A short-range high-precision time-frequency synchronization positioning method and system

Abstract

This invention discloses a short-range, high-precision time-frequency synchronization positioning method and system, comprising: constructing a frequency-modulated continuous wave (FM-CVT) signal; embedding the FM-CVT signal into a Wi-Fi signal; loading the FM-CVT signal into the digital domain to obtain an initial FM-CVT signal; converting the initial FM-CVT signal into an analog signal via digital-to-analog conversion, and up-converting the analog signal; receiving the up-converted analog signal, down-converting the analog signal, and obtaining a received FM-CVT signal via analog-to-digital conversion; calculating the time delay and frequency offset between the initial FM-CVT signal and the received FM-CVT signal to obtain a time-frequency offset value; and compensating the time-frequency offset value for subsequent FM-CVT signals to obtain a synchronized FM-CVT signal. This invention utilizes the high time-frequency resolution characteristics of FM-CVT signals, accurately estimates the time delay and frequency offset through cross-correlation or Fourier transform, and performs closed-loop compensation, significantly improving the time-frequency synchronization accuracy and positioning accuracy in short-range scenarios.

Description

Technical Field

[0001] This invention relates to the field of positioning technology, and in particular to a short-range, high-precision time-frequency synchronous positioning method and system. Background Technology

[0002] A current positioning system is an interconnected collection or device designed to determine spatial location. This system ensures that at any given time, at least four satellites can be simultaneously observed from any point on Earth, allowing the satellites to collect the latitude, longitude, and altitude of that point for navigation, positioning, and timing functions. This technology can be used to guide aircraft, ships, vehicles, and individuals safely and accurately along selected routes to their destinations on time.

[0003] In the prior art, patent document CN110769401A discloses a short-range high-precision positioning method, including the following steps: a first mobile terminal obtains a first location of an object; a second mobile terminal obtains a second location of the object; the first mobile terminal obtains a resource set for D2D communication from a base station; the second mobile terminal obtains the resource set for D2D communication from the base station; a central mobile terminal obtains the resource set for D2D communication from the base station; the central mobile terminal broadcasts a synchronization signal on a subset of the resource set for D2D communication; the first mobile terminal captures the synchronization signal, and the second mobile terminal also captures the synchronization signal; in response to capturing the synchronization signal, the first mobile terminal obtains the data channel and control channel of the central mobile terminal, and the second mobile terminal also obtains the data channel and control channel of the central mobile terminal.

[0004] Existing short-range positioning systems use traditional training sequences (L-STF and L-LTF) for time-frequency synchronization, with short training sequences for coarse synchronization and long training sequences for fine synchronization. The algorithms used are typically autocorrelation and cross-correlation. However, the synchronization position under this method is easily affected by multipath effects, channel interference, and sampling clock deviations, resulting in synchronization accuracy only reaching the order of several sampling clock cycles. Although this deviation is usually accommodated by the cyclic prefix and does not affect data demodulation, existing solutions are insufficient for precise clock synchronization and positioning applications requiring extremely high time synchronization accuracy (such as sub-microsecond or even nanosecond levels). Therefore, it is necessary to improve this structure to overcome the aforementioned shortcomings. Summary of the Invention

[0005] The purpose of this invention is to provide a short-range, high-precision time-frequency synchronization positioning method and system to solve the problem that the synchronization position under the existing method is easily affected by multipath effects, channel interference and sampling clock deviation, resulting in the synchronization accuracy only reaching the order of several sampling clock cycles.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] A short-range, high-precision time-frequency synchronous positioning method includes the following steps:

[0008] Construct a frequency-modulated continuous wave signal;

[0009] Incorporating frequency-modulated continuous wave signals into Wi-Fi signals;

[0010] The frequency-modulated continuous wave signal is loaded into the digital domain to obtain the initial frequency-modulated continuous wave signal;

[0011] The initial frequency-modulated continuous wave signal is converted into an analog signal through digital-to-analog conversion, and the analog signal is then up-converted.

[0012] The system receives the up-converted analog signal, down-converts the analog signal, and obtains the received frequency-modulated continuous wave signal through analog-to-digital conversion.

[0013] Calculate the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal to obtain the time-frequency offset value;

[0014] The time-frequency offset is compensated for and applied to the subsequent frequency-modulated continuous wave signal to obtain a synchronous frequency-modulated continuous wave signal.

[0015] A further provision of the present invention is that the expression for the initial frequency-modulated continuous wave signal is as follows:

[0016] ;

[0017] Where FT is the initial frequency-modulated continuous wave signal, j is the imaginary unit, fc is the carrier start frequency, K = B / Tc, B is the carrier bandwidth, Tc is the duration of a single frequency-modulated continuous wave signal, t is the time variable, and exp is the natural constant. Pi is a constant.

[0018] A further provision of the present invention is that the expression for receiving a frequency-modulated continuous wave signal is as follows:

[0019] ;

[0020] Where FR is the received FM continuous wave signal, df is the frequency offset estimate, and dt is the time delay estimate.

[0021] A further provision of the present invention is that the expression for the time delay estimate is any one of the following:

[0022] Method 1: ;

[0023] Method 2: ;

[0024] Where conj is the complex conjugate operation, FFT is the Fourier transform, flip is the reverse operation, conv is the convolution operation, and the position of the maximum value of dt is the number of samples delayed.

[0025] A further provision of the present invention is that the expression for the frequency offset estimate is as follows:

[0026] ;

[0027] Where Tc is the duration of a single chirp signal. This represents the phase difference of the complex signal at the maximum value of adjacent chirp signals.

[0028] A further provision of the present invention is that the frequency offset estimate is obtained by performing a Fourier transform on the maximum value sequence of multiple chirp signals, and the peak position of the maximum value sequence after Fourier transform is the frequency offset estimate.

[0029] A further feature of the present invention is that the frequency-modulated continuous wave signal is set at the beginning or end of the frame of the WIFI signal.

[0030] A further feature of the present invention is that the duration and number of individual chirps of the frequency-modulated continuous wave signal are customized according to the requirements of time-frequency synchronization accuracy and positioning accuracy.

[0031] A short-range, high-precision time-frequency synchronous positioning system includes:

[0032] The digital-to-analog converter module is used to convert the initial frequency-modulated continuous wave signal into an analog signal.

[0033] Analog-to-digital converter module, used to convert the down-converted analog signal into a receive frequency-modulated continuous wave signal;

[0034] The radio frequency (RF) transmission module is used to upconvert analog signals and transmit the upconverted analog signals into the airspace.

[0035] Radio frequency (RF) receiver module: This module is used to receive analog signals and down-convert them.

[0036] The time-frequency offset calculation module is used to calculate the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal to obtain the time-frequency offset value.

[0037] The time-frequency offset compensation module is used to compensate the time-frequency offset value for the subsequent frequency-modulated continuous wave signal to obtain a synchronous frequency-modulated continuous wave signal.

[0038] In summary, the present invention has the following beneficial effects:

[0039] 1. Using frequency-modulated continuous wave signals as a synchronization reference, and taking advantage of their linear frequency modulation characteristics, high-resolution estimation of time delay and frequency offset can be performed through cross-correlation or Fourier transform, which can realize time delay measurement and frequency offset correction, and meet the requirements of short-range high-precision positioning.

[0040] 2. The duration of a single chirp and the number of chirps for the frequency modulated continuous wave signal can be customized according to the actual needs of time-frequency synchronization accuracy and positioning accuracy. For example, increasing the bandwidth or increasing the number of chirps can further improve the estimation resolution, achieve a dynamic balance between accuracy and overhead, and adapt to various application scenarios.

[0041] 3. Frequency modulated continuous wave signals can be embedded in the frame header or frame tail of WIFI signals, occupying the same frequency band as WIFI, without affecting the demodulation process of standard WIFI signals. This facilitates direct upgrades and deployments on existing WIFI hardware, reducing system modification costs. Attached Figure Description

[0042] Figure 1 This is a flowchart illustrating the present invention.

[0043] Figure 2 This is a schematic diagram of the wave time frequency of a frequency-modulated continuous wave signal. Detailed Implementation

[0044] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to the figures and specific embodiments.

[0045] like Figures 1 to 2 As shown, the present invention proposes a short-range, high-precision time-frequency synchronous positioning method, which includes the following steps:

[0046] Step 1: Construct a frequency-modulated continuous wave signal;

[0047] Step 2: Implant the frequency modulated continuous wave signal into the WIFI signal;

[0048] Specifically, frequency-modulated continuous wave signal implantation includes the following two methods:

[0049] Frame header insertion: The frequency modulated continuous wave signal is placed before the traditional L-STF and L-LTF as part of the preamble, which makes it easier for the receiver to capture and complete time-frequency synchronization first, and is suitable for high dynamic scenarios.

[0050] Frame tail insertion: The FMCW signal is placed at the end of the data packet for post-processing or two-way ranging, without affecting the standard WiFi demodulation process. During insertion, the FM continuous wave signal occupies the same frequency band as the WiFi signal.

[0051] Step 3: Load the frequency-modulated continuous wave signal into the digital domain to obtain the initial frequency-modulated continuous wave signal;

[0052] Step 4: Convert the initial frequency-modulated continuous wave signal into an analog signal through digital-to-analog conversion, and then up-convert the analog signal.

[0053] Step 5: Send the up-converted analog signal into the airspace;

[0054] Step 6: Receive the analog signal, down-convert the analog signal, and obtain the received frequency-modulated continuous wave signal through analog-to-digital conversion;

[0055] Step 7: Calculate the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal to obtain the time-frequency offset value;

[0056] Step 8: Compensate the time-frequency offset for the subsequent frequency-modulated continuous wave signal to obtain a synchronous frequency-modulated continuous wave signal.

[0057] Frequency-modulated continuous wave (FM-CW) is a continuous wave signal whose frequency varies linearly with time. Due to its unique frequency modulation characteristics, it is widely used in radar, ranging, and positioning applications. Its main advantage lies in its ability to accurately measure distance and speed by analyzing the frequency changes of the received signal.

[0058] Digital-to-analog conversion refers to the process of converting digital signals into analog signals.

[0059] Upconversion refers to the process of increasing the carrier frequency of a signal from a lower frequency to a higher frequency.

[0060] Downconversion refers to the process of reducing the carrier frequency of a signal from a higher frequency to a lower frequency.

[0061] Analog-to-digital conversion (ADC) refers to the process of converting analog signals into digital signals.

[0062] Delay refers to the time required for a signal to travel from the transmitter to the receiver.

[0063] Frequency offset refers to the deviation of the received signal frequency from the transmitted signal frequency.

[0064] The time-frequency offset is a calculated result of the combined quantization of time delay and frequency offset. This value reflects the deviation of the received signal from the transmitted signal in time and frequency.

[0065] Time-frequency offset compensation refers to correcting the measured time-frequency offset to eliminate its impact on subsequent signal processing and system performance.

[0066] Synchronous frequency-modulated continuous wave (FM-MCW) signal refers to an FM-MCW signal that has undergone time-frequency offset compensation. This signal is synchronized with the original transmitted signal in both time and frequency, thus providing a basis for high-precision positioning and data transmission.

[0067] In practice, the first step is to construct a frequency-modulated continuous wave (FM continuous wave) signal. This FM continuous wave signal is then embedded into the Wi-Fi signal. This embedding process can be achieved by transmitting the FM continuous wave signal as a specific component of the Wi-Fi signal. For example, the FM continuous wave signal can be inserted into a specific location within the Wi-Fi data frame. Next, the FM continuous wave signal is loaded into the digital domain to obtain the initial FM continuous wave signal. Then, the initial FM continuous wave signal is converted into an analog signal via digital-to-analog conversion, and this analog signal is up-converted to an analog signal. Following this, the up-converted analog signal is transmitted into the airspace. This step radiates the up-converted radio frequency analog signal through a transmitting antenna, allowing it to propagate in the wireless channel. The signal transmission power and antenna directivity can be adjusted according to specific application scenarios and coverage requirements.

[0068] At the receiving end, an analog signal is received, down-converted, and then converted to a received frequency-modulated continuous wave (FM) signal via analog-to-digital conversion. Subsequently, this down-converted analog signal is converted to a digital signal by an analog-to-digital converter, forming the received FM FM signal for further processing.

[0069] Furthermore, the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal are calculated to obtain the time-frequency offset value. This calculation process is used to quantify the time delay and frequency shift experienced by the signal during propagation.

[0070] Finally, this time-frequency offset is compensated for by applying it to the subsequent FM continuous wave signal, resulting in a synchronized FM continuous wave signal. The compensation process can perform time shifting and frequency correction on the subsequent FM continuous wave signal based on the calculated time delay and frequency offset. For example, the time delay can be compensated by adjusting the sampling start point of the subsequent signal, and the frequency offset can be compensated by fine-tuning the carrier frequency of the subsequent signal using a digital frequency synthesizer. Through this compensation, the subsequent FM continuous wave signal maintains a high degree of synchronization with the transmitter in both time and frequency, thus providing a stable reference for high-precision positioning.

[0071] The expression for the initial frequency-modulated continuous wave signal is as follows:

[0072] ;

[0073] Where FT is the initial frequency-modulated continuous wave signal, j is the imaginary unit, fc is the carrier start frequency, K = B / Tc, B is the carrier bandwidth, Tc is the duration of a single frequency-modulated continuous wave signal, t is the time variable, and exp is the natural constant. Pi is a constant.

[0074] The expression for receiving a frequency-modulated continuous wave signal is as follows:

[0075] ;

[0076] Where FR is the received FM continuous wave signal, df is the frequency offset estimate, and dt is the time delay estimate.

[0077] The expression for the time delay estimate can be any of the following:

[0078] Method 1: ;

[0079] Method 2: ;

[0080] Where conj is the complex conjugate operation, FFT is the Fourier transform, flip is the reverse operation, conv is the convolution operation, and the position of the maximum value of dt is the number of samples delayed.

[0081] The expression for the frequency offset estimate is as follows:

[0082] ;

[0083] Where Tc is the duration of a single chirp signal. This represents the phase difference of the complex signal at the maximum value of adjacent chirp signals.

[0084] The frequency offset estimate is obtained by performing a Fourier transform on the maximum value sequence of multiple chirp signals. The peak position of the maximum value sequence after Fourier transform is the frequency offset estimate.

[0085] Frequency-modulated continuous wave signals are set at the beginning or end of the frame of a WIFI signal.

[0086] The duration and number of individual chirps of the frequency modulated continuous wave signal can be customized according to the requirements of time-frequency synchronization accuracy and positioning accuracy.

[0087] Example 1:

[0088] In this embodiment, the technical solution of the present invention will be described in detail below using WIFI 20M multiple signal as an example.

[0089] Assuming the baseband sampling frequency is fs = 20MHz and the duration of a single chirp signal is Tc = 0.8μs, then the number of sampling points for a single chirp signal is:

[0090]

[0091] Where N is the number of sampling points, Tc is the duration of a single chirp signal, and fs is the sampling frequency.

[0092] That is, each chirp signal contains 16 time-domain digital complex signal sampling points, and the time variable t=(0:N-1) / fs.

[0093] I. Transmitter signal structure;

[0094] According to steps one to four of this invention, an initial frequency-modulated continuous wave signal (FT) is first constructed. Assuming the carrier start frequency fc = 20MHz and the carrier bandwidth B = 20MHz (consistent with the WIFI signal bandwidth), the frequency modulation slope K = B / Tc = 20MHz / 0.8μs = 2.5 × 10¹³ Hz / s.

[0095] The expression for the initial frequency-modulated continuous wave signal is:

[0096] ;

[0097] Substituting the above parameters, a discrete complex signal sequence with 16 sampling points is obtained. Specifically, for n=0,1,...,15, t=n / 20MHz, the sample values ​​of the FT are calculated sequentially.

[0098] The constructed frequency-modulated continuous wave signal is implanted into the frame header of the WiFi signal. After being loaded into the digital domain, the initial frequency-modulated continuous wave signal is converted into an analog signal by the digital-to-analog converter module, and then up-converted by the radio frequency transmission module before being sent to the airspace.

[0099] II. Signal processing at the receiving end;

[0100] According to step six of the present invention, the receiving end receives the analog signal through the radio frequency receiving module, performs down-conversion on the analog signal, and obtains the received frequency-modulated continuous wave signal FR through analog-to-digital conversion.

[0101] The expression for receiving a frequency-modulated continuous wave signal is:

[0102] ;

[0103] Where df is the frequency offset estimate and dt is the time delay estimate.

[0104] III. Delay Estimation;

[0105] According to step seven of the present invention, the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal are calculated.

[0106] The time delay estimation uses the cross-correlation method, and the expression for its estimated value is as follows:

[0107] dt=conv(FT,conj(flip(FR)));

[0108] Here, `conj` is the complex conjugate operation, `flip` is the reverse operation, and `conv` is the convolution operation. The modulus of the convolution result is calculated, and the position of the maximum modulus value represents the number of samples delayed.

[0109] IV. Frequency offset estimation;

[0110] Frequency offset estimation is obtained by performing a Fourier transform on a sequence of maximum values ​​from multiple chirp signals. Specifically, the complex values ​​at the positions of the maximum amplitudes of multiple consecutive chirp signals are taken to form a sequence of maximum values. A Fourier transform is then performed on this sequence, and the position of the peak value after the transform is the estimated frequency offset.

[0111] Taking 8 chirp signals as an example, the complex values ​​at the maximum values ​​of the 8 chirp signals are extracted to obtain a sequence of length 8. FFT is performed on the sequence, and the frequency index corresponding to the peak value of FFT is the frequency offset estimate df.

[0112] V. Time-frequency offset compensation;

[0113] According to step eight of this invention, the calculated time delay estimate dt and frequency offset estimate df are used to compensate the subsequent frequency-modulated continuous wave signal. During compensation, the sampling start point of the subsequent signal is time-shifted to cancel the time delay dt, and the carrier frequency of the subsequent signal is finely adjusted to cancel the frequency offset df, thereby obtaining a synchronized frequency-modulated continuous wave signal that is highly synchronized with the transmitting end in time and frequency.

[0114] In the above embodiments, the duration Tc of a single chirp (0.8 μs) and the number of chirps (e.g., 8) can be customized according to the actual requirements of time-frequency synchronization accuracy and positioning accuracy. Increasing Tc or increasing the number of chirps can improve the accuracy of time-frequency synchronization.

[0115] The calculation parameters are shown in Table 1:

[0116]

[0117] Table 1

[0118] Substituting the numerical values ​​into the expression for the time delay estimate, the simulation result is as follows: dt = 50 ns.

[0119] Substituting the input into the expression for the frequency offset estimate, the simulation result is as follows: df = 20 kHz.

[0120] A short-range, high-precision time-frequency synchronous positioning system includes:

[0121] The digital-to-analog converter module is used to convert the initial frequency-modulated continuous wave signal into an analog signal.

[0122] Analog-to-digital converter module, used to convert the down-converted analog signal into a receive frequency-modulated continuous wave signal;

[0123] The radio frequency (RF) transmission module is used to upconvert analog signals and transmit the upconverted analog signals into the airspace.

[0124] Radio frequency (RF) receiver module: This module is used to receive analog signals and down-convert them.

[0125] The time-frequency offset calculation module is used to calculate the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal to obtain the time-frequency offset value.

[0126] The time-frequency offset compensation module is used to compensate the time-frequency offset value for the subsequent frequency-modulated continuous wave signal to obtain a synchronous frequency-modulated continuous wave signal.

[0127] During system operation, the initial frequency-modulated continuous wave (FM) signal generated in the digital domain is first converted into an analog signal by a digital-to-analog converter (DAC), then up-converted by an RF transmitter module and transmitted into the airspace via an antenna. After receiving the signal, the receiver antenna performs down-conversion on the signal by an RF receiver module, and then converts it back into a digital FM FM signal by the DAC module. The time-frequency offset calculation module calculates the time delay and frequency offset based on the initial and received FM FM signals, and the time-frequency offset compensation module compensates for the calculated time-frequency offset value in subsequent signals, thereby achieving high-precision time-frequency synchronization.

[0128] The modules are connected via a high-speed data bus (such as an AXI bus or LVDS interface), and the central control unit (such as an FPGA or DSP) coordinates the working timing and data flow.

[0129] The digital-to-analog converter module is used to convert the initial frequency-modulated continuous wave signal generated in the digital domain into an analog signal, and to convert the analog signal after down-conversion by the RF receiver module into a received frequency-modulated continuous wave signal in the digital domain.

[0130] In practical implementation, the digital-to-analog conversion module can be implemented using a high-speed digital-to-analog conversion chip. Taking a DAC with a sampling frequency of fs=20MHz and a resolution of 12 bits as an example, the sampling point sequence of the initial frequency-modulated continuous wave signal FT generated in the digital domain (each chirp contains N=fs×Tc sampling points) is sequentially sent to the DAC chip according to the system clock cycle. The DAC converts the digital sequence into a continuous analog signal output.

[0131] For the receiving link, the analog-to-digital conversion module can use a high-speed ADC chip to sample and quantize the down-converted analog intermediate frequency signal at the same sampling frequency fs, and convert it into a digital domain received frequency-modulated continuous wave signal FR.

[0132] Preferably, the digital-to-analog conversion module and the analog-to-digital conversion module can be integrated on the same FPGA development board and connected to the DAC / ADC chip through the FPGA's serial interface (such as JESD204B) to ensure the synchronization and low latency of data conversion.

[0133] The radio frequency (RF) transmission module is used to up-convert analog signals and transmit the up-converted analog signals into the airspace. In specific implementations, the RF transmission module includes an up-conversion mixer. The analog signal output from the digital-to-analog converter (DAC) is fed into the up-conversion mixer and finally radiated into the airspace through the antenna.

[0134] When an FM continuous wave signal is incorporated into a Wi-Fi signal, the RF transmission module processes both the Wi-Fi baseband signal and the FM continuous wave baseband signal simultaneously. Specifically, after inserting the FM continuous wave signal into the frame header or frame tail of the Wi-Fi signal in the digital domain, the merged baseband signal is transmitted uniformly after digital-to-analog conversion and up-conversion. The FM continuous wave signal occupies the same frequency band as the Wi-Fi signal.

[0135] The radio frequency (RF) receiver module is used to receive analog signals in the airspace and down-convert the analog signals.

[0136] In practice, the RF receiving module includes a down-conversion mixer. The RF signal received by the antenna is first pre-amplified by a low-noise amplifier to improve signal strength and suppress noise interference from subsequent circuits. The amplified RF signal is then fed into the down-conversion mixer.

[0137] In the receiving link, the down-converted analog signal is output to the digital-to-analog converter module for digital processing.

[0138] The time-frequency offset calculation module is used to calculate the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal, and obtain the time-frequency offset value.

[0139] In practice, the time-frequency offset calculation module can be implemented in an FPGA or DSP using digital signal processing algorithms.

[0140] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. These terms are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connect" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. In this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0141] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A short-range high-precision time-frequency synchronization positioning method, characterized in that, Includes the following steps: Construct a frequency-modulated continuous wave signal; Incorporating frequency-modulated continuous wave signals into Wi-Fi signals; The frequency-modulated continuous wave signal is loaded into the digital domain to obtain the initial frequency-modulated continuous wave signal; The initial frequency-modulated continuous wave signal is converted into an analog signal through digital-to-analog conversion, and the analog signal is then up-converted. The system receives the up-converted analog signal, down-converts the analog signal, and obtains the received frequency-modulated continuous wave signal through analog-to-digital conversion. Calculate the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal to obtain the time-frequency offset value; The time-frequency offset is compensated for and applied to the subsequent frequency-modulated continuous wave signal to obtain a synchronous frequency-modulated continuous wave signal.

2. The short-range high-precision time-frequency synchronization positioning method according to claim 1, characterized in that, The expression for the initial frequency-modulated continuous wave signal is as follows: ； where FT is the initial frequency-modulated continuous wave signal, j is the imaginary unit, fc is the carrier start frequency, K = B / Tc, B is the carrier bandwidth, Tc is the duration of a single frequency-modulated continuous wave signal, t is the time variable, exp is the natural constant, is the constant of the circle.

3. The short-range high-precision time-frequency synchronous positioning method according to claim 2, characterized in that, The expression for receiving a frequency-modulated continuous wave signal is as follows: ； Where FR is the received FM continuous wave signal, df is the frequency offset estimate, and dt is the time delay estimate.

4. The short-range high-precision time-frequency synchronous positioning method according to claim 3, characterized in that, The expression for the time delay estimate can be any of the following: Method 1: ; Method 2: ; Where conj is the complex conjugate operation, FFT is the Fourier transform, flip is the reverse operation, and conv is the convolution operation. The value of dt is the estimated time delay, and the location of the maximum value of dt is the number of sample points for the delay.

5. The short-range high-precision time-frequency synchronous positioning method according to claim 1, characterized in that, The expression for the frequency offset estimate is as follows: ； in, Here, Tc is the frequency offset estimate, and Tc is the duration of a single chirp signal. The phase difference of the complex signal representing the maximum value of adjacent chirp signals. Pi is a constant.

6. The short-range high-precision time-frequency synchronous positioning method according to claim 1, characterized in that, The frequency offset estimate is obtained by performing a Fourier transform on the maximum value sequence of multiple chirp signals. The peak position of the maximum value sequence after Fourier transform is the frequency offset estimate.

7. The short-range high-precision time-frequency synchronous positioning method according to claim 1, characterized in that, Frequency-modulated continuous wave signals are set at the beginning or end of the frame of a WIFI signal.

8. The short-range high-precision time-frequency synchronous positioning method according to claim 1, characterized in that, The duration and number of individual chirps of the frequency modulated continuous wave signal can be customized according to the requirements of time-frequency synchronization accuracy and positioning accuracy.

9. A short-range, high-precision time-frequency synchronous positioning system, characterized in that, include: The digital-to-analog converter module is used to convert the initial frequency-modulated continuous wave signal into an analog signal. Analog-to-digital converter module, used to convert the down-converted analog signal into a receive frequency-modulated continuous wave signal; The radio frequency (RF) transmission module is used to upconvert analog signals and transmit the upconverted analog signals into the airspace. Radio frequency (RF) receiver module: This module is used to receive analog signals and down-convert them. The time-frequency offset calculation module is used to calculate the time delay and frequency offset between the initial FM continuous wave signal and the received FM continuous wave signal to obtain the time-frequency offset value. The time-frequency offset compensation module is used to compensate the time-frequency offset value for the subsequent frequency-modulated continuous wave signal to obtain a synchronous frequency-modulated continuous wave signal.

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