A high-precision velocity measurement method for FSK radar and a computer readable medium

Abstract

The application discloses a high-precision velocity measurement method for an FSK radar and a computer readable medium. The method comprises the following steps: sampling a beat frequency signal obtained by mixing a target-reflected echo signal received by the FSK radar with a transmission signal of the FSK radar, to obtain two discrete beat frequency signals with different frequencies; performing fast Fourier transform on the two discrete beat frequency signals, to obtain FFT spectrums of the two discrete beat frequency signals, and taking the frequencies of the spectrum peak positions of the two FFT spectrums as coarse estimation frequencies; taking a range of adjacent spectrum lines on both sides of the coarse estimation frequencies as a reference interval, calculating a periodogram according to the reference interval, and taking a frequency corresponding to a maximum value of the periodogram as a final fine estimation frequency; and calculating a velocity of the target based on the fine estimation frequency. The application can more accurately obtain a specific value of a required frequency, thereby improving the velocity measurement precision of the FSK radar. Compared with a CZT algorithm, the application can greatly reduce an operation amount, and is thus better applied to engineering.

Description

Technical Field

[0001] This invention relates to the field of radar speed measurement technology, specifically to a high-precision speed measurement method for FSK radar and a computer-readable medium. Background Technology

[0002] Radar is an electronic device that uses electromagnetic waves to detect the spatial location of targets. It obtains the required information by processing and analyzing the transmitted signals and received echo signals. Currently, radar is widely used in many fields, such as automotive, structural health monitoring, and biomedical environments. Different radar waveforms are used depending on the application. For example, frequency-modulated continuous wave radar (FMCW) has rich frequency-modulated waveforms and strong anti-interference capabilities, making it suitable for applications such as automotive obstacle avoidance. Frequency-shift keying (FSK) continuous wave radar, due to its low hardware cost and minimal frequency band requirements, is attracting attention from researchers in many fields. Therefore, research on how to improve speed measurement accuracy based on FSK radar is of great significance.

[0003] FSK radar primarily acquires velocity information through the Doppler effect, while frequency information is typically obtained through Fourier transform. However, due to the picket fence effect caused by the discretization of continuous signals, the frequency resolution is often insufficient. Common improvement methods involve either reducing the sampling rate while keeping the number of sampling points constant, or increasing the number of sampling points while keeping the sampling rate constant. These methods suffer from drawbacks such as high complexity, high computational resource consumption, and high storage overhead. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-precision velocity measurement method and a computer-readable medium for FSK radar.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a high-precision velocity measurement method for FSK radar, comprising:

[0006] Step 1: Perform N-point sampling on the difference frequency signal after mixing the target reflected echo signal received by the FSK radar with its transmitted signal to obtain two discrete difference frequency signals of different frequencies.

[0007] Step 2: Perform Fast Fourier Transform on the two discrete difference frequency signals to obtain the FFT spectrum of the two discrete difference frequency signals, and use the frequency of the peak position of the spectrum as the coarse estimated frequency.

[0008] Step 3: Take the adjacent spectral line ranges on both sides of the coarsely estimated frequency as the reference interval, calculate the periodogram based on the reference interval, and take the frequency corresponding to the maximum value of the periodogram as the final finely estimated frequency.

[0009] Step 4: Calculate the target's velocity based on the finely estimated frequency.

[0010] Furthermore, the discrete difference frequency signal is represented as:

[0011]

[0012] in, Let i be the i-th discrete difference frequency signal, i = {1, 2}; n = 0, 1…N-1. For Doppler frequency, Here, C represents the frequency of the transmitted signal, and T represents the speed of light. s R0 is the sampling period, and R0 is the target position at time zero.

[0013] Furthermore, the FFT spectrum of the discrete difference frequency signal is expressed as follows:

[0014]

[0015] in, Let be the FFT spectrum of the i-th discrete difference frequency signal, k = 0, 1…N-1, e j(·) Let λ be the phase spectrum of the Fourier transform. i The wavelength of the transmitted signal;

[0016] The frequency corresponding to the peak position of the spectrum is:

[0017]

[0018] in, Let f be the peak position of the FFT spectrum of the i-th discrete difference frequency signal. i f is a coarse estimate of the FFT spectrum of the i-th discrete difference frequency signal. s The sampling frequency of the signal.

[0019] Furthermore, the reference interval is (f i -Δf, f i +Δf), where Δf=f s / N.

[0020] Furthermore, the method for calculating the periodic chart is as follows:

[0021]

[0022] in, For the calculated periodogram, T is the transpose of the matrix, X is the observed sequence of the difference frequency signal, x = [x(0), x(1), ..., x(N-1)],

[0023]

[0024]

[0025] Then in the reference interval (f) i -Δf, f i Searching within +Δf) makes The largest value As a fine estimate of frequency

[0026] Furthermore, the target's velocity is calculated as follows:

[0027]

[0028] In a second aspect, the present invention provides a computer-readable medium storing a computer program that, when executed by a processor, implements the above-described method.

[0029] Beneficial effects: This invention combines FFT transform with frequency estimation to obtain the specific value of the required frequency more accurately, thereby improving the accuracy of FSK radar speed measurement; compared with the CZT algorithm, this invention can greatly reduce the amount of computation, thus making it better applicable to engineering. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating a high-precision velocity measurement method for FSK radar according to an embodiment of the present invention.

[0031] Figure 2 It is a time-domain plot of a discrete difference frequency signal;

[0032] Figure 3 This is a schematic diagram comparing the speed measurement results obtained by the high-precision speed measurement method for FSK radar and the speed measurement results obtained by the CZT algorithm according to an embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0034] like Figure 1 As shown, this embodiment of the invention provides a high-precision speed measurement method for FSK radar, including:

[0035] Step 1: Perform N-point sampling on the difference frequency signal obtained by mixing the target-reflected echo signal received by the FSK radar with its transmitted signal, to obtain two discrete difference frequency signals of different frequencies. Specifically, the discrete difference frequency signals are represented as follows:

[0036]

[0037] in, Let i be the i-th discrete difference frequency signal, i = {1, 2}, n = 0, 1…N-1. For Doppler frequency, Where C is the frequency of the transmitted signal, C is the speed of light, and T is the frequency of the transmitted signal. s Let R0 be the sampling period and i be the target position at time zero. When i is 1, the corresponding value is... This is the first discrete difference frequency signal. That is, the Doppler frequency corresponding to the first discrete difference frequency signal. That is, the transmitted signal corresponding to the first discrete difference frequency signal. and The following relationship must be satisfied:

[0038]

[0039] When i is 2, the derivation can be performed as described above, and will not be repeated here. The resulting time-domain graph is as follows. Figure 2 As shown.

[0040] Step 2: Perform a Fast Fourier Transform (FFT) on the two discrete difference frequency signals to obtain their FFT spectra, and use the frequencies at the peak positions of these spectra as coarse estimates. Specifically, the FFT spectrum of the discrete difference frequency signal is expressed as:

[0041]

[0042] in, Let be the FFT spectrum of the i-th discrete difference frequency signal, k = 0, 1…N-1, e j(.) Let λ be the phase spectrum of the Fourier transform. i The wavelength of the transmitted signal;

[0043] The frequencies corresponding to the peak positions in the spectrum are:

[0044]

[0045] in, Let f be the peak position of the FFT spectrum of the i-th discrete difference frequency signal. i f is a coarse estimate of the FFT spectrum of the i-th discrete difference frequency signal. s Let f be the sampling frequency of the signal. From this, we can obtain a rough estimate of the frequencies f1 and f2.

[0046] Step 3: Use the adjacent spectral line ranges on both sides of the coarsely estimated frequency as the reference interval. Calculate the periodogram based on the reference interval, and use the frequency corresponding to the maximum value of the periodogram as the final finely estimated frequency. Specifically, the reference interval is selected empirically. Since the frequency error obtained from the FFT coarse estimation will not exceed two spectral lines, the preferred range is (f... i -Δf, f i +Δf) is used as the reference interval, where Δf = f s / N. The method for calculating the periodic chart is as follows:

[0047]

[0048] in, For the calculated periodogram, T is the transpose of the matrix, X is the observed sequence of the difference frequency signal, x = [x(0), x(1), ..., x(N-1)],

[0049]

[0050]

[0051] The derivation process of the above periodic chart is as follows:

[0052] With the frequency of Taking the difference frequency signal as an example, its probability density function can be written as follows according to the central limit theorem:

[0053]

[0054] Where, σ 2 Let p(x) be the variance, in order to make the above equation... 最大 The problem can be transformed into finding x that minimizes the value of the following formula:

[0055]

[0056] make,

[0057]

[0058]

[0059] Expanding the above equation with a cosine function yields the following result:

[0060]

[0061] make,

[0062]

[0063]

[0064]

[0065]

[0066] The above formula can then be rewritten as:

[0067]

[0068] This shows that it is a quadratic function, and its minimum value can be determined by finding the extreme points through its derivative. Therefore, its extreme points can be calculated as follows:

[0069]

[0070] Therefore, the minimum value of F(x) can be calculated as follows:

[0071]

[0072] In the above formula, I is the identity matrix, which transforms the problem into finding the maximum value of the periodic graph.

[0073] Then in the reference interval (f) i -Δf, f i Searching within +Δf) makes The largest value As a fine estimate of frequency

[0074] Step 4: Calculate the target's velocity based on the detailed estimated frequency. Specifically, the target's velocity is calculated as follows:

[0075]

[0076] Based on the above embodiments, those skilled in the art can easily understand that the present invention also provides a computer-readable medium storing a computer program that, when executed by a processor, implements the above-described method.

[0077] To verify the above speed measurement method, the target was placed on a servo motor-controlled guide rail, while the FSK radar was fixed at one end, aligned with the guide rail. The target object reciprocated along the guide rail at a speed of 50 cm / s. The radar board parameters were set as follows:

[0078] symbol illustrate numerical values f0 (GHz) Starting frequency 5.8 B(MHz) bandwidth 15 f s (Hz) Sampling rate 1500 N Number of sampling points in one frame 64

[0079] To demonstrate the superior performance of the FSK radar speed measurement method proposed in this invention, the Chirp-Z Transform (CZT) algorithm was used for comparative verification. The speed measurement results of the two methods are as follows: Figure 3 As shown in the figure, the speed estimated by frequency in this invention is very close to the speed measured by the CZT algorithm, with an error of about 2-3 centimeters per second.

[0080] The above description is merely a preferred embodiment of the present invention. It should be noted that for those skilled in the art, other parts not specifically described are existing technology or common knowledge. Several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-precision velocity measurement method for FSK radar, characterized in that, include: Step 1: Perform N-point sampling on the difference frequency signal after mixing the target reflected echo signal received by the FSK radar with its transmitted signal to obtain two discrete difference frequency signals of different frequencies. Step 2: Perform Fast Fourier Transform on the two discrete difference frequency signals to obtain the FFT spectrum of the two discrete difference frequency signals, and use the frequency of the peak position of the spectrum as the coarse estimated frequency. Step 3: Take the adjacent spectral line ranges on both sides of the coarsely estimated frequency as the reference interval, calculate the periodogram based on the reference interval, and take the frequency corresponding to the maximum value of the periodogram as the final finely estimated frequency. Step 4: Calculate the target's velocity based on the finely estimated frequency.

2. The high-precision velocity measurement method for FSK radar according to claim 1, characterized in that, The discrete difference frequency signal is represented as follows: in, Let i be the i-th discrete difference frequency signal, i = {1, 2}; n = 0, 1…N-1. For Doppler frequency, Here, C represents the frequency of the transmitted signal, and T represents the speed of light. s R0 is the sampling period, and R0 is the target position at time zero.

3. The high-precision velocity measurement method for FSK radar according to claim 2, characterized in that, The FFT spectrum of the discrete difference frequency signal is represented as follows: in, Let be the FFT spectrum of the i-th discrete difference frequency signal, k = 0, 1…N-1, e j(.) Let λ be the phase spectrum of the Fourier transform. i The wavelength of the transmitted signal; The frequency corresponding to the peak position of the spectrum is: in, Let f be the peak position of the FFT spectrum of the i-th discrete difference frequency signal. i f is a coarse estimate of the FFT spectrum of the i-th discrete difference frequency signal. s The sampling frequency of the signal.

4. A high-precision velocity measurement method for FSK radar according to claim 3, characterized in that, The reference interval is (f i -Δf, f i +Δf), where Δf=f s / N.

5. A high-precision velocity measurement method for FSK radar according to claim 4, characterized in that, The method for calculating the periodic chart is as follows: in, For the calculated periodogram, T is the transpose of the matrix, x is the observed sequence of the difference frequency signal, x = [x(0), x(1), ..., x(N-1)], Then in the reference interval (f) i -Δf, f i +Δf) search within the range makes The largest value As a fine estimate of frequency 6. A high-precision velocity measurement method for FSK radar according to claim 5, characterized in that, The target's velocity is calculated as follows:

7. A computer-readable medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-6.

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