CN109932710A - Distant object speed modification method based on sawtooth LFMCW waveform system velocity radar - Google Patents
Distant object speed modification method based on sawtooth LFMCW waveform system velocity radar Download PDFInfo
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Abstract
The present invention relates to a kind of distant object speed modification method based on sawtooth LFMCW waveform system velocity radar, the speed modification method includes: fast time dimension FFT measurement target range；Slow time dimension FFT obtains Doppler frequency shift and remote echo frequency displacement；Carrier frequency is corrected to obtain the velocity amplitude of distant object.Modification method of the invention can solve the error occurred when the slow time dimension FFT calculating speed of linear frequency modulation continuous wave radar on distant object and big chirp rate at all, consumption resource is smaller in the signal processing, is easily achieved, and can be widely used in coherent system LFMCW radar.
Description
Technical field
The invention belongs to Radar Signal Processing Technology fields, more particularly to a kind of sawtooth LFMCW waveform system that is based on to test the speed
The distant object speed modification method of radar.
Background technique
Linear frequency modulation continuous wave (Linear Frequency Modulated Continuous Wave, LFMCW) radar
With very high range resolution and range accuracy, have in terms of low blind range zone than pulse radar more obvious excellent
Point.
It is illustrated in fig. 1 shown below as zigzag LFMCW waveform.
LFMCW radar emission signal model may be expressed as:
s1(t)=cos (2 π f0t+πμt2), 0≤t≤Te (1)
In formula, μ=B/Te, μ is LFM slope, and B is modulating bandwidth, TeFor frequency modulation period sweep frequency band time；f0Linearly to adjust
The initial frequency (carrier frequency) of frequency pulse.
Assuming that being that the position R has a point scatter in distance, radar receives its echo-signal are as follows:
sr(t)=acos [2 π f0(t-Δτ)+πμ(t-Δτ)2], 0≤t- Δ τ≤Te (2)
In formula, a is signal amplitude, with target radar scattering cross-section product (RadarCrossSection, RCS), distance,
Antenna gain is related；Δ τ=2R/c is time delay, and c is the light velocity.
The reference signal of frequency mixer input are as follows:
sref(t)=cos (2 π fr0+πμt2), 0≤t≤Te (3)
In formula, fr0For the initial frequency of reference signal LFM, f is usually enabledr0=f0。
Receive signal be mixed with reference signal, the complex signal model after low-pass filtering are as follows:
The instantaneous frequency of the signal are as follows:
Above formula shows that the distance of target is directly proportional to instantaneous frequency.So carrying out sampling and to sampling sequence to signal is received
Column carry out FFT, are f in frequencyiThe corresponding target range of peak position be
Practical LFMCW radar is fast time dimension FFT in sweep frequency band, and frequency peak calculates mesh according to above formula (6)
Subject distance.Slow time dimension FFT is between each sweep frequency band, frequency peak corresponds to target velocity.
However when being tested the speed using sawtooth LFMCW waveform, distant object causes carrier frequency to change, and then influences whether
The calculated result of distant object, therefore it cannot ignore, the velocity amplitude after needing to correct detection, to improve computational accuracy.
Summary of the invention
The object of the present invention is to provide a kind of distant object speed based on sawtooth LFMCW waveform system velocity radar to repair
Correction method, when being tested the speed for correcting using sawtooth LFMCW waveform, distant object causes carrier frequency to change, and then will affect
To distant object calculated result the problem of.
In order to achieve the above objectives, the technical solution adopted by the present invention is that: one kind is tested the speed thunder based on sawtooth LFMCW waveform system
The distant object speed modification method reached, the speed modification method include:
Fast time dimension FFT measures target range；
Slow time dimension FFT obtains Doppler frequency shift and remote echo frequency displacement；
Carrier frequency is corrected to obtain the velocity amplitude of distant object.
Further, the target range are as follows:
In formula: fiFor frequency, c is the light velocity, and μ is LFM slope, μ=B/Te, B is modulating bandwidth, TeFor the frequency modulation period.
Further, revised target speed value is
In formula: fiFor frequency, foFor frequency published originally, c is the light velocity, and μ is LFM slope, μ=B/Te, B is modulating bandwidth, TeTo adjust
Frequency period, R0For target range.
Modification method of the invention can solve linear frequency modulation continuous wave on distant object and big chirp rate at all
The error occurred when the slow time dimension FFT calculating speed of radar, consumes that resource is smaller, is easily achieved in the signal processing, and
It can be widely used in coherent system LFMCW radar.
Detailed description of the invention
The drawings herein are incorporated into the specification and forms part of this specification, and shows and meets implementation of the invention
Example, and be used to explain the principle of the present invention together with specification.
Fig. 1 is to emit signal transient frequency and time relationship schematic diagram in the prior art.
Fig. 2 is distant object speed modification method flow chart of the invention.
Fig. 3 is the echo-signal three-dimensional spectrogram obtained according to the simulation parameter in the embodiment of the present invention.
Specific embodiment
To keep the purposes, technical schemes and advantages of the invention implemented clearer, below in conjunction in the embodiment of the present invention
Attached drawing, technical solution in the embodiment of the present invention is further described in more detail.
Practical short distance and distant object echo simulation process, each parameter declaration of simulation process, which is given below, see the table below
1:
1 simulated program of table inputs parameter
| Parameter description | Unit | State | Simulation parameter |
| Frequency modulation cycle Te | S | Input | 1e-3 |
| Modulating bandwidth B | Hz | Input | 1e8 |
| Target range R0 | m | Input | [1.1e6,5e3,2.5e4] |
| Target velocity v | m/s | Input | [23,7,33] |
| Target signal to noise ratio | dB | Input | [20,15,10] |
| Carrier frequency fo | Hz | Input | 1e10 |
| Fast time dimension sample rate fs | Hz | Input | 2.5e7 |
| Fast time dimension FFT points N fft2 | Input | 4096 | |
| Slow time dimension FFT points N fft1 | Input | 64 |
Simulation result is as shown in Fig. 2, may determine that three target range door simulation results are followed successively by according to echo signal-to-noise ratio
[2732,3551,1367], actual distance are [1.1e6,5e3,2.5e4].
First verify that whether emulation is correct: not fuzzy distance Ru, it may be assumed that
Ru=c*Te/2 (9)
Wherein, TeFor the frequency modulation period, c is the light velocity.
Distance R after fuzzy0, it may be assumed that
Wherein, fsFor fast time dimension sample rate, Nfft2 is fast time dimension FFT points.Distance after three object removals are fuzzy
Door is [2731.8,3551,1366.2].
It can be seen that range gate simulation result is consistent with calculated result, simulation result is errorless, and emulation data are available.
Three target velocity dimension simulation results are followed successively by [28,31,14], and true velocity is [23,7,33].
Do not obscure speed Vu, it may be assumed that
Wherein, f0For carrier frequency, speed V after obscuring0, it may be assumed that
Wherein, Nfft1 is slow time dimension FFT points.Carrier frequency is according to f0It calculates, is tied after the not fuzzy speed of three object removals
Fruit is [35.13,30.86,13.8].It can be seen that short distance (km or so) target, speed is according to carrier frequency f0Calculate, as a result and
Simulation value is essentially the same, but remote echo wave speed and simulation value are widely different.
The method of the present invention be exactly given from principle remote echo wave speed and the widely different reason of simulation value and
Solution.Slow time dimension echo-signal is chirped in fact it can be seen from formula before, and practical FFT is calculated
To frequency be broadband, centre frequency is
Revised carrier frequency is f0', it may be assumed that
Carrier frequency is calculated using above formula, obtain result after the not fuzzy speed of three object removals be [27.4274,30.86,
13.8], it can be seen that and simulation result is almost the same.
By above-mentioned steps as can be seen that the method for the present invention can correct remote echo LFMCW Computational Method of Velocity Measurement due to
Carrier frequency changes bring error, there is important application prospect in practical projects.
The method of the present invention can solve linear frequency modulation continuous wave body on distant object and big chirp rate from principle
The error occurred when the slow time dimension FFT calculating speed of radar processed, has the advantages that compared with prior art
(1) it is easily achieved in this method engineering, it is smaller that signal processing consumes resource；
(2) the method for the present invention solves bring error when LFMCW waveform tests the speed from principle；
(3) the method for the present invention can be widely used in coherent system LFMCW radar.
The above, optimal specific embodiment only of the invention, but scope of protection of the present invention is not limited thereto,
In the technical scope disclosed by the present invention, any changes or substitutions that can be easily thought of by anyone skilled in the art,
It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection model of the claim
Subject to enclosing.
Claims (3)
1. the distant object speed modification method based on sawtooth LFMCW waveform system velocity radar, which is characterized in that the speed
Spending modification method includes:
Fast time dimension FFT measures target range；
Slow time dimension FFT obtains Doppler frequency shift and remote echo frequency displacement；
Carrier frequency is corrected to obtain the velocity amplitude of distant object.
2. the distant object speed amendment side according to claim 1 based on sawtooth LFMCW waveform system velocity radar
Method, which is characterized in that the target range are as follows:
In formula: fiFor frequency, c is the light velocity, and μ is LFM slope, μ=B/Te, B is modulating bandwidth, TeFor the frequency modulation period.
3. the distant object speed amendment side according to claim 2 based on sawtooth LFMCW waveform system velocity radar
Method, which is characterized in that revised target speed value is
In formula: fiFor frequency, foFor frequency published originally, c is the light velocity, and μ is LFM slope, μ=B/Te, B is modulating bandwidth, TeFor frequency modulation week
Phase, R0For target range.
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| CN201810898984.8A CN109932710B (en) | 2018-08-08 | 2018-08-08 | Long-distance target speed correction method based on sawtooth LFMCW waveform system speed measurement radar |
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Citations (5)
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|---|---|---|---|---|
| US20080129582A1 (en) * | 2006-12-05 | 2008-06-05 | Hung-Tao Hsieh | Tracking target method of radar with frequency modulation continuous wave |
| CN106842166A (en) * | 2017-03-31 | 2017-06-13 | 东南大学 | A kind of solution velocity ambiguity method suitable for LFMCW radar system |
| WO2017165728A1 (en) * | 2016-03-24 | 2017-09-28 | RFNAV, Inc. | Low cost 3d sonar, lidar, all weather radar imaging and 3d association method for autonomous vehicle navigation |
| CN108279403A (en) * | 2018-01-04 | 2018-07-13 | 电子科技大学 | Parallel Implementation method is converted based on the Keystone apart from framing |
| CN108287335A (en) * | 2018-04-19 | 2018-07-17 | 广州合智瑞达科技有限公司 | A method of ranging and range rate being carried out to multiple target using the frequency modulated signal of LFMCW radars |
-
2018
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080129582A1 (en) * | 2006-12-05 | 2008-06-05 | Hung-Tao Hsieh | Tracking target method of radar with frequency modulation continuous wave |
| WO2017165728A1 (en) * | 2016-03-24 | 2017-09-28 | RFNAV, Inc. | Low cost 3d sonar, lidar, all weather radar imaging and 3d association method for autonomous vehicle navigation |
| CN106842166A (en) * | 2017-03-31 | 2017-06-13 | 东南大学 | A kind of solution velocity ambiguity method suitable for LFMCW radar system |
| CN108279403A (en) * | 2018-01-04 | 2018-07-13 | 电子科技大学 | Parallel Implementation method is converted based on the Keystone apart from framing |
| CN108287335A (en) * | 2018-04-19 | 2018-07-17 | 广州合智瑞达科技有限公司 | A method of ranging and range rate being carried out to multiple target using the frequency modulated signal of LFMCW radars |
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