CN104656064B - Error estimating and compensating method for intermediate frequency sampling echo of LFM radar - Google Patents

Error estimating and compensating method for intermediate frequency sampling echo of LFM radar Download PDF

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Publication number
CN104656064B
CN104656064B CN201310606586.1A CN201310606586A CN104656064B CN 104656064 B CN104656064 B CN 104656064B CN 201310606586 A CN201310606586 A CN 201310606586A CN 104656064 B CN104656064 B CN 104656064B
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signal
lfm
frequency
intermediate frequency
digital
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CN104656064A (en
Inventor
耿旭朴
徐志明
卢永革
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Beijing Institute of Environmental Features
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Beijing Institute of Environmental Features
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/2813—Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
    • G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
    • G01S13/28—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses
    • G01S13/282—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave with time compression of received pulses using a frequency modulated carrier wave
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/288—Coherent receivers

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The invention belongs to an estimation method, and particularly relates to an error estimating and compensating method for an intermediate frequency sampling echo of LFM (Linear Frequency Modulation) radar. The method comprises the following steps: firstly, selecting intermediate frequency; secondly, decomposing a signal; thirdly, calculating; fourthly, performing phase unwrapping; fifthly, deriving; sixthly, fitting; seventhly, searching zero frequency; eighthly, demodulating. The error estimating and compensating method has the benefits that digital demodulating and matching filtering processing are respectively performed on the digital intermediate frequency LFM echo acquired by an actual radar system by adopting modified fI' and k', so that the pulse compression effect can be effectively improved; the signal-to-noise ratio of the signal is improved; the side lobe level is reduced.

Description

The estimation error of LFM radar mean frequency sampled echos and compensation method
Technical field
The invention belongs to method of estimation, and in particular to the estimation error of LFM radar mean frequency sampled echos and compensation method.
Background technology
To solve the contradiction between radar range and range resolution ratio, modern radar generally uses pulse compression skill Art, radar waveform of the transmitting with big time width and bandwidth, improving transmission signal energy, and dock the collection of letters number carries out pulse compression Treatment, obtains the data with High Range Resolution.The linear frequency modulation of common pulse compression signal The matched filtering treatment of (LinearFrequencyModulation, LFM) signal and phase-coded signal, wherein LFM signals is right The Doppler of echo is insensitive, thus application widely is obtained in actual radar system.
To carry out pulse compression, it is necessary to retain the phase information of LFM echoes, so that carrying out coherent reception.Tradition connects Receipts machine mostly carries out being converted to vision signal after coherent quadrature detector by crystal detector, then is carried out respectively in I, Q two-way A/D samples.The significant drawback of this method is that the sensor gain and phase uncertainties that analog demodulator device brings can directly affect pulse compression Effect.
With the development of high-speed ADC and large scale integrated circuit technology, ADC can replace crystal detector in intermediate frequency Even radio frequency is directly sampled, then demodulates I, Q signal with digital method, such that it is able to fundamentally avoid analog demodulator Sensor gain and phase uncertainties.But, by the distortion to LFM of imperfection and power amplifier, filtering of the LFM of the emitter comprehensive generation of frequency, Still influence can be produced on impulse compressing result, prior art there is no good processing method.
The content of the invention
This purpose is directed to prior art defect, there is provided a kind of estimation error of LFM radar mean frequencies sampled echo and benefit Compensation method.
What the present invention was realized in：A kind of estimation error of LFM radar mean frequencies sampled echo and compensation method, including under State step：
Step one：Choose frequency
fI=-fI0+kfs(1)
Wherein, fI0It is the intermediate frequency of system, fsIt is A/D sample rates, k is integer,
Step 2：
To the closed signal s for sampling0, use fIIntermediate frequency digital demodulation is carried out, the digital I and Q signal of time domain is obtained：
sI=cos (- 2 π nfI/fs)
sQ=sin (- 2 π nfI/fs)(2)
Wherein, n=0,1,2 ..., Nr-1, Nr represent s0Length,
Step 3：
According to I and Q signal, phase is calculated
Step 4：
It is rightPhase unwrapping is carried out, is obtained
Step 5：
It is rightSeek first derivative f (n)
Step 6：
Linear fit is carried out to f (n), the LFM signal modulation rates k ' for being estimated：
f(n)≈f0+k′n(5)
Wherein, f0 is constant,
Step 7：
According to I and the waveform of Q signal, the position n ' where finding the zero-frequency of LFM signals,
Step 8：
Use n ' and k ', the intermediate frequency demodulation frequency slope f for being correctedI′：
fI'=fI+k′(n′-fsτ/2)
Wherein, τ is fire pulse width,
Using the f after finishingI' and k ' carries out digital demodulation respectively and matched filtering is processed.
A kind of estimation error of LFM radar mean frequencies sampled echo as described above and compensation method, wherein, described step To k according to following principle values in one, taking makes fIAbsolute value it is minimum when k values.
A kind of estimation error of LFM radar mean frequencies sampled echo as described above and compensation method, wherein, described step Position where seven zero-frequency is exactly that oscillating waveform is most slowly located.
It is using effect of the invention：The digital intermediate frequency LFM echoes collected to actual radar system, using revised FI ' and k ' carry out digital demodulation and matched filtering treatment respectively, can be effectively improved impulse compressing result, improve signal noise Than reducing sidelobe level.
Specific embodiment
A kind of chirp rate method of estimation based on picture contrast, comprises the steps：
Step one：Choose frequency
fI=-fI0+kfs(6)
Wherein, fI0It is the intermediate frequency of system, fsIt is A/D sample rates, k is integer, and typically take makes f in practiceIAbsolute value most The k values of hour, it is also possible to take other numerical value as needed.
Step 2：
To the closed signal s for sampling0, use fIIntermediate frequency digital demodulation is carried out, the digital I and Q signal of time domain is obtained：
sI=cos (- 2 π nfI/fs)
sQ=sin (- 2 π nfI/fs)(7)
Wherein, n=0,1,2 ..., Nr-1, Nr represent s0Length,
Step 3：
According to I and Q signal, phase is calculated
Step 4：
It is rightPhase unwrapping is carried out, is obtained
Step 5：
It is rightSeek first derivative f (n)
Step 6：
Linear fit is carried out to f (n), the LFM signal modulation rates k ' for being estimated：
f(n)≈f0+k′n(5)
Wherein, f0 is constant,
Linear fit can be realized using any existing approximating method.
Step 7：
According to I and the waveform of Q signal, the position n ' where finding the zero-frequency of LFM signals,
Videlicet oscillating waveform is most slowly located for position where described zero-frequency.
Step 8：
Use n ' and k ', the intermediate frequency demodulation frequency slope f for being correctedI′：
fI'=fI+k′(n′-fsτ/2)
Wherein, τ is fire pulse width,
Using the f after finishingI' and k ' carries out digital demodulation respectively and matched filtering is processed.
Accompanying drawing 1 is the accompanying drawing before error compensation, and Fig. 2 is the accompanying drawing after error compensation, it can be seen that by the place of the application Reason impulse compressing result number, improves Signal-to-Noise, reduces sidelobe level.

Claims (3)

1. a kind of estimation error of LFM radar mean frequencies sampled echo and compensation method, it is characterised in that comprise the steps：
Step one：Choose frequency
fI=-fI0+kfs(1)
Wherein, fI0It is the intermediate frequency of system, fsIt is A/D sample rates, k is integer,
Step 2：
To the closed signal s for sampling0, use fIIntermediate frequency digital demodulation is carried out, the digital I and Q signal of time domain is obtained：
sI=cos (- 2 π nfI/fs)
sQ=sin (- 2 π nfI/fs)(2)
Wherein, n=0,1,2 ..., Nr-1, Nr represent s0Length,
Step 3：
According to I and Q signal, phase is calculated
Step 4：
It is rightPhase unwrapping is carried out, is obtained
Step 5：
It is rightSeek first derivative f (n)
Step 6：
Linear fit is carried out to f (n), the LFM signal modulation rates k ' for being estimated：
f(n)≈f0+k′n(5)
Wherein, f0 is constant,
Step 7：
According to I and the waveform of Q signal, the position n ' where finding the zero-frequency of LFM signals,
Step 8：
Use n ' and k ', the intermediate frequency demodulation frequency slope f for being correctedI′：
fI'=fI+k′(n′-fsτ/2)
Wherein, τ is fire pulse width,
Using the f after finishingI' and k ' carries out digital demodulation respectively and matched filtering is processed.
2. a kind of estimation error of LFM radar mean frequencies sampled echo as claimed in claim 1 and compensation method, its feature exists In：To k according to following principle values in described step one, taking makes fIAbsolute value it is minimum when k values.
3. a kind of estimation error of LFM radar mean frequencies sampled echo as claimed in claim 2 and compensation method, its feature exists In：Position where the zero-frequency of described step seven is exactly that oscillating waveform is most slowly located.
CN201310606586.1A 2013-11-25 2013-11-25 Error estimating and compensating method for intermediate frequency sampling echo of LFM radar Active CN104656064B (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6700536B1 (en) * 2001-10-25 2004-03-02 Richard J. Wiegand System and method for determining a direction of incident electromagnetic signals
CN101833082A (en) * 2010-04-20 2010-09-15 中国科学院空间科学与应用研究中心 Wideband frequency-modulation stepping signal processing method based on full deskew

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6700536B1 (en) * 2001-10-25 2004-03-02 Richard J. Wiegand System and method for determining a direction of incident electromagnetic signals
CN101833082A (en) * 2010-04-20 2010-09-15 中国科学院空间科学与应用研究中心 Wideband frequency-modulation stepping signal processing method based on full deskew

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