Multi-scanning-angle parallel phase calibration method for waveguide grating antenna

Abstract

The invention discloses a multi-scanning-angle parallel phase calibration method for a waveguide grating antenna, and the method comprises the steps: receiving light emitted by a one-dimensional waveguide grating antenna with M units through a receiving screen disposed in a far field, and shooting a far-field image through a camera; n detection points # imgabs0 # with different scanning angles are arranged on the far-field image; any unit m of the one-dimensional waveguide grating antenna is selected as a control object, the phase of emergent light of the unit m is changed from 0 to 2 pi by the control voltage with the step length of # imgabs1 #, and the corresponding control voltage when the energy of a detection point # imgabs2 # at different scanning angles reaches the maximum value serves as the calibration voltage # imgabs3 # of the grating antenna unit m at different scanning angles. According to the method, parallel calibration of control voltages at different scanning angles of the waveguide grating antennas is realized in a mode of circularly applying voltages to each waveguide grating antenna, and the calibration efficiency of the phases of the waveguide grating antennas is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wavefront phase calibration, and in particular relates to a multi-scanning angle parallel phase calibration method for a waveguide grating antenna. Background Art

[0002] LiDAR is a mainstream cutting-edge technology for accurately and quickly acquiring three-dimensional images of targets. Currently, mechanical devices are widely used to achieve laser scanning, such as turntables and rotating mirrors. This optical mechanical system is very sensitive to temperature and shock, has extremely high costs, and has slow scanning speeds, which limits its use in military and civilian fields. Waveguide grating antennas use phased array technology to achieve beam scanning, and control the direction of light wave propagation by controlling the phase between a large number of small optical antenna units on the surface.

[0003] However, due to manufacturing defects, there are inevitably differences in the length of the optical path between waveguide grating antennas, which causes the outgoing light to produce a randomly distributed and time-constant phase error. Therefore, it is necessary to calibrate the phase of different waveguide grating antenna units at different scanning angles to avoid the reduction of main lobe energy and increase of side lobes caused by the dispersion of the far-field scanning spot, or even the fragmentation of the scanning spot, which will cause a reduction in detection distance and the generation of false alarms.

[0004] At present, the phase calibration of waveguide grating antenna at different scanning angles is mainly based on the far-field spot quality at a single angle as the evaluation index, and an optimization algorithm is used for iterative optimization. Its technical limitations are that the phase of the waveguide grating antenna can only be calibrated at one scanning angle at a time, and the iterative optimization algorithm has the problems of long calibration time and low calibration efficiency. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a multi-scanning angle parallel phase calibration method for a waveguide grating antenna. Multiple detection points are set in the far field and voltage is cyclically applied to each waveguide grating antenna to achieve parallel calibration of the control voltage at different scanning angles of the waveguide grating antenna, which greatly improves the calibration efficiency of the waveguide grating antenna phase.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A multi-scanning angle parallel phase calibration method for a waveguide grating antenna, the method comprising: firstly, light emitted by a one-dimensional waveguide grating antenna having M units is received by a receiving screen placed in the far field, and a far-field image of the waveguide grating antenna on the receiving screen is captured by a camera;

[0008] After that, set N detection points with different scanning angles on the far-field image captured by the camera. (1≤n≤N);

[0009] Then, select any unit m (1≤m≤M) of the one-dimensional waveguide grating antenna as the control object, and use the step size as The control voltage changes the phase of the waveguide from 0 to 2π, and the detection points at different scanning angles on the far-field image are calculated synchronously. The energy change of the detection points at different scanning angles The control voltage corresponding to the maximum energy is used as the calibration voltage of the grating antenna unit m at different scanning angles. ;

[0010] Finally, the above process is performed on all grating antenna units to obtain the calibration voltage of each grating antenna unit at different angles. (1≤n≤N,1≤m≤M).

[0011] The beneficial effects of the present invention are:

[0012] The present invention realizes parallel phase calibration of waveguide grating antennas at multiple angles by cyclically applying voltage to each waveguide grating antenna, greatly improving the calibration efficiency. The present invention can be used not only for one-dimensional waveguide grating antennas but also for two-dimensional waveguide grating antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A flowchart of a multi-scanning angle parallel phase calibration method for a waveguide grating antenna according to the present invention;

[0014] Figure 2 It is a schematic diagram of an implementation device of a multi-scanning angle parallel phase calibration method for a waveguide grating antenna according to the present invention;

[0015] Figure 3 Schematic diagram of a waveguide grating antenna according to an embodiment of the present invention;

[0016] Figure 4 A before-and-after comparison diagram of the implementation effect of an embodiment of the present invention;

[0017] Figure 5 The graph is a strength variation curve of the waveguide grating antenna unit at the detection point as the control voltage changes according to the embodiment of the present invention. DETAILED DESCRIPTION

[0018] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms, and the present disclosure should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0019] like Figure 1 FIG. 1 is a flow chart of a multi-scanning angle parallel phase calibration method for a waveguide grating antenna according to the present invention, wherein the method comprises: firstly, light emitted by a one-dimensional waveguide grating antenna having M units is received by a receiving screen placed in the far field, and a far-field image of the waveguide grating antenna on the receiving screen is captured by a camera;

[0020] After that, set N detection points with different scanning angles on the far-field image captured by the camera. (1≤n≤N);

[0021] Then, select any unit m (1≤m≤M) of the one-dimensional waveguide grating antenna as the control object, and use the step size as The control voltage changes the phase of the waveguide from 0 to 2π, and the detection points at different scanning angles on the far-field image are calculated synchronously. The energy changes of the detection points at different scanning angles The control voltage corresponding to the maximum energy is used as the calibration voltage U of the grating antenna unit m at different scanning angles. nm ;

[0022] Finally, the above process is performed on all grating antenna units to obtain the calibration voltage of each grating antenna unit at different angles. (1≤n≤N,1≤m≤M).

[0023] like Figure 2 As shown, a device used in a multi-scanning angle parallel phase calibration method for a waveguide grating antenna of the present invention is as follows: the light emitted by a laser light source is input to a fiber optic beam splitter via an optical fiber, and the fiber optic beam splitter divides the input light into M paths, providing input light for a one-dimensional waveguide grating antenna having M units. The outgoing light of the waveguide grating antenna propagates through space to reach a far-field receiving screen, forming a far-field light spot of the waveguide grating antenna. A camera is used to capture the far-field light spot image of the waveguide grating antenna, and the light spot image is transmitted back to the computer. The light spot of the far-field light spot image is concentrated in the dotted frame of the receiving screen, and N detection points are set in the dotted frame, each detection point corresponding to a different scanning angle of the waveguide grating antenna. The computer can send a control voltage signal to the controller, and the controller can independently adjust the phase of the outgoing light of each unit of the waveguide grating antenna.

[0024] The electric field of the mth grating antenna unit at any point Q in the far field is:

[0025] (1)

[0026] in, is the amplitude of the mth grating antenna unit; is the angular frequency; i represents the imaginary unit, and t is the time; is the wave vector of the mth grating antenna unit; is the position vector of the far-field point relative to the mth grating antenna element; is the initial phase of the mth grating antenna unit; is the polarization unit vector.

[0027] Since the distance between the far-field point and the waveguide grating antenna is much larger than the aperture of the waveguide grating antenna, and since the light of the waveguide grating antenna comes from the same light source, the polarization direction is the same. Therefore, the total electric field at any point Q in the far field can be written as:

[0028] (2)

[0029] When the jth grating antenna unit undergoes a phase change When , the intensity (i.e., energy) of Q at any point in the far field changes to:

[0030] (3)

[0031] Defining intermediate parameters , , :

[0032] (4)

[0033] Then the Q intensity change of any point in the far field is:

[0034] (5)

[0035] From the above formula, it can be seen that by adjusting the phase of the jth grating antenna unit, the intensity at any point Q in the far field shows a cosine function change law, and is independent of the intensity change caused by the phase change of other antenna units except the jth grating antenna unit. Therefore, the additional phase change that maximizes the Q intensity at any point in the far field can be obtained by adjusting the phase of each waveguide grating antenna unit in turn. , and the corresponding control voltage is used as the calibration voltage. And according to the formula, this rule still holds true at other points except the arbitrary point Q in the far field, that is, the phase change of any waveguide grating antenna unit will cause the sinusoidal change of the intensity of other points in the far field except the arbitrary point Q, and it is independent of other waveguide grating antennas. Therefore, the present invention proposes to set multiple detection points in the far field, select any unit m (1≤m≤M) of the grating antenna as the control object, and use the step size as The control voltage of makes the phase of the light emitted by unit m change from 0 to 2π, and synchronously calculates the detection points at different scanning angles on the far-field image. The energy changes of different scanning angles The control voltage corresponding to the maximum energy of the monitoring point is used as the calibration voltage of the grating antenna unit m at different angles. Finally, the above process is performed on all grating antenna units to obtain the calibration voltage of each grating antenna unit at different angles. (n=1~N,m=1~M). Multithreading can be used to perform parallel calculation and processing on the intensity change data at each detection point to further improve the calibration efficiency.

[0036] Furthermore, the voltage step size can be adjusted , obtain calibration voltages of different accuracies, The smaller it is, the more accurate the calibration is.

[0037] Furthermore, a Gaussian function can be used to fit the intensity variation at the far-field detection point under different control voltages, and the voltage corresponding to the peak position of the fitted Gaussian function is used as the calibration voltage to achieve the purpose of improving the calibration accuracy.

[0038] Furthermore, the method can be used not only for one-dimensional waveguide grating antennas, but can also be directly extended to two-dimensional waveguide grating antennas, and each unit in the two-dimensional waveguide grating antenna can be operated according to the above steps.

[0039] Furthermore, this method can not only use the energy change at the detection point as an evaluation index, but also use parameters such as peak-to-sidelobe ratio and power in the bucket as evaluation indicators.

[0040] Example

[0041] like Figure 3 As shown in the figure, it is a specific embodiment of the present invention, assuming that the wavelength of the laser light source is 1550nm, the number of waveguide grating antenna units is 11, the width w of the waveguide grating antenna unit is 1.6 microns, the spacing s is 2 microns, the length L is 17 microns, and the control voltage range is 0 to 5V, corresponding to the variation range of one wavelength of the waveguide grating antenna unit. Control voltage step length It is 0.25V, corresponding to one twentieth of a wavelength.

[0042] like Figure 4 As shown, the far-field image before calibration is diffuse, and detection points ①, ②, and ③ are set at -13 degrees, 0 degrees, and 7.8 degrees, respectively. According to the method described in the present invention, the far-field image after calibration is obtained. It can be seen from the figure that the energy of the far-field image after calibration is concentrated at the detection point position, and the calibration of the waveguide grating antenna at multiple angles is completed.

[0043] Figure 5 The intensity variation curves of the first five units of the waveguide grating antenna at three calibration points (i.e., detection points ①, ②, and ③) as the control voltage changes are given, and the curves show sine / cosine function changes.

[0044] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0045] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-scanning angle parallel phase calibration method for a waveguide grating antenna, characterized in that: The following steps are involved: The light emitted by the one-dimensional waveguide grating antenna having M grating antenna units is received by a receiving screen placed in the far field, and a far-field image of the one-dimensional waveguide grating antenna on the receiving screen is captured by a camera; Set N detection points with different scanning angles on the far-field image captured by the camera , 1≤n≤N; Select any grating antenna unit m included in the one-dimensional waveguide grating antenna as the control object, 1≤m≤M, with a step size of The control voltage of makes the phase of the light emitted by unit m change from 0 to 2π, and synchronously calculates the detection points at different scanning angles on the far-field image The energy at the point is used as the evaluation index, and the detection points at different scanning angles are The control voltage corresponding to the maximum energy at the grating antenna unit m is used as the calibration voltage at different scanning angles. ; All grating antenna units are sequentially used as the control objects to perform voltage-phase control, so as to obtain the calibration voltage of each grating antenna unit under different scanning angles.

2. The multi-scanning angle parallel phase calibration method for a waveguide grating antenna according to claim 1, characterized in that: The outgoing light of the one-dimensional waveguide grating antenna propagates through space to reach a receiving screen in the far field, forming a far-field light spot of the one-dimensional waveguide grating antenna, and a camera is used to collect the far-field light spot image of the one-dimensional waveguide grating antenna.

3. The multi-scanning angle parallel phase calibration method for a waveguide grating antenna according to claim 2, characterized in that: The light spot of the far-field light spot image is concentrated in a preset area of ​​the receiving screen, and N detection points are set in the preset area. , each detection point Corresponding to different scanning angles of the waveguide grating antenna, it is used to realize multi-scanning angle parallel phase calibration of the waveguide grating antenna.

4. The multi-scanning angle parallel phase calibration method for a waveguide grating antenna according to claim 3, characterized in that: Using multi-threading, each detection point The energy change data at the locations are calculated and processed in parallel.

5. The multi-scanning angle parallel phase calibration method for waveguide grating antenna according to claim 1, characterized in that: The phase change of each grating antenna unit of the waveguide grating antenna causes the energy at the detection point at different scanning angles in the far field to produce a cosine function change rule, and is independent of the energy changes at the detection point at different scanning angles in the far field caused by the phase changes of other grating antenna units except itself.

6. The multi-scanning angle parallel phase calibration method for waveguide grating antenna according to claim 1, characterized in that: By adjusting the control voltage step size , obtain calibration voltages of different accuracies.

7. The multi-scanning angle parallel phase calibration method for waveguide grating antenna according to claim 1, characterized in that: A Gaussian function is used to fit the energy change at the far-field detection point under different control voltages, and the voltage corresponding to the peak position of the fitted Gaussian function is used as the calibration voltage.

8. The multi-scanning angle parallel phase calibration method for waveguide grating antenna according to claim 1, characterized in that: The method is applicable to a one-dimensional waveguide grating antenna or a two-dimensional waveguide grating antenna.

9. The multi-scanning angle parallel phase calibration method for waveguide grating antenna according to claim 1, characterized in that: The evaluation indicators also include peak sidelobe ratio and barrel power.

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