CN112558030A - Broadband vibration measurement radar signal-to-noise ratio improvement method based on orthogonal demodulation blind source separation - Google Patents
Broadband vibration measurement radar signal-to-noise ratio improvement method based on orthogonal demodulation blind source separation Download PDFInfo
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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
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
Abstract
The invention discloses a method for improving the signal-to-noise ratio of a broadband vibration measuring radar based on orthogonal demodulation blind source separation. The method comprises the following implementation steps: carrying out quadrature demodulation on echo signals of a broadband vibration measurement radar to respectively obtain I-path and Q-path quadrature baseband echo signals of the radar; differentiating the baseband signals of the path I and the path Q; thirdly, blind source separation is carried out on differential signals of the path I and the path Q by adopting a principal component analysis (ICA) -based method to obtain two independent signal components which respectively correspond to a vibration differential signal and a phase noise differential signal; and step four, integrating the vibration differential signal and restoring the vibration differential signal. By adopting the method, the high-precision extraction of the vibration signal of the broadband vibration measuring radar can be realized, and the method has the advantages of simple calculation and capability of simplifying the complexity of system realization.
Description
Technical Field
The invention belongs to the technical field of radar vibration measurement, and particularly relates to a broadband vibration measurement radar signal-to-noise ratio improvement method based on orthogonal demodulation blind source separation.
Background
The vibration measuring radar is a special radar which utilizes microwave band electromagnetic waves to irradiate a vibration target and demodulates vibration information at the target from an echo. According to the Doppler theorem, when electromagnetic waves irradiate a vibration target, the target can modulate the radar echo Doppler, and the vibration information of the target can be obtained as long as an echo signal is demodulated, so that the function of vibration measurement is achieved. The vibration measuring radar is widely applied to the fields of bridges, building safety monitoring, vital sign measurement, public safety, anti-terrorism stability maintenance and the like.
The measurement accuracy of the vibration measuring radar on the target vibration signal is mainly determined by the ratio of the vibration signal to the system noise in the vibration modulation echo. The system noise includes radar receiver thermal noise and phase noise. The signal-to-noise ratio of the vibration signal of the vibration measuring radar to the phase noise is synchronously reduced along with the reduction of the signal-to-noise ratio. The actual measurement environment is usually faced with a strong clutter condition, so that the signal-to-noise ratio of the vibration measuring radar is seriously degraded. Therefore, effective techniques for improving the signal-to-noise ratio are needed.
The traditional vibration measurement radar usually adopts a self-adaptive carrier cancellation technology to improve the signal-to-noise ratio in a clutter environment, the technology needs to attach a complex closed loop cancellation circuit at a radar receiving end, and only has a good signal-to-noise ratio improvement effect on a single-frequency system, so that the technology is not suitable for a broadband radar system. A part of broadband vibration measuring radars adopt a circumference digital cancellation technology to improve the signal-to-noise ratio, but circumference cancellation parameters need to be searched according to the performance of a vibration signal output after cancellation. The calculation amount is large, the real-time processing is not suitable, and the working performance is unstable.
Disclosure of Invention
In view of this, the invention provides a method for improving the signal-to-noise ratio of a broadband vibration measuring radar based on orthogonal demodulation blind source separation, so as to realize high-precision extraction of a target vibration signal of the broadband vibration measuring radar.
The specific embodiment for implementing the invention is as follows:
a broadband vibration measurement radar signal-to-noise ratio improvement method based on orthogonal demodulation blind source separation comprises the following steps:
carrying out quadrature demodulation on echo signals of a broadband vibration measurement radar to respectively obtain I-path and Q-path quadrature baseband echo signals of the radar;
differentiating the baseband signals of the path I and the path Q, wherein the differential signals of the path I and the path Q, the vibration differential signals and the phase noise differential signals meet a linear relation on the premise that radar phase noise is dominant, and the linear relation is unknown;
thirdly, blind source separation is carried out on differential signals of the path I and the path Q by adopting a principal component analysis (ICA) -based method to obtain two independent signal components which respectively correspond to a vibration differential signal and a phase noise differential signal;
and step four, integrating the vibration differential signal, restoring the vibration differential signal and basically stripping the radar phase noise in the original result.
Has the advantages that:
(1) the invention provides a signal-to-noise ratio improving method based on signal processing, aiming at the problem that the ratio of vibration signals to radar phase noise is deteriorated due to clutter in the actual measurement environment of a broadband vibration measuring radar, and the vibration measurement precision of the broadband vibration measuring radar can be improved.
(2) Compared with other methods aiming at the same purpose, the method does not need complex circuit design or parameter search and feedback calculation with large calculation amount, has low signal processing complexity and is easy to realize the real-time signal processing.
Drawings
Fig. 1 is a flow chart of a method for improving the signal-to-noise ratio of a broadband vibration radar based on orthogonal demodulation blind source separation.
FIG. 2 is a one-dimensional image of an object scene in an embodiment;
FIG. 3 is a vibration signal applied to an object in the embodiment;
FIG. 4 is an instantaneous power spectrum of a vibration signal loaded on a target in an embodiment;
FIG. 5 is a vibration signal obtained by directly extracting a phase of a target echo without signal-to-noise enhancement processing in the embodiment;
FIG. 6 is an instantaneous power spectrum of a vibration signal obtained by directly extracting a phase of a target echo without signal-to-noise enhancement processing in an embodiment;
FIG. 7 is a vibration signal obtained by quadrature demodulation blind source separation in the embodiment;
FIG. 8 is an instantaneous power spectrum of a vibration signal obtained by quadrature demodulation blind source separation in the embodiment;
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
A flow chart of a method for improving the signal-to-noise ratio of a broadband vibration measuring radar based on orthogonal demodulation blind source separation is shown in fig. 1, and the specific implementation steps include:
the method comprises the following steps of firstly, carrying out quadrature demodulation on echo signals of the broadband vibration measurement radar to respectively obtain I-path and Q-path quadrature baseband echo signals of the radar, wherein the specific implementation mode is as follows:
without loss of generality, assuming that the target is located at the radar 0 delay position, the original echo of the broadband vibration-measuring radar is:
s(t，η)＝S0p0(t)sin(ωt+φs0+φm(η)+φn(η))
+C0p0(t)sin(ωt+φc0+φn(η))
where t is a fast time factor measuring the time within 1 radar pulse repetition period, η is a slow time factor measuring the time during different radar pulse repetition periods, S0，C0Amplitude of echo signal, p, of target and clutter respectively0(t) is the transmitted baseband pulse signal, ω is the angular frequency of the transmitted signal carrier, φs0，φc0The initial phases of the target echo and clutter, phi, respectivelym(η)，φn(η) is a target vibration modulation signal and a radar phase noise signal, which are respectively changed along with slow time and are random signals with 0 mean value independently distributed;
performing the following orthogonal demodulation processing steps on the original echo to obtain two paths of baseband orthogonal demodulation signals, wherein the specific operation is S101: quadrature down conversion (DDC)
Iddc(t，η)＝LPF(t)*(S(t，η)sin(ωt))
Qddc(t，η)＝LPF(t)*(S(t，η)cos(ωt))
Wherein LPF (t) is a low pass filter with a pass band width of p0(t) 1/2 of bandwidth, setting the other filter parameters according to specific requirements, and representing the linear convolution operation of the signal;
s102: matched filter (DPC)
Idpc(t，η)＝p0(-t)*Iddc(t，η)
Qdpc(t，η)＝p0(-t)*Qddc(t，η)
S103: target detection (CFAR)
This is a basic operation of radar signal processing, and the processing steps are complex and not described in detail here, the target position t is detected to be 0,
I(η)＝Idpc(0，η)
Q(η)＝Qdpc(0，η)
from the original echo model, there are
I(η)＝S0sin(φs0+φm(η)+φn(η))+C0sin(φc0+φn(η))
Q(η)＝S0cos(φs0+φm(η)+φn(η))+C0cos(φc0+φn(η))
Wherein, I (eta), Q (eta) are indirect measurement quantities of the original echo after orthogonal demodulation, S0，C0，φs0，φc0Is an unknown parameter, phim(η) is the result of the reduction required.
Step two, differentiating the baseband signals of the path I and the path Q, and the specific implementation mode is
Wherein the content of the first and second substances,
is differential operation, and can be replaced by discrete difference in actual operation, so long as the differential time interval is ensured to be 10 times phim(η) signal bandwidth;
according to a first order Taylor approximation, there are
That is, the differential signals of the I path and the Q path satisfy a linear relationship with the vibration differential signal and the phase noise differential signal.
Thirdly, blind source separation is carried out on differential signals of the path I and the path Q by adopting a principal component analysis (ICA) -based method to obtain two independent signal components which respectively correspond to the vibration differential signal and the phase noise differential signal, and the specific implementation mode is as follows:
s301: solving covariance matrix
Wherein, W is a 2 x 2 matrix, and the binary operation <, > represents the cross-correlation function of the 2 real signals;
s302: eigenvalue decomposition of covariance matrix
The method is a linear algebra basic operation, has complex specific steps, is not described in detail and can obtain
Wherein e isu，evIs two characteristic values of W, both positive, u ═ u1，u2]T，V＝[v1，v2]TIs its corresponding feature vector (.)TIndicating vector transposition, evd is a calculation for finding eigenvalue;
s303: extracting a target vibration signal having
Step four, integrating the vibration differential signal, and restoring the vibration differential signal
Wherein the content of the first and second substances,
is a target oscillator obtained by orthogonal demodulation blind source separationThe dynamic signal should be under the premise that the vibration signal and the phase noise signal are statistically independent
The integration operation is replaced by the cumulative summation of the discrete time signals in actual processing.
Examples
The invention provides an embodiment by adopting a radar with a linear frequency modulation pulse system, and the test conditions are shown in table 1.
TABLE 1 test conditions
| Parameter(s) | Parameter value |
| Working waveform | Linear frequency modulated pulse |
| Medium frequency/GHz | 0.5 |
| Radio frequency center frequency/ |
10 |
| Signal bandwidth/MHz | 300 |
| Pulse repetition frequency/ |
20 |
| Sampling rate/MHz | 1440 |
| Pulse width/[ mu ] |
1 |
| Length of observation time/ |
1 |
| Target form | Point target |
| Target-to-radar initial distance/m | About 10 |
| Maximum amplitude/mum of |
10 |
One-dimensional image of the target scene as shown in fig. 2, the target is located at a distance of about 10m in front of the radar. Fig. 3 and 4 show vibration signals and instantaneous power spectrums thereof loaded on a target, fig. 5 and 6 show vibration signals and instantaneous power spectrums thereof obtained by directly extracting a target echo phase without signal-to-noise enhancement processing, and fig. 7 and 8 show vibration signals and instantaneous power spectrums thereof obtained by separation based on an orthogonal demodulation blind source.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A broadband vibration measurement radar signal-to-noise ratio improvement method based on orthogonal solution blind source separation is characterized by comprising the following steps:
carrying out quadrature demodulation on echo signals of a broadband vibration measurement radar to respectively obtain I-path and Q-path quadrature baseband echo signals of the radar;
differentiating the baseband signals of the path I and the path Q, wherein the differential signals of the path I and the path Q, the vibration differential signals and the phase noise differential signals meet a linear relation on the premise that radar phase noise is dominant, and the linear relation is unknown;
thirdly, blind source separation is carried out on differential signals of the path I and the path Q by adopting a principal component analysis (ICA) -based method to obtain two independent signal components which respectively correspond to a vibration differential signal and a phase noise differential signal;
and step four, integrating the vibration differential signal, restoring the vibration differential signal and basically stripping the radar phase noise in the original result.
2. The method for improving the signal-to-noise ratio of the broadband vibration measuring radar based on the quadrature demodulation blind source separation as claimed in claim 1, wherein the specific process of the step one is as follows:
performing the following quadrature demodulation processing steps on the original echo S (t, eta) to obtain two paths of baseband quadrature demodulation signals, which is specifically operated as
S101: quadrature down conversion (DDC)
Iddc(t，η)＝LPF(t)*(S(t，η)sin(ωt))
Qddc(t，η)＝LPF(t)*(S(t，η)cos(ωt))
Wherein LPF (t) is a low pass filter with a pass band width of p0(t) 1/2 of bandwidth, setting the other filter parameters according to specific requirements, and representing the linear convolution operation of the signal;
s102: matched filter (DPC)
Idpc(t，η)＝p0(-t)*Iddc(t，η)
Qdpc(t，η)＝p0(-t)*Qddc(t，η)
S103: target detection (CFAR)
This is a basic operation of radar signal processing, and the processing steps are complex and not described in detail here, the target position t is detected to be 0,
I(η)＝Idpc(0，η)
Q(η)＝Qdpc(0，η)
3. the method for improving the signal-to-noise ratio of the broadband vibration measuring radar based on the orthogonal demodulation blind source separation as claimed in claim 1, wherein the specific process of the second step is as follows:
differentiating the baseband signals of the I path and the Q path
Wherein the content of the first and second substances,
is differential operation, and can be replaced by discrete difference in actual operation, so long as the differential time interval is ensured to be 10 times phim(η) signal bandwidth.
4. The method for improving the signal-to-noise ratio of the broadband vibration measuring radar based on the orthogonal demodulation blind source separation as claimed in claim 1, wherein the specific process of the third step is as follows:
the method comprises the following steps of performing blind source separation on differential signals of an I path and a Q path by using a principal component analysis (ICA) -based method to obtain two independent signal components which respectively correspond to a vibration differential signal and a phase noise differential signal, wherein the specific implementation mode is as follows:
s301: solving covariance matrix
Wherein, W is a 2 x 2 matrix, and binary operation <, > represents the cross-correlation function of two paths of real signals;
s302: eigenvalue decomposition of covariance matrix
The method is a linear algebra basic operation, has complex specific steps, is not described in detail and can obtain
Wherein e isu，evIs two characteristic values of W, both positive, u ═ u1，u2]T，v＝[v1，v2]TIs the corresponding characteristic vector, (-) represents the vector transpose, evd is the calculation of characteristic value;
s303: extracting a target vibration signal having
5. The method for improving the signal-to-noise ratio of the broadband vibration measuring radar based on the orthogonal demodulation blind source separation as claimed in claim 1, wherein the specific process of the step four is as follows:
integrating the vibration differential signal, restoring the vibration differential signal, having
Wherein the content of the first and second substances,
is a target vibration signal obtained by orthogonal demodulation blind source separation.
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| CN106644030A (en) * | 2016-08-31 | 2017-05-10 | 上海交通大学 | Doppler radar-based non-contact type vibration measuring method |
| CN109946656A (en) * | 2019-03-18 | 2019-06-28 | 西安电子科技大学 | Based on the MIMO radar blind source separate technology research for improving Detection model |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120293371A1 (en) * | 2011-05-19 | 2012-11-22 | Itt Manufacturing Enterprises, Inc. | System and Method for Geolocation of Multiple Unknown Radio Frequency Signal Sources |
| JP2015097638A (en) * | 2013-11-19 | 2015-05-28 | 株式会社ユーシン | Biological information measurement method |
| CN105997093A (en) * | 2016-04-24 | 2016-10-12 | 西安电子科技大学 | Limb motion separation method based on radar principle component analysis |
| CN106644030A (en) * | 2016-08-31 | 2017-05-10 | 上海交通大学 | Doppler radar-based non-contact type vibration measuring method |
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