US 11,624,817 B2 · Method for conformal array pattern synthesis based on solution space pruning particle swarm optimization algorithm

Abstract

The present disclosure provides a method for conformal array pattern synthesis based on a solution space pruning particle swarm optimization algorithm (PSO), the method comprises taking a suppression index of a peak side lobe level (SLL) as a first index, obtaining the first array element excitation satisfying the first index under the constraint of the dynamic range ratio (DRR) of the array element excitation amplitude through iterations; obtaining a second array element excitation satisfying the multiple optimization objectives under the constraint of the DRR of the array element excitation amplitude by a solution algorithm according to the first array element excitation.

A method implemented on an electromagnetic transceiver including an array antenna for conformal array pattern synthesis based on a solution space pruning particle swarm optimization algorithm (PSO), comprising:

S1:
taking a suppression index of a peak side lobe level (SLL) as an only index, performing an array element excitation conversion between a conformal array and a uniform array based on an excitation conversion relationship between a projection array and the conformal array as well as a least square relationship between array element excitation of the projection array and array element excitation of the uniform array, and applying an inverse fast Fourier transform algorithm (IFFT) and a fast Fourier transform algorithm (FFT) to a pattern to generate an array element excitation of the conformal array satisfying the suppression index of the peak SLL under a constraint of a dynamic range ratio (DRR) of array element excitation amplitude;
S2:
according to the array element excitation of the conformal array obtained by the S1, pruning a solution space of the PSO, designing a nonlinear updated weight coefficient to ensure sufficient global search, designing a fitness function according to multiple optimization objectives, and further optimizing the conformal array pattern to generate the array element excitation of the conformal array satisfying the multiple optimization objectives under the constraint of the DRR of the array element excitation amplitude,
wherein the S1 is realized by following sub steps:
S1.1:
setting the multiple optimization objectives according to design indexes, the multiple optimization objectives including a suppression index of a peak SLL in a normalized far-field pattern, a first null maximum width of main beam (FNMWe), expected null positions (NULLpointe), and null depths (NULLvaluee);
S1.2:
calculating a wavelength λ by setting a count of array elements as N, serial numbers of the array elements as 1˜N, a working center frequency of array elements as ƒ:
λ
=
c
f
(
1
)
where c=3×108 m/s, c denotes an electromagnetic wave velocity in vacuum;
setting a spacing of the array elements as λ/2, establishing a global coordinate system by taking a tangent direction of a symmetrical center point of an array as an x-axis direction and a normal direction of the symmetrical center point of the array as a y-axis direction, converting a pattern function ƒ(θ) of each array element among the array elements in a local coordinate system to a pattern function ƒn(θ) of each array element among the array elements in the global coordinate system, and calculating a far-field pattern F(θ) of the conformal array:
F
⁢
(
θ
)
=
∑
1
N
A
n
⁢
f
n
⁢
(
θ
)
·
exp
⁢
(
jk
⁢
r
n
→
·
r
→
)
(
2
)
where An is an excitation of a nth array element;
k
=
2
⁢
π
λ
,
which is a wavenumber;
{right arrow over (r)} is a far-field direction of the main beam;
{right arrow over (rn)} is a position vector of the nth array element in the global coordinate system;
and j represents an imaginary unit;
S1.3:
setting a maximum DRR of the array element excitation amplitude of the conformal array as drr, and expressing the array element excitation An as:
An=In·exp(jαn) (3)
where In is an excitation amplitude of the nth array element, αn is an excitation phase of the nth array element, calculating a range of In to be
[
1
drr
,
1
]
,
αn=−k{right arrow over (rn)}·{right arrow over (r0)}, where {right arrow over (r0)} is a position vector of a direction of the main beam in the global coordinate system;
S1.4:
randomly initializing the array element excitation of the conformal array within the range of the excitation amplitude determined by the S1.3;
S1.5:
setting the direction of the main beam θ0=0° as a y-axis direction of the global coordinate system, projecting the conformal array in the direction of the main beam to obtain the projection array, wherein x-axis coordinates of array elements of the projection array are equal to those of corresponding array elements of the conformal array, and a y-axis coordinate is 0;
based on an approximately equal peak side lobe level relationship, calculating the excitation conversion relationship between the projection array and the conformal array by following formula:
I
p
⁢
n
=
I
n
·
❘
"\[LeftBracketingBar]"
f
n
(
θ
0
)
❘
"\[RightBracketingBar]"
❘
"\[LeftBracketingBar]"
f
⁡
(
θ
0
)
❘
"\[RightBracketingBar]"
(
4
)
where Ipn is an excitation amplitude of the nth array element of the projection array;
|ƒn(θ0)| is an array element pattern amplitude of the nth array element of the conformal array in the direction of the main beam;
|ƒ(θ0)| is an array element pattern amplitude of the projection array in the direction of the main beam;
converting the projection array into the uniform array with a smaller spacing by interpolating the projection array according to the smaller spacing, wherein array element of each projection array is represented by a section of array elements of the uniform array centered on the array element of the projection array element;
based on a least square relationship between a guidance vector matrix of the projection array and a guidance vector matrix of the uniform array, obtaining an excitation conversion relationship matrix between the projection array and the uniform array:
EC−(EeHEe)−1EeHEp (5)
where Ep is a guidance vector matrix of the projection array, Ee is a guidance vector matrix of the uniform array, EC is a conversion matrix satisfying the least square relationship;
S1.6:
obtaining a far-field pattern of the uniform array, which is a product of an array factor and an array element pattern, wherein the array factor is calculated according to an inverse Fourier transform between the uniform array and the array factor;
S1.7:
according to the suppression index of the peak SLL, correcting a value of a pattern sampling point exceeding the suppression index of the peak SLL to a value satisfying the suppression index of the peak SLL;
S1.8:
obtaining the array factor by dividing a corrected pattern by the array element pattern, and obtaining array element excitation of the uniform array by Fourier transform;
S1.9:
obtaining the array element excitation of the conformal array by inverse operation of the formulas (4) and (5);
S1.10:
according to the range of the array element excitation amplitude being
[
1
drr
,
1
]
,
correcting the array element excitation of the conformal array to cause it satisfying the constraint of the DRR of the array element excitation amplitude;
S1.11:
iteratively performing the S1.5-S1.10, if the array element excitation of the conformal array satisfies the DRR of the array element excitation amplitude and the pattern satisfies the suppression index of the peak SLL, stopping iterations, otherwise, running to a set maximum number of the iterations to obtain the array element excitation of the conformal array satisfying the suppression index of the peak SLL;
and
S3:
performing at least one operation of optimizing a design of an array feed network or providing the optimized design of the array feed network based on the conformal array pattern satisfying the suppression index of the peak SLL and the constraint of the DRR of the array element excitation amplitude.

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Method for conformal array pattern synthesis based on solution space pruning particle swarm optimization algorithm

Life of this patent

Method for conformal array pattern synthesis based on solution space pruning particle swarm optimization algorithm

Life of this patent

Abstract

Claims2