CN104656064A - 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
CN104656064A
CN104656064A CN201310606586.1A CN201310606586A CN104656064A CN 104656064 A CN104656064 A CN 104656064A CN 201310606586 A CN201310606586 A CN 201310606586A CN 104656064 A CN104656064 A CN 104656064A
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China
Prior art keywords
signal
intermediate frequency
lfm
frequency
error estimating
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CN201310606586.1A
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CN104656064B (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 of error of LFM radar mean frequency sampled echo and compensation method
Technical field
The invention belongs to method of estimation, be specifically related to estimation of error and the compensation method of LFM radar mean frequency sampled echo.
Background technology
For solving the contradiction between radar range and range resolution, modern radar generally adopts pulse compression technique, launches radar waveform that is wide when having large and bandwidth, improves transmit signal energy, and carry out process of pulse-compression to received signal, obtain the data with High Range Resolution.The linear frequency modulation of common pulse compression signal (Linear Frequency Modulation, LFM) signal and phase-coded signal, wherein the Doppler of matched filtering process to echo of LFM signal is insensitive, in actual radar system, thus obtain application widely.
For carrying out pulse compression, the phase information of LFM echo must be retained, thus needing to carry out coherent reception.Traditional receivers is converted to vision signal after mostly carrying out coherent quadrature detector by pyron detector, then carries out A/D sampling respectively at I, Q two-way.The remarkable shortcoming of this method is that the sensor gain and phase uncertainties that analog demodulator device brings directly can affect impulse compressing result.
Along with the development of high-speed ADC and large scale integrated circuit technology, ADC can replace pyron detector intermediate frequency even radio frequency directly sample, demodulate I, Q signal with numerical approach again, thus fundamentally can avoid the sensor gain and phase uncertainties of analog demodulator.But frequently combine the imperfection of the LFM produced and power amplifier, filtering to the distortion of LFM by transmitter, still can have an impact by paired pulses compression effectiveness, prior art there is no good disposal route.
Summary of the invention
This object is for prior art defect, provides a kind of estimation of error and compensation method of LFM radar mean frequency sampled echo.
The present invention is achieved in that a kind of chirp rate method of estimation based on picture contrast, comprises the steps:
Step one: choose frequently
f I=-f I0+kf s(1)
Wherein, f i0the intermediate frequency of system, f sbe A/D sampling rate, k is integer,
Step 2:
To the closed signal s of sampling 0, use f icarry out intermediate frequency digital demodulation, obtain digital I and the Q signal of time domain:
s I=cos(-2πnf I/f s)
s Q=sin(-2πnf I/f s) (2)
Wherein, n=0,1,2 ..., N r-1, N rrepresent s 0length,
Step 3:
According to I and Q signal, calculate phase place
Step 4:
Right carry out phase unwrapping, obtain
Step 5:
Right ask first order derivative f (n):
Step 6:
Linear fit is carried out to f (n), obtains the LFM signal madulation rate k ' estimated:
f(n)≈f 0+k′n (5)
Wherein, f 0for constant.
Step 7:
According to the waveform of I and Q signal, find the position n ' at the zero-frequency place of LFM signal,
Step 8:
Use n ' and k ', obtain the intermediate frequency demodulation frequency f frequently revised i':
f I′=f I+k′(n′-f sτ/2)
Wherein, τ is fire pulse width.
As above based on a chirp rate method of estimation for picture contrast, wherein, getting in described step one makes f iabsolute value minimum time k value.
As above based on a chirp rate method of estimation for picture contrast, wherein, the position at the zero-frequency place of described step 7 is exactly that oscillating waveform is the most slowly located.
Effect of the present invention is used to be: the digital intermediate frequency LFM echo collected actual radar system, adopts revised f i' carry out digital demodulation and matched filtering process respectively with k ', effectively can improve impulse compressing result, improve Signal-to-Noise, reduce sidelobe level.
Embodiment
Based on a chirp rate method of estimation for picture contrast, comprise the steps:
Step one: choose frequently
f I=-f I0+kf s(6)
Wherein, f i0the intermediate frequency of system, f sbe A/D sampling rate, k is integer, generally gets and make f in reality iabsolute value minimum time k value, also can get other numerical value as required.
Step 2:
To the closed signal s of sampling 0, use f icarry out intermediate frequency digital demodulation, obtain digital I and the Q signal of time domain:
s I=cos(-2πnf I/f s)
s Q=sin(-2πnf I/f s) (7)
Wherein, n=0,1,2 ..., N r-1, N rrepresent s 0length.
Step 3:
According to I and Q signal, calculate phase place
Step 4:
Right carry out phase unwrapping, obtain
Step 5:
Right ask first order derivative f (n):
Step 6:
Linear fit is carried out to f (n), obtains the LFM signal madulation rate k ' estimated:
f(n)≈f 0+k′n (10)
Wherein, f 0for constant.
Linear fit can adopt any existing approximating method to realize.
Step 7:
According to the waveform of I and Q signal, find the position n ' at the zero-frequency place of LFM signal.
The position at described zero-frequency place videlicet oscillating waveform is the most slowly located.
Step 8:
Use n ' and k ', obtain the intermediate frequency demodulation frequency f frequently revised i':
f I′=f I+k′(n′-f sτ/2)
Wherein, τ is fire pulse width.
Accompanying drawing 1 is the accompanying drawing before error compensation, and Fig. 2 is the accompanying drawing after error compensation, can find out the process impulse compressing result number by the application, improve Signal-to-Noise, reduce sidelobe level.

Claims (3)

1., based on a chirp rate method of estimation for picture contrast, it is characterized in that, comprise the steps:
Step one: choose frequently
f I=-f I0+kf s(1)
Wherein, f i0the intermediate frequency of system, f sbe A/D sampling rate, k is integer,
Step 2:
To the closed signal s of sampling 0, use f icarry out intermediate frequency digital demodulation, obtain digital I and the Q signal of time domain:
s I=cos(-2πnf I/f s)
s Q=sin(-2πnf I/f s) (2)
Wherein, n=0,1,2 ..., N r-1, N rrepresent s 0length,
Step 3:
According to I and Q signal, calculate phase place
Step 4:
Right carry out phase unwrapping, obtain
Step 5:
Right ask first order derivative f (n):
Step 6:
Linear fit is carried out to f (n), obtains the LFM signal madulation rate k ' estimated:
f(n)≈f 0+k′n (5)
Wherein, f 0for constant.
Step 7:
According to the waveform of I and Q signal, find the position n ' at the zero-frequency place of LFM signal,
Step 8:
Use n ' and k ', obtain the intermediate frequency demodulation frequency f frequently revised i':
f I′=f I+k′(n′-f sτ/2)
Wherein, τ is fire pulse width.
2. a kind of chirp rate method of estimation based on picture contrast as claimed in claim 1, is characterized in that: getting in described step one makes f iabsolute value minimum time k value.
3. a kind of chirp rate method of estimation based on picture contrast as claimed in claim 2, is characterized in that: the position at the zero-frequency place of described step 7 is exactly that oscillating waveform is the 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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