A velocity extension method based on angle spectrum estimation in TDM-MIMO FMCW radar

Abstract

The application discloses a velocity expansion method based on angle spectrum estimation in a TDM-MIMO FMCW radar, relates to the millimeter wave radar field, and solves the problem of the problem that the velocity range of an existing TDM-MIMO FMCW system radar is reduced by several times, and the following scheme is provided, which comprises the following steps: firstly, a two-dimensional FFT is performed on an array antenna channel amplitude phase complex vector X to perform velocity compensation and calculate a compensated antenna channel amplitude phase complex vector X'; X' is taken as input, a DOA algorithm based on a Bartlett-DBF (Bartlett beamformer) is used to obtain an angle search spectrum S; S is taken as input, a target signal-to-noise ratio is calculated; and a velocity value corresponding to S with the highest signal-to-noise ratio is selected as an expanded velocity. The device is not sensitive to channel noise, has good robustness, and the calculation correctness of the expanded velocity is also greatly improved. In addition, the scheme used in the application only needs to calculate eigenvalues, and the estimation amount is very small.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of millimeter wave radar, in particular to a speed expansion method based on angle spectrum estimation in TDM-MIMO FMCW radar. BACKGROUND

[0002] TDM-MIMO FMCW is the full name of Time Division Multiplexing-Multiple Input Multiple Output Frequency Modulated Continuous Wave, which corresponds to Chinese as time division multiplexing multiple input multiple output frequency modulated continuous wave. The millimeter wave radar based on TDM-MIMO FMCW takes the linear frequency modulated continuous fast sawtooth wave as the basic waveform of radar transmission, uses the time division alternately transmitted waveform of the transmission channel, that is, the TDM-MIMO technology to form an expanded virtual array, so that the radar aperture is greatly expanded compared with the physical aperture, thereby improving the angle measurement capability of the radar.

[0003] However, while the TDM-MIMO technology brings the improvement of the angle measurement capability, due to the lengthening of the time interval of the adjacent two sawtooth waves of the same transmission channel, the technology also causes the speed measurement range to be reduced by several times. For example, if there are N transmission channels for alternately transmitting, the speed measurement range will be reduced to one Nth. For the application fields of intelligent vehicles and intelligent transportation, the speed measurement range is one of the key indicators of the millimeter wave radar, and a smaller speed measurement range will limit the application scenarios.

[0004] Therefore, there is an urgent need for a new speed expansion method to solve this problem. Therefore, a speed expansion method based on angle spectrum estimation in TDM-MIMO FMCW radar is proposed. SUMMARY

[0005] The purpose of the present application is to provide a speed expansion method based on angle spectrum estimation in TDM-MIMO FMCW radar, which solves the problem of the existing TDM-MIMO FMCW system radar speed range being reduced by several times.

[0006] To achieve the above purpose, the present application provides the following technical scheme: a speed expansion method based on angle spectrum estimation in TDM-MIMO FMCW radar, characterized by comprising the following steps:

[0007] (1) According to the number of MIMO transmission channels The possible speed expansion coefficient vector M is calculated according to the following formula;

[0008] (2) All possible speed expansion coefficients are traversed;

[0009] (3) Calculate the compensated phase value after velocity expansion according to the velocity expansion coefficient value and the Doppler value V of the target before expansion ; according to the phase of each array channel to form an amplitude-phase complex vector X, and the compensated amplitude-phase complex vector X' after velocity compensation is obtained :

[0010] S1: Calculate the basic phase compensation value according to V and :

[0011] ;

[0012] wherein #Tx represents the number of transmitting channels, V represents the Doppler value of the target before expansion, and N is the number of Doppler points (the number of Doppler points of two-dimensional FFT);

[0013] S2: Calculate the expansion phase compensation value according to the velocity expansion coefficient value and the basic phase compensation value :

[0014] wherein #Tx represents the number of transmitting channels;

[0015] S3: Calculate the final velocity compensation phase vector P according to the array channel and reference channel transmission interval difference vector T and :

[0016] ;

[0017] wherein ; t j represents the transmission time interval difference between the array channel j and the reference channel, and T represents the transpose;

[0018] S4: Calculate according to P and X:

[0019] represents the Hadamard product (the multiplication of corresponding elements of two vectors or matrices), , represents the amplitude-phase value after velocity compensation of the jth channel, and T represents the transpose; (4) Use

[0020] to calculate the angle spectrum of Bartlett-DBF according to the following formula :

[0021] =​ ], is the horizontal angle corresponding Bartlett-DBF angle spectrum value, The value range and step value can be selected according to the actual scene and demand, such as-75°~+75°, step value is step 1;

[0022] (5) Based on the angle spectrum , the signal-to-noise ratio of the target is calculated by calculating the ratio of the maximum value to the average value ;

[0023] (6) Select the maximum value in all , corresponding is the velocity expansion coefficient value m, and then the expanded velocity V is calculated according to m and V .

[0024] Preferably, the calculation formula of the velocity expansion coefficient vector M in the (1) is: .

[0025] Preferably, the (3)~(5) are all operations in the step (2) traversal cycle.

[0026] Preferably, the calculation method of in the (4) is as follows:

[0027] ;

[0028] is the corresponding steering vector, represents the expectation, represents the expectation of the covariance matrix of under multiple shots, represents the conjugate transpose.

[0029] Preferably, the calculation formula of in the (5) is:

[0030] ;

[0031] max() represents the maximum value, and mean() represents the average value.

[0032] Preferably, the calculation formula of in the (6) is: =m* +V.

[0033] ​​Compared with the related art, the TDM-MIMO FMCW radar speed extension method based on angle spectrum estimation has the following beneficial effects:

[0034] The application provides a TDM-MIMO FMCW radar speed extension method based on angle spectrum estimation. Figure 1 The application can effectively solve the problem of small speed range of the TDM-MIMO FMCW radar (such as the radar shown in the figure) and has no constraint on the antenna layout, so that the antenna channels can be maximally utilized.

[0035] In addition, the application itself utilizes the characteristics of the target signal-to-noise ratio and considers the influence of the array channel noise, so the application is not sensitive to the channel noise, has good robustness, and greatly improves the calculation accuracy of the extended speed. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The figure is a waveform diagram of the TDM-MIMO FMCW waveform system radar.

[0037] Figure 2 The figure is a schematic diagram of the MIMO virtual array of the TDM-MIMO FMCW waveform system radar.

[0038] Figure 3 The figure is a speed extension flowchart of the TDM-MIMO FMCW radar speed extension method based on angle spectrum estimation. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0040] Embodiment one: please refer to Figure 1 The application provides a technical solution: a TDM-MIMO FMCW radar speed extension method based on angle spectrum estimation, characterized by comprising the following steps:

[0041] (1) According to the number of MIMO transmitting channels The possible speed extension coefficient vector M is calculated according to the following formula:

[0042] (2) All possible speed extension coefficients are traversed;

[0043] (3) Based on the velocity expansion coefficient value The compensated phase value after velocity expansion is calculated using the Doppler value V of the target before expansion. ;according to Velocity compensation is performed on the amplitude-phase complex vector X formed by the phases of each array channel to obtain the compensated amplitude-phase complex vector. :

[0044] S1: According to V and Calculate the basic phase compensation value :

[0045] ;

[0046] Where: #Tx represents the number of transmission channels, and V represents the Doppler value of the target before it expands. The number of Doppler points (Doppler points of a two-dimensional FFT);

[0047] S2: Based on the velocity expansion coefficient value and basic phase compensation value Calculate the extended phase compensation value :

[0048] Where: #Tx represents the number of transmission channels;

[0049] S3: Based on the transmission interval difference vector T between the array channel and the reference channel, and Calculate the final velocity compensation phase vector P:

[0050] ;

[0051] in, ;t j This represents the time interval difference between the transmission of array channel j and the reference channel, and T represents transpose;

[0052] S4: Calculate based on P and X ;

[0053] Hadamard product (the element-wise multiplication of two vectors or matrices). , Indicates the first The amplitude and phase values ​​after speed compensation for each channel, where T represents transpose;

[0054] (4) Utilization Calculate the angular spectrum of Bartlett-DBF using the following formula. :

[0055] =[ ], horizontal angle The corresponding Bartlett-DBF angular spectrum values, The value range and step value can be selected according to the actual scenario and needs, such as -75°~+75°, with a step value of 1 step.

[0056] (5) Based on angular spectrum The signal-to-noise ratio of the target is calculated by dividing the maximum value by the mean value. ;

[0057] (6) in all Select the maximum value from the middle , Corresponding Let m be the velocity expansion coefficient, and then calculate the expanded velocity based on m and V. .

[0058] (1) The formula for calculating the velocity spread coefficient vector M is: .

[0059] (3) to (5) are all operations within the loop of step (2).

[0060] (4) The calculation method is as follows:

[0061] ;

[0062] for The corresponding guide vector, Represents expectations, How quickly to take the picture? The expectation of the covariance matrix, This indicates the conjugate transpose.

[0063] (5) The calculation formula is:

[0064] ;

[0065] `max()` represents the maximum value, and `mean()` represents the mean value.

[0066] (5) The calculation formula is: =m* +V.

[0067] The current mainstream solution is to use antenna design to enable the virtual array (such as...) after MIMO. Figure 2The virtual receiving channels corresponding to different transmitting channels in the array overlap. The real speed is calculated by using the phase difference between the overlapping channels. However, this method has great constraints on the antenna layout and cannot fully utilize the antenna channel resources. Moreover, due to the influence of noise, the phase difference between the overlapping channels has great error, which can lead to a serious problem of incorrect calculation of the real speed.

[0068] The present application can effectively solve the problem of small radar speed range of the TDM-MIMO FMCW system (such as the radar shown in the figure) and has no constraints on the antenna layout, so that the antenna channels can be maximally utilized. Figure 1

[0069] In addition, since the present application itself utilizes the characteristics of the target signal-to-noise ratio and has considered the influence of the array channel noise, the present application is not sensitive to the channel noise and has good robustness and greatly improved correctness of the calculated speed.​

Claims

1. A velocity extension method based on angle spectrum estimation in TDM-MIMO FMCW radar, characterized in that, Comprising the steps of: (1) the number of transmission channels according to MIMO The velocity expansion coefficient vector M is calculated according to the following equation; The calculation formula of the speed expansion coefficient vector M is: ; (2) iterate over all speed expansion coefficients ; (3) The compensated phase value after velocity expansion is calculated according to the velocity expansion coefficient value and the Doppler value V before expansion of the target ; according to The amplitude-phase complex vector X composed of the phases of each array channel is velocity-compensated to obtain the compensated amplitude-phase complex vector : S1 : according to V and Computing the base phase compensation value : ； wherein: #Tx represents the number of transmit channels, V represents the target pre- expansion Doppler value, is the number of Doppler points; S2: according to the speed expansion coefficient value and the base phase compensation value calculating the expansion compensation phase value : wherein: #Tx represents the number of transmit channels; S3: Compute the final velocity-compensated phase vector P from the array channel to reference channel transmit interval difference vector T and Compute the final velocity-compensated phase vector P: ； wherein ; t j denotes the difference in the emission time interval of array channel j from the reference channel, T denotes the transpose; S4: Calculate according to P and X : denotes a Hadamard product, , denotes the amplitude and phase values of the channel after velocity compensation, T denotes transpose; (4) using The angular spectrum of the Bartlett-DBF is calculated as follows : [ ], for horizontal angle corresponding Bartlett-DBF angular spectrum value, ranging from -75° to +75° with a step of 1 (5) Based on the angle spectrum , the signal-to-noise ratio of the target is calculated by calculating the ratio of the maximum value to the average value ; (6) In all maximum value is selected , corresponding to is the speed expansion coefficient value m, and then according to m and V, the expanded speed is calculated; In the (5) The calculation formula is: ; max() represents the maximum value, and mean() represents the average value.

2. The velocity extension method based on angle spectrum estimation in a TDM-MIMO FMCW radar according to claim 1, characterized in that, Said (3)~(5) are all the operations in the step (2) traversal loop.

3. The velocity extension method based on angle spectrum estimation in a TDM-MIMO FMCW radar according to claim 1, characterized in that, In the above (4) The calculation method is as follows: ； for a corresponding steering vector, representing a desired, representing how fast to take the expectation of the covariance matrix, denotes the conjugate transpose.

4. The velocity extension method based on angle spectrum estimation in a TDM-MIMO FMCW radar according to claim 1, characterized in that, In the (6) The calculation formula is: = m* + V.

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