CN105629224A - Frequency-modulated continuous-wave radar high-precision distance measuring method - Google Patents

Abstract

The invention discloses a frequency-modulated continuous-wave radar high-precision distance measuring method. The method comprises the following steps: (1) according to an estimated detection distance, low pass filtering and re-sampling processing are carried out on discrete echo data; (2) through spectrum analysis on the echo data, a to-be-processed frequency band range of CZT is selected; (3) according to the selected frequency band range and needed frequency measuring precision requirements, initial parameters for a CZT algorithm are set, and a spectrum after refinement is obtained; and (4) an energy center of gravity method is used for carrying out spectrum condensation on the refined spectrum. The frequency-modulated continuous-wave radar high-precision distance measuring method has the advantages of small operation quantity, high spectrum refinement precision, good anti-noise performance, and good detection effects especially for weak targets.

Description

Frequency modulated continuous wave radar precision distance measurement method

" technical field "

The invention belongs to radar communication and technical field of automotive electronics, particularly a kind of automobile initiatively collision avoidance radar precision distance measurement method.

" background technology "

The extraction to target Distance geometry speed information is realized owing to frequency modulated continuous wave radar Detection Techniques system is based in frequency domain to the frequency measurement of echo intermediate frequency signal. If directly adopting leaf transformation in N point discrete Fourier, due to " fence effect " of discrete Fourier transformation, make the frequency resolving power of intermediate frequency signal low, the distance accuracy of the LFMCW detection system of gained is lower, for this reason in order to improve the measuring accuracy of LFMCW radar system, need the frequency spectrum of first refinement intermediate frequency signal, it is to increase frequency resolution.

Frequency spectrum refinement method conventional at present increases sampling method, time domain zero padding method, Chirp_Z converter technique and ZFFT converter technique primarily of direct extraction, cascade FFT method, frequency domain.

Direct extraction compresses data rate by multi-stage bandpass filtering, calculates FFT and obtains higher frequency resolution. But when the range of frequency extracted changes, extract than adjusting, thus bandpass filter also must redesign, and is thus unfavorable for the design of hardware structure.

First cascade FFT method by carrying out overlapping sampling to input signal, and every section of data from the sample survey is N point, and the Duplication between section and section is ��, i.e. overlapping �� N point. Every one piece of data carrying out N point FFT computing, is then reset by the frequency spectrum corner of M section, take out corresponding to each section of upper identical spectral component value, complete the FFT computing of M point, the FFT finally obtaining Frequence zooming exports. The method can obtain the overall picture of frequency spectrum by first step FFT, after the selected frequency range needing accurate spectrum analysis, carry out second stage FFT computing again, it is provided that the zoom FFT structure of multiple dispersion frequency section, it is applicable to the FFT situation of the frequency spectrum refinement simultaneously calculated in several narrow bandwidth range.

Frequency domain increases sampling method, adopts frequency domain to increase sampling method and intermediate frequency signal discrete spectrum is carried out refinement, with the sampling interval reduced in whole frequency domain, thus realizes realizing the full name refinement to intermediate frequency signal with less computing amount, it is provided that distance accuracy. Easily realize although frequency interpolation method is simple, but require that each scatter point effectively, otherwise could will cause error increase of finding range due to the spectral leakage of each scatter point at a distance of time very far away, be therefore applicable to the target that each scatter point is apart from each other.

Time domain zero padding method by directly increasing sampling number to the method for signal zero padding in time domain, namely the points N increasing FFT reduces spectrum line interval, it is the most direct method of one, but the method computing amount is big, is applicable to the less demanding frequency spectrum refinement of real-time.

ZFFT frequency spectrum refinement method be a kind of can to specify, sampling rate carries out the algorithm of refinement analysis to any frequency band in frequency spectrum, under data processing counts identical volume situation, use ZFFT that signal carries out process and can obtain the frequency resolution higher than FFT, but the method only analyzes the positive frequency part in signal, although decreasing computing amount, but frequency spectrum and actual spectrum after refinement exist inconsistent phenomenon, result in spectrum position skew, range observation accuracy must be affected.

The fourier transformation of Chirp_Z Spectrum thinning method by any one section of curve on unit circle is carried out with appointed interval, output is counted be greater than input and count, thus realize frequency spectrum refinement, the distance accuracy of raising system, but the method needs to set in advance observation simulation, it is necessary to use with FFT cascade.

" summary of the invention "

It is an object of the invention to provide a kind of frequency modulated continuous wave radar high-precision frequency measurement method with actual application value, thus realize the precision distance measurement of frequency modulated continuous wave radar, promote the through engineering approaches application of high-precision ranging radar. The object of the present invention is realized by following technical scheme:

A kind of frequency modulated continuous wave radar high-precision frequency measurement method, comprises the steps:

(1) according to the range of detector estimated, the echo data of discretize is carried out low-pass filtering and sampling processing again;

(2) by the spectral decomposition to echo data, the frequency band range that selected CZT is pending;

(3) according to selected frequency band range and required frequency measurement accuracy requirement, CZT algorithm initial parameter is set, and obtains the frequency spectrum after refinement;

(4) utilize power enhanced that the frequency spectrum of refinement is carried out frequency spectrum cohesion.

The advantage of the present invention: it is little that the present invention has computing amount, frequency spectrum refinement precision height, the advantages such as anti-noise performance is excellent, particularly for Weak target, still have good Effect on Detecting.

" accompanying drawing explanation "

Fig. 1 is the FB(flow block) of high-precision frequency measurement method provided by the invention.

Fig. 2 is the schematic diagram of base 2FFT frequency measurement precision.

Fig. 3 is the frequency measurement precision based on CZT algorithm.

Fig. 4 is the schematic diagram of the frequency measurement precision of high-precision frequency measurement method provided by the invention.

" embodiment "

Shown in composition graphs 1 and Fig. 4, the present invention, a kind of frequency modulated continuous wave radar high-precision frequency measurement method, mainly comprises the steps:

(1) according to the range of detector estimated, the echo data of discretize is carried out low-pass filtering and sampling processing again, so that the spectral resolution using identical N point fourier transformation acquisition relatively high.

(2) by the spectral decomposition to echo data, the frequency band range that selected CZT is pending. Specifically the data after sampling again being carried out base 2FFT process, not enough part carries out zero padding operation. In addition, in order to reduce false dismissal probability, selected frequency band can reserve protection sideband.

(3) according to selected frequency band range and required frequency measurement accuracy requirement, CZT algorithm initial parameter is set, and obtains the frequency spectrum after refinement. Specifically comprise:

Observation bandwidth: hypothetical target distance is R, then its position in intermediate frequency spectrum can represent and isIt is included in the kth frequency cells of base 2FFT, then the range of frequency initial value of CZT algorithm is set to f₁=k-1 frequency cells, the termination value of range of frequency is f₂=k+1, in upper formula, B is radar system radio frequency bandwidth of operation; T is the sawtooth phase modulation cycle; C is the light velocity 3 �� 108m/s;

The span of frequency spectrum refinement:�� f=f in formula₂-f₁; f_sIt it is the data sampling frequency after sampling; M is refinement precision.

Frequency spectrum after the refinement obtained $X\left(z_k\right)=\underset{n=0}{\overset{N-1}{\Σ}}x\left(n\right)z_k^{-n},z_k={\mathrm{AW}}^{-k},k=0,1,...,M-1,$ A=exp (1j �� in formula₀),WhereinIt it is the sampling interval of refinement;

(4) utilize power enhanced (PowerCenterdTracking) that the frequency spectrum of refinement is carried out frequency spectrum cohesion, improve frequency measurement precision further, reduce false-alarm. Specifically comprise:

A. in the frequency spectrum of refinement, position L corresponding to peak-peak is searched for, then realistic objective spectrum prediction central position $i=\frac{\left(\right(k-1)M+2L)N}{f_{s}M};$

B. for the Q bar spectrum line of target expansion, it is truly composed line and isBy i in formula₀It is multiplied byThe real frequency spectrum of target can be obtained, its distance

The frequency modulated continuous wave radar precision distance measurement method that above-described embodiment provides, wherein carries out sampling operation again for target echo data, under the prerequisite not changing calculated amount, it is to increase the distance accuracy of target; For the target data after sampling again, carrying out CZT conversion process, under the prerequisite suitably increasing computing amount, radar ranging precision significantly improves; For the frequency spectrum of refinement, utilize PCT algorithm matching living target frequency, thus obtain the true distance of target.

Above embodiment is only fully open and unrestricted the present invention, based on the present invention innovate purport, without creative work etc. the replacement of effect technique feature, it should belong to the scope that the application discloses.

Claims (5)

1. a frequency modulated continuous wave radar precision distance measurement method, it is characterised in that, comprise the steps:

(1) according to the range of detector estimated, the echo data of discretize is carried out low-pass filtering and sampling processing again;

(2) by the spectral decomposition to echo data, the frequency band range that selected CZT is pending;

(3) according to selected frequency band range and required frequency measurement accuracy requirement, CZT algorithm initial parameter is set, and obtains the frequency spectrum after refinement;

(4) utilize power enhanced that the frequency spectrum of refinement is carried out frequency spectrum cohesion.

2. frequency modulated continuous wave radar precision distance measurement method according to claim 1, it is characterised in that, the data after sampling are more specifically carried out base 2FFT process by step (2), and not enough part carries out zero padding operation.

3. frequency modulated continuous wave radar precision distance measurement method according to claim 1 and 2, it is characterised in that, band reservation protection sideband selected in step (2).

4. frequency modulated continuous wave radar precision distance measurement method according to claim 2, it is characterised in that, step (3) arranges CZT algorithm initial parameter, specifically comprises:

Observation bandwidth: hypothetical target distance is R, then its position in intermediate frequency spectrum can represent and isIt is included in the kth frequency cells of base 2FFT, then the range of frequency initial value of CZT algorithm is set to f₁=k-1 frequency cells, the termination value of range of frequency is f₂=k+1, in upper formula, B is radar system radio frequency bandwidth of operation; T is the sawtooth phase modulation cycle; C is the light velocity 3 �� 108m/s;

The span of frequency spectrum refinement:�� f=f in formula₂-f₁; f_sIt it is the data sampling frequency after sampling; M is refinement precision.

Frequency spectrum after the refinement obtained is $X\left(z_k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)z_k^{-n},z_k={\mathrm{AW}}^{-k},k=0,1,...,M-1,$ A=exp (1j �� in formula₀),WhereinIt it is the sampling interval of refinement.

5. frequency modulated continuous wave radar precision distance measurement method according to claim 4, it is characterised in that, step (4) utilizes power enhanced that the frequency spectrum of refinement is carried out frequency spectrum cohesion, specifically comprises:

A. in the frequency spectrum of refinement, position L corresponding to peak-peak is searched for, then realistic objective spectrum prediction central position $i=\frac{\left(\right(k-1)M+2L)N}{f_{s}M};$

B. for the Q bar spectrum line of target expansion, it is truly composed line and isBy i in formula₀It is multiplied byThe real frequency spectrum of target can be obtained, its distance