Optimization method for optical phased array non-equidistant arrangement

Abstract

The application relates to an optimization method of an optical phased array non-equidistant arrangement, comprising the following steps: obtaining a far-field light intensity distribution expression of an optical phased array; setting a sequence formed by intervals of each channel in the optical phased array as a to-be-optimized vector; taking the to-be-optimized vector as an immune individual, and using an immune optimization algorithm to obtain optimal intervals of each channel, so that the optical phased array has the lowest grating lobe suppression ratio in a preset scanning range. The application can realize grating lobe suppression under a large waveguide interval, improve a transmitting aperture, and reduce a beam divergence angle.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical phased array technology, in particular to an optimization method of non-equidistant periodic arrangement of optical phased array. BACKGROUND

[0002] Optical phased array (OPA) is a kind of all-solid-state beam scanning technology, which does not contain any mechanical structure, can point to any direction in the field of view, and has small beam divergence angle and flexible beam switching. It has a huge and broad prospect in the field of laser radar. However, the traditional uniformly arranged antenna of optical phased array is limited in market range due to the appearance of grating lobes. In order to avoid beam confusion and ensure a large field of view, the spacing between antennas needs to be reduced, which may cause crosstalk between waveguides. In order to balance the divergence angle, the number of antennas must be increased, but the driving control of OPA will become extremely complex. SUMMARY

[0003] The technical problem to be solved by the present application is to provide an optimization method of non-equidistant periodic arrangement of optical phased array, which can suppress grating lobes under large waveguide spacing, increase the emission aperture and reduce the beam divergence angle.

[0004] The technical solution adopted by the present application to solve the technical problem is to provide an optimization method of non-equidistant periodic arrangement of optical phased array, comprising the following steps:

[0005] obtaining a far-field light intensity distribution expression of the optical phased array;

[0006] setting a sequence composed of the spacing of each channel in the optical phased array as a to-be-optimized vector;

[0007] using the to-be-optimized vector as an immune individual, and using an immune optimization algorithm to obtain optimal spacing of each channel, so that the optical phased array has the lowest grating lobe suppression ratio in a preset scanning range.

[0008] The affinity function of the immune optimization algorithm is the grating lobe suppression ratio at the maximum deflection angle in the global scanning range.

[0009] The far-field light intensity distribution expression is: wherein E is the far-field light intensity distribution of the optical phased array, N is the number of array elements, A i is the amplitude intensity of the i th array element, f is the array element factor, x i is the position of the i th array element, λ is the working wavelength, θ s is the deflection angle, and θ is the field of view angle of the optical phased array scanning.

[0010] The grating lobe suppression ratio is calculated by the far-field light intensity distribution expression.

[0011] The optimal interval of each channel is obtained by using the immune optimization algorithm, and specifically is:

[0012] The population size, the dimension of immune individuals and the iteration number are set;

[0013] An antigen is identified and an initialized population is created; each immune individual in the population is a sequence composed of intervals of each channel in the optical phased array;

[0014] The affinity function of each immune individual in the population is calculated, and the local best immune individual and the global best immune individual are updated;

[0015] It is judged whether the termination condition is met;

[0016] If not, the immune individual with an affinity value exceeding a threshold value is selected for memory, and the immune individual is inhibited and promoted;

[0017] The population is updated by immune operation, and the affinity function of each immune individual in the population is calculated again until the termination condition is met.

[0018] The termination condition is whether the current iteration number reaches the set iteration number.

[0019] Advantages

[0020] Compared with the prior art, the present application has the following advantages and positive effects: by considering the array element factor in the immune optimization stage and substituting it into the algorithm for optimization, the influence of the direction factor on the weakening of the main beam when deflected in the actual scene is combined, the obtained far-field light intensity distribution can better represent the real scanning condition, the non-periodic optical phased array optimized by using the algorithm has a low grating lobe suppression ratio in the set scanning range, and the emitting aperture can be improved and the beam divergence angle can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a flowchart of the optimization method of the non-equiperiodic arrangement of the optical phased array in the embodiment of the present application;

[0022] Figure 2 is a flowchart of the immune optimization algorithm in the embodiment of the present application. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not used to limit the scope of the present application. In addition, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or changes to the present application, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

[0024] Embodiments of the present application relate to an optimization method of optical phased array non-equidistant arrangement, as shown in the formula (1), mainly divided into two stages of modeling and optimization. Figure 1 The modeling stage is to model the optical phased array, obtain the far-field light intensity expression, and specifically includes:

[0025] The modeling stage is to model the optical phased array, obtain the far-field light intensity expression, and specifically includes:

[0026] Step one: express the array element factor of the optical phased array in the formula, and substitute it into the far-field light intensity expression of the optical phased array.

[0027] The key part of the optical phased array to realize beam scanning is the transmitting array, each array element is a transmitting antenna of the phased array, and each transmitting antenna is controlled by the preceding phase modulator, thereby having a specific phase. The n transmitting antennas form an array, and the final effect is to form a convergent main beam (scanning main beam) at a certain angle. Wherein, the spacing between the i-th and i+1-th channels is denoted as di.

[0028] The far-field light intensity expression can be used to solve the light intensity distribution of the optical phased array within ±90° range at a specified deflection angle and the grating lobe suppression ratio at the deflection angle. When the array element factor is f, the far-field light intensity distribution expression of the optical phased array is:

[0029]

[0030] In the formula, E is the far-field light intensity distribution of the optical phased array, and the independent variable θ is [-90°, 90°]; N is the number of array elements (i.e. the number of channels); A i is the amplitude intensity of the i-th array element; f is the array element factor, which is a function of the independent variable θ [-90°, 90°] and is determined by the structural parameters of the transmitting antenna; x i is the position of the i-th array element; λ is the working wavelength; θ s is the deflection angle, and θ is the field of view angle of the phased array scanning; in this embodiment, it is set that is the phase difference between the array elements.

[0031] The optimization stage is to obtain a one-dimensional array [d1, d2, d3, …, d N-1 ] through the immune optimization algorithm, so that the optical phased array arranged according to the array can have the lowest grating lobe suppression ratio in the preset scanning range, and specifically includes:

[0032] Step two: set the parameters of the optical phased array, including the maximum channel spacing d max and the minimum channel spacing d min of the non-periodic array, the number of array elements N, and the set scanning range [-θ s , θ s ]. Wherein, the maximum channel spacing dmax and minimum channel spacing d min is the range of the spacing of each channel, d1, d2, d3, …, d N-1 are randomly taken within the range; the number of elements N of the array, the set scanning range [-θ s , +θ s ] defines the desired N-element optical phased array, and the lowest grating lobe suppression ratio is achieved within [-θ s , +θ s ].

[0033] Step three: set the related parameters of the immune optimization algorithm, including: population size NP, iteration number G, local best immune individual Na, global best immune individual Bestf, and affinity function F. Wherein, the immune individual p is a one-dimensional array of channel spacing [d1, d2, d3, …, d N-1 ]; the population size NP represents the population as [p1, p2, p3, …, p NP ], wherein each individual is a one-dimensional array with N-1 dimensions, representing the N-1 channel spacing of the N-element optical phased array; substituting the above data into the far-field light intensity distribution expression, the light intensity distribution of the phased array at each angle within the preset scanning range can be obtained, and the sidelobe suppression ratio of the non-periodic phased array at different deflection angles within the predetermined scanning range under the spacing can be calculated. The affinity function F in the embodiment is set as the grating lobe suppression ratio at the maximum deflection angle within the global scanning range, so as to ensure the lowest sidelobe level within the entire steering range.

[0034] Step four, the optimal channel spacing is obtained by solving the immune optimization algorithm, so as to obtain the optimal transmitting array, as shown in Figure 2 , including the following steps:

[0035] Identify the antigen and create the initial population, that is, randomly initialize the value of the immune individual within the channel interval.

[0036] Calculate the affinity function value of each immune individual, update the local best immune individual and the global best immune individual, that is, calculate the sidelobe suppression ratio of the non-periodic phased array at different deflection angles within the predetermined scanning range under the spacing, obtain the grating lobe suppression ratio at the maximum deflection angle value within the global scanning range, compare the obtained affinity function value with the local best immune individual Na and the global best immune individual Bestf, if it is better than the local best immune individual Na and the global best immune individual Bestf, then replace the local best immune individual Na and the global best immune individual Bestf with the obtained affinity function value.

[0037] Determine whether the termination condition is met;

[0038] If the condition is not satisfied, memory is selected for the immune individuals with the affinity value exceeding the threshold value, and the immune individuals are inhibited and promoted;

[0039] The immune operation (including cloning, variation and cloning inhibition) is performed to update the population, and the affinity function value of each immune individual in the population is recalculated until the termination condition is satisfied. When the termination condition is satisfied, the global optimal immune individual Bestf obtained is the optimal transmitting array, and the termination condition in the embodiment is whether the current iteration number reaches the set iteration number.

[0040] It can be found that, by considering the array element factor in the immune optimization stage, substituting into the algorithm for optimization, combining the influence of the main light beam weakening due to the direction factor when the main light beam is deflected in the actual scene, the far-field light intensity distribution obtained can better represent the real scanning condition, the non-periodic optical phased array optimized by using the algorithm has a low grating lobe suppression ratio in the set scanning range, and can improve the transmitting aperture and reduce the beam divergence angle.

Claims

1. An optimization method of optical phased array non-equal periodic arrangement, characterized in that, The method comprises the following steps: obtaining a far-field light intensity distribution expression of the optical phased array; the far-field light intensity distribution expression is: where E is the far-field light intensity distribution of the optical phased array, N is the number of array elements, A i is the amplitude intensity of the i-th array element, f is the array element factor, x i is the position of the i-th array element, λ is the operating wavelength, θ s is the deflection angle, and θ is the field of view angle of the optical phased array scanning. The sequence of the intervals of the channels in the optical phased array is set as the vector to be optimized, wherein the intervals of the channels in the optical phased array are within the range of the maximum channel interval d max and the minimum channel interval d min defined. using an immune optimization algorithm to obtain optimal channel spacing of each channel by taking the to-be-optimized vector as an immune individual, so that the optical phased array has a lowest grating lobe suppression ratio in a preset scanning range.

2. The method of claim 1, wherein, The affinity function of the immune optimization algorithm is a grating lobe suppression ratio at a maximum deflection angle in a global scanning range.

3. The method of claim 1, wherein, The grating lobe suppression ratio is calculated by using the far-field light intensity distribution expression.

4. The method of claim 1, wherein, The immune optimization algorithm is used to obtain the optimal channel spacing of each channel, and specifically: a population size, a dimension of the immune individual, and an iteration number are set; an antigen is identified and an initialized population is created; each immune individual in the population is a sequence composed of channel spacing of the optical phased array; an affinity function of each immune individual in the population is calculated, and a local best immune individual and a global best immune individual are updated; whether a termination condition is met is determined; if not, an immune individual with an affinity value exceeding a threshold value is selected for memory, and the immune individual is inhibited and promoted; the population is updated through an immune operation, and the affinity function of each immune individual in the population is recalculated until the termination condition is met.

5. The method of claim 4, wherein, The termination condition is whether the current iteration number reaches the set iteration number.

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