Continuous wave radar high-precision speed measurement theory and method

Abstract

The invention belongs to the technical field of continuous wave radar speed measurement, and discloses a continuous wave radar high-precision speed measurement theory and method, and the method comprises the following steps: obtaining a discrete mixing signal; obtaining a low-order frequency mixing signal after frequency shift; solving a first-order derivative signal of the low-order mixing signal; constructing a Hankel square matrix of the low-order frequency mixing signal and a first-order derivative signal of the low-order frequency mixing signal; constructing a generalized characteristic equation; and solving the generalized eigenvalue. The high-precision speed measurement theory and method for the continuous wave radar are different from a traditional frequency fine estimation method, and the method can obtain a theoretical solution of the frequency of a frequency mixing signal while solving the barrier effect and spectrum leakage existing in FFT transformation, so that accurate solution of the speed of a measured target is realized, and the speed measurement precision of the target is improved. And the method is not limited by sampling frequency and time interval.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous wave radar speed measurement, and in particular to a continuous wave radar high-precision speed measurement theory and method. Background Art

[0002] As the foundation of a country's economy, the sustainable development of transportation has a direct impact on the sustained, stable and healthy development of the economy. With the continuous development of science and technology, radar speed measurement technology has continued to mature. Based on the continuous emphasis on road traffic safety, radar speed measurement technology has been widely used in traffic road control and active automobile safety technology. Continuous wave radar transmits electromagnetic waves to the measurement target through a microwave module, and then receives the reflected signal. Through a series of signal processing such as mixing and low-frequency filtering, the Doppler frequency of the signal is obtained, thereby calculating the speed of the measured target. Although this method is simple to calculate and can achieve real-time measurement, the accuracy of this method is greatly affected by the calculation algorithm and the selection of system components. When designing the system, each replacement part needs to be carefully considered.

[0003] At present, the frequency estimation method is mainly used for the frequency extraction of Doppler signals. Specifically, it includes: time domain analysis method and frequency domain refinement method. Among them, the time domain analysis method mainly includes zero-crossing detection method and count cycle method. Because the zero-crossing detection method is mixed with the signals reflected by the surrounding environment and other objects, the voltage of the received echo signal also varies with different environmental changes; the count cycle method has problems such as signal voltage sensitivity and low measurement accuracy; the frequency domain refinement method mainly includes modern spectrum estimation and classical spectrum estimation methods. Among them, non-parametric model method and parameter model method are the main algorithms of modern spectrum estimation, and parameter model method includes AR model, MA model and ARMA model; other analysis methods: wavelet transform, time-frequency analysis, etc. These methods require a large amount of data to carry out, take a long time to calculate, and are mostly used to analyze the offline data of the signal. In summary, the current method is mainly based on refined frequency measurement, and there is still a lack of accurate solution of Doppler frequency in theory.

[0004] To this end, this patent proposes a continuous wave radar high-precision speed measurement theory and method. Starting from theoretical derivation, it provides an accurate solution formula for Doppler frequency, and uses characteristic equation to solve the accurate solution expression of Doppler frequency, thereby achieving accurate measurement of target speed. Summary of the invention

[0005] The purpose of the present invention is to provide a continuous wave radar high-precision speed measurement theory and method. Different from the traditional frequency refinement estimation method, this method can obtain the theoretical solution of the mixing signal frequency while solving the fence effect and spectrum leakage existing in FFT transformation, thereby realizing the accurate solution of measuring target speed without being limited by sampling frequency and time interval.

[0006] To achieve the above object, the present invention provides a continuous wave radar high-precision speed measurement theory and method, comprising the following steps:

[0007] Step S1, obtaining a discrete mixing signal;

[0008] Step S2, obtaining a frequency-shifted low-order mixing signal;

[0009] Step S3, solving the first-order derivative signal of the low-order mixing signal;

[0010] Step S4, constructing a Hankel matrix of a low-order mixing signal and its first-order derivative signal;

[0011] Step S5, constructing a generalized characteristic equation;

[0012] Step S6: solving the generalized eigenvalue.

[0013] Preferably, in step S1, a discrete mixing signal is obtained, and the specific process is as follows:

[0014] Step S11: The continuous wave radar transmits a signal with a frequency of f c , the period is T, and the initial phase is The continuous wave signal is as follows:

[0015]

[0016] Wherein, the subscript t represents the transmitted signal;

[0017] Step S12: After being reflected by the measurement target with a speed of v, the corresponding received signal is as follows:

[0018]

[0019] Wherein, τ = 2vt / c represents the echo delay caused by the measurement target, and the subscript r represents the received signal;

[0020] Step S13: Mix the received signal and the transmitted signal and perform low-pass filtering to obtain a mixed signal, as shown below:

[0021]

[0022] Wherein, the superscript * indicates conjugation;

[0023] Step S14: Perform digital A / D sampling on the mixed signal at a sampling frequency of F s , the number of sampling points is N, and the discretized mixing signal is obtained as follows:

[0024]

[0025] Preferably, in step S2, the frequency-shifted low-order mixing signal is obtained, and the specific process is as follows:

[0026] Step S21: IF (n) Performing N-point FFT transformation to obtain the spectrum information of the measurement target;

[0027] Step S22: According to the peak point f of the measured target spectrum max , select the left frequency point f l =f max -Δf is used as the reference Doppler frequency point, Δf = F s / N is the sampling frequency interval;

[0028] Step S23: construct a frequency shift reference signal, as shown below:

[0029]

[0030] Step S24: Perform frequency shift processing according to the mixing signal and the frequency shift reference signal to obtain a low-order mixing signal, as shown below:

[0031]

[0032] in,

[0033] Preferably, in step S3, according to the discrete low-order mixing signal The first-order derivative signal is solved by difference as follows:

[0034]

[0035] Preferably, in step S4, according to the low-order mixing signal and its first-order derivative signal Construct the corresponding Hankel matrix as follows:

[0036]

[0037] in,

[0038] Preferably, in step S5, according to the Hankel matrix of the low-order mixing signal and its first-order derivative signal and The generalized characteristic equation is established as follows:

[0039]

[0040] in,

[0041] Preferably, in step S6, the generalized characteristic equation is solved to obtain an eigenvalue matrix λ, and the maximum eigenvalue λ is selected. max , and perform relationship conversion to obtain the precise speed of the measured target, as shown below:

[0042]

[0043] Therefore, the present invention adopts the above-mentioned continuous wave radar high-precision speed measurement theory and method. Different from the traditional frequency refinement estimation method, this method can obtain the theoretical solution of the mixing signal frequency while solving the fence effect and spectrum leakage existing in the FFT transform, thereby realizing the accurate solution of the measured target speed without being limited by the sampling frequency and time interval.

[0044] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A flow chart of a continuous wave radar high-precision speed measurement theory and method of the present invention;

[0046] Figure 2 It is the result of traditional FFT transformation calculation;

[0047] Figure 3 The present invention provides a calculation result of a continuous wave radar high-precision speed measurement theory and method. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0049] like Figure 1 As shown, the present invention provides a continuous wave radar high-precision speed measurement theory and method, comprising the following steps:

[0050] Step S1, obtaining a discrete mixing signal.

[0051] Step S11: The continuous wave radar transmits a signal with a frequency of f c , the period is T, and the initial phase is The continuous wave signal is as follows:

[0052]

[0053] Wherein, the subscript t represents the transmitted signal.

[0054] Step S12: After being reflected by the measurement target with a speed of v, the corresponding received signal is as follows:

[0055]

[0056] Wherein, τ=2vt / c represents the echo delay caused by the measurement target, and the subscript r represents the received signal.

[0057] Step S13: Mix the received signal and the transmitted signal and perform low-pass filtering to obtain a mixed signal, as shown below:

[0058]

[0059] The superscript * indicates conjugation.

[0060] Step S14: Perform digital A / D sampling on the mixed signal at a sampling frequency of F s , the number of sampling points is N, and the discretized mixing signal is obtained as follows:

[0061]

[0062] Step S2: Obtain the frequency-shifted low-order mixing signal.

[0063] Step S21: IF (n) Perform N-point FFT transformation to obtain the spectrum information of the measurement target.

[0064] Step S22: According to the peak point f of the measured target spectrum max , select the left frequency point f l =f max -Δf is used as the reference Doppler frequency point, Δf = F s / N is the sampling frequency interval.

[0065] Step S23: construct a frequency shift reference signal, as shown below:

[0066]

[0067] Step S24: Perform frequency shift processing according to the mixing signal and the frequency shift reference signal to obtain a low-order mixing signal, as shown below:

[0068]

[0069] in,

[0070] Step S3, solving the first-order derivative signal of the low-order mixing signal.

[0071] According to the above discrete low-order mixing signal The first-order derivative signal is solved by difference as follows:

[0072]

[0073] Step S4: construct a Hankel matrix of the low-order mixing signal and its first-order derivative signal.

[0074] According to the low-order mixing signal and its first-order derivative signal Construct the corresponding Hankel matrix as follows:

[0075]

[0076] in,

[0077] Step S5: construct a generalized characteristic equation.

[0078] According to the Hankel matrix of the above low-order mixing signal and its first-order derivative signal and The generalized characteristic equation is established as follows:

[0079]

[0080] in,

[0081] Step S6: solving the generalized eigenvalue.

[0082] Solve the above generalized characteristic equation to obtain the eigenvalue matrix λ, and select its maximum eigenvalue λ max , and perform relationship conversion to obtain the precise speed of the measured target, as shown below:

[0083]

[0084] Example

[0085] Step S1: Let the microwave radar emit a starting frequency of f c =24GHz; period is T=5ms, initial phase Continuous wave signal. Simulate a scene of a single moving target with a target speed of v = 30.12345 m / s.

[0086] The transmitted signal is reflected by the moving target and received to obtain a mixed signal. Suppose the sampling frequency of the digital A / D sampling is f s =10KHz, the corresponding number of sampling points is N=50, and a discrete mixing signal can be obtained.

[0087] Step S2: First, directly perform N-point FFT transformation on the discrete difference frequency signal obtained in step S1 to obtain the spectrum information of the moving target, such as Figure 2 As shown, the peak point of the spectrum identified is f max =4000Hz, the corresponding target speed is v FFT=30m / s, which is different from the original setting value.

[0088] Then, according to the peak point f of the measured target spectrum max , select the left frequency point f l =4600Hz as the reference Doppler frequency point, construct the frequency shift reference signal as shown below:

[0089]

[0090] Frequency shift processing is performed according to the mixing signal and the frequency shift reference signal to obtain a low-order mixing signal.

[0091] Step S3: according to the discrete mixing signal, obtain its first-order derivative signal by difference.

[0092] Step S4: construct the corresponding Hankel matrix according to the low-order mixing signal and its first-order derivative signal and

[0093] Step S5: Based on the Hankel matrix of the low-order mixing signal and its first-order derivative signal and Establish the generalized characteristic equation.

[0094] Step S6: Solve the generalized characteristic equation to obtain the eigenvalue matrix λ, and select the maximum eigenvalue λ max =1379.646, and perform relationship conversion, such as Figure 3 As shown, the precise speed of the measured target is obtained as follows:

[0095] v=30.12344m / s.

[0096] Therefore, the present invention adopts the above-mentioned continuous wave radar high-precision speed measurement theory and method. Different from the traditional frequency refinement estimation method, this method can obtain the theoretical solution of the mixing signal frequency while solving the fence effect and spectrum leakage existing in the FFT transform, thereby realizing the accurate solution of the measured target speed without being limited by the sampling frequency and time interval.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A continuous wave radar high-precision speed measurement theory and method, characterized in that: The following steps are involved: Step S1, obtaining a discrete mixing signal; Step S2, obtaining a frequency-shifted low-order mixing signal; Step S3, solving the first-order derivative signal of the low-order mixing signal; Step S4, constructing a Hankel matrix of a low-order mixing signal and its first-order derivative signal; Step S5, constructing a generalized characteristic equation; Step S6: solving the generalized eigenvalue.

2. The high-precision speed measurement theory and method of continuous wave radar according to claim 1 is characterized in that: In step S1, a discrete mixing signal is obtained, and the specific process is as follows: Step S11: The continuous wave radar transmits a signal with a frequency of f c , the period is T, and the initial phase is The continuous wave signal is as follows: Wherein, the subscript t represents the transmitted signal; Step S12: After being reflected by the measurement target with a speed of v, the corresponding received signal is as follows: Wherein, τ = 2vt / c represents the echo delay caused by the measurement target, and the subscript r represents the received signal; Step S13: Mix the received signal and the transmitted signal and perform low-pass filtering to obtain a mixed signal, as shown below: Wherein, the superscript * indicates conjugation; Step S14: Perform digital A / D sampling on the mixed signal at a sampling frequency of F s , the number of sampling points is N, and the discretized mixing signal is obtained as follows:

3. The high-precision speed measurement theory and method of continuous wave radar according to claim 2 is characterized in that: In step S2, the low-order mixing signal after frequency shift is obtained, and the specific process is as follows: Step S21: IF (n) Performing N-point FFT transformation to obtain the spectrum information of the measurement target; Step S22: According to the peak point f of the measured target spectrum max , select the left frequency point f l =f max -Δf is used as the reference Doppler frequency point, Δf = F s / N is the sampling frequency interval; Step S23: construct a frequency shift reference signal, as shown below: Step S24: Perform frequency shift processing according to the mixing signal and the frequency shift reference signal to obtain a low-order mixing signal, as shown below: in, 4. The high-precision speed measurement theory and method of continuous wave radar according to claim 3 is characterized in that: In step S3, according to the discrete low-order mixing signal The first-order derivative signal is solved by difference as follows:

5. The high-precision speed measurement theory and method of continuous wave radar according to claim 4 is characterized in that: In step S4, according to the low-order mixing signal and its first-order derivative signal Construct the corresponding Hankel matrix as follows: in, 6. The high-precision speed measurement theory and method of continuous wave radar according to claim 5 is characterized in that: In step S5, according to the Hankel matrix of the low-order mixing signal and its first-order derivative signal and The generalized characteristic equation is established as follows: in, 7. The high-precision speed measurement theory and method of continuous wave radar according to claim 6 is characterized in that: In step S6, the generalized characteristic equation is solved to obtain the eigenvalue matrix λ, and its maximum eigenvalue λ is selected. max , and perform relationship conversion to obtain the precise speed of the measured target, as shown below:

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