difference, which is the second equation; Step 4.7: The first and second equations form a system of equations, and the azimuth angle of the incident signal is finally calculated as θ, which determines the direction of the incoming wave of the incident signal.

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