Method and system for improving FMCW radar ranging accuracy based on frequency combination

Abstract

The present invention discloses a method and system for improving the ranging accuracy of FMCW radar based on frequency combination. The method comprises: obtaining a beat frequency signal s0(t) obtained by mixing a first chirp signal and a first echo signal reflected by a target, and obtaining a beat frequency signal s1(t) obtained by mixing a second chirp signal and a second echo signal reflected by the target; selecting any beat frequency signal as a target processing signal and calculating an initial value R of the target distance according to its frequency. f ; Based on the wide-term combined phase ranging relationship, let R WL =R f Find the initial value N of the combined integer number WL ; N WL Substitute the wide-term combined phase ranging relationship again to inversely calculate the target distance estimate R WL ; Based on the target processing signal and R WL , use the frequency phase combination ranging algorithm to calculate the estimated value of the number of cycles of the target processing signal; and then use the phase ranging algorithm to calculate the final value of the target distance. WL Estimate the integer ambiguity of the original signal, solve the half-wavelength jump problem, and obtain more accurate ranging results.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar signal processing, and more specifically, relates to a method and a system for improving the ranging accuracy of an FMCW radar based on frequency combination. Background Art

[0002] All ranging systems that use the FMCW (Frequency Modulated Continuous Wave) system have ranging accuracy issues.

[0003] In FMCW radar ranging, the simplest method is to directly measure the difference frequency between the transmitted wave and the echo signal to obtain the distance, but this method suffers from low ranging accuracy. Currently, FMCW radar ranging generally uses the FFT method to obtain the echo's power spectrum curve (range spectrum) on the range axis. By sampling the signal and analyzing it with the FFT algorithm, the distance measurement value is extracted, achieving high range resolution and high measurement accuracy. However, due to the "fence effect" inherent in the FFT, the range spectrum obtained directly using the FFT has a fixed sampling interval, resulting in large ranging errors.

[0004] Compared to frequency-based ranging, phase-based ranging offers higher accuracy, typically about two orders of magnitude higher than frequency estimation, and offers greater stability. However, phase-based ranging suffers from phase ambiguity and can only measure distances within a circle.

[0005] Another approach is to combine the frequency method with the phase method. The error distance measured using the frequency method can be used to estimate the number of phase ambiguity integer cycles corresponding to the signal transmission distance. As long as the integer cycle number can be accurately estimated, the frequency and phase combined ranging algorithm can achieve high-precision ranging with a single measurement result. However, due to the significant measurement errors of the frequency method, the estimation of the integer cycle number can be subject to significant deviations, directly affecting the correct resolution of the integer cycle ambiguity and, consequently, affecting ranging accuracy. Summary of the Invention

[0006] In response to the above-mentioned deficiencies or improvement needs of the prior art, the present invention provides a method and system for improving the ranging accuracy of FMCW radar based on frequency combination, the purpose of which is to reduce the probability of incorrectly estimating integer ambiguity in the frequency and phase combination ranging method, thereby improving ranging accuracy.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for improving the ranging accuracy of an FMCW radar based on frequency combination is provided, wherein the method is used to measure the range of a target after the FMCW radar transmits a first chirp signal and a second chirp signal with the same frequency sweep bandwidth, wherein the frequency sweep starting frequency of the first chirp signal is f0, and the frequency sweep starting frequency of the second chirp signal is f1. B is the sweep bandwidth; the method comprises:

[0008] Step S1: obtaining a beat signal s0(t) obtained by mixing a first echo signal reflected by a target and the first chirp signal, and obtaining a beat signal s1(t) obtained by mixing a second echo signal reflected by a target and the second chirp signal;

[0009] Step S2: Analyze the phase of the beat signal s0(t) and the phase of the beat signal s1(t) Select any beat frequency signal as the target processing signal and calculate the initial value R of the target distance according to its frequency f ;

[0010] Step S3: Phase ranging relationship based on wide-term combination Let the target distance estimate R WL =R f Find the initial value N of the combined integer number WL ; Among them, the combined phase Combined wavelength λ0 is the wavelength corresponding to the starting frequency f0 of the frequency sweep, and λ1 is the wavelength corresponding to the starting frequency f1 of the frequency sweep;

[0011] Step S4: Set the initial value N of the combined whole week number WL Substitute the wide-term combined phase ranging relationship again to inversely calculate the target distance estimate R WL ;

[0012] Step S5: Based on the target processing signal and the target distance estimation value R WL , using the frequency-phase combination ranging algorithm to calculate the estimated value of the number of integer cycles of the phase ambiguity of the corresponding target processing signal;

[0013] Step S6: Calculate the final target distance value using a phase ranging algorithm based on the target processing signal and the estimated value of the integer number of cycles.

[0014] In one embodiment, in step S3, the target distance initial value R f The formula for calculating the initial value of the combined whole week number is:

[0015]

[0016] Among them, round(*) is a rounding operation.

[0017] In one embodiment, in step S4, based on the initial value N of the combined whole week number WL The formula for calculating the target distance estimate is:

[0018]

[0019] In one embodiment, in step S5, based on the target processing signal and the target distance estimation value R WL The calculation formula for the estimated value of the number of integer cycles corresponding to the phase ambiguity of the target processing signal is:

[0020]

[0021] Among them, N f is the estimated value of the integer number of phase ambiguity corresponding to the target processing signal, is the phase of the target processing signal, λ f The wavelength corresponding to the chirp signal sweep start frequency corresponding to the target processing signal.

[0022] In one embodiment, in step s6, based on the combined whole week number estimate N f The formula for calculating the final value R of the target distance is:

[0023]

[0024] In one embodiment, when measuring a moving target, the first chirp signal and the second chirp signal are transmitted alternately in sequence, and the distance to the target is measured based on the adjacent first chirp signal and the second chirp signal.

[0025] According to a second aspect of the present invention, a system for improving the ranging accuracy of an FMCW radar based on frequency combination is provided, which is used to measure the range of a target after the FMCW radar transmits a first chirp signal and a second chirp signal with the same frequency sweep bandwidth, wherein the frequency sweep starting frequency of the first chirp signal is f0, and the frequency sweep starting frequency of the second chirp signal is f1. B is the sweep bandwidth; the system includes:

[0026] a beat signal receiving unit, configured to receive a beat signal s0(t) obtained by mixing a first echo signal reflected by a target and the first chirp signal, and a beat signal s1(t) obtained by mixing a second echo signal reflected by a target and the second chirp signal;

[0027] Target distance initial value calculation unit, used to analyze the phase of the beat signal s0(t) and the phase of the beat signal s1(t) Select any beat frequency signal as the target processing signal and calculate the initial value R of the target distance according to its frequency f ;

[0028] Combined integer cycle initial value calculation unit, used for phase ranging relationship based on wide-term combination Let the target distance estimate R WL =R f Find the initial value N of the combined integer numberWL ; Among them, the combined phase Combined wavelength λ0 is the wavelength corresponding to the starting frequency f0 of the frequency sweep, and λ1 is the wavelength corresponding to the starting frequency f1 of the frequency sweep;

[0029] The target distance estimation value calculation unit is used to combine the initial value N of the whole number of cycles WL Substitute the wide-term combined phase ranging relationship again to inversely calculate the target distance estimate R WL ;

[0030] Integer number estimation value calculation unit for processing target signal and target distance estimation value R based on target WL , using the frequency-phase combination ranging algorithm to calculate the estimated value of the number of integer cycles of the phase ambiguity of the corresponding target processing signal;

[0031] The target distance final value calculation unit is used to calculate the target distance final value based on the target processing signal and the integer number estimation value using the phase ranging algorithm.

[0032] In one embodiment, it further includes:

[0033] The FMCW radar transmitting unit is used to respectively transmit a first chirp signal and a second chirp signal with the same sweep bandwidth to measure the distance to the target, wherein the sweep starting frequency of the first chirp signal is f0, and the sweep starting frequency of the second chirp signal is f1. B is the sweep bandwidth.

[0034] According to a third aspect of the present invention, an electronic device is provided, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0035] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of the above method when executed by a processor.

[0036] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0037] This invention incorporates the wide-lane combination principle into FMCW frequency and phase combination ranging calculations, reducing the probability of incorrectly estimating integer ambiguities. Directly using frequency and phase combination ranging methods results in distance errors measured in half-wavelength units. However, the distance calculated using the wide-lane combination method presented here avoids the half-wavelength jump problem. Considering that wide-lane combination amplifies phase measurement noise, which can also lead to errors in ranging results, the present invention first estimates the integer ambiguities of the selected signal based on the wide-lane combination principle, and then combines this with phase ranging to obtain accurate ranging results. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A flow chart of a conventional frequency and phase combination ranging algorithm according to an embodiment;

[0039] Figure 2 A flowchart of a method for improving FMCW radar ranging accuracy based on frequency combination according to an embodiment;

[0040] Figure 3 A flowchart of a method for improving FMCW radar ranging accuracy based on frequency combination according to a specific embodiment;

[0041] FIG4( a ) shows the result of directly estimating the number of whole cycles N0 using f0 using a conventional frequency-phase combination ranging method according to an embodiment;

[0042] FIG4( b ) is an embodiment of the combination of the initial value of the number of combined full cycles N after the wide lane combination WL the result;

[0043] FIG4(c) is an example of an embodiment of the target distance estimation value R WL The result of estimating the number of whole weeks N0;

[0044] FIG5( a ) shows the displacement calculated using a conventional frequency-phase combination ranging method according to an embodiment;

[0045] FIG5(b) is an embodiment of the R calculation directly using the wide lane combination WL Schematic diagram;

[0046] FIG5(c) is an embodiment of an embodiment based on R WL Schematic diagram of the displacement obtained further. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0048] In order to better understand the present invention, first, a simple description of the traditional distance measurement algorithm combining the frequency method and the phase method is given. Figure 1 The figure shows the flow chart of the traditional frequency and phase combination ranging algorithm, the main process of which is as follows:

[0049] S01. FMCW radar sends chirp signal.

[0050] S02, the echo signal after being reflected by the target is mixed with the corresponding chirp signal to obtain the beat frequency signal s0(t), which is expressed as:

[0051]

[0052] Among them, frequency f and phase The expression is as follows:

[0053]

[0054]

[0055] Where R is the true value of the distance between the radar and the target. f is the beat frequency, f0 is the sweep start frequency, represents the phase of the beat signal. B is the sweep bandwidth, T is the sweep duration of the chirp signal, and c represents the propagation speed of the electromagnetic wave. From the above formula, we can see that according to f and R can be calculated. There is a phase ambiguity problem, and it can only represent the distance within one circle. And f will have a certain error due to the discretization (Discretizition) and DFT (Discrete Fourier Transform).

[0056] S03. After performing discretization operation, discrete Fourier transform (DFT) and CZT transform on the beat frequency signal in sequence, determine the corresponding frequency value f.

[0057] S04. Knowing the frequency value f, calculate the distance R according to formula (2). Here, the distance calculated based on f is recorded as R f ,Right now:

[0058]

[0059] S05, then calculate the distance R based on f f , let R = R f Substitute into the phase method ranging formula:

[0060]

[0061] Calculate the number of integer cycles N0 required for the phase method, that is, the number of integer cycles of phase ambiguity corresponding to the chirp signal transmission distance:

[0062]

[0063] Considering that N0 has the integer characteristic, round(*) is a rounding operation.

[0064] S06, then the phase Substitute the calculated N0 into formula (5) to obtain the distance R.

[0065] As analyzed above, f will have a certain error due to the discretization and DFT transform (discrete Fourier transform). Therefore, the distance R calculated based on the frequency f f There is a large error, which leads to inaccurate estimation of the subsequent whole cycle number N0, thus affecting the final distance measurement R.

[0066] Based on this, in order to improve ranging accuracy, the present invention proposes the following method for improving FMCW radar ranging accuracy based on frequency combination, which is used to measure the distance to the target after the FMCW radar respectively transmits a first chirp signal and a second chirp signal with the same frequency sweep bandwidth.

[0067] like Figure 2 and Figure 3 As shown in FIG, the flow chart of the steps of the method for improving the ranging accuracy of FMCW radar based on frequency combination is as follows:

[0068] Step S100: obtaining a beat signal s0(t) obtained by mixing a first echo signal reflected by a target and the first chirp signal, and obtaining a beat signal s1(t) obtained by mixing a second echo signal reflected by a target and the second chirp signal.

[0069] In this embodiment, it is assumed that there is only one reflective target.

[0070]

[0071]

[0072] Among them, f s0 、 are the frequency and phase of the beat signal s0(t) respectively; f s1 、 are the frequency and phase of the beat signal s1(t) respectively.

[0073] Step S200: Analyze the phase of the beat signal s0(t) and the phase of the beat signal s1(t) Select any beat frequency signal as the target processing signal and calculate the initial value R of the target distance according to its frequency f .

[0074] After discretization, discrete Fourier transform (DFT) and CZT transform, the phase and frequency of each beat signal can be determined.

[0075] Select one of the beat frequency signals s0(t) and s1(t) as the target processing signal, and record its frequency as f and its phase as According to the relationship between frequency and distance in formula (2), the distance R is preliminarily calculated and recorded as the initial value of the target distance Rf :

[0076]

[0077] Since f will have certain errors due to discretization and DFT transformation (discrete Fourier transform), the distance R calculated based on the frequency f f There is a certain error and it is only used as the initial value of the target distance.

[0078] For example, if the beat frequency signal s0(t) is selected as the target processing signal, then the frequency f s0 The frequency f of the target processing signal is Phase of the target processing signal At this time, the initial value of the target distance R f for:

[0079]

[0080] Step S300: Phase ranging relationship based on wide-term combination Let the target distance estimate R WL =R f Find the initial value N of the combined integer number WL .

[0081] Among them, the combined phase Combined wavelength λ0 is the wavelength corresponding to the starting frequency of the first chirp signal frequency sweep, and λ1 is the wavelength corresponding to the starting frequency of the second chirp signal frequency sweep.

[0082] The construction principle of the wide-term combination phase ranging relationship is as follows:

[0083] The phase ranging formulas obtained from the two beat frequency signals are expressed as follows:

[0084]

[0085]

[0086] Subtracting equation (11) from equation (12), we get:

[0087]

[0088] Define wide item combinations:

[0089]

[0090] N WL =N1-N0 (15)

[0091]

[0092] This gives the phase ranging formula based on wide term combination:

[0093]

[0094] The distance R at this time is recorded as the target distance estimate R WL , then formula (17) is transformed into:

[0095]

[0096] Among them, the parameters λ WL It can be directly determined by calculation, N WL and R WL is an unknown quantity. At this time, the target distance initial value R obtained by formula (9) f As the target distance estimate R WL Substitute into formula (18) to find the initial value N of the combined integer number of cycles WL :

[0097]

[0098] Among them, round(*) is a rounding operation.

[0099] Step S400: Set the initial value N of the combined whole week number WL Substitute the wide-term combined phase ranging relationship again to inversely calculate the target distance estimate R WL .

[0100] The initial value N of the combined integer number calculated by formula (19) WL Substitute into formula (18) again to inversely calculate the target distance estimate R WL :

[0101]

[0102] In this case, a more accurate estimate of the real distance is obtained based on the virtual wide-lane combined signal.

[0103] Step S500: Based on the target processing signal and the target distance estimation value R WL , use the frequency-phase combination ranging algorithm to calculate the estimated value of the number of integer cycles of the phase ambiguity of the corresponding target processing signal.

[0104] The target distance estimation value R is obtained by wide lane combination. WL Then, return to the target processing signal and let R f =R WL ,make Substituting into formula (6), we can get the integer number N of phase ambiguity corresponding to the target processing signal: f :

[0105]

[0106] λ f The wavelength corresponding to the chirp signal sweep start frequency corresponding to the target processing signal.

[0107] For example, the beat frequency signal s0(t) is selected as the target processing signal, and the number of integer cycles of its phase ambiguity N0 is:

[0108]

[0109] Step S600: Calculate the final target distance value using a phase ranging algorithm based on the target processing signal and the integer cycle number estimation value.

[0110] After obtaining the integer number of phase ambiguity cycles, the final value R of the target distance is calculated directly according to the phase ranging algorithm, that is, according to formula (5):

[0111]

[0112] For example, the beat frequency signal s0(t) is selected as the target processing signal. After obtaining the integer number of phase ambiguity N0, the final value of the target distance R is calculated according to formula (5):

[0113]

[0114] This further allows for a more accurate value of the target distance. It is understood that the beat signal s1(t) can also be used as the target processing signal, ie, the processing process is the same.

[0115] Compared with the formula for calculating the phase ambiguity integer number corresponding to the signal transmission distance in the traditional frequency-phase combination ranging algorithm, the present invention uses the wide term combination defined and λ WL Replaces the traditional formula and λ0, even if R f There is an error, but its impact on the estimation of the number of weeks has been greatly weakened, so a more accurate N can be obtained. WL The estimated value is brought back into the phase ranging formula based on the virtual wide term combination to calculate a more accurate distance estimate R WL At this time R WL There is no half-wavelength jump problem in the original frequency-phase combination ranging algorithm, but since the wide-lane combination amplifies the phase measurement noise, its ranging result will also have errors and cannot be directly used for high-precision positioning. Therefore, further based on R WL Estimate the integer ambiguity of the original signal to obtain more accurate ranging results.

[0116] It is worth noting that the most critical step in solving the half-wavelength jump problem in the above algorithm is to combine the more accurate distance estimation value R obtained based on the virtual width term. WL It replaces R in the original frequency-phase combination ranging algorithm formula (6). f Therefore, the parameters of the first and second chirp signals must be such that the calculated R WL The standard deviation σ(R WL ) is less than R f The standard deviation σ(R f ) can effectively improve the accuracy of the final ranging result.

[0117] Let the starting frequency of the first chirp signal sweep be f0, the target distance measured by s0(t) using the phase method be R0, and the starting frequency of the second chirp signal sweep be f1, the target distance measured by s1(t) using the phase method be R1. The conditions that f0 and f1 need to meet will be derived below.

[0118] According to the definition of wide term combination:

[0119]

[0120] Therefore, we can get R WL The standard deviation σ(R WL ) and the standard deviation of R0 and R1:

[0121]

[0122] Considering the phase method ranging CRB (Cramér-Rao lower bound) is:

[0123]

[0124] So there is

[0125]

[0126] Considering the CRB of frequency ranging method is

[0127]

[0128] Then we can get R f The standard deviation σ(R f ) satisfies the following formula:

[0129]

[0130] To satisfy R WL The standard deviation σ(R WL ) is less than R f The standard deviation σ(R f ) can effectively improve the accuracy of the final ranging result, namely:

[0131] σ(R WL )<σ(R f )

[0132] According to the above formula, we can get:

[0133]

[0134] Therefore, by properly setting the transmitted chirp signal frequencies f0 and f1 and the sweep bandwidth B, Only in this way can the accuracy of the ranging results be effectively improved.

[0135] In one embodiment, the target is moving and target ranging needs to be continuously performed. Therefore, the radar needs to alternately transmit the first chirp signal and the second chirp signal in sequence and perform ranging on the target based on adjacent first chirp signals and second chirp signals.

[0136] Accordingly, the present invention also relates to a system for improving the ranging accuracy of an FMCW radar based on frequency combination, which is used to measure the distance to a target after the FMCW radar transmits a first chirp signal and a second chirp signal with the same frequency sweep bandwidth. The system comprises:

[0137] a beat signal receiving unit, configured to receive a beat signal s0(t) obtained by mixing a first echo signal reflected by a target and the first chirp signal, and a beat signal s1(t) obtained by mixing a second echo signal reflected by a target and the second chirp signal;

[0138] Target distance initial value calculation unit, used to analyze the phase of the beat signal s0(t) and the phase of the beat signal s1(t) Select any beat frequency signal as the target processing signal and calculate the initial value R of the target distance according to its frequency f ;

[0139] Combined integer cycle initial value calculation unit, used for phase ranging relationship based on wide-term combination Let the target distance estimate R WL =R f Find the initial value N of the combined integer number WL ; Among them, the combined phase Combined wavelength λ0 is the wavelength corresponding to the starting frequency of the first chirp signal sweep, and λ1 is the wavelength corresponding to the starting frequency of the second chirp signal sweep;

[0140] The target distance estimation value calculation unit is used to combine the initial value N of the whole number of cycles WL Substitute the wide-term combined phase ranging relationship again to inversely calculate the target distance estimate R WL;

[0141] Integer number estimation value calculation unit for processing target signal and target distance estimation value R based on target WL , using the frequency-phase combination ranging algorithm to calculate the estimated value of the number of integer cycles of the phase ambiguity of the corresponding target processing signal;

[0142] The target distance final value calculation unit is used to calculate the target distance final value based on the target processing signal and the integer number estimation value using the phase ranging algorithm.

[0143] In one embodiment, the system further comprises:

[0144] The FMCW radar transmitting unit is used to respectively transmit a first chirp signal and a second chirp signal with the same sweep bandwidth to measure the distance to the target, wherein the sweep starting frequency of the first chirp signal is f0, and the sweep starting frequency of the second chirp signal is f1. B is the sweep bandwidth.

[0145] It can be understood that the system for improving the ranging accuracy of FMCW radar based on frequency combination is used to execute the method for improving the ranging accuracy of FMCW radar based on frequency combination mentioned above, and its various functional units are used to execute corresponding steps. For details, please refer to the above introduction and will not be repeated here.

[0146] Accordingly, the present invention also relates to an electronic device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method described above when executing the computer program. Specifically, the electronic device may be a computing device such as a computer, a laptop, or a cloud server.

[0147] Accordingly, the present invention also relates to a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method described above when the computer program is executed by a processor. Specifically, the computer-readable storage medium may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash memory card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage device.

[0148] To more intuitively demonstrate the effectiveness of this method in improving ranging accuracy, the following simulation experiments compare it with the traditional frequency-phase combination ranging method. It should be noted that although the simulation parameters are based on the millimeter-wave radar frequency band, this method is effective for all FMCW radars.

[0149] The method of the present invention is abbreviated as FMCW-WL, and the traditional frequency and phase combination ranging is abbreviated as FMCW-COMB.

[0150] The simulation parameters of FMCW radar are as follows: sampling rate f s =5MHz, the FMCW radar sends two chirp signals with a sweep bandwidth of B = 1GHz in sequence, whose starting frequencies are f0 = 60GHz and f1 = 63GHz respectively. In this embodiment, the zero-filling method FFT is used to improve the frequency resolution so that the R f To be more accurate, the number of sampling points N = 512 and the number of zero-padding points M = 512, that is, the number of points in the zero-padding FFT is 512 × 512. The initial target distance is set to 0.5m, and the displacement is stepped by 0.5mm until it reaches 0.55m.

[0151] Figure 4(a) shows the number of whole cycles estimated directly from f0 using the traditional frequency-phase combination ranging method under a 10dB SNR (signal-to-noise ratio). It can be seen that the estimated number of whole cycles, N0, has a significant counting error (as shown in the dotted box).

[0152] Figure 4(b) shows the whole cycle estimation result after the wide lane combination. It can be seen that during the whole displacement process, the number of wide lane whole cycles N corresponding to the distance is WL There was only one normal jump: from 10 weeks to 11 weeks.

[0153] FIG4( c ) shows the estimation result of the number of whole cycles of f0 using this method. It can be seen that no half-wavelength jump occurs at this time.

[0154] Figure 5(a) plots the displacement calculated directly using the traditional frequency and phase combination ranging method. It can be seen that directly using the traditional frequency and phase combination ranging (FMCW-COMB) method will result in a distance error in units of half a wavelength.

[0155] Figure 5(b) shows the R calculated directly using the wide lane combination. WL . It can be clearly seen that: R WL The half-wavelength jump problem has been eliminated, but the wide-lane combination amplifies the phase measurement noise, so the ranging result will also have errors. The calculated RMSE (root mean square error) is 0.21mm, which cannot be directly used for high-precision positioning. WL Only by estimating the integer ambiguity of the original signal can we obtain more accurate ranging results.

[0156] Figure 5(c) shows the displacement calculated by this method. It can be seen that the displacement detection result is consistent with the actual displacement result, and the calculated RMSE result is 0.007mm.

[0157] It will be easily understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for improving the ranging accuracy of FMCW radar based on frequency combination, characterized in that: It is used to measure the distance to the target after the FMCW radar transmits the first chirp signal and the second chirp signal with the same sweep bandwidth respectively, wherein the sweep starting frequency of the first chirp signal is f0, the sweep starting frequency of the second chirp signal is f1, B is the sweep bandwidth; the method comprises: Step S1: obtaining a beat signal s0(t) obtained by mixing a first echo signal reflected by a target and the first chirp signal, and obtaining a beat signal s1(t) obtained by mixing a second echo signal reflected by a target and the second chirp signal; Step S2: Analyze the phase of the beat signal s0(t) and the phase of the beat signal s1(t) Select any beat frequency signal as the target processing signal and calculate the initial value R of the target distance according to its frequency f ; Step S3: Phase ranging relationship based on wide-term combination Let the target distance estimate R WL =R f Find the initial value N of the combined integer number WL ; Among them, the combined phase Combined wavelength λ0 is the wavelength corresponding to the starting frequency f0 of the frequency sweep, and λ1 is the wavelength corresponding to the starting frequency f1 of the frequency sweep; Step S4: Set the initial value N of the combined whole week number WL Substitute the wide-term combined phase ranging relationship again to inversely calculate the target distance estimate R WL ; Step S5: Based on the target processing signal and the target distance estimation value R WL , using the frequency-phase combination ranging algorithm to calculate the estimated value of the number of integer cycles of the phase ambiguity of the corresponding target processing signal; Step S6: Calculate the final target distance value using a phase ranging algorithm based on the target processing signal and the estimated value of the integer number of cycles.

2. The method for improving FMCW radar ranging accuracy based on frequency combination according to claim 1, characterized in that: In step S3, the target distance initial value R f The formula for calculating the initial value of the combined whole week number is: Among them, round(*) is a rounding operation.

3. The method for improving FMCW radar ranging accuracy based on frequency combination according to claim 1, characterized in that: In step S4, based on the initial value N of the combined integer number WL The formula for calculating the target distance estimate is:

4. The method for improving FMCW radar ranging accuracy based on frequency combination according to claim 1, characterized in that: In step S5, based on the target processing signal and the target distance estimation value R WL The calculation formula for the estimated value of the number of integer cycles corresponding to the phase ambiguity of the target processing signal is: Among them, N f is the estimated value of the integer number of phase ambiguity corresponding to the target processing signal, is the phase of the target processing signal, λ f The wavelength corresponding to the chirp signal sweep start frequency corresponding to the target processing signal.

5. The method for improving the ranging accuracy of FMCW radar based on frequency combination according to claim 4, characterized in that: In step S6, based on the combined integer number estimate N f The formula for calculating the final value R of the target distance is:

6. The method for improving FMCW radar ranging accuracy based on frequency combination according to claim 1, characterized in that: If a moving target is to be measured, the first chirp signal and the second chirp signal are transmitted alternately in sequence, and the distance to the target is measured based on the adjacent first chirp signal and the second chirp signal.

7. A system for improving the ranging accuracy of FMCW radar based on frequency combination, characterized in that: It is used to measure the distance to the target after the FMCW radar transmits the first chirp signal and the second chirp signal with the same sweep bandwidth respectively, wherein the sweep starting frequency of the first chirp signal is f0, the sweep starting frequency of the second chirp signal is f1, B is the sweep bandwidth; the system includes: a beat signal receiving unit, configured to receive a beat signal s0(t) obtained by mixing a first echo signal reflected by a target and the first chirp signal, and a beat signal s1(t) obtained by mixing a second echo signal reflected by a target and the second chirp signal; Target distance initial value calculation unit, used to analyze the phase of the beat signal s0(t) and the phase of the beat signal s1(t) Select any beat frequency signal as the target processing signal and calculate the initial value R of the target distance according to its frequency f ; Combined integer cycle initial value calculation unit, used for phase ranging relationship based on wide-term combination Let the target distance estimate R WL =R f Find the initial value N of the combined integer number WL ; Among them, the combined phase Combined wavelength λ0 is the wavelength corresponding to the starting frequency f0 of the frequency sweep, and λ1 is the wavelength corresponding to the starting frequency f1 of the frequency sweep; The target distance estimation value calculation unit is used to combine the initial value N of the whole number of cycles WL Substitute the wide-term combined phase ranging relationship again to inversely calculate the target distance estimate R WL ; Integer number estimation value calculation unit for processing target signal and target distance estimation value R based on target WL , using the frequency-phase combination ranging algorithm to calculate the estimated value of the number of integer cycles of the phase ambiguity of the corresponding target processing signal; The target distance final value calculation unit is used to calculate the target distance final value based on the target processing signal and the integer number estimation value using the phase ranging algorithm.

8. The system for improving FMCW radar ranging accuracy based on frequency combination according to claim 7, characterized in that: Also includes: The FMCW radar transmitting unit is used to respectively transmit a first chirp signal and a second chirp signal with the same sweep bandwidth to measure the distance to the target, wherein the sweep starting frequency of the first chirp signal is f0, and the sweep starting frequency of the second chirp signal is f1. B is the sweep bandwidth.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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