A multi-source DOA estimation method based on digitally programmable metasurface

Abstract

The present invention discloses a multi-source DOA estimation method based on a digital programmable metasurface, including a programmable metasurface for regulating electromagnetic waves in space and a process of high-precision DOA estimation using a sparse signal recovery algorithm. The metasurface is composed of a plurality of units integrated with diodes, and the working state of the units can be dynamically changed by loading different voltages. The present invention uses a digital programmable metasurface to generate a set of random dual-beam surface codes to construct a perception matrix, uses a receiving horn to sample incident wave information from multiple directions, and uses a sparse signal recovery algorithm to calculate the sampled information, thereby obtaining high-precision incident angle information. The present invention can achieve high-precision estimation of the direction of arrival of waves while reducing sampling costs while avoiding complex phase-shifting networks and a large number of sensors. This work is expected to have important application prospects in the fields of radar and wireless communications.

Description

Technical Field

[0001] The invention belongs to the field of radar and electromagnetic perception, and in particular relates to a multi-source DOA estimation method based on digital programmable metasurface. Background Art

[0002] As a two-dimensional planar form of metamaterials, digital programmable metasurfaces can achieve flexible control of electromagnetic waves in space due to their reconfigurable unit characteristics. Based on this feature, digital programmable metasurfaces can be used as a new type of antenna in fields such as radar and communication systems. DOA estimation technology, as one of the key technologies in the field of radar and wireless communications, has been studied for many years. However, traditional DOA estimation methods are based on phased array antennas, which often require complex shifted network structures or a large number of sensor receiving arrays. These complex hardware designs will bring high production costs and computational complexity. How to simplify the antenna array structure while achieving high-precision DOA estimation has become an important issue in this field. Summary of the invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the prior art, the present invention provides a multi-source DOA estimation method based on a digital programmable metasurface. The method can achieve high-precision wave direction estimation while reducing sampling costs while avoiding complex phase-shifting networks and a large number of sensors.

[0004] Technical solution: A multi-source DOA estimation method based on a digital programmable metasurface, wherein the programmable metasurface is used to control electromagnetic waves in space and uses a sparse signal recovery algorithm to perform high-precision DOA estimation. The programmable metasurface is composed of a plurality of reflective units with integrated diodes, and the working state of the reflective units can be dynamically changed by loading different voltages. The present invention uses a digital programmable metasurface to generate a series of random dual-beam surface codes to construct a perception matrix, uses a receiving horn to sample incident wave information from multiple directions, and uses a sparse signal recovery algorithm to calculate the sampled information, thereby obtaining high-precision incident angle information.

[0005] A multi-source DOA estimation method based on a digital programmable metasurface of the present invention comprises the following steps:

[0006] Step 1: Generate M groups of random dual-beam surface codes using a programmable metasurface, each group of dual-beam surface codes corresponds to a fixed dual-beam angle, and each group of dual-beam pointing angles is different. The M groups refer to 40 groups or more.

[0007] The programmable metasurface includes an array formed by reflective units and a receiving horn; the array formed by the reflective units is used to generate dual-beam surface coding, and the receiving horn is used to receive energy.

[0008] The reflective unit includes a first metal copper column, a second metal copper column, a diode, a metal fan-shaped branch, and a metal patch layer, a first dielectric layer, a metal ground layer of an isolation dielectric, a second dielectric layer, a third dielectric layer, and a feed layer arranged in sequence from top to bottom;

[0009] The first metal copper pillar penetrates the metal patch layer, the first dielectric layer, the metal ground layer, the second dielectric layer, the third dielectric layer and the feed layer, connecting the metal patch layer and the bottom feed layer; the metal fan-shaped branch is loaded between the feed layer and the third dielectric layer, and is connected to the first metal copper pillar 7, which is used for radio frequency (RF) signal isolation and DC voltage bias; the second metal copper pillar penetrates the metal patch layer, the first dielectric layer and the metal ground layer, connecting the metal patch and the metal ground layer, the diode is arranged on the surface of the metal patch layer, and the diode is connected between the first metal copper pillar and the second metal copper pillar, and the diode state is controlled by changing the voltage between the first metal copper pillar and the second metal copper pillar, and each group of dual-beam surface coding corresponds to a group of diode states.

[0010] The present invention provides 400 reflective units, that is, 400 diodes, each of which has two states. The states of the 400 diodes correspond to a set of dual-beam surface codes. Dynamic regulation of spatial electromagnetic waves is achieved by setting the states of the 400 diodes in the programmable metasurface.

[0011] Step 2, using the M groups of surface codes generated in step 1, establish a complete sensing matrix in MATLAB; the sensing matrix represents the signal energy that should be sampled for incoming waves from all directions in space.

[0012] Step 3, use a standard horn to illuminate the metasurface, and the horn's illumination distance is far-field source illumination. Then, M groups of dual-beam surface codes are sequentially programmed into the programmable metasurface using FPGA, and finally, the irradiation energy is sampled using a receiving horn to obtain M groups of sampling results. The receiving horn is a standard rectangular horn.

[0013] For a fixed set of surface codes, the sampling signal of the receiving horn should satisfy equation (1):

[0014]

[0015] Among them, q is the state of the reflective unit, and the specific value is "0" or "1"; θm is the mth incoming wave signal in the space; s m is the energy intensity of the wave coming from the mth target; θ m and φ mis the angle of the wave coming from the mth target; λ is the free space wave impedance; (x r ,y r , Z r ) is the relative coordinate of the phase center of the sampling horn; i is the i-th reflective unit on the metasurface; (x i ,y i ) is the relative coordinate of the ith unit on the hypersurface; N represents the total number of units on the hypersurface.

[0016] Step 4: Compare the M groups of sampling results with the sensor matrix by projection, and use the OMP algorithm to calculate the obvious wave angle information.

[0017] Beneficial effects: The present invention realizes multi-source DOA estimation by using digital programmable metasurface. The method proposed in the present invention can achieve high-precision wave direction estimation while reducing sampling cost under the condition of avoiding complex phase shifting network and a large number of sensors. This work is expected to have important application prospects in the fields of radar and wireless communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the digital programmable metasurface provided by the present invention.

[0019] Figure 2 It is a schematic diagram of the unit structure of the digital programmable metasurface provided by the present invention.

[0020] Figure 3 Schematic diagram of using digitally programmable metasurface to achieve dual beams

[0021] Figure 3 a is a schematic diagram of dual-beam aperture coding.

[0022] Figure 3 b is the far-field simulation schematic diagram of dual beams.

[0023] Figure 3 c is a schematic diagram of the E-plane simulation of the dual-beam.

[0024] Figure 3 d is a schematic diagram of the dual-beam test results.

[0025] Figure 4 This is a diagram of the estimation model for multi-source DOA using digital programmable metasurfaces.

[0026] Figure 5 It is the correlation coefficient matrix diagram of 40 sets of coding modes.

[0027] Figure 6 It is a normalized energy value matrix diagram of 40 groups of coding modes.

[0028] Figure 7It is a graph of the normalized average energy values ​​at each angle under 40 groups of coding modes.

[0029] Figure 8 This is a comparison diagram of the simulation and measured results under a single incident source.

[0030] Figure 8 a is the simulation sampling value diagram under single incident source.

[0031] Figure 8 b is the sampling value diagram obtained from the experiment under a single incident source

[0032] Figure 8 c is the DOA estimation value diagram calculated by the projection method under a single incident source.

[0033] Figure 8 d is the DOA estimation value diagram calculated by the projection method experiment under a single incident source.

[0034] Figure 8 e is the DOA estimation value diagram of the OMP algorithm simulation calculation under a single incident source.

[0035] Figure 8 f is the DOA estimation value diagram calculated by the OMP algorithm experiment under a single incident source.

[0036] Fig. 9 This is a comparison diagram of the simulation and measured results under double incident sources.

[0037] Fig. 9 a is the sampling value diagram obtained by simulation under double incident sources.

[0038] Fig. 9 b is the sampling value diagram obtained from the experiment under double incident sources.

[0039] Fig. 9 c is the DOA estimation value diagram calculated by the projection method under double incident sources.

[0040] Fig. 9 d is the DOA estimation value diagram calculated by the projection method experiment under double incident sources.

[0041] Fig. 9 e is the DOA estimation value diagram of the OMP algorithm simulation calculation under double incident sources.

[0042] Fig. 9 f is the DOA estimation value diagram calculated by the OMP algorithm experiment under double incident sources.

[0043] Among them, 1. metal patch layer; 2. first dielectric layer; 3. metal ground layer; 4. second dielectric layer; 5. third dielectric layer; 6. feed layer; 7. first metal copper column; 8. second metal copper column; 9. diode; 10. metal fan-shaped branch DETAILED DESCRIPTION

[0044] The technical solution of the present invention is now further described in conjunction with the accompanying drawings and embodiments.

[0045] A multi-source DOA estimation method based on a digital programmable metasurface of the present invention comprises the following steps:

[0046] Step 1: Use the programmable metasurface to generate 40 groups of random dual-beam surface codes. Each group of surface codes corresponds to a set of fixed dual-beam angles, and the pointing angles of each group of dual beams are different.

[0047] The structural diagram of the digital programmable metasurface is as follows: Figure 1 As shown in the figure, the programmable metasurface is an array formed by 400 (20×20) reconfigurable reflective units. The array uses a standard rectangular horn for air feeding. In order to prevent the shielding effect of the feed source, the incident angle of the standard rectangular horn is set to 45°. The phase center of the standard rectangular horn is 150mm away from the center of the programmable metasurface.

[0048] The structure of the reflective unit is as follows Figure 2 The reflective unit includes a first metal copper column 7, a second metal copper column 8, a diode 9, a metal fan-shaped branch 10, and a metal patch layer 1, a first dielectric layer 2, a metal ground layer 3 of an isolation dielectric, a second dielectric layer 4, a third dielectric layer 5, and a feed layer 6 arranged in sequence from top to bottom;

[0049] The first metal copper pillar 7 penetrates the metal patch layer 1, the first dielectric layer 2, the metal ground layer 3, the second dielectric layer 4, the third dielectric layer 5 and the feed layer 6, connecting the metal patch layer 1 and the bottom feed layer 6. The metal fan-shaped branch 10 is loaded between the feed layer 6 and the third dielectric layer 5, and is connected to the first metal copper pillar 7 for radio frequency (RF) signal isolation and DC voltage bias. The second metal copper pillar 8 penetrates the metal patch layer 1, the first dielectric layer 2 and the metal ground layer 3, connecting the metal patch and the metal ground layer 3. The diode 9 is arranged on the surface of the metal patch layer 1. The diode 9 is connected between the first metal copper pillar 7 and the second metal copper pillar 8. The state of the diode is controlled by changing the voltage between the first metal copper pillar 7 and the second metal copper pillar 8. The dynamic regulation of spatial electromagnetic waves is achieved by setting the state of 400 diodes in the programmable metasurface.

[0050] Figure 3 Schematic diagram of realizing dual beams using digitally programmable metasurface, where the angles of the dual beams are 10° and -30° respectively. Figure 3 a is the aperture coding for generating dual beams, where different colors represent different diode switch states. Black represents the "0" state, i.e. the diode is off. White represents the "1" state, i.e. the diode is on. Figure 3 b is a schematic diagram of the simulated dual-beam far field. Figure 3c is the E-plane simulation schematic diagram of the dual-beam far field. Figure 3 d is the test effect diagram of the E-surface in the dual-beam far field. The test results prove that the digital programmable metasurface proposed in the present invention can achieve a good dual-beam effect.

[0051] Step 2: Use 40 sets of surface codes in MATLAB to establish a complete sensing matrix. The sensing matrix represents the signal energy that should be sampled for incoming waves from all directions in space.

[0052] Figure 5 is the correlation coefficient of the perception matrix generated by 40 sets of codes, where the brighter the white area, the stronger the correlation. The simulation results show that the columns of the generated perception matrix meet good orthogonality. Figure 6 It is a normalized energy value matrix calculated for 40 groups of codes in the entire space, which means the size of the sampling energy at each angle in the space. Figure 7 The normalized average energy value at each angle is calculated, representing that the random dual beam covers the test range from -60° to 60°.

[0053] Step 3: Use a standard horn to illuminate the metasurface, and the illumination distance of the standard horn is far-field source illumination. Then, 40 sets of dual-beam surface codes are sequentially programmed into the programmable metasurface using FPGA, and finally a rectangular horn is used to sample the illumination energy.

[0054] For a fixed set of surface codes, the sampling signal of the receiving horn should satisfy equation (1):

[0055]

[0056] Among them, q is the state of the reflective unit, and the specific value is "0" or "1"; θm is the mth incoming wave signal in the space; s m is the energy intensity of the wave coming from the mth target; θ m and φ m is the angle of the wave coming from the mth target; λ is the free space wave impedance; (x r ,y r , Z r ) is the relative coordinate of the phase center of the sampling horn; i is the i-th reflective unit on the metasurface; (x i ,y i ) is the relative coordinate of the ith unit on the hypersurface; N represents the total number of units on the hypersurface.

[0057] Step 4: Compare the 40 sets of sampling results with the sensor matrix by projection, and use the OMP algorithm to calculate the obvious angle information of the incoming wave.

Claims

1. A multi-source DOA estimation method based on digital programmable metasurface, characterized in that: The following steps are involved: Step 1: Use a programmable metasurface to generate M groups of random dual-beam surface codes, each group of dual-beam surface codes corresponds to a set of fixed dual-beam angles, and the pointing angles of each group of dual beams are different; The programmable metasurface includes an array formed by reflective units and a receiving horn; the array formed by the reflective units is used to generate dual-beam surface coding, and the receiving horn is used to receive energy; Step 2, using the M groups of surface codes generated in step 1 to establish a complete sensing matrix in Matlab; Step 3, use a standard horn to illuminate the metasurface, then use FPGA to sequentially program M groups of dual-beam surface codes into the programmable metasurface, and finally use a receiving horn to sample the irradiated energy to obtain M groups of sampling results; Step 4, by comparing the M groups of sampling results with the sensor matrix, and using the OMP algorithm to calculate the obvious wave angle information; In step 1, the reflective unit includes a first metal copper column, a second metal copper column, a diode, a metal fan-shaped branch, and a metal patch layer, a first dielectric layer, a metal ground layer of an isolation dielectric, a second dielectric layer, a third dielectric layer, and a feed layer arranged in sequence from top to bottom; The first metal copper column penetrates the metal patch layer, the first dielectric layer, the metal stratum, the second dielectric layer, the third dielectric layer and the feed layer, and connects the metal patch layer and the bottom feed layer. The metal fan-shaped branch is loaded between the feed layer and the third dielectric layer, and is connected to the first metal copper column. The second metal copper column penetrates the metal patch layer, the first dielectric layer and the metal stratum, and connects the metal patch and the metal stratum. The diode is arranged on the surface of the metal patch layer, and the diode is connected between the first metal copper column and the second metal copper column. The state of the diode is controlled by changing the voltage between the first metal copper column and the second metal copper column, and each group of dual-beam surface coding corresponds to a group of diode states. In step 3, for a fixed set of surface codes, the sampling signal result of the receiving speaker should satisfy equation (1): Wherein, q is the state of the reflective unit, and its specific value is "0" or "1"; θm is the mth incoming wave signal in the space; s m is the energy intensity of the wave coming from the mth target; θ m and φ m is the angle of the wave coming from the mth target; λ is the free space wave impedance; (x r ,y r , Z r ) is the relative coordinate of the phase center of the sampling horn; i is the i-th reflective unit on the metasurface; (x i ,y i ) is the relative coordinate of the ith unit on the hypersurface; N represents the total number of units on the hypersurface.

2. According to claim 1, a multi-source DOA estimation method based on digital programmable metasurface is characterized in that: The receiving horn in step 1 is a standard rectangular horn.

3. According to claim 1, a multi-source DOA estimation method based on digital programmable metasurface is characterized in that: In step 1, the M groups refer to 40 groups or more.

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