A phased array weather radar beam forming method based on directional diagram fitting

Abstract

The application provides a phased array weather radar beam forming method based on a directional diagram fitting, and the method comprises the following steps: S1, constructing an ideal directional diagram; S2, calculating a weighting vector initial value; S3, iteratively optimizing the weighting vector initial value according to the ideal directional diagram to obtain a transmitting directional diagram; S4, calculating a receiving directional diagram; and S5, forming a beam by using the transmitting directional diagram and the receiving directional diagram. The method forms transmitting and receiving beams by designing a directional diagram and weighting an array, improves the detection efficiency of the weather radar, doubles the scanning period, and effectively prolongs the response time of the aircraft to the weather threat. In theory, the more the transmitting beam width covers the receiving beams, the more times the scanning rate can be improved; the method can be applied to the field of airborne weather radars, can flexibly adjust the beam coverage range according to the advantages and disadvantages of the signal processing performance of different weather radars, has strong applicability, and has a good market application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of airborne weather radar, and particularly relates to a phased array weather radar beam forming method based on pattern fitting. BACKGROUND

[0002] The weather radar can detect weather targets on the air route, thereby helping the aircraft to avoid weather threats. With the development of aviation technology, the flight speed and maneuverability of the aircraft are continuously improved, so that the response time of the aircraft to weather threats is reduced, which requires the weather radar to also shorten the time required for periodic detection and improve the detection efficiency.

[0003] The weather radar radiates electromagnetic waves through a transmitting beam, irradiates the weather target, and receives the reflected electromagnetic waves through a receiving beam. The phased array can individually control the phases of each array element in the radar array, quickly points the beam to the interested direction through electronic scanning, controls the beam shape through phase weighting by using the phase change of the signal transmitted by each array element. The array pattern of the radar can represent the spatial distribution characteristics of the electromagnetic wave energy, wherein the main lobe part is the main beam, and the main lobe width is the beam width. The transmitting pattern can reflect the radar. The traditional airborne weather radar realizes weather detection through scanning of a single transmitting and receiving beam, and periodically scans the fan-shaped area. The scanning period is related to the beam width.

[0004] At present, the beam forming of the weather radar is mostly based on amplitude weighting of each array element of the array, which can control the main lobe width and side lobe level of the beam, and changes the beam pointing direction through phase shifting. The main shortcomings are as follows: 1. Amplitude weighting is generally the attenuation of the control signal amplitude, which can cause the transmission power of the weather radar to be reduced, the detection distance to be shortened, and the radar performance to be lost; 2. Most of the classical window functions in amplitude weighting are designed to reduce the side lobe, and few window functions are designed to increase the beam width, which does not meet the use scenario of increasing the beam width of the weather radar.

[0005] Therefore, a new weather radar beam forming method needs to be provided. SUMMARY

[0006] The application aims at the problem of long scanning period and low detection efficiency of the traditional weather radar, uses the phase weighting of the phased array on the array elements, fits the ideal pattern, forms a transmitting wide beam and a receiving narrow beam, improves the detection efficiency without losing the transmission power and detection accuracy, and effectively shortens the scanning period.

[0007] The application aims at providing a phased array weather radar beam forming method based on pattern fitting, which comprises the following steps:

[0008] S1: Constructing an ideal pattern;

[0009] S2: calculating the initial value of the weighting vector;

[0010] S3: iteratively optimizing the initial value of the weighting vector calculated in S2 according to the ideal pattern in S1 to obtain a transmitting pattern;

[0011] S4: calculating a receiving pattern;

[0012] S5: forming a beam by using the transmitting pattern in S3 and the receiving pattern constructed in S4,

[0013] wherein the initial value of the weighting vector is set by phase weighting in the space frequency in S2.

[0014] The phased array weather radar beam forming method based on pattern fitting provided by the application further has the characteristics that the ideal pattern in S1 is:

[0015]

[0016] wherein θ is the radar observation angle and R is the radar observation range.

[0017] The phased array weather radar beam forming method based on pattern fitting provided by the application further has the characteristics that S2 comprises the following steps:

[0018] S2.1: performing fast Fourier transform on the received signal to obtain a space frequency;

[0019] S2.2: when the signal wave direction angle range is [-90°, 90°], setting the array element weight vector as a quadratic distribution, and calculating the initial value of the weighting vector according to the space frequency.

[0020] The phased array weather radar beam forming method based on pattern fitting provided by the application further has the characteristics that the initial value of the weighting vector is

[0021]

[0022] wherein M is the number of elements of the uniform linear array receiving array, w m is the weight vector of the mth element, m=1, 2,...M, which is used to control the width of the beam and has a value range of [0, 90°].

[0023] The phased array weather radar beam forming method based on pattern fitting provided by the application further has the characteristics that S3 comprises the following steps:

[0024] S3.1: taking the initial value of the weighting vector obtained in S2 as the first generation weighting vector, determining the iteration amount ΔW according to the iteration method, and performing phase weighting to obtain the second generation weighting vector;

[0025] S3.2: constructing a cost function, judging whether a termination condition is met according to the ideal pattern and the cost function of S1, if yes, obtaining a transmitting pattern according to the optimized weighting vector, if no, entering the next step;

[0026] S3.3: repeating S3.1-S3.2 until the transmitting pattern is obtained.

[0027] The phased array weather radar beam forming method based on pattern fitting provided by the application also has the following features: the cost function in S3.2 is

[0028]

[0029] wherein, the epsilon is a weight coefficient, the theta is an azimuth angle, the W is a weighting vector, the R is a radar observation range, and the F(theta,W) is a normalized pattern.

[0030] The phased array weather radar beam forming method based on pattern fitting provided by the application also has the following features: in S4, the weather radar receives a return wave through multiple narrow beams, constructs a steering matrix A of the phased array, obtains an output result of the array, and constructs a receiving pattern.

[0031] The phased array weather radar beam forming method based on pattern fitting provided by the application also has the following features: in S5, the weather radar beam is formed by using the transmitting pattern and the receiving pattern, and a Kronecker product is performed on the transmitting and receiving patterns to obtain a total pattern of the system.

[0032] Compared with the prior art, the application has the following advantages:

[0033] The phased array weather radar beam forming method based on pattern fitting provided by the application can improve the detection efficiency of the weather radar, multiply shorten the scanning period, and effectively prolong the response time of the aircraft to the weather threat by designing a pattern, weighting the array, forming transmitting and receiving beams, and covering multiple receiving beams with the transmitting beam width. Theoretically, the scanning rate can be improved by several times. The application can be applied to the field of airborne weather radars, and the beam coverage range can be flexibly adjusted according to the advantages and disadvantages of the signal processing performance of different weather radars, so that the application has strong applicability and good market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the application, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 The flowchart of the phased array weather radar beamforming method based on pattern fitting provided in this embodiment of the invention is shown below.

[0036] Figure 2 The following is a schematic diagram of beamforming in the phased array weather radar beamforming method based on pattern fitting provided in this embodiment of the invention. Detailed Implementation

[0037] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the beamforming method provided by the present invention.

[0038] In the description of the embodiments of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0039] Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0040] The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art will understand the specific meaning of these terms in this invention based on the specific circumstances.

[0041] like Figure 1 As shown, a beamforming method for phased array weather radar based on pattern fitting is described, the method comprising the following steps:

[0042] S1: Constructing an ideal radiation pattern:

[0043] Radar pattern can characterize the spatial characteristics of radar-radiated electromagnetic waves. An ideal radar pattern is as follows:

[0044]

[0045] wherein θ is a radar observation angle, R is a radar observation range, the larger R is, the wider the beam is, and the larger the area that the radar system can simultaneously observe is;

[0046] S2: calculating a weighted vector initial value;

[0047] S2.1: a signal matrix received by the phased array is X = AS + N, wherein A is a steering matrix, S is a signal matrix, and N is a noise matrix. A signal direction of arrival is θ, a signal source transmits a symbol b, the number of array elements of the uniform linear array receiving array is M, the element spacing is d, and the signal wavelength is λ, and then the received signal is

[0048]

[0049] performing M-point FFT on x to obtain a corresponding spatial frequency of x

[0050] S2.2: considering that d = λ / 2, when the range of θ is [-90°, 90°], the range of f spatial is 0.5 to -0.5, and the array element weight vector is a quadratic distribution, then the corresponding transmitting direction pattern is also approximately rectangular, and the array element weight vector can be expressed as

[0051]

[0052] wherein w m is the weight vector of the mth array element, m = 1, 2,..., M, is used to control the width of the beam, and the value range thereof is [0, 90°];

[0053] S3: iteratively optimizing the weighted vector initial value of S2 according to the ideal direction pattern of S1 to obtain a transmitting direction pattern:

[0054] S4: calculating a receiving direction pattern;

[0055] S5: forming a beam by using the transmitting direction pattern of S3 and the receiving direction pattern constructed by S4,

[0056] wherein the weighted vector initial value is set by phase weighting through the spatial frequency in S2.

[0057] In some embodiments, S3 includes the following steps:

[0058] S3.1: taking the weighted vector initial value obtained by S2 as a first-generation weighted vector, determining an iteration amount ΔW according to an iteration method, and performing phase weighting to obtain a second-generation weighted vector;

[0059] S3.2: constructing a cost function, judging whether a termination condition is met according to the ideal directivity pattern of S1 and the cost function, if yes, obtaining the transmit directivity pattern according to the optimized weighting vector, if not, entering the next step;

[0060] S3.3: repeating S3.1-S3.2 until the transmit directivity pattern is obtained.

[0061] In some embodiments, the cost function in S3.2 is

[0062]

[0063] wherein, the ε is a weight coefficient, θ is an azimuth angle, W is a weighting vector, R is a radar observation range, and F(θ,W) is a normalized directivity pattern.

[0064] In some embodiments, in S4, the weather radar receives echoes through multiple narrow beams, constructs a steering matrix A of the phased array, obtains an output result of the array, and constructs a receiving directivity pattern.

[0065] In some embodiments, in S5, the weather radar beam is formed using the transmit directivity pattern and the receiving directivity pattern, a Kronecker product is performed on the transmit and receiving directivity patterns, and a total directivity pattern of the system is obtained, as shown in the following formula: Figure 2

[0066] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application. The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A beamforming method for phased array weather radar based on pattern fitting, characterized in that, The method includes the following steps: S1: Construct an ideal radiation pattern; S2: Calculate the initial value of the weighted vector; S3: The emission pattern is obtained by iteratively optimizing the initial value of the weighted vector of S2 based on the ideal radiation pattern of S1; S4: Calculate the receiver pattern; S5: Beam is formed using the transmit pattern of S3 and the receive pattern constructed in S4. In S2, the initial value of the weighting vector is set by phase weighting through spatial frequency, and the ideal radiation pattern in S1 is: Where θ is the azimuth angle and R is the radar observation range. S3 includes the following steps: S3.1: Use the initial value of the weighted vector obtained in S2 as the first-generation weighted vector, and determine the iteration amount according to the iterative method. Phase weighting is then performed to obtain the second-generation weighted vector; S3.2: Construct the cost function. Based on the ideal radiation pattern and cost function in S1, determine whether the termination condition is met. If it is met, obtain the emission radiation pattern based on the optimized weighted vector. If it is not met, proceed to the next step. S3.3: Repeat S3.1-S3.2 until the transmission pattern is obtained. The cost function in S3.2 is Among them, the These are the weighting coefficients. For weighted vectors, This is a normalized direction plot.

2. The beamforming method for phased array weather radar based on pattern fitting according to claim 1, characterized in that, S2 includes the following steps: S2.1: Perform a fast Fourier transform on the received signal to obtain the spatial frequency. S2.2: When the signal wave arrival direction angle range is When the array element weighting vector is set to a quadratic distribution, the initial value of the weighting vector is calculated based on the spatial frequency.

3. The beamforming method for phased array weather radar based on pattern fitting according to claim 2, characterized in that, The initial value of the weighted vector is in, The number of array elements for a uniform linear array receiver. For the first The weighted vector of each array element , Used to control the beamwidth, its value range is: .

4. The beamforming method for phased array weather radar based on pattern fitting according to claim 1, characterized in that, In step S4, the weather radar receives echoes through multiple narrow beams to construct the guidance matrix of the phased array. The output of the array is obtained, and the receiving pattern is constructed.

5. The beamforming method for phased array weather radar based on pattern fitting according to claim 1, characterized in that, In step S5, a weather radar beam is formed using the transmit and receive patterns, and the Kronecker product is performed on the transmit and receive patterns to obtain the overall pattern of the system.

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