CN114185018B - A digital real-time estimation method and system for phase noise of frequency modulated continuous wave radar - Google Patents
A digital real-time estimation method and system for phase noise of frequency modulated continuous wave radar Download PDFInfo
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Abstract
本发明提供一种调频连续波雷达的相位噪声数字式实时估计方法及系统，通过对目标回波信号进行处理得到数字差频信号，利用二维快速傅立叶变换将数字差频信号矩阵进行处理得到综合频谱能量矩阵，并进一步得到目标参数，再根据预先设定的矩阵运算得到去除相互混叠后各目标的回波信号，然后计算相位噪声采样序列并进行频谱分析获取相位噪声功率谱。本发明无需添加额外硬件，且无论单个或多个目标情况，均能够直接提取相位噪声采样值，进而估计出相位噪声的功率谱，估计精度不易受到多目标和其它类型噪声的影响，并且能够克服现有技术中相位噪声估算方法存在的一些技术问题。
The present invention provides a digital real-time estimation method and system for phase noise of frequency modulated continuous wave radar, which processes the target echo signal to obtain a digital difference frequency signal, processes the digital difference frequency signal matrix using a two-dimensional fast Fourier transform to obtain a comprehensive spectrum energy matrix, and further obtains the target parameters, and then obtains the echo signal of each target after removing the mutual aliasing according to a pre-set matrix operation, and then calculates the phase noise sampling sequence and performs spectrum analysis to obtain the phase noise power spectrum. The present invention does not need to add additional hardware, and can directly extract the phase noise sampling value regardless of single or multiple targets, and then estimate the power spectrum of the phase noise. The estimation accuracy is not easily affected by multiple targets and other types of noise, and can overcome some technical problems existing in the phase noise estimation method in the prior art.
Description
Technical Field
The present invention relates to Frequency Modulated Continuous Wave (FMCW) radars, and in particular to extracting phase noise samples from a mid-frequency received digital signal to estimate a phase noise power spectrum.
Background
The phase of the transmitted signal of the frequency modulation continuous wave radar has random jitter due to the instability of the phase and frequency of the oscillator, and the random phase jitter called phase noise has negative influence on the detection performance of the radar, and the estimation of the phase noise is an important subject for designing a low-phase noise radar and eliminating the influence of the phase noise. The existing FMCW radar phase noise estimation method can be mainly categorized into two types: firstly, the method directly carries out spectrum analysis on echo signals, no matter real-time or off-line processing can be carried out through spectrum analysis, and the method has the defect that the estimation accuracy can be influenced by multi-target and other types of noise; secondly, a virtual target echo is generated by adding a radio frequency delay line to the radar transceiver module, and the virtual target echo is compared with a real target echo to estimate phase noise, which has the disadvantage of adding additional hardware, such as adding a radio frequency delay line and a corresponding mixer.
The invention provides a method for estimating the power spectrum of phase noise in real time by receiving a digital signal from an intermediate frequency, which does not need to add extra hardware, can directly extract a sampling value of the phase noise no matter what single or multiple target conditions are, further estimates the power spectrum of the phase noise, is not easy to be influenced by multiple targets and other types of noise, and can overcome some technical problems of the two noise estimation methods in the background art.
Disclosure of Invention
In view of the above-mentioned shortcomings or drawbacks of the prior art, the present invention provides a method for estimating the phase noise power spectrum in real time from a mid-frequency received digital signal, without adding additional hardware, and no matter single or multiple target conditions, the sampling value of the phase noise can be directly extracted, so that the power spectrum of the phase noise is estimated, and the estimation precision is not easy to be influenced by multiple targets and other types of noise.
In order to achieve the above purpose, the present invention provides a digital real-time estimation method for phase noise of a frequency modulation continuous wave radar, which specifically comprises the following steps:
s1: transmitting a frame of sweep frequency signals by a transmitting antenna, wherein the frame of sweep frequency signals of the transmitting antenna array comprise a plurality of sweep frequency signals;
S2, receiving a receiving signal of the sweep frequency signal by a plurality of receiving antennas of a receiving antenna array, wherein the receiving signal is superposition of a plurality of target echo signals;
S3, processing the target echo signal by a data processing unit to obtain an analog difference frequency signal, wherein the analog difference frequency signal is an analog difference frequency signal of an I channel and an analog difference frequency signal of a Q channel;
s4: performing low-pass filtering and analog-to-digital conversion on the analog difference frequency signal to obtain a digital difference frequency signal, wherein the digital difference frequency signal is a digital difference frequency signal of an I channel and a digital difference frequency signal of a Q channel;
S5: performing matrix arrangement on digital difference frequency signals corresponding to a plurality of sweep frequency signals in a frame, performing two-dimensional fast Fourier transform on the matrix arrangement to obtain a frequency spectrum matrix, and further performing calculation on the frequency spectrum matrix to obtain a comprehensive frequency spectrum energy matrix P;
s6, calculating the comprehensive spectrum energy matrix P to obtain target parameters;
s7: determining a sweep frequency signal at will, acquiring digital difference frequency signals of each receiving antenna in the receiving antenna array corresponding to the sweep frequency signal, and acquiring target echo signals of each target after mutual mixing is removed according to preset matrix operation;
s8: selecting any target echo signal after the mutual mixing is removed, and calculating a phase sequence of the target echo signal;
s9: calculating a phase noise sampling sequence according to the phase sequence;
S10: and carrying out spectrum analysis on the phase noise sampling sequence to obtain a phase noise power spectrum.
Wherein a swept time signal is referred to as a swept frequency signal. The target echo signals received by the receiving antenna are mixed, and the analog difference frequency signals obtained by low-pass filtering are sent to a digital signal processing module to extract target information after analog-to-digital conversion (ADC).
Further, each frame of sweep signal comprises L (L is an integer and is greater than zero) sweep signals s (t). The sub-sweep signal s (t) at time t can be expressed as a function of the following time variable t:
Wherein A is a constant representing the voltage amplitude, f c is the center frequency, k=B/T c is the sweep slope, B is the sweep bandwidth, T c is the sweep time, For the initial phase position,Is the phase noise at time t.
Further, the L sweep signals, wherein L has a value of 16, 32, 64 or 128.
Further, the receiving antenna array has D receiving antennas, and the receiving signal of the frequency sweep signal s (t) corresponding to each receiving antenna D (d=1, 2,) is a superposition of a plurality of target echo signals.
Further, the target echo signal of the d sub-receiving antenna at the time t is represented by a function of the following time variable t:
wherein M is the target number, For the intensity of the echo signal of the mth target received by the d-th antenna, f dm is the Doppler frequency of the mth target, and the echo delay of the mth target is
τm＝2Rm/c (3)
R m is the distance of the mth target, and c is the speed of light.
Further, the data processing unit processes the target echo signal to obtain an analog difference frequency signal, and the method further comprises the steps of amplifying the echo signal with low noise, mixing and amplifying the echo signal with intermediate frequency to obtain the analog difference frequency signals of the I channel and the Q channel.
Further, for the D-th receive antenna D (d=1, 2,., D), the analog difference frequency signals of the I and Q channels corresponding to one swept frequency signal s (t) can be expressed as:
Further, the analog difference frequency signal is subjected to low-pass filtering and analog-to-digital conversion to obtain digital difference frequency signals of an I channel and a Q channel, and further, for a D-th receiving antenna (d=1, 2,.., D), the digital difference frequency signals of the I channel and the Q channel corresponding to one sweep signal s (t) may be expressed as:
Where n=1,..n, N is the number of sampling points, T s is the sampling period,
Round () is a rounded integer. The digital difference frequency signal y (d) (n) expressed in complex form is:
Where j is the imaginary part representing the symbol.
Further comprising arranging digital difference frequency signals (as expressed by formula (9)) of the receiving antennas D (d=1, 2,., D) corresponding to a frequency sweep signal into an N-dimensional column vector:
y(d)＝(y(d)(1) y(d)(2) ... y(d)(N))T,(d＝1,2,...D) (10)
Wherein the upper right corner T represents a vector transpose operation.
Further, arranging digital difference frequency signals corresponding to all L sweep frequency signals in a frame into a matrix with N rows and L columns in one dimension, and performing two-dimensional fast Fourier transform on the matrix to obtain a spectrum matrix with the same dimension; and respectively repeating the two-dimensional fast Fourier transform operation on each receiving antenna in the receiving antenna array to obtain D frequency spectrum matrixes after the operation: f (d) (d=1, 2,., D); and squaring the modes of each frequency spectrum matrix point by point to obtain D frequency spectrum energy matrixes: e (d) (d=1, 2,., D); and further averaging the D frequency spectrum energy matrixes to obtain a comprehensive frequency spectrum energy matrix P.
Further, the comprehensive spectrum energy matrix P is calculated to obtain target parameters, and parameters of each target are further obtained according to coordinate index values of M peaks of the comprehensive spectrum energy matrix P.
Further included is a distance R m and doppler frequency f dm for target M from row index value I m and column index value J m, respectively, for the M (m=1, 2,) th peak.
Further, a sweep frequency signal is determined at will, a digital difference frequency signal of each receiving antenna corresponding to the sweep frequency signal is obtained according to a formula (10), and echo signals x m of targets after mutual mixing is removed are obtained through preset matrix operation.
Further, the preset matrix operation is expressed as follows:
(x1 x2 ... xM)＝(y(1) y(2) ... y(D))C-1 (11)
Wherein y (d), (d=1, 2, D) a digital difference frequency signal defined by formula (10); x m is the column vector of N dimensions:
xm＝(xm(1) xm(2) ... xm(N))T,(m＝1,2,...M) (12)
F (d)(Im,Jm) (d=1, 2,.; m=1, 2, M) is the (I m,Jm) th element of the spectrum matrix F (d). I m and J m are the row index value and the column index value of the target m, respectively.
Further, calculating the phase sequence of each target echo signal after the mutual mixing is removed, comprising calculating the phase sequence of the M (m=1, 2., M) target echo signals x m as:
am(n)＝arctan(Imag(xm(n)/Real(xm(n)),(n＝1,2,...,N) (14)
wherein arctan () is an arctangent function, real () is a Real operator, and Imag () is an imaginary operator;
From the calculations of equation (6) and equation (7), it can be derived:
Wherein,
Further, equation (15) is converted into:
Wherein:
bm(n)＝am(n)-Ф(n) (18)
From equation (17), it is known that for any-target m, the phase noise sample value Φ (nT s) is b m (N) (n=1, 2,) N is given by an order Is provided for the digital filter output sequence.
Further, calculating the phase noise sample sequence Φ (nT s) (n=1, 2..once, N), further comprises arbitrarily determining a target, i.e. optionally one me (1, 2..once, M), passing said b m (N) sequence through a digital filter of the following transfer function:
Where z is the argument of the transfer function, representing the look-ahead operation of one unit. The output sequence of the filter is the phase noise sample value phi (nT s), (n=1, 2, …, N). Wherein b m (n) is calculated by equation (18), equation (15) and equation (16), the parameter τ m is calculated by equation (3), Calculated by equation (8).
Further, the spectral analysis is a fast fourier transform.
In order to achieve the above object, according to another aspect of the present invention, there is provided a digital real-time estimation system of phase noise of a frequency modulated continuous wave radar. The digital real-time estimation system of phase noise of the frequency modulation continuous wave radar comprises: the transmitting antenna is used for transmitting the sweep frequency signal; the receiving array antenna is used for receiving the target echo signal of the sweep frequency signal; the data processing module is used for carrying out data processing on the target echo signal, and is characterized in that the digital real-time estimation system of the phase noise of the frequency modulation continuous wave radar is used for realizing a digital real-time estimation method of the phase noise of the frequency modulation continuous wave radar.
The beneficial effects of the invention are as follows: the invention provides a method for estimating phase noise power spectrum in real time by receiving digital signals from intermediate frequency, which is characterized in that a digital difference frequency signal is obtained by processing target echo signals, a comprehensive spectrum energy matrix is obtained by processing a digital difference frequency signal matrix through two-dimensional fast Fourier transformation, target parameters are further obtained, target echo signals of targets after mutual mixing is removed are obtained according to preset matrix operation, a phase noise sampling sequence is calculated, and spectrum analysis is carried out to obtain the phase noise power spectrum. The method and the device have the advantages that no extra hardware is required to be added, no matter the condition of single or multiple targets, the phase noise sampling value can be directly extracted, the power spectrum of the phase noise is estimated, the estimation accuracy is not easy to be influenced by multiple targets and other types of noise, and some technical problems of the two noise estimation methods in the background technology can be overcome.
Drawings
Fig. 1: schematic diagram of frequency modulation continuous wave radar system and time (t) frequency (f) relation of transmitted signal.
Fig. 2: an embodiment one of a digital real-time estimation method for phase noise of a frequency modulation continuous wave radar is provided.
FIG. 3 comparison of estimated phase noise power spectrum and actual value case one.
Fig. 4: comparison of estimated phase noise power spectrum and actual value case two.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
It should be noted that: like reference numerals and letters denote like items in the following figures or embodiments, and thus, once an item is defined in one figure or embodiment, no further definition or explanation thereof is necessary in the following figures or embodiments.
The present invention belongs to the technology of the digital signal processing module in fig. 1. The transmitted signal is a periodic swept continuous wave. B is the frequency sweep bandwidth, and T c is the frequency sweep time. A swept time signal is referred to as a swept frequency signal. A transmitting-side Voltage Controlled Oscillator (VCO) generates a frequency modulated sine wave signal. The receiving antenna receives echo signals, mixes the echo signals, and sends difference frequency signals obtained by low-pass filtering to the digital signal processing module to extract target information after analog-to-digital conversion (ADC). According to an embodiment of the present invention, as shown in fig. 2, a digital real-time estimation method for phase noise of a frequency modulated continuous wave radar is provided, which specifically includes the following steps:
step 1, a frame of sweep frequency signals are transmitted by a transmitting antenna, wherein the frame of sweep frequency signals of the transmitting antenna comprise a plurality of sweep frequency signals;
step 2, receiving a receiving signal of the one-frame sweep signal by a plurality of receiving antennas of a receiving antenna array, wherein the receiving signal is superposition of a plurality of target echo signals;
step 3, processing the target echo signal by a data processing unit to obtain an analog difference frequency signal, wherein the analog difference frequency signal is an analog difference frequency signal of an I channel and a Q channel;
Step 4, carrying out low-pass filtering and analog-to-digital conversion on the analog difference frequency signal to obtain a digital difference frequency signal, wherein the digital difference frequency signal is a digital difference frequency signal of an I channel and a Q channel;
step 5, performing matrix arrangement on digital difference frequency signals corresponding to a plurality of sweep frequency signals in a frame, performing two-dimensional fast Fourier transform on the matrix arrangement to obtain a frequency spectrum matrix, and further performing calculation on the frequency spectrum matrix to obtain a comprehensive frequency spectrum energy matrix P;
Step 6, calculating the comprehensive spectrum energy matrix P to obtain target parameters;
Step 7, randomly determining a sweep frequency signal, acquiring digital difference frequency signals of all receiving antennas in a receiving antenna array corresponding to the sweep frequency signal, and obtaining target echo signals of all targets after mutual mixing removal according to preset matrix operation;
Step 8, selecting any target echo signal after the mutual mixing is removed, and calculating a phase sequence of the target echo signal;
step 9, calculating a phase noise sampling sequence according to the phase sequence;
and (10) performing spectrum analysis on the phase noise sampling sequence to obtain a phase noise power spectrum.
According to another embodiment of the present invention, there is provided a digital real-time estimation method of phase noise of a frequency modulated continuous wave radar, including the steps of:
And (2) transmitting a frame of sweep frequency signal. One frame of the swept frequency signal comprises L (L is typically 16,32, 64 or 128) swept frequency signals. A swept frequency signal can be described as a function of the following time variable t:
where a is a constant representing the voltage amplitude, f c is the center frequency, k=b/T c is the sweep slope, For the initial phase position,Is phase noise.
And (2) receiving an echo signal of the transmitting signal.
Assuming that there are D receive antennas, each receive antenna D (d=1, 2,., D) the received signal corresponding to the one swept frequency signal is a superposition of multiple target echo signals, and can be described as a function of the following time variable t:
where M is the number of targets, For the intensity of the echo signal of the mth target received by the d-th antenna, f dm is the Doppler frequency of the mth target, and the echo delay of the mth target is
τm＝2Rm/c (3)
R m is the distance of the mth target, and c is the speed of light.
And (3) processing the echo signals to obtain analog difference frequency signals. The echo signals are amplified by low noise, mixed and amplified by intermediate frequency to obtain analog difference frequency signals of the I channel and the Q channel. For a receive antenna D (d=1, 2,., D), the analog difference frequency signal corresponding to one sweep signal can be expressed as:
And (4) performing low-pass filtering and analog-to-digital conversion on the analog difference frequency signal to obtain digital difference frequency signals of the I channel and the Q channel. For a receive antenna D (d=1, 2,., D), the digital difference frequency signal corresponding to one sweep signal can be expressed as:
where n=1,..n, N is the number of sampling points, T s is the sampling period,
Round () is a rounded integer. The digital difference frequency signal expressed in complex form is:
Where j is the imaginary part representing the symbol.
And (5) performing two-dimensional fast Fourier transform on the digital difference frequency signal. The digital difference frequency signals (as shown in equation (9)) of the receive antennas D (d=1, 2,., D) corresponding to a swept frequency signal are arranged into an N-dimensional column vector:
y (d)＝(y(d)(1) y(d)(2) ... y(d)(N))T, (d=1, 2, D) (10) here the upper right corner T represents the vector transpose operation. And arranging the digital difference frequency signals corresponding to all L sweep frequency signals in a frame into a matrix with N rows and L columns in one dimension, and performing two-dimensional fast Fourier transform on the matrix to obtain a spectrum matrix with the same dimension. After each receiving antenna performs such operations, D spectrum matrices are obtained: f (d) (d=1, 2,) D. Square each spectrum matrix point by point modulo to obtain D spectrum energy matrixes: e (d) (d=1, 2,) D. And averaging the D spectrum energy matrixes to obtain a comprehensive spectrum energy matrix P.
And (6) solving target parameters. The coordinate index values of the M peaks of the comprehensive spectrum energy matrix P correspond to the parameters of each target. Specifically, row index value I m and column index value J m of the M (m=1, 2,) th spike correspond to distance R m and doppler frequency f dm of target M, respectively.
And (7) solving echo signals of the targets after mutual aliasing is removed. Optionally determining a sweep frequency signal, taking digital difference frequency signals (see formula (10)) of each receiving antenna corresponding to the sweep frequency signal, and obtaining echo signals x m of each target after mutual mixing removal through the following matrix operation:
(x1 x2 ... xM)＝(y(1) y(2) ... y(D))C-1 (11)
Here x m is the column vector of N dimensions:
xm＝(xm(1) xm(2) ... xm(N))T,(m＝1,2,...M) (12)
F (d)(Im,Jm) (d=1, 2,.; m=1, 2, M) is the (I m,Jm) th element of the spectrum matrix F (d). I m and J m are the row index value and the column index value of the target m obtained in step 6, respectively.
And (8) calculating the phase sequence of each target echo signal after the mutual aliasing is removed. The phase sequence of the M (m=1, 2., M) target echo signals x m is:
am(n)＝arctan(Imag(xm(n)/Real(xm(n)),(n＝1,2,...,N) (14)
Here arctan () is an arctangent function, real () is a Real-taking operator, and Imag () is an imaginary-taking operator.
As can be seen from the formula (6) and the formula (7):
Here, the
Equation (15) can be converted into:
here:
bm(n)＝am(n)-Ф(n) (18)
Equation (17) shows that for any target m, the phase noise sample value phi (nT s) is b m (N) (n=1, 2,) N is passed through an order of Is provided for the digital filter output sequence.
A phase noise sampling sequence is calculated [ step 9 ]. Optionally determining a target, i.e. optionally an mε (1, 2,., M), passing said b m (n) sequence through a digital filter of the following transfer function:
Where z is the argument of the transfer function, representing the look-ahead operation of one unit. The filter output sequence is the phase noise sampling value phi (nT s), (n=1, 2, …, N). Here, b m (n) is calculated from the formula (18), the formula (15) and the formula (16). The required parameter τ m is calculated by equation (3), Calculated from equation (8), the Doppler frequency f dm is obtained from step 6.
Step 10 performs a spectral analysis (e.g., by fast fourier transform) on the sequence of phase noise samples phi (nT s) to obtain a phase noise power spectrum.
According to another embodiment of the present invention, there is provided a digital real-time estimation system of phase noise of a frequency-modulated continuous wave radar, the digital real-time estimation system of phase noise of the frequency-modulated continuous wave radar including: the transmitting antenna is used for transmitting the sweep frequency signal; the receiving array antenna is used for receiving the target echo signal of the sweep frequency signal; the data processing module is used for carrying out data processing on the target echo signal, and is characterized in that the phase noise digital real-time estimation system of the frequency modulation continuous wave radar is used for realizing the phase noise digital real-time estimation method of the medium frequency modulation continuous wave radar.
As shown in fig. 3, one test case of the present invention, radar parameters: the sweep bandwidth is 180 MHz, the sweep time is 17.5 microseconds, one frame of sweep signal comprises 16 sweep signals, and the antenna is 1 to 2 to receive. A stationary target with a reflection area of 10 square meters is located 25 meters directly in front of the radar. Fig. 3 is an actual phase noise power spectrum and an estimated phase noise power spectrum. As shown in FIG. 4, another test case of the present invention, radar parameters are as case one. The two targets have reflection areas of 10 square meters and 20 square meters respectively, distances of 25 meters and 37.5 meters respectively, azimuth angles of-10 degrees and 30 degrees respectively, pitch angles of 0 degrees and 30 degrees respectively, and speeds of 13.91 meters/second and 34.79 meters/second respectively. Fig. 4 is an actual phase noise power spectrum and an estimated phase noise power spectrum. Fig. 3 and 4 illustrate that the estimated phase noise power spectrum coincides with the actual value.
According to the technical scheme of the embodiment of the invention, no additional hardware is required, no matter the condition of single or multiple targets, the sampling value of the phase noise can be directly extracted, the power spectrum of the phase noise is further estimated, and the estimation precision is not easy to be influenced by multiple targets and other types of noise.
The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives can occur depending upon design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.
Claims (18)
1. A digital real-time estimation method for phase noise of a frequency modulation continuous wave radar comprises the following steps:
s1: transmitting a frame of sweep frequency signals by a transmitting antenna, wherein the frame of sweep frequency signals of the transmitting antenna comprise a plurality of sweep frequency signals;
S2, receiving a receiving signal of the one-frame sweep signal by a plurality of receiving antennas of a receiving antenna array, wherein the receiving signal is superposition of a plurality of target echo signals;
S3, processing the target echo signal by a data processing unit to obtain an analog difference frequency signal, wherein the analog difference frequency signal is an analog difference frequency signal of an I channel and an analog difference frequency signal of a Q channel;
s4: performing low-pass filtering and analog-to-digital conversion on the analog difference frequency signal to obtain a digital difference frequency signal, wherein the digital difference frequency signal is a digital difference frequency signal of an I channel and a digital difference frequency signal of a Q channel;
s5: matrix arrangement is carried out on digital difference frequency signals corresponding to a plurality of sweep frequency signals in a frame, two-dimensional fast Fourier transform is carried out on the matrix arrangement to obtain a frequency spectrum matrix, and calculation is carried out on the frequency spectrum matrix to obtain a comprehensive frequency spectrum energy matrix ；
S6, for the comprehensive spectrum energy matrixCalculating to obtain target parameters;
S7: selecting any sweep frequency signal in the frame of sweep frequency signals, acquiring digital difference frequency signals of each receiving antenna in the receiving antenna array corresponding to the sweep frequency signals, and acquiring target echo signals of each target after mutual mixing removal according to preset matrix operation;
s8: selecting any target echo signal after the mutual mixing is removed, and calculating a phase sequence of the target echo signal;
s9: calculating a phase noise sampling sequence according to the phase sequence;
S10: and carrying out spectrum analysis on the phase noise sampling sequence to obtain a phase noise power spectrum.
2. The method for digital real-time estimation of phase noise of a frequency modulated continuous wave radar according to claim 1, wherein said one frame of swept signals comprises L sweep signals, where L is an integer and greater than zero, said sweep signals at time tThis can be expressed as a function of the following time variable t:
(1)
wherein A is a constant representing the magnitude of the voltage, As a result of the center frequency,For the slope of the frequency sweep,For the frequency sweep bandwidth,For the time of the sweep frequency,For the initial phase position,Is the phase noise at time t.
3. The method of claim 2, wherein the L sweep signals have values of 16, 32, 64 or 128.
4. The method for digital real-time estimation of phase noise of a frequency modulated continuous wave radar according to claim 1, wherein said receiving antenna array has D sub-receiving antennas, wherein the firstThe sweep frequency signals corresponding to the receiving antennasIs a superposition of a plurality of target echo signals, wherein。
5. The method for digital real-time estimation of phase noise in a frequency modulated continuous wave radar according to claim 4, wherein the first step ofThe target echo signals of the receiving antennas at the time t are expressed as a function of the following time variable t:
(2)
wherein M is the target number, For the echo signal strength of the mth target received by the d-th receiving antenna,The Doppler frequency of the mth target is set as the echo delay of the mth target
(3)
The distance to the mth target, c is the speed of light.
6. The method for digital real-time estimation of phase noise of frequency modulated continuous wave radar according to claim 1, wherein the data processing unit processes the target echo signal to obtain an analog difference frequency signal, and further comprises amplifying the echo signal with low noise, mixing, and amplifying with intermediate frequency to obtain analog difference frequency signals of the I channel and the Q channel.
7. The method for digital real-time estimation of phase noise in a frequency modulated continuous wave radar according to claim 6, wherein for the d-th receiving antennaThe saidWhich corresponds to a swept frequency signalThe analog difference frequency signals of the I and Q channels of (a) can be expressed as:
(4)
(5)。
8. The method for digital real-time estimation of phase noise of a frequency modulated continuous wave radar according to claim 1, wherein the analog difference signal is subjected to low-pass filtering and analog-to-digital conversion to obtain digital difference signals of an I channel and a Q channel, further comprising, for a d-th receiving antenna, the steps of Which corresponds to a swept frequency signalThe digital difference frequency signals of the I and Q channels of (a) can be expressed as:
(6)
(7)
Wherein, N is the number of sampling points,In order to sample the period of time,
(8)
To round down to integer, digital difference frequency signals are represented in complex formThe method comprises the following steps:
(9)
Where j is the imaginary part representing the symbol.
9. The method for digital real-time estimation of phase noise of frequency modulated continuous wave radar according to claim 8, wherein the receiving antenna is，The digital difference frequency signals corresponding to a swept frequency signal are arranged into an N-dimensional column vector:
y(d)＝(y(d)(1) y(d)(2) ... y(d)(N))T(10)
wherein the upper right corner T represents a vector transpose operation.
10. The method for digital real-time estimation of phase noise of frequency modulated continuous wave radar according to claim 9, wherein a matrix formed by arranging the digital difference frequency signals is subjected to two-dimensional fast fourier transform to obtain a spectrum matrix, and the spectrum matrix is calculated to obtain a comprehensive spectrum energy matrixFurther comprises the steps of arranging the digital difference frequency signals corresponding to all L sweep frequency signals in a frame into a dimension ofRow of linesA matrix of columns and performing two-dimensional fast Fourier transform on the matrix to obtain a spectrum matrix with the same dimension; and respectively repeating the two-dimensional fast Fourier transform operation on each receiving antenna in the receiving antenna array to obtain D frequency spectrum matrixes after the operation:， ; and squaring the modes of each frequency spectrum matrix point by point to obtain D frequency spectrum energy matrixes: ， ; further averaging the D spectrum energy matrixes to obtain a comprehensive spectrum energy matrix 。
11. The method for digital real-time estimation of phase noise of a frequency modulated continuous wave radar according to claim 8, wherein said integrated spectral energy matrixCalculating to obtain target parameters, further comprising, according to the comprehensive spectrum energy matrixThe coordinate index values of the M peaks of each target are obtained.
12. The method for digital real-time estimation of phase noise of a frequency modulated continuous wave radar according to claim 11, wherein said integrated spectral energy matrix is based onThe coordinate index value of M peaks of each object is obtained, further comprises, according to the firstLine index value for individual peaksSum column index valueRespectively obtain the targetsDistance of (2)Doppler frequency。
13. The method for digital real-time estimation of phase noise of frequency modulated continuous wave radar according to claim 8, wherein a sweep signal is arbitrarily determined, digital difference signals of the respective receiving antennas corresponding to the sweep signal are obtained, and echo signals of the respective targets after the mutual aliasing removal are obtained by a predetermined matrix operation。
14. The method for digital real-time estimation of phase noise of a frequency modulated continuous wave radar according to claim 13, wherein the predetermined matrix operation is represented as follows:
=(11)
Wherein, A digital difference frequency signal defined for equation (10); For an N-dimensional column vector:
xm＝(xm(1) xm(2) ... xm(N))T(12)
(13)
Is a frequency spectrum matrix Is the first of (2)The number of elements to be added to the composition,AndThe row index value and the column index value of the obtained object m are respectively.
15. The method for digital real-time estimation of phase noise of a frequency modulated continuous wave radar according to claim 8, wherein calculating the phase sequence of each target echo signal after the removal of the mutual aliasing, further comprises selecting any one of the target echo signalsThe phase sequence is calculated as:
am(n)＝arctan(Imag(xm(n)/Real(xm(n)))) (14)
Wherein, () Real () is a Real operator and Imag () is an imaginary operator;
From the calculations of equation (6) and equation (7), it can be derived:
(15)
Wherein,
(16)
Further, equation (15) is converted into:
(17)
Wherein:
(18)
as can be seen from the formula (17), for any target m, the phase noise sampling value Are allBy an order ofIs provided for the digital filter output sequence.
16. The method for digital real-time estimation of phase noise of a frequency modulated continuous wave radar according to claim 15, wherein the phase noise sampling value is calculatedFurther comprising, optionally determining a target, i.e. optionally oneThe saidThe sequence passes through a digital filter of the following transfer function:
(19)
Wherein z is an argument of a transfer function, and represents an advance operation of a unit, and the output sequence of the filter is a sampling value of phase noise: wherein, the method comprises the steps of, wherein, Calculated from equation (18), equation (15) and equation (16), parametersCalculated from the formula (3) of the present invention,Calculated by equation (8).
17. A method for digital real-time estimation of the phase noise of a frequency modulated continuous wave radar according to any of the claims 1-15, characterized in that the spectral analysis is a fast fourier transform.
18. A digital real-time estimation system of phase noise of a frequency modulated continuous wave radar, comprising a transmitting antenna, a receiving antenna array, and a data processing module, wherein the digital real-time estimation system of phase noise of a frequency modulated continuous wave radar is configured to implement the method of any one of claims 1-17.
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