CN114252881A

CN114252881A - Target detection method and device, storage medium and terminal equipment

Info

Publication number: CN114252881A
Application number: CN202111491848.5A
Authority: CN
Inventors: 陈锦贤; 李国东; 江吉朝; 黄华栋
Original assignee: Guangzhou Xaircraft Technology Co Ltd
Current assignee: Guangzhou Xaircraft Technology Co Ltd
Priority date: 2021-12-08
Filing date: 2021-12-08
Publication date: 2022-03-29

Abstract

The application provides a target detection method, a device, a storage medium and a terminal device, firstly, a target point is determined based on echo data received by a receiving antenna group; constructing a corresponding two-dimensional angle spectrum according to the target point; determining coordinate values of the target point according to the two-dimensional angle spectrum, wherein the coordinate values comprise vertical coordinates of the target point in the vertical direction; and determining the vertical azimuth angle of the target point according to the vertical coordinate, the vertical direction array antenna interval and the carrier frequency wavelength. By acquiring the vertical coordinate and the vertical azimuth angle, the problem that the conventional radar system does not have vertical resolution is solved.

Description

Target detection method and device, storage medium and terminal equipment

Technical Field

The application relates to the field of radars, in particular to a target detection method, a target detection device, a storage medium and terminal equipment.

Background

With the industrial development and the popularization of intellectualization, the measuring radar is widely applied to vehicles, ships and flight equipment by people. For example, drones for agricultural operations, irrigation vehicles for automatic irrigation, other equipment for transportation.

Most of the current measuring radars are 24Ghz millimeter wave radars, including angle radars, range radars, speed measuring radars and the like. The angle radar, the range radar and the speed measuring radar are all used for measuring aiming at the horizontal plane and have no vertical resolution capability. When information such as a target angle, a distance, and a speed in the vertical direction is required, the target in the vertical direction needs to be equal to the target in the horizontal direction, which results in misdetection of the information such as the target angle, the distance, and the speed.

Disclosure of Invention

It is an object of the present application to provide an object detection method, apparatus, storage medium and terminal device to at least partially improve the above problems.

In order to achieve the above purpose, the embodiments of the present application employ the following technical solutions:

in a first aspect, an embodiment of the present application provides a target detection method, which is applied to a radar device, where the radar device includes a receiving antenna group and a transmitting antenna group, the receiving antenna group includes at least two groups of receiving antennas, the transmitting antenna group includes at least two groups of transmitting antennas, the at least two groups of receiving antennas keep horizontal arrangement at a fixed interval, the at least two groups of transmitting antennas keep sequential arrangement at the fixed interval in both a horizontal direction and a vertical direction, and the method includes:

determining a target point based on the echo data received by the receiving antenna group;

constructing a corresponding two-dimensional angle spectrum according to the target point;

determining coordinate values of the target point according to the two-dimensional angle spectrum, wherein the coordinate values comprise vertical coordinates of the target point in the vertical direction;

and determining the vertical azimuth angle of the target point according to the vertical coordinate, the vertical direction array antenna interval and the carrier frequency wavelength.

In a second aspect, an embodiment of the present application provides a target detection apparatus, which is applied to a radar device, where the radar device includes a receiving antenna group and a transmitting antenna group, the receiving antenna group includes at least two groups of receiving antennas, the transmitting antenna group includes at least two groups of transmitting antennas, the at least two groups of receiving antennas keep horizontal arrangement at a fixed interval, the at least two groups of transmitting antennas keep horizontal and vertical arrangement at the fixed interval, and the apparatus includes:

the preprocessing unit is used for determining a target point based on the echo data received by the receiving antenna group; constructing a corresponding two-dimensional angle spectrum according to the target point;

the calculating unit is used for determining a coordinate value of the target point according to the two-dimensional angle spectrum, wherein the coordinate value comprises a vertical coordinate of the target point in the vertical direction; and determining the vertical azimuth angle of the target point according to the vertical coordinate, the vertical direction array antenna interval and the carrier frequency wavelength.

In a third aspect, an embodiment of the present application provides a radar apparatus, which includes a receiving antenna group, a transmitting antenna group, and a signal processing module; the receiving antenna group comprises at least two groups of receiving antennas, the transmitting antenna group comprises at least two groups of transmitting antennas, the at least two groups of receiving antennas are horizontally arranged at a fixed interval, and the at least two groups of transmitting antennas are sequentially arranged at the fixed interval in the horizontal direction and the vertical direction; the signal processing module is respectively connected with the receiving antenna group and the transmitting antenna group and is used for determining and obtaining the vertical azimuth angle of the target by the target detection method.

In a fourth aspect, an embodiment of the present application provides a movable platform, which includes the radar apparatus described above.

In a fifth aspect, the present application provides a storage medium, on which a computer program is stored, and the computer program, when executed by a processor, implements the method described above.

In a sixth aspect, an embodiment of the present application provides a terminal device, where the terminal device includes: a processor and memory for storing one or more programs; the one or more programs, when executed by the processor, implement the methods described above.

Compared with the prior art, the target detection method, the target detection device, the storage medium and the terminal device provided by the embodiment of the application firstly determine a target point based on echo data received by a receiving antenna group; constructing a corresponding two-dimensional angle spectrum according to the target point; determining coordinate values of the target point according to the two-dimensional angle spectrum, wherein the coordinate values comprise vertical coordinates of the target point in the vertical direction; and determining the vertical azimuth angle of the target point according to the vertical coordinate, the vertical direction array antenna interval and the carrier frequency wavelength. By acquiring the vertical coordinate and the vertical azimuth angle, the problem that the conventional radar system does not have vertical resolution is solved.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and it will be apparent to those skilled in the art that other related drawings can be obtained from the drawings without inventive effort.

Fig. 1 is a schematic structural diagram of a terminal device according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a radar system according to an embodiment of the present disclosure;

fig. 3 is a schematic diagram of an antenna array arrangement according to an embodiment of the present application;

fig. 4a is a schematic view of an antenna array arrangement according to an embodiment of the present application;

fig. 4b is a schematic diagram of an antenna array arrangement according to an embodiment of the present application;

fig. 5 is a schematic layout view of a virtual aperture array provided in an embodiment of the present application;

fig. 6 is a schematic flowchart of a target detection method according to an embodiment of the present application;

fig. 7 is a schematic view of substeps of S101 provided in an embodiment of the present application;

fig. 8 is a schematic view of the substep of S103 according to an embodiment of the present application;

fig. 9 is a schematic diagram illustrating the substeps of S102 according to an embodiment of the present application;

fig. 10 is a schematic flowchart of a target detection method according to an embodiment of the present application;

fig. 11 is a schematic unit diagram of an object detection apparatus according to an embodiment of the present application.

In the figure: 10-a processor; 11-a memory; 12-a bus; 13-a communication interface; 201-a pre-processing unit; 202-a calculation unit.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present application, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", and the like indicate orientations or positional relationships based on orientations or positional relationships shown in the drawings or orientations or positional relationships conventionally found in use of products of the application, and are used only for convenience in describing the present application and for simplification of description, but do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present application.

In the description of the present application, it is also to be noted that, unless otherwise explicitly specified or limited, the terms "disposed" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The embodiments described below and the features of the embodiments can be combined with each other without conflict.

As described above, in the case where the radar does not have the vertical resolution, when information such as the angle, distance, and speed of a target in the vertical direction is required, the target in the vertical direction needs to be identical to the target in the horizontal direction, which results in erroneous detection of the information such as the angle, distance, and speed of the target. Meanwhile, since there is no vertical resolution, a two-dimensional plane picture cannot be formed by a radar imaging technique.

The embodiment of the application provides a radar equipment, radar equipment can be applied to among the movable platform, but movable platform can be unmanned aerial vehicle or unmanned vehicles or other survey equipment.

Referring to fig. 2, in one possible implementation, the radar device may be a millimeter wave imaging radar system, such as a 24Ghz millimeter wave imaging radar. As shown in fig. 2, the 24Ghz millimeter wave imaging radar includes a receiving antenna group, a transmitting antenna group, a 24Ghz signal transmitting and receiving module, and an MCU signal processing module.

The transmit antenna group includes at least two sets of transmit antennas (TX), illustrated as 4 transmit antennas in fig. 3, and the receive antenna group includes at least two sets of receive antennas (RX), illustrated as 12 receive antennas in fig. 3. Optionally, the antenna is a 24Ghz transceiver antenna. 4 transmitting antennas are used for radiating 24Ghz signals into the air, and 12 receiving antennas are used for receiving the 24Ghz +/-X signals reflected by the obstacles from the air. As shown in fig. 3, at least two groups of receiving antennas are horizontally arranged with a fixed distance therebetween, and at least two groups of transmitting antennas are sequentially arranged with the fixed distance therebetween in both the horizontal direction and the vertical direction. In one possible implementation, at least two sets of transmitting antennas are time division multiplexed according to a preset frequency.

As shown in FIG. 3, each 8 chips of array elements form 1 24Ghz millimeter wave antenna, and there are 12 receiving antennas (RX 1-12) and 4 transmitting antennas (TX 1-TX 4) in total. The spacing between each receiving antenna is D1-6.2 mm (half wavelength of 24 Ghz), the horizontal spacing between each transmitting antenna is D2-6.2 mm, and the vertical spacing between each transmitting antenna is H-6.2 mm. Because of the limitation of the size of the board, for example, the size is 73.13mmx98.02mm, the transceiver antennas are placed diagonally, and if the space is enough, the transceiver antennas can be placed horizontally or vertically, as shown in fig. 4a and 4 b. Regardless of the placement of the transmitting and receiving antennas, the millimeter wave radar in the MIMO (multiple transmission and multiple reception) system can be equivalent to a 4X12 parallelogram area array (virtual aperture array) as shown in fig. 5. Under the transmitting and receiving area array, the 24Ghz millimeter wave radar has not only 12 horizontal receiving antennas but also 4 vertical receiving antennas.

The 24Ghz signal transmitting and receiving module includes a frequency detection/control circuit, an FMCW Transmitter, a VCO (24Ghz voltage-controlled oscillator), a directional coupler, a Power AMP, an RF SWITCH, an LNA (bottom noise amplifier), a mixer, a Power divider, and a BPF (band pass filter).

The frequency detection/control circuit is used for detecting the frequency of the modulation signal and feeding back the frequency to the MCU signal processing module, and controlling the frequency of the modulation signal in time, thereby forming a closed loop with controllable frequency.

An FMCW Transmitter (FMCW modulated signal Transmitter) is used to modulate the digital signal emitted by the MCU into an analog FMCW modulated signal.

The VCO (24Ghz voltage controlled oscillator) is used for frequency doubling and mixing FMCW modulation signals into millimeter wave signals of 24Ghz and has certain power amplification.

The directional coupler is used for generating another path of 24Ghz millimeter wave signal, namely a so-called LO (local oscillator signal), by coupling the 24Ghz millimeter wave signal through energy.

The POWER AMP (POWER amplifier) is used to POWER-amplify the millimeter wave signal of 24 Ghz.

The 3 power dividers are used for transmitting the LO (local oscillator signal) with constant frequency and equal power division to the mixer in a transmission mode.

The LNA (bottom noise amplifier) is used to amplify and deliver to the mixer the ultra-low power wanted signal in the air.

The mixer is used to mix the LNA-amplified desired signal with the LO for conversion to an IF (low frequency signal).

A BPF (band pass filter) is used to filter out unnecessary low-frequency components and high-frequency components in the IF, and amplify the IF signal in the band of the BPF.

The MCU signal processing module comprises a master MCU (micro controller unit) and a slave MCU (micro controller unit), wherein the master MCU and the slave MCU can respectively carry out independent FFT (fast Fourier transform) operation, both are provided with a plurality of A/D converters (analog-to-digital converters), and data exchange can be carried out between the A/D converters and the analog-to-digital converters through SPI (high-speed data exchange bus). The FFT (fast fourier transform) mainly functions to convert a time domain signal into a frequency domain signal. The a/D converter (analog-to-digital converter) is used to collect analog signals and convert the analog signals into digital signals.

Referring to fig. 6, a target detection method provided in the embodiment of the present application may be applied to, but is not limited to, a radar device, and includes: s101, S102, S103, and S104.

S101, determining a target point based on the echo data received by the receiving antenna group.

In one possible implementation, the echo signals received by the receiving antenna set are collected by an a/D converter as shown in fig. 2, and echo data is obtained.

Regarding the content in S101, how to determine the target point, the embodiment of the present application further provides a possible implementation manner, please refer to fig. 7, where S101 includes: s101-1, S101-2, S101-3, S101-4 and S101-5.

And S101-1, removing low-frequency components in the echo data.

Optionally, fitting the echo data by a polynomial fitting manner to obtain a fitting curve, where the fitting curve is approximately equal to the low-frequency component in the signal, and subtracting the fitting curve from the echo data to remove the low-frequency component in the echo signal.

Optionally, a curve is fitted to the echo signal in the echo signal preprocessing section by means of N-order polynomial fitting, and the fitted polynomial curve is subtracted from the original echo signal to achieve the goal of removing low-frequency components, where N is generally not greater than 5.

And S101-2, performing distance Fourier transform and Doppler fast Fourier transform on the echo data with the low-frequency components removed to obtain an RD domain signal spectrum.

It should be noted that, in the radar system in the embodiment of the present application, an alternate transmission system is adopted, TX 1-TX 4 transmit in turn, each transmitting antenna corresponds to 12 receiving channels, each receiving channel adopts Nr points, and Na wheels are transmitted alternately, so that Nr × Na × 48 echo data are obtained. And performing Na × 48 times of N-point windowing Fourier transform along the Nr direction, and then performing N × 48 times of Na-point windowing Fourier transform along the Na direction to obtain the RD signal domain signal spectrum with the size of N × Na × 48.

And S101-3, performing modulus calculation on the RD domain signal spectrum to obtain a modulus value of the RD domain signal spectrum.

And S101-4, performing incoherent superposition on the RD domain signal spectrum modulus values to obtain the RD domain signal spectrum amplitude.

Alternatively, the RD domain signal spectral amplitude may be obtained by the following equation:

D(i，j)＝∑_k|RD(i，j，k)|

wherein, | RD (i, j, k) | represents the module value of the RD domain signal spectrum of the kth receiving channel of the jth Doppler unit of the ith distance unit, and D (i, j) represents the result of incoherent superposition of the jth Doppler unit of the ith distance unit along the receiving channel. The first dimension of the RD domain signal spectral amplitude represents distance and the second dimension represents doppler (velocity).

And S101-5, acquiring a one-dimensional distance spectrum according to the RD domain signal spectrum amplitude.

Optionally, after obtaining the incoherent superposition result D of the RD domain signal spectrum amplitude, searching a maximum value of the doppler dimension (second dimension) in the direction of the distance dimension (first dimension) in D, recording the maximum value of the doppler direction and its coordinates corresponding to each distance cell, and obtaining a sequence from the maximum values as a one-dimensional distance spectrum sequence, i.e., a one-dimensional distance spectrum. Its index is used for target velocity estimation and target motion compensation.

And S101-6, determining a point in the one-dimensional distance spectrum, which is higher than the one-dimensional distance threshold, as a target point.

Optionally, the one-dimensional distance threshold consists of three parts: curve model, signal-to-noise ratio threshold, and background noise. The curve model is fitted according to the principle that the signal described by the radar equation attenuates along with the distance, and a formula is given; the signal-to-noise ratio threshold is a preset value and is given according to actual requirements; the background noise is the average of the one-dimensional range signals. All points in the one-dimensional distance spectrum above the corresponding threshold are determined as target points.

Optionally, the expression of the one-dimensional distance threshold is as follows:

wherein Th (i) represents the threshold value of the ith distance unit, N is the distance dimension FFT point number, a is the model parameter, and is obtained by analyzing the actual echo pattern.

And S102, constructing a corresponding two-dimensional angle spectrum according to the target point.

In one possible implementation, the arrangement of elements in the two-dimensional angular spectrum is the same as the virtual aperture array shown in fig. 5, which is the arrangement of the set of receive antennas with respect to different transmit antennas.

Optionally, the two-dimensional angle spectrum is a two-dimensional matrix formed by performing horizontal and vertical dimension windowing FFT on a two-dimensional angle input value (virtual aperture array), and the amplitude value in the RD domain signal spectrum is a modulus value of a corresponding two-dimensional angle spectrum element.

S103, determining the coordinate value of the target point according to the two-dimensional angle spectrum.

Wherein the coordinate values include vertical coordinates of the target point in the vertical direction.

It is to be understood that the coordinate values of the target point may be coordinate values of the target point in a coordinate system of the radar system, and the vertical direction may be a direction vertical to the ground. The vertical coordinate of the target point in the vertical direction is acquired, so that the target point has vertical resolution.

And S104, determining the vertical azimuth angle of the target point according to the vertical coordinate, the vertical direction array antenna interval and the carrier frequency wavelength.

In an embodiment, the step S104 may include the steps of: determining the ratio of the array antenna interval and the carrier frequency wavelength in the vertical direction and the number of FFT points in the vertical direction; and determining the vertical azimuth angle of the target point according to the vertical coordinate, the ratio and the FFT point number.

Optionally, the vertical array antennas are spaced apart by a fixed pitch as described previously. The expression for the vertical azimuth is:

wherein the content of the first and second substances,

characterizing the vertical azimuth angle in radians;

representing a vertical coordinate; n is a radical of₂The number of FFT points in the vertical direction is represented; d_intAnd characterizing the ratio of the interval of the array antennas in the vertical direction to the wavelength of the carrier frequency.

To sum up, the embodiment of the present application provides a target detection method, which is applied to a radar device, where the radar device includes a receiving antenna group and a transmitting antenna group, the receiving antenna group includes at least two groups of receiving antennas, the transmitting antenna group includes at least two groups of transmitting antennas, the at least two groups of receiving antennas keep a fixed-distance horizontal arrangement, the at least two groups of transmitting antennas keep a fixed-distance horizontal arrangement in both horizontal and vertical directions, and a target point is determined based on echo data received by the receiving antenna group; constructing a corresponding two-dimensional angle spectrum according to the target point; determining coordinate values of the target point according to the two-dimensional angle spectrum, wherein the coordinate values comprise vertical coordinates of the target point in the vertical direction; and determining the vertical azimuth angle of the target point according to the vertical coordinate, the vertical direction array antenna interval and the carrier frequency wavelength. By acquiring the vertical coordinate and the vertical azimuth angle, the problem that the conventional radar system does not have vertical resolution is solved.

On the basis of fig. 6, regarding the content in S103, the embodiment of the present application further provides a possible implementation manner, please refer to fig. 8, where S103 includes: s103-1 to S103-5.

S103-1, performing modular calculation on the two-dimensional angle spectrum.

Alternatively, taking the array shown in fig. 3 as an example, the expression of the two-dimensional angular spectrum is as follows:

wherein A is a two-dimensional angular spectrum, a_t，kIndicating the value of the target at the RD signal spectrum corresponding to the kth receiving channel of the tth transmitting antenna. S103-2, searching the two-dimensional angle spectrum after the modulus calculation along the horizontal direction to obtain a vertical maximum value, and performing dimensionality reduction processing according to the index of the vertical maximum value to obtain a horizontal angle spectrum.

Optionally, only the angle corresponding to the vertical maximum value is detected in the vertical direction, dimension reduction processing is performed according to the index of the vertical maximum value, the vertical maximum value is selected as the angle spectrum value corresponding to the horizontal direction, and a one-dimensional angle spectrum in the horizontal direction, that is, a horizontal angle spectrum, is obtained.

S103-3, determining an angle spectrum threshold value according to the average value and the maximum value of the horizontal angle spectrum and a preset angle spectrum threshold parameter.

Optionally, the expression of the angular spectral threshold is:

A_th＝(A_max-A_ref)F_th

wherein A is_thCharacterizing the angular spectral threshold, A_maxMaximum value of the horizontal angular spectrum, A_refCharacterizing the mean value of the horizontal angular spectrum, F_thAnd characterizing an angle spectrum threshold parameter.

S103-4, screening out the maximum value larger than the threshold value of the angle spectrum from the horizontal angle spectrum.

In the present embodiment, the number of maximum values is not limited.

S103-5, carrying out quadratic curve interpolation processing on the maximum value to obtain the coordinate value of the target point.

Alternatively, the coordinates of the target in the horizontal direction and the vertical direction are obtained through quadratic curve interpolation processing, that is, the coordinates are obtained

On the basis of fig. 6, for the content in S102, the embodiment of the present application further provides a possible implementation manner, please refer to fig. 9, where S102 includes: s102-1 and S102-2.

S102-1, arranging the amplitudes of the target points in the RD domain signal spectrum to obtain the corresponding virtual aperture array.

Optionally, distance and speed detection of the target is performed on the RD domain signal spectrum amplitude to obtain coordinates of the target in the RD domain signal spectrum, a value of the target point is obtained in the RD domain signal spectrum according to the coordinates, and the amplitudes of the target point in the RD domain signal spectrum are arranged to obtain a corresponding virtual aperture array. The virtual aperture array is an arrangement of a receiving antenna group relative to different transmitting antennas, as shown in fig. 5.

Specifically, each target point corresponds to 4 × 12 values, and these values are filled in one by one according to the position of the "virtual aperture array shown in fig. 5", and the unfilled value is set to 0, so as to obtain the virtual aperture array of the target point DOA.

Alternatively, a_t，kRD (i, j, (t-1) × 12+ k); wherein i represents the distance dimension index of the target point in the RD domain signal spectrum, j represents the Doppler dimension index of the target point in the RD domain signal spectrum, and a_t，kIndicating the value of the target at the RD signal spectrum corresponding to the kth receiving channel of the tth transmitting antenna.

S102-2, adding a Hanning window to the virtual aperture array along the horizontal direction, performing horizontal direction Fourier transform, and then performing frequency spectrum moving; and adding a Hanning window to the virtual aperture array along the vertical direction, performing Fourier transform in the vertical direction, and then performing frequency spectrum shifting, thereby obtaining a two-dimensional angle spectrum.

Alternatively, horizontal direction FFT: adding Hanning window along the direction of horizontal receiving antenna to make N₁Performing point FFT and carrying out frequency spectrum shifting; vertical direction FFT: adding a Hanning window along the direction perpendicular to the receiving antenna to obtain N₂And performing point FFT and carrying out spectrum shifting, thereby obtaining a two-dimensional angle spectrum.

It will be appreciated that FFT is a mathematical operation, and the horizontal direction of the virtual aperture array is the horizontal direction shown in fig. 5, and the vertical direction is the vertical direction shown in fig. 5. The horizontal windowed FFT consists of first multiplying each of the 12 points in the transverse direction by the value of the window function (the length of the window is the same as the number of real signals for that direction [ single row "1" in fig. 5 ]); then, front and back zero padding is carried out according to the virtual aperture position [ the front of the first row does not need to be padded with zero, the back is padded with N1-12 zeros, the front of the second row is padded with 1 zero, and the back is padded with N1-12-1 zeros …, and so on); finally, an N1 point FFT is performed for each row. The vertical windowed FFT consists of first multiplying each of the 4 points vertically by the value of the window function (the length of the window is the same as the number of single columns "1" in fig. 5) for that direction; then, post zero padding is carried out according to the position of the virtual aperture [ N2-4 zeros are padded after the first column, N2-4 zeros … are padded after the second column, and the like in sequence ]; and finally, performing N2-point FFT on each column to complete the conversion from the virtual aperture array to a two-dimensional angular spectrum.

The two-dimensional angle spectrum is determined after coordinates of a target point at the one-dimensional signal spectrum amplitude value are obtained, the target point higher than a threshold has a one-dimensional distance coordinate and a corresponding Doppler direction coordinate, and a two-dimensional coordinate formed by the coordinates is obtained through a formula.

In a possible implementation manner, the coordinate values further include a horizontal coordinate of the target point in the horizontal direction, and on the basis of fig. 6, regarding how to obtain the horizontal azimuth angle, the embodiment of the present application further provides a possible implementation manner, please refer to fig. 10, and the target detection method further includes S105.

And S110, determining a horizontal azimuth angle of a target point according to the horizontal coordinate, the array antenna interval in the horizontal direction and the carrier frequency wavelength.

Optionally, the expression of the horizontal azimuth is:

wherein theta represents the horizontal azimuth angle in radians; theta_indexCharacterizing the horizontal coordinate; n is a radical of₁Representing the number of FFT points in the horizontal direction; d_intAnd characterizing the ratio of the horizontal array antenna interval to the carrier frequency wavelength.

The target detection method provided by the embodiment of the application is suitable for the 4T12R antenna array shown in FIG. 3 and an imaging radar array with lower corner resolution in the vertical direction. The beam width of the array antenna in the vertical direction is +/-15 degrees, the beam width of the array antenna in the vertical direction is quite close to 28.65 degrees of the angular resolution in the vertical direction, so that the capability of resolving a plurality of targets at the same distance and the same speed in the vertical direction is poor, meanwhile, the beam width in the horizontal direction is +/-60 degrees, and the angular resolution in the horizontal direction is much greater than 9.55 degrees, so that the method for estimating the single angle in the vertical direction and estimating the multiple angles in the horizontal direction is adopted. The array is suitable for scenes with few targets in the vertical direction, such as open farmlands, areas above forest zones and the like.

In one possible implementation, the horizontal array spacing is the same as the vertical array spacing, so the same notation is used to denote the ratio of the horizontal array antenna spacing to the carrier frequency wavelength and the ratio of the vertical array antenna spacing to the carrier frequency wavelength.

In the target detection method provided by the embodiment of the application, the 24Ghz millimeter wave radar has not only the angular resolution of the horizontal dimension, but also the angular resolution of the vertical dimension. The unmanned aerial vehicle can be well helped, the unmanned vehicle and other equipment can separate and clear the ground and sky obstacles, and the system can better plan and avoid obstacle paths. In addition, because the radar has the resolution of three dimensions, namely a vertical dimension, a horizontal dimension and a distance dimension, the radar can help a software device to establish a three-dimensional point cloud picture.

Referring to fig. 11, fig. 11 is a diagram of an object detection apparatus according to an embodiment of the present application, where the object detection apparatus is optionally applied to the radar device described above.

The object detection device includes: a preprocessing unit 201 and a calculation unit 202.

A preprocessing unit 201, configured to determine a target point based on echo data received by the receiving antenna group; and constructing a corresponding two-dimensional angle spectrum according to the target point.

A calculating unit 202, configured to determine coordinate values of the target point according to the two-dimensional angle spectrum, where the coordinate values include vertical coordinates of the target point in a vertical direction; and determining the vertical azimuth angle of the target point according to the vertical coordinate, the vertical direction array antenna interval and the carrier frequency wavelength.

Alternatively, the preprocessing unit 201 may perform S101 and S102 described above, and the calculation unit 202 may perform S103 to S105 described above.

It should be noted that the object detection apparatus provided in this embodiment may execute the method flows shown in the above method flow embodiments to achieve the corresponding technical effects. For the sake of brevity, the corresponding contents in the above embodiments may be referred to where not mentioned in this embodiment.

The embodiment of the application also provides a storage medium, wherein the storage medium stores computer instructions and programs, and the computer instructions and the programs execute the target detection method of the embodiment when being read and run. The storage medium may include memory, flash memory, registers, or a combination thereof, etc.

The following provides a terminal device, which may be a remote controller or other handheld device, and the terminal device may communicate with the radar system in a wired or wireless manner. The terminal device is shown in fig. 1, and the radar system is shown in fig. 2, and the target detection method can be realized by the cooperation of the terminal device and the radar system. In some embodiments, the radar system may be incorporated into the terminal device such that the terminal device is directly provided with the radar system; in other embodiments, the radar system and the terminal device may be provided separately; specifically, the terminal device includes: processor 10, memory 11, bus 12. The processor 10 may be a CPU. The memory 11 is used for storing one or more programs, which when executed by the processor 10, perform the object detection method of the above-described embodiments.

The processor 10 may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the object detection method may be performed by integrated logic circuits of hardware or instructions in the form of software in the processor 10. The Processor 10 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; the device can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, a discrete Gate or transistor logic device, or a discrete hardware component.

The Memory 11 may comprise a high-speed Random Access Memory (RAM) and may further comprise a non-volatile Memory (non-volatile Memory), such as at least one disk Memory.

The bus 12 may be an ISA (Industry Standard architecture) bus, a PCI (peripheral Component interconnect) bus, an EISA (extended Industry Standard architecture) bus, or the like. Only one bi-directional arrow is shown in fig. 1, but this does not indicate only one bus 12 or one type of bus 12.

The memory 11 is used for storing programs, such as programs corresponding to the object detection device. The object detection means comprise at least one software function which may be stored in the memory 11 in the form of software or firmware or may be fixed in the Operating System (OS) of the terminal device. The processor 10, upon receiving the execution instruction, executes the program to implement the object detection method.

Possibly, the terminal device provided by the embodiment of the present application further includes a communication interface 13. The communication interface 13 is connected to the processor 10 via a bus. The terminal device can perform communication interaction with other devices through the communication interface 13. It should be understood that the structure shown in fig. 1 is only a schematic structural diagram of a portion of a terminal device, and the terminal device may also include more or fewer components than shown in fig. 1, or have a different configuration than shown in fig. 1. The components shown in fig. 1 may be implemented in hardware, software, or a combination thereof.

In the embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. The apparatus embodiments described above are merely illustrative, and for example, the flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

In addition, functional modules in the embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

The functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

It will be evident to those skilled in the art that the present application is not limited to the details of the foregoing illustrative embodiments, and that the present application may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Claims

1. A target detection method is applied to a radar device, the radar device comprises a receiving antenna group and a transmitting antenna group, the receiving antenna group comprises at least two groups of receiving antennas, the transmitting antenna group comprises at least two groups of transmitting antennas, the at least two groups of receiving antennas are horizontally arranged at a fixed interval, the at least two groups of transmitting antennas are sequentially arranged at the fixed interval in the horizontal direction and the vertical direction, and the method comprises the following steps:

2. The target detection method of claim 1, wherein the step of determining the coordinate values of the target point according to the two-dimensional angular spectrum comprises:

performing a modulus calculation on the two-dimensional angle spectrum;

searching the two-dimensional angle spectrum subjected to the modulus calculation along the horizontal direction to obtain a vertical maximum value, and performing dimensionality reduction processing according to an index of the vertical maximum value to obtain a horizontal angle spectrum;

determining an angle spectrum threshold value according to the mean value and the maximum value of the horizontal angle spectrum and a preset angle spectrum threshold parameter;

screening out maxima from the horizontal angle spectrum that are greater than the threshold of the angle spectrum;

and carrying out quadratic curve interpolation processing on the maximum value to obtain the coordinate value of the target point.

3. The object detection method of claim 2, wherein the angular spectrum threshold is expressed by:

A_th＝(A_max-A_ref)F_th

wherein A is_thCharacterizing the angular spectral threshold, A_maxCharacterizing the maximum of the horizontal angular spectrum, A_refCharacterizing the mean value of the horizontal angular spectrum, F_thCharacterizing the angular spectral threshold parameter.

4. The object detection method of claim 1, wherein the step of determining a target point based on the echo data received by the set of receive antennas comprises:

removing low-frequency components in the echo data;

performing distance Fourier transform and Doppler fast Fourier transform on the echo data with the low-frequency components removed to obtain an RD domain signal spectrum;

performing modulus calculation on the RD domain signal spectrum to obtain a modulus value of the RD domain signal spectrum;

performing incoherent superposition on the RD domain signal spectrum modulus value to obtain an RD domain signal spectrum amplitude value;

acquiring a one-dimensional distance spectrum according to the RD domain signal spectrum amplitude;

and determining a point in the one-dimensional distance spectrum which is higher than a one-dimensional distance threshold as the target point.

5. The target detection method of claim 4, wherein the step of constructing a corresponding two-dimensional angular spectrum from the target point comprises:

arranging the amplitudes of the target points in the RD domain signal spectrum to obtain a corresponding virtual aperture array;

wherein the virtual aperture array is a permutation and combination of the set of receive antennas with respect to different transmit antennas;

adding a Hanning window to the virtual aperture array along the horizontal direction, performing Fourier transform in the horizontal direction, and then performing frequency spectrum moving; and adding a Hanning window to the virtual aperture array along the vertical direction, performing Fourier transform in the vertical direction, and then performing frequency spectrum shifting, thereby obtaining the two-dimensional angle spectrum.

6. The method of claim 1, wherein said determining a vertical azimuth of said target point based on said vertical coordinate, vertical array antenna spacing, and carrier frequency wavelength comprises:

determining the ratio of the array antenna interval and the carrier frequency wavelength in the vertical direction and the number of FFT points in the vertical direction;

and determining the vertical azimuth angle of the target point according to the vertical coordinate, the ratio and the FFT point number.

7. The object detection method of claim 6, wherein the expression of the vertical azimuth angle is:

wherein the content of the first and second substances,

characterizing the vertical azimuth angle in radians;

characterizing the vertical coordinate;N₂the number of FFT points in the vertical direction is represented; d_intAnd characterizing the ratio of the interval of the array antennas in the vertical direction to the wavelength of the carrier frequency.

8. The object detection method according to claim 1, wherein the coordinate values further include horizontal coordinates of the object point in a horizontal direction, the method further comprising:

and determining the horizontal azimuth angle of the target point according to the horizontal coordinate, the array antenna interval in the horizontal direction and the carrier frequency wavelength.

9. The object detection method of claim 8, wherein the expression of the horizontal azimuth angle is:

wherein θ represents the horizontal azimuth in radians; theta_indexCharacterizing the horizontal coordinate; n is a radical of₁Representing the number of FFT points in the horizontal direction; d_intAnd characterizing the ratio of the array antenna interval in the horizontal direction to the carrier frequency wavelength.

10. A target detection device is applied to radar equipment, wherein the radar equipment comprises a receiving antenna group and a transmitting antenna group, the receiving antenna group comprises at least two groups of receiving antennas, the transmitting antenna group comprises at least two groups of transmitting antennas, the at least two groups of receiving antennas are horizontally arranged at a fixed interval, the at least two groups of transmitting antennas are sequentially arranged at the fixed interval in the horizontal direction and the vertical direction, and the device comprises:

11. The radar equipment is characterized by comprising a receiving antenna group, a transmitting antenna group and a signal processing module; the receiving antenna group comprises at least two groups of receiving antennas, the transmitting antenna group comprises at least two groups of transmitting antennas, the at least two groups of receiving antennas are horizontally arranged at a fixed interval, and the at least two groups of transmitting antennas are sequentially arranged at the fixed interval in the horizontal direction and the vertical direction; the signal processing module is respectively connected with the receiving antenna group and the transmitting antenna group and is used for determining and obtaining the vertical azimuth angle of the target by the method of any one of claims 1-9.

12. A movable platform comprising the radar apparatus of claim 11.

13. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the method according to any one of claims 1-9.

14. A terminal device, comprising: a processor and memory for storing one or more programs; the one or more programs, when executed by the processor, implement the method of any of claims 1-9.