阅读说明：本技术 高精度fmcw测距方法、装置及存储介质 (High-precision FMCW ranging method, device and storage medium ) 是由 修剑平 杨垒 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种高精度FMCW测距方法,该方法适用于具有SoC芯片的测距装置,在该方法中SoC芯片的模数转换器的采样时间为整个Chirp周期。本发明公开了一种用于实现前述方法的高精度FMCW测距装置。本发明提供的高精度FMCW测距方法,利用整个Chirp周期采集到的数据进行快速傅里叶变换,等效为将整个快速傅里叶变换时间扩大,以提高测频精度,从而提高测距精度；而且该方法可直接在SoC芯片上完成高精度距离计算,无需外接单片机,可以降低测距系统的成本。(The invention discloses a high-precision FMCW distance measurement method which is suitable for a distance measurement device with an SoC chip. The invention discloses a high-precision FMCW distance measuring device for realizing the method. The high-precision FMCW distance measurement method provided by the invention has the advantages that the data acquired by the whole Chirp period are utilized to carry out fast Fourier transform, and equivalently, the whole fast Fourier transform time is expanded to improve the frequency measurement precision, so that the distance measurement precision is improved; and the method can directly finish high-precision distance calculation on the SoC chip without an external singlechip, and can reduce the cost of the distance measuring system.)

1. A high-precision FMCW ranging method for a ranging device having an SoC chip, the method comprising:

transmitting a Chirp signal with a specific waveform to a target to form an echo signal of the Chirp signal;

receiving the echo signal and mixing the echo signal with the Chirp signal to form an intermediate frequency signal;

sampling the intermediate frequency signal in the whole Chirp period by an analog-to-digital converter based on an SoC chip to obtain sampling data;

carrying out fast Fourier transform on the sampling data to obtain frequency data;

and calculating the target distance according to the frequency data.

2. The high accuracy FMCW ranging method of claim 1, wherein the Chirp period consists of a pre-modulation stage, a modulation stage and a post-modulation stage, the pre-modulation stage being a constant frequency band, the modulation stage being an up-conversion band, the post-modulation stage being a down-conversion band.

3. The high accuracy FMCW ranging method of claim 2, wherein the fast fourier transforming the sampled data comprises:

and fitting the sampled data with a window function of fast Fourier transform, and then carrying out fast Fourier transform on the sampled data.

4. The high accuracy FMCW ranging method of claim 3, wherein the sampled data when fitted to a window function of a fast fourier transform corresponds data collected during the modulation phase in the sampled data to a main lobe of the window function.

5. The high accuracy FMCW ranging method of claim 4 wherein the window function is a Hanning window.

6. The high accuracy FMCW ranging method of claim 1, wherein the calculating a target distance from the frequency data specifically comprises:

and calculating the target distance by adopting a three-point interpolation method according to the frequency data.

7. A high precision FMCW ranging device comprising an SoC chip, the SoC chip comprising:

the transmitting module is used for transmitting a Chirp signal with a specific waveform to a target so as to form an echo signal of the Chirp signal;

the receiving module is used for receiving the echo signal and mixing the echo signal with a Chirp signal to form an intermediate frequency signal;

the analog-to-digital converter is used for sampling the intermediate frequency signal to obtain sampling data;

the processing module is used for carrying out fast Fourier transform on the sampling data to obtain frequency data and calculating a target distance according to the frequency data;

and the sampling time of the analog-to-digital converter is the whole Chirp period.

8. The high accuracy FMCW ranging device of claim 7, wherein the Chirp period consists of a pre-modulation stage, a modulation stage and a post-modulation stage, the pre-modulation stage being a constant frequency band, the modulation stage being an up-conversion band, the post-modulation stage being a down-conversion band.

9. The high-precision FMCW ranging device of claim 7, wherein the processing module is specifically configured to:

fitting the sampled data with a window function of fast Fourier transform, carrying out fast Fourier transform on the sampled data to obtain frequency data, and calculating a target distance according to the frequency data.

10. A computer-readable storage medium, in which a computer program is stored which, when run on a processor, implements the method of any one of claims 1-6.

Technical Field

The present invention relates to the field of FMCW ranging technology, and more particularly, to a high-precision FMCW ranging method, apparatus and storage medium.

Background

The FMCW (frequency modulated continuous wave) large-bandwidth radar has high distance resolution and ranging accuracy, and particularly has obvious advantages on high-precision short-distance measurement. At present, FMCW radar ranging generally adopts an FFT (fast Fourier transform) method to obtain a power spectrum curve of an intermediate frequency of an echo on a distance axis, so that the purposes of obtaining high distance resolution and high measurement precision are achieved.

In the United states, FCC certification and CE certification are provided in Europe, the use of the 24G millimeter wave band is subjected to compliance limitation, the current 24G millimeter wave radar can only be used in the frequency sweep bandwidth of 250M between 24GHz and 24.25GHz, and China radio Committee also has relevant regulatory requirements. The accuracy of the distance measurement is greatly limited for only using 250M bandwidth, and compared with the sweep frequency bandwidth of 4G, the difference of the accuracy of the distance measurement is 16 times, so that the sweep frequency bandwidth of 250M cannot meet the requirement on the use occasion needing high distance measurement accuracy.

In order to overcome the problem, the current general method is to adopt a sampling sequence zero filling method, and perform interpolation zero filling on data obtained by sampling, so as to perform FFT (fast Fourier transform) operation on more data and refine frequency spectrum, thereby improving the precision of frequency measurement and the precision of distance measurement. The method has the following limitations and disadvantages: 1) the method can be only carried out on the original data collected by the millimeter wave chip ADC (analog-to-digital converter), and for the millimeter wave SoC (system-on-chip) with higher integration level, the method is not applicable because the output of the chip per se is the result of 1dfft, so the application range of the method is limited; 2) even if the millimeter wave SoC can output the original data collected by the ADC, the subsequent interpolation zero-padding method for the data of the ADC meets the requirement, the SoC itself is abandoned with the integrated 1dfft operation function, which causes the resource waste, and the phase-change improves the cost of the scheme.

Therefore, in view of the above technical problems, it is necessary to provide a new FMCW ranging method with high precision.

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Disclosure of Invention

The invention aims to provide a high-precision FMCW ranging method which can be suitable for SoC radars with higher integration level so as to obtain higher ranging precision.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

in a first aspect, the present invention provides a high-precision FMCW ranging method for a ranging apparatus having an SoC chip, the method including:

transmitting a Chirp signal with a specific waveform to a target to form an echo signal of the Chirp signal; receiving the echo signal and mixing the echo signal with the Chirp signal to form an intermediate frequency signal; sampling the intermediate frequency signal in the whole Chirp period by an analog-to-digital converter based on an SoC chip to obtain sampling data; carrying out fast Fourier transform on the sampling data to obtain frequency data; and calculating the target distance according to the frequency data.

With reference to the first aspect, in one or more embodiments of the present invention, the Chirp period is composed of a pre-modulation stage, a modulation stage and a post-modulation stage, where the pre-modulation stage is a constant frequency band, the modulation stage is an up-conversion band, and the post-modulation stage is a down-conversion band.

With reference to the first aspect, in one or more embodiments of the present invention, the performing fast fourier transform on the sample data specifically includes: and fitting the sampled data with a window function of fast Fourier transform, and then carrying out fast Fourier transform on the sampled data.

With reference to the first aspect, in one or more embodiments of the present invention, when the sampled data is fitted to a window function of a fast fourier transform, data acquired in the modulation stage in the sampled data corresponds to a main lobe of the window function.

With reference to the first aspect, in one or more embodiments of the invention, the window function is a hanning window.

With reference to the first aspect, in one or more embodiments of the present invention, the calculating a target distance according to the frequency data specifically includes: and calculating the target distance by adopting a three-point interpolation method according to the frequency data.

In a second aspect, the present invention provides a high precision FMCW ranging device, which includes an SoC chip including: the device comprises a transmitting module, a receiving module, an analog-to-digital converter and a processing module; the transmitting module is used for transmitting a Chirp signal with a specific waveform to a target so as to form an echo signal of the Chirp signal; the receiving module is used for receiving the echo signal and mixing the echo signal with a Chirp signal to form an intermediate frequency signal; the analog-to-digital converter is used for sampling the intermediate frequency signal to obtain sampling data; the processing module is used for carrying out fast Fourier transform on the sampling data to obtain frequency data and calculating a target distance according to the frequency data; and the sampling time of the analog-to-digital converter is the whole Chirp period.

With reference to the second aspect, in one or more embodiments of the present invention, the Chirp period is composed of a pre-modulation stage, a modulation stage and a post-modulation stage, the pre-modulation stage is a constant frequency band, the modulation stage is an up-frequency band, and the post-modulation stage is a down-frequency band.

With reference to the second aspect, in one or more embodiments of the present invention, the processing module is specifically configured to: fitting the sampled data with a window function of fast Fourier transform, carrying out fast Fourier transform on the sampled data to obtain frequency data, and calculating a target distance according to the frequency data.

In a third aspect, the invention provides a computer-readable storage medium having stored thereon a computer program which, when run on a processor, implements the aforementioned method.

Compared with the prior art, the high-precision FMCW distance measurement method provided by the invention has the advantages that the data acquired by the whole Chirp period are utilized to carry out fast Fourier transform, equivalently, the whole fast Fourier transform time is expanded, so that the frequency measurement precision is improved, and the distance measurement precision is improved; and the method can directly finish high-precision distance calculation on the SoC chip without an external singlechip, and can reduce the cost of the distance measuring system.

Drawings

FIG. 1 is a flow chart of a high precision FMCW ranging method provided in accordance with an embodiment of the present invention;

fig. 2 is a waveform diagram illustrating an entire Chirp period according to an embodiment of the present invention.

Detailed Description

The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.

Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.

According to the FCC and CE compliance requirements, the bandwidth in the 24G band is only 250MHz, the frequency range is 24 GHz-24.25 GHz, and the highest effective bandwidth is typically 240MHz, according to the following formula:

distance resolution:wherein c is the speed of light, and B is the effective bandwidth of the signal;

distance resolution after sampling:wherein c is the speed of light, k is the signal modulation frequency, and T is the fast Fourier transform processing time.

From the above, it can be seen that the range resolution is about 0.625M at a bandwidth of 240M. The mechanism of FMCW shows that the ranging is frequency measurement, and the frequency measurement error determines the error of the ranging. Under the condition of continuous measurement, after Fourier transform is carried out on the difference frequency signal, the spectrum amplitude peak value of the difference frequency signal can be accurately found, so that the measurement precision is mainly determined by the signal-to-noise ratio. However, in practice, the intermediate frequency signal is typically subjected to discrete sampling and then the sampled signal is subjected to fast fourier transform, which results in the discretization of the frequency spectrum, and the correct peak of the spectral amplitude cannot be found, resulting in a quantization error of the frequency. The measurement noise and the quantization noise are independent statistics, so the distance measurement precision is determined by the root mean square error sigma of the distance measurement_RRepresents:

wherein σ_RNFor the distance measurement root mean square error, σ, determined by the signal-to-noise ratio_RQIs the range root mean square error caused by frequency quantization.

In equations (2) and (3), σ_fnIs the minimum mean square error of frequency measurement in a noise environment, T is the sweep frequency period of an FMCW radar, B is the sweep frequency bandwidth of a transmitting signal, sigma_fqThe frequency measurement root mean square error caused by frequency quantization.

Will sigma_RNAnd σ_RQCan be substituted into the formula (1):

as can be seen from equation (4), the ranging accuracy depends on the frequency measurement accuracy under the condition of a fixed bandwidth.

Based on the above derivation, the present invention provides a high precision FMCW ranging method, as shown in fig. 1, which is suitable for a ranging device with SoC chip, and includes but is not limited to the following steps:

transmitting a Chirp signal with a specific waveform to a target to form an echo signal of the Chirp signal;

receiving the echo signal and mixing the echo signal with the Chirp signal to form an intermediate frequency signal;

sampling the intermediate frequency signal in the whole Chirp period by an analog-to-digital converter based on an SoC chip to obtain sampling data;

carrying out fast Fourier transform on the sampled data to obtain frequency data;

and calculating the target distance according to the frequency data.

In particular, the object may be any item, which may be, for example, a person, a mountain, a vehicle, a tree, a building, and so on.

In an exemplary embodiment, referring to fig. 2, the Chirp period is determined by the time of the pre-modulation stage Chirp pre and the modulation stage T₁Time and post-modulation phase T₂And (4) time composition. The pre-modulation stage is a constant frequency band, the modulation stage is an up-conversion band, and the post-modulation stage is a down-conversion band.

In an exemplary embodiment, performing a fast fourier transform on the sampled data specifically includes: fitting the sampled data with a window function of fast Fourier transform, and then carrying out fast Fourier transform on the sampled data.

Specifically, when sampling data is fitted with a window function of fast Fourier transform, a modulation phase T in the sampling data is enabled₁The data acquired in time corresponds to the main lobe of the window function. Modulation phase T₁The data acquired in time corresponds to the main lobe of the window function, so that the influence caused by the data acquired in the pre-modulation stage chirp pre time and the post-modulation stage T2 time can be reduced, and the signal-to-noise ratio is improved. Wherein the window function is preferably a hanning window.

In an exemplary embodiment, calculating the target distance according to the frequency data specifically includes: and calculating the target distance by adopting a three-point interpolation method according to the frequency data.

The invention will be further illustrated with reference to specific examples:

referring to fig. 2, in the FMCW modulation waveform, the Chirp period is determined by the Chirp pre time in the premodulation stage and the modulation stage T₁Time and post-modulation phase T₂The time is composed of three parts. Wherein the real FMCW modulation time is T₁Time. In the prior art, the digital-to-analog converter would be at T₁Valid data is collected over time, and the total number of sampled data is related to the sampling rate of the digital-to-analog converter.

Taking the above case as an example, within an effective bandwidth of 240M, if the Chirp pre time is 100 μ s, T₁Time was 100. mu.s, T₂Time 200. mu.s, whole Chirp when the cycle time is 400 mus and the sampling rate of the DAC is 2.5M/s, T is₁The effective data collected in time is 250 points. In the prior art, the distance precision is about 0.625m according to calculation by performing fast fourier transform on the 250 effective data points.

The high-precision FMCW distance measuring method provided by the invention is characterized in that all data acquired in the whole Chirp period are subjected to fast Fourier transform, namely the sampling time comprises Chirp pre time and T₁Time and T₂Time is three parts, the sampling time of the digital-to-analog converter is 400 mu s, and 1000 data points can be acquired in total. In addition, when the fast fourier transform is performed, the 1000 data points are calculated, and the data points for the fast fourier transform are 4 times (depending on T) of the prior art₁The percentage of data points collected in time among the data points collected in the whole Chirp period) and the accuracy of frequency measurement is also 4 times that of the prior art, namely the accuracy of distance measurement is 4 times that of the prior art and is about 0.156 m.

In order to reduce Chirp pre time and T₂The influence brought by the data collected in time can fit the sampled data of the whole Chirp period with a window function of fast Fourier transform when the fast Fourier transform is carried out. Due to T₁The data collected by time is effective data, when fitting with a fast Fourier transform window function, the waveform design is needed, and T is tried to the greatest extent according to Chirp pre time and translation waveform₁The temporal waveform corresponds to the main lobe of the window function, i.e., the middle part of the entire window function, to reduce Chirp pre and T₂The influence of time improves the signal-to-noise ratio.

And calculating to obtain the target distance by adopting a three-point interpolation method according to the frequency data obtained by performing fast Fourier transform on the sampling data.

In summary, the high-precision FMCW ranging method provided by the invention utilizes Chirp pre time and T before and after the modulation stage in the Chirp period₂The data collected by time is used as zero padding, and the equivalent is to enlarge the whole fast Fourier transform time so as to improve the frequency measurement precision and improve the distance measurement precisionDegree; and the method can directly finish high-precision distance calculation on the SoC chip without an external singlechip, and can reduce the cost of the distance measuring system.

The method of embodiments of the present invention is set forth above in detail and the apparatus of embodiments of the present invention is provided below.

The high-precision FMCW distance measuring device in one embodiment of the invention comprises an SoC chip, wherein the SoC chip comprises: the device comprises a transmitting module, a receiving module, an analog-to-digital converter and a processing module.

The transmitting module is used for transmitting a Chirp signal with a specific waveform to a target so as to form an echo signal of the Chirp signal. And the receiving module is used for receiving the echo signal and mixing the echo signal with a Chirp signal to form an intermediate frequency signal. The processing module is used for carrying out fast Fourier transform on the sampling data to obtain frequency data, and calculating the target distance according to the frequency data.

And the sampling time of the analog-to-digital converter is the whole Chirp period. The Chirp period consists of a pre-modulation stage, a modulation stage and a post-modulation stage; the pre-modulation stage is a constant frequency band, the modulation stage is an up-conversion band, and the post-modulation stage is a down-conversion band.

In an exemplary embodiment, the processing module is specifically configured to fit the sampled data to a window function of fast fourier transform, perform fast fourier transform on the sampled data to obtain frequency data, and calculate a target distance according to the frequency data.

The invention also provides a computer-readable storage medium in which a computer program is stored which, when run on a processor, implements the method flow shown in fig. 1.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-readable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.