A star flash anti-multipath phase ranging method based on fast fourier transform and bimodal ratio rechecking

Abstract

The application belongs to the field of signal processing and communication positioning, and discloses a star flash anti-multipath phase ranging method based on fast Fourier transform and double-peak ratio review. The method collects phase responses under the multi-frequency frequency hopping channel of the star flash communication protocol, constructs a complex frequency domain signal, and obtains a time delay spectrum and maps it into a distance spectrum through fast Fourier transform. In the distance spectrum, first, a threshold is set according to the amplitude distribution, and the first candidate peak exceeding the threshold is found as the preliminary result. Then, the second candidate peak is found. When the distance between the two candidate peaks is less than the set threshold D and the amplitude ratio is greater than the preset threshold gamma, the first candidate peak is determined as a false peak, and the distance corresponding to the second candidate peak is output as the final result. The application adds threshold screening and double-peak ratio review mechanism under the original FFT ranging framework, effectively suppresses the false peak misjudgment caused by multipath interference, significantly improves the ranging accuracy and robustness, and is suitable for high-precision short-range positioning applications in complex indoor environments.

Description

Technical Field

[0001] This invention relates to the field of signal processing and communication positioning, specifically to a star-flash multi-antenna ranging method for use in wireless short-range communication or intelligent connected vehicles. Background Technology

[0002] With the increasing demand for low-power, low-latency, and high-precision communication, SparkLink technology, as a new generation of short-range high-speed wireless communication standard, is gradually entering key application scenarios such as smart terminals, industrial interconnection, vehicle sensing, and indoor positioning. Ranging and positioning systems based on the SparkLink protocol, utilizing its multi-frequency hopping characteristics and low latency features, provide a new approach to achieving sub-meter and even centimeter-level high-precision ranging. Among these methods, phase ranging, due to its ability to achieve high-precision estimation within limited bandwidth, has become an important research direction in SparkLink positioning systems.

[0003] Existing phase ranging methods are typically based on the principle of multi-frequency phase difference, constructing a complex frequency domain response and mapping it to the range domain using Fast Fourier Transform (FFT), with the time delay or distance corresponding to the spectral peak position as the ranging result. These methods are simple to implement and computationally efficient, achieving high accuracy in single-path or weak multipath environments. However, due to the limited number and discontinuous distribution of frequency points in star-flash protocols, the range domain spectrum obtained by directly applying FFT often exhibits strong sidelobes and wide peaks, making it easy for spurious peaks in multipath environments to be confused with direct path peaks, thus reducing the stability and reliability of the ranging measurement.

[0004] Existing FFT-based ranging methods select the first peak as the dominant peak to obtain the ranging result. However, in complex environments, multipath reflections often cause false peaks to cross the threshold before the direct path peaks, leading to misjudgments. Furthermore, the relative amplitude relationships between different peaks are not fully utilized, resulting in insufficient robustness of the algorithm in strong multipath or non-line-of-sight scenarios. Especially in typical indoor and vehicle-mounted applications of starbursts, where the number of reflection paths is large and power differences are significant, traditional FFT-based ranging methods struggle to meet the demands for high accuracy and high reliability.

[0005] Therefore, there is an urgent need for a method that can further enhance multipath discrimination capabilities based on FFT ranging within the framework of the Starflash protocol, so as to effectively distinguish direct paths from false peaks in complex environments, thereby improving ranging accuracy and system robustness. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of false peak misjudgment, insufficient ranging accuracy, and poor robustness of existing star-flash protocol-based phase ranging methods in multipath environments. This invention provides a star-flash anti-multipath phase ranging method based on fast Fourier transform and double-peak ratio verification, so as to improve the ability to identify direct paths and the ranging accuracy of the system under complex channel conditions.

[0007] Technical solution A star-flash anti-multipath phase ranging method based on fast Fourier transform and bimodal ratio verification includes the following steps: S1. Phase Acquisition and Frequency Domain Signal Construction: Under the Star Flash Communication Protocol, carrier signals are transmitted in multiple preset frequency hopping channels and IQ data after reflection are received. Phase information at different frequencies is extracted to construct complex frequency domain response signals for subsequent frequency domain-range domain transformation.

[0008] S2, FFT Transformation and Threshold Filtering: Perform Fast Fourier Transform (FFT) on the complex frequency domain signal from step S1 to obtain the time delay spectrum, and map it to the distance spectrum; in the distance spectrum, set a threshold according to the amplitude distribution, and search for the first candidate peak that exceeds the threshold in the direction from small to large distance, as the preliminary ranging result.

[0009] S3. Double-peak ratio verification: Continue searching for the second adjacent candidate peak exceeding the threshold in the distance domain spectrum, and calculate the amplitude ratio of the first candidate peak to the second candidate peak; when the ratio is greater than a preset threshold, it is determined that the first candidate peak may be a spurious peak caused by multipath reflection, and the distance corresponding to the second candidate peak is selected as the final result; otherwise, the distance corresponding to the first candidate peak is output. When there is only one peak exceeding the threshold in the distance spectrum, the distance corresponding to that peak is directly output.

[0010] Beneficial effects This invention, based on the traditional FFT phase ranging framework, proposes for the first time a two-stage judgment mechanism combining threshold screening and bi-peak ratio verification. Threshold screening avoids interference from weak-amplitude spurious peaks in ranging, while bi-peak ratio verification identifies direct and reflected paths, effectively suppressing false peak misjudgments caused by multipath effects. Without increasing bandwidth or hardware complexity, this invention significantly improves ranging accuracy and robustness in complex indoor and vehicle-mounted multipath environments under the Starflash protocol, demonstrating strong practical value and promising prospects for widespread application. Attached Figure Description

[0011] Figure 1 This is a flowchart of the process of the present invention; Figure 2 This is a schematic diagram of the actual measurement scenario of the present invention; Figure 3 This is an FFT result diagram of an example signal according to an embodiment of the present invention; Figure 4 This is an FFT result diagram of an embodiment of the present invention without triggering the bimodal ratio verification mechanism; Figure 5 This is an FFT result diagram of the bimodal ratio verification mechanism triggered in an embodiment of the present invention. Detailed Implementation

[0012] The following description illustrates specific embodiments of the present invention, and is not intended to limit the exemplary embodiments according to this application. To avoid confusion or obscuring the focus of the present invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0013] A star-flash anti-multipath phase ranging method based on fast Fourier transform and bimodal ratio verification includes the following steps: (e.g.) Figure 1 ) S1. Phase Acquisition and Frequency Domain Signal Construction This invention relates to a star-flash phase ranging system, whose signal flow includes signal generation, channel propagation, reflection response, return transmission and sampling, and complex signal modeling. The system transmits a continuous sinusoidal carrier signal in each communication channel. At the beginning, the baseband signal can be represented as... in, This is the baseband frequency of the local oscillator. After modulating this signal to the center frequency, a wireless transmission signal is generated. in, Given the carrier frequency, after the signal propagates to the reflecting end, it undergoes channel attenuation and time delay. The received signal can be expressed as: in, Channel gain; This represents the propagation delay from the starting end to the reflecting end.

[0014] The reflecting end demodulates the signal using its local carrier wave to obtain... in, Define the phase offset and phase components. The reflector transmits the IQ signal back and modulates it into... in The signal is the result of demodulating the received signal with its local carrier at the reflecting end, and this signal undergoes another attenuation on the return path. With delay Received at the starting end Finally, demodulation at the starting end yields: If we assume It can be simplified to: Among them, the overall phase is For each phase measurement at a given frequency, each sample is measured at a separate frequency. The frequency step size between samples during sampling is... It needs to be kept constant to facilitate subsequent fast Fourier transform and sparse optimization.

[0015] exist Repeat the above steps at each frequency point to construct a phase sample sequence. Subsequently, the phase sample sequence Considering the angles as vectors on the complex plane, in the algorithm of this invention, it is assumed that the lengths (magnitudes) of all vectors are constant. Here, it is assumed that all... The amplitude of each sample is always 1 / This ensures that the overall signal energy is independent of the number of samples and effectively limits the peak amplitude of the Fast Fourier Transform (FFT). Ultimately, the frequency response of the transmission channel between the two radio transceivers can be expressed as a complex signal. It is represented as: in, For frequency points, For the first Phase measurements at each frequency.

[0016] S2, FFT transformation and threshold filtering Frequency step size between samples during sampling This determines the maximum measurable propagation delay. As shown in the formula below By The maximum distance can be calculated by multiplying it by the wave speed of the signal (usually the speed of light). As shown in the formula below: After constructing the frequency domain signal of S1, the frequency domain response vector will be... Transform to the time domain to obtain the impulse response of the radio channel. Specifically, the frequency domain response vector. Perform an M-point Fast Fourier Transform (FFT) to represent the signal amplitude sequence after transforming these complex vectors as follows: The time-domain sampling interval is expressed as .

[0017] It should be noted that after FFT transformation, inverting the time axis is equivalent to performing IFFT, and it is more convenient to implement in engineering. Therefore, the frequency domain to time domain transformation in this step is implemented using FFT.

[0018] In this embodiment, M is set to 1024.

[0019] The resulting time-domain signal contains positive and negative delays; the positive delay can be directly interpreted as... The distance within the range. Negative delay will be interpreted as aliasing and greater than... The distance, i.e. The distance within the range, where the maximum negative delay is ( )correspond Minimum negative delay ( )correspond .

[0020] FFT uses the corresponding time as An array of the form `FFT` returns the FFT result. Therefore, any point in the FFT output... corresponding distance This can be directly explained using the formula below. Values ​​within the range.

[0021] This method allows us to correlate time delay with distance, resulting in a spectrum (distance spectrum) with distance as the horizontal axis. Figure 3 As shown.

[0022] However, multipath propagation introduces additional peaks into the FFT results. The peaks resulting from multipath propagation represent distances that are always longer than, but not shorter than, the direct path. Therefore, peaks caused by multipath propagation are expected to appear at relatively far distances in the FFT results. Thus, when determining the ranging result, the first peak in the FFT result should be chosen, rather than the highest peak.

[0023] To address this, this invention proposes a threshold filtering mechanism based on FFT, which effectively distinguishes effective peaks from noise or weak reflection peaks by setting a threshold. The specific method is as follows: First, analyze the distance spectrum amplitude sequence. Sort and extract the first... The value corresponding to each percentile P This value serves as a baseline threshold, reflecting the level of most background noise and low-amplitude components in the spectrum. The maximum amplitude of the full spectrum is then calculated. Q And calculate the threshold using the following formula : Where parameters This is an adjustment coefficient used for adjustment. P and Q The impact on threshold calculation. When When the threshold is larger, it is closer to the maximum peak, and can more strictly suppress weak peaks; when The smaller the threshold, the closer it is to the statistical level, and the easier it is to preserve weaker effective peaks. Calculate the threshold. T Then, the algorithm will search for the first (leftmost) one that is higher than... T The peak value.

[0024] In this embodiment, the following settings are provided: =96, .

[0025] This screening method filters out most spurious peaks, retaining only candidate peaks with higher intensity. Therefore, threshold screening not only provides reliable candidate peak input for subsequent bimodal ratio verification, but also significantly reduces the risk of noise peaks and weak reflection peaks being misidentified as direct paths in complex multipath environments.

[0026] S3, Bimodal Ratio Verification To further enhance multipath resistance, this invention proposes a bimodal ratio verification mechanism. After completing the FFT transformation and threshold screening in step S2, the first candidate peak exceeding the threshold is obtained, denoted as the first candidate peak, and its corresponding FFT point is... Distance is denoted as Peak amplitude is Then, in the distance spectrum, continue searching for the second adjacent peak that exceeds the threshold, denoted as the second candidate peak, whose FFT corresponding point is... Distance is denoted as Peak amplitude is If the distance between the two candidate peaks is less than 1 / 3, then... D (The typical value range is 2~5m, and 3m is used in this embodiment), then the bimodal ratio verification mechanism is activated to calculate the amplitude ratio of the two peaks. Set preset threshold (Typical values ​​range from 1.2 to 1.4; in this embodiment, 1.3 is used). Based on the ratio... With threshold The relationship between the two factors determines the final ranging result. If... When the second candidate peak is significantly stronger than the first candidate peak, the first candidate peak is determined to be a spurious peak caused by multipath reflection, and the distance corresponding to the second candidate peak is selected. As the final ranging result; if That is, if the second candidate peak is not significant enough, the distance corresponding to the first candidate peak is retained. This serves as the final ranging result.

[0027] In addition, to ensure the applicability of the algorithm, the present invention handles special cases as follows: when there is only one peak in the distance spectrum that exceeds the threshold, the distance corresponding to the peak is directly output as the final ranging result.

[0028] Through the aforementioned bi-peak ratio verification steps, this invention can utilize the relative amplitude information of adjacent peaks to further identify and eliminate spurious peaks caused by multipath reflection. In typical starburst indoor and vehicle-mounted application scenarios, this method can effectively reduce the probability of spurious peak misjudgment, making the ranging results more stable and closer to the true direct path. Measurement experiments show that in strong multipath environments, using the threshold screening and bi-peak ratio verification method of this invention can reduce the error by approximately 25%. Figure 1 The flowchart below illustrates the method of this invention. The process includes: phase response extraction, signal conversion, FFT processing, threshold setting and first candidate peak search, determining whether a second candidate peak exists, and whether the candidate peak spacing meets the threshold. Calculation of the bimodal amplitude ratio and its relationship with the threshold The results are compared, and the final ranging result is output. This figure visually illustrates the complete processing logic of this invention, which introduces "threshold filtering + bimodal ratio verification" on the basis of traditional FFT.

[0029] Figure 2 This is a schematic diagram of an actual measurement scenario. The diagram illustrates the deployment of the transmitting and receiving equipment in an indoor corridor environment. The scenario includes strong reflective surfaces such as walls and glass, which easily lead to multipath propagation. This diagram is used to illustrate the application environment and multipath resistance requirements of the method of this invention.

[0030] Figure 3 This is an FFT result plot of a real signal. The horizontal axis represents distance, and the vertical axis represents spectral amplitude, showing the distance spectrum without thresholding. The plot contains several high-amplitude peaks, reflecting the aliasing problem between direct paths and multipath reflection paths, indicating that directly taking the highest peak carries a risk of misjudgment.

[0031] Figure 4 This is a graph showing the thresholded FFT results for the same signal, with the threshold represented by a red dashed line. TThe figure marks the first two candidate peaks that exceed the threshold, along with their amplitudes. This is because the distance between the candidate peaks exceeds the set threshold. Therefore, the ratio verification step was not performed, and the distance corresponding to the first candidate peak was directly output as the ranging result. Figure 5 This is also an FFT result after threshold filtering on the same signal, showing the case where the threshold setting is not ideal. In this case, the threshold line... T If the value is too low, the first candidate peak exceeding the threshold will not be a direct path peak, but a false peak. In this case, the bi-peak ratio verification mechanism of this invention will check the first candidate peak... and the adjacent second candidate peak Then it is determined that the distance is less than the set threshold. Then calculate its amplitude ratio. R Calculation results R If the peak value exceeds a preset threshold γ, the first candidate peak is determined to be a false peak, and the second candidate peak is selected. The corresponding distance is used as the final result. Therefore, even if the threshold is occasionally set undesirably, this invention can still eliminate erroneous peaks and output the correct distance measurement result.

[0032] The above description is merely a specific embodiment of the present invention. It should be noted that those skilled in the art should not consider the specific implementation of the present invention to be limited to these descriptions. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Those skilled in the art can make various changes in form and detail, including making some simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A star-flash anti-multipath phase ranging method based on fast Fourier transform and bimodal ratio verification, characterized in that, Includes the following steps: S1. Phase acquisition and frequency domain signal construction: Under the Star Flash communication protocol, carrier signals are transmitted in multiple preset frequency hopping channels and IQ data after reflection are received. Phase information at different frequencies is extracted to construct complex frequency domain response signals for subsequent frequency domain-range domain transformation. S2, FFT Transformation and Threshold Filtering: Perform a Fast Fourier Transform on the complex frequency domain signal from step S1 to obtain the time delay spectrum, and map it to the distance spectrum; in the distance spectrum, set a threshold according to the amplitude distribution, and search for the first candidate peak that exceeds the threshold in the direction from small to large distance, as the preliminary ranging result; S3. Double-peak ratio verification: Continue searching for the second adjacent candidate peak exceeding the threshold in the distance spectrum, and calculate the amplitude ratio of the first candidate peak to the second candidate peak; when the ratio is greater than the preset threshold, it is determined that the first candidate peak may be a pseudo-peak caused by multipath reflection, and the distance corresponding to the second candidate peak is selected as the final result; otherwise, the distance corresponding to the first candidate peak is output; when there is only one peak exceeding the threshold in the distance spectrum, the distance corresponding to that peak is directly output. In step S2, the distance spectrum is calculated as follows: After constructing the frequency domain signal of S1, the frequency domain response vector will be... By converting to the time domain, the impulse response of the radio channel is obtained; where, Given the number of frequency points, the signal amplitude sequence is represented as follows: Maximum propagation delay The time-domain sampling interval is expressed as , The number of points for the Fast Fourier Transform; Based on the corresponding time An array of the form returns the FFT result; any point in the FFT output... corresponding distance as follows: Among them, the maximum distance as follows, For the wave speed of the signal: By mapping time delay to distance in this way, a spectrum with distance on the horizontal axis is obtained; In step S2, the threshold filtering mechanism distinguishes effective peaks from noise or weak reflection peaks by setting a threshold; the specific method is as follows: First, analyze the distance spectrum amplitude sequence. Sort and extract the first... The value corresponding to each percentile P As a baseline threshold; Then calculate the maximum amplitude of the full spectrum. Q And calculate the threshold using the following formula : Where parameters This is an adjustment coefficient used for adjustment. P and Q Impact on threshold calculation; Calculate the threshold T Then, search for the first higher distance in the distance spectrum. T The candidate peaks were used as preliminary ranging results.

2. The star-flash anti-multipath phase ranging method based on fast Fourier transform and bimodal ratio verification according to claim 1, characterized in that, In step S1, the complex frequency domain response signal is: in, For frequency points, For the first Phase measurements at each frequency.

3. The star-flash anti-multipath phase ranging method based on fast Fourier transform and bimodal ratio verification according to claim 1, characterized in that, The value is 96. The value is 15.

4. The star-flash anti-multipath phase ranging method based on fast Fourier transform and bimodal ratio verification according to claim 1, characterized in that, In step S3, the bimodal ratio verification mechanism is specifically as follows: After completing the FFT transformation and threshold filtering in step S2, the first candidate peak exceeding the threshold has been obtained, denoted as the first candidate peak, and its corresponding FFT point is... Distance is denoted as Peak amplitude is Then, in the distance spectrum, continue searching for the second adjacent peak that exceeds the threshold, denoted as the second candidate peak, and its FFT corresponding point is... Distance is denoted as Peak amplitude is ; If the distance between the two candidate peaks is less than D Then the bimodal ratio verification mechanism is activated to calculate the amplitude ratio of the two peaks: Set preset threshold According to the ratio With threshold The relationship is used to determine the final ranging result: like When the second candidate peak is significantly stronger than the first candidate peak, the first candidate peak is determined to be a spurious peak caused by multipath reflection, and the distance corresponding to the second candidate peak is selected. As the final distance measurement result; like That is, if the second candidate peak is not significant enough, the distance corresponding to the first candidate peak is retained. This serves as the final ranging result.

5. The star-flash anti-multipath phase ranging method based on fast Fourier transform and bimodal ratio verification according to claim 4, characterized in that, Preset threshold The typical value range is 1.2 to 1.4.

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