CN214174613U - Absolute distance measuring device based on microwave frequency domain interference - Google Patents
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Abstract
The utility model provides an absolute distance measuring device based on microwave frequency domain interferes, the device include broadband microwave radiation source module, frequency domain interference module, signal processing module, wherein, broadband microwave radiation source module comprises ASE light source, narrow band filter, photoelectric detector. The utility model discloses an adopt broadband microwave frequency domain interference technique, overcome the tradition based on among the space-time domain microwave range finding technique the restriction of factors such as microwave wavelength, electronic components response rate and oscilloscope bandwidth to measuring range and precision. Adopt this patent to interfere principle range finding technique based on microwave frequency domain and can utilize current components and parts can realize that long range high accuracy absolute distance measures, the utility model discloses the device has simple structure, the range is long, advantage that the precision is high.
Description
Technical Field
The utility model belongs to microwave radar range finding field, concretely relates to absolute distance measuring device based on microwave frequency domain is interfered.
Background
The microwave radar technology realizes non-contact measurement of targets in smoke, dust, plasma, non-metallic materials and the like, so the microwave radar technology has wide application prospects in various military and civil fields such as industrial deformation monitoring, medium/short-range material level measurement, multi-target identification, internal flaw detection and the like.
At present, the existing microwave ranging technology mainly obtains target distance information by establishing a space-time domain mapping relation and calculating the change of a measurement signal along with time, and the existing microwave ranging technology mainly comprises a single-frequency microwave interference ranging technology, a microwave doppler radar, a pulse microwave radar and a frequency modulation continuous wave radar. The single-frequency microwave interference distance measurement technology can obtain the relative displacement information of a target body, but the precise measurement range of the microwave is smaller than the microwave wavelength because the microwave wavelength is basically in the order of centimeters to millimeters, and the precise measurement of the absolute distance cannot be independently realized in practical application; the single-frequency microwave Doppler radar realizes the absolute distance measurement of a static target body, the measurement precision of the single-frequency microwave Doppler radar is basically in the order of centimeters to millimeters, and the single-frequency microwave Doppler radar has great limitation in practical application; the pulse microwave radar has simple technical principle and larger measurement range, but is limited by the precision of the timing module, and the measurement precision is usually more than centimeter magnitude; regarding the frequency modulation continuous wave radar technology, the document "nondestructive testing depth of internal damage of non-metallic component by using microwave frequency domain interferometer", aerospace measurement technology, in 1989, 05, the adopted radiation source is FMCW microwave source, the microwave source is frequency sweep radiation source, only single frequency microwave signal can be emitted at one time, meanwhile, the interference signal is time domain interference signal generated in a photoelectric detector and acquired by an oscilloscope. The frequency modulation continuous wave radar is limited by the bandwidth of an oscilloscope and the linearity of a sweep frequency microwave radiation source, the technology is mainly applied to middle and short distance measurement, the measurement precision of the frequency modulation continuous wave radar in a meter-level range is in a millimeter-to-submillimeter level, meanwhile, the system structure is complex, and the frequency modulation continuous wave radar needs a high-linearity broadband sweep frequency microwave radiation source and a high-bandwidth oscilloscope, so that the cost is high.
So far, a microwave absolute distance measurement technology with simple structure, long measuring range and micron-scale precision is still one of the leading directions to be urgently developed in the field. The absolute distance measurement technology based on frequency domain interference is one of the fast-developing high-precision distance measurement means in recent years, and is based on a space-frequency domain mapping relation, two beams of wide-spectrum signals with optical path difference form an interference pattern on a frequency domain, and the frequency domain interference signals are inverted to obtain the carried space absolute distance information. At present, an absolute distance measurement technology based on optical band frequency domain interference is developed, a wide-spectrum optical signal of the absolute distance measurement technology is generally near a 1550nm band, and submicron-level high-precision absolute distance measurement can be achieved. However, the wavelength of light is short, the penetrability is poor, and the target body in smoke, dust, plasma, non-metal materials and the like cannot be directly measured, so that the application of the method in the fields is limited. But is limited by the deficiency of a broadband microwave radiation generation method and a distance information analysis method based on a microwave band frequency domain interference pattern, and an absolute distance measurement technology based on a microwave frequency domain interference principle is not reported yet.
Disclosure of Invention
In view of this, the utility model discloses aim at breaking through above-mentioned key technology bottleneck, provide an absolute distance measuring device based on microwave frequency domain interferes, the utility model discloses measure that the technique is brand-new, simple structure, measure journey length, precision height.
The utility model discloses specifically adopt following technical scheme:
the absolute distance measuring device based on microwave frequency domain interference is characterized by comprising a broadband microwave radiation source module, a frequency domain interference module and a signal processing module, wherein the broadband microwave radiation source module consists of an ASE light source, a narrow-band filter and a photoelectric detector, and the connection relation is as follows: the output end of the ASE light source is connected with the input end of the narrow-band filter, the output end of the narrow-band filter is connected with the optical input end of the photoelectric detector, and the broadband microwave signal generated by the photoelectric detector is output by the output end of the photoelectric detector through a cable.
Furthermore, the frequency domain interference module is composed of a microwave power divider, a microwave transmitting antenna, a microwave receiving antenna, an adjustable attenuator, a microwave power synthesizer and a spectrum analyzer, wherein the output end of the photoelectric detector is connected to the input end of the microwave power divider, 2 output ends of the microwave power divider are respectively connected with the input ends of the adjustable attenuator and the microwave transmitting antenna, the output ends of the adjustable attenuator and the microwave receiving antenna are respectively connected with 2 input ends of the microwave power synthesizer, and the output end of the microwave power synthesizer is connected to the spectrum analyzer through a cable.
Furthermore, the frequency domain interference module is composed of a microwave circulator, a microwave receiving and transmitting antenna and a spectrum analyzer, wherein the output end of the photoelectric detector is connected to a port 1 of the microwave circulator, and a port 2 and a port 3 of the microwave circulator are respectively connected with the microwave receiving and transmitting antenna and the spectrum analyzer.
Further, the signal processing module is a microcomputer.
The utility model also provides an absolute distance measuring method based on microwave frequency domain interference, its characteristics are, this method includes following step:
s1: generating a broadband microwave signal based on a broadband microwave radiation source module, and entering a frequency domain interference module;
s2: dividing a broadband microwave signal into two beams based on a frequency domain interference module, wherein one beam is used as a reference wave Eref (t), the other beam is transmitted to a target body to be detected, and a reflection signal of the beam is received and is used as a signal wave Epr (t); mixing a reference wave and a signal wave, interfering, and performing complete sampling on a frequency domain according to the Nyquist theorem by utilizing a signal period to obtain a frequency domain interference signal I (f, T);
s3: based on the signal processing module, carrying out inverse Fourier transform on the obtained frequency domain interference signal I (f, T) to obtain a transmission time difference T, and obtaining a function relation between the absolute distance S and the transmission time difference T
And calculating to obtain an absolute distance S, wherein c is the speed of light, n is the refractive index of the transmission medium, and T satisfies the formula:
in the formula, F [ I (F, T) ] is an inverse Fourier transform function of a frequency domain interference field spectral intensity distribution function, I (F, T) is the frequency domain interference field spectral intensity distribution function, F is microwave frequency, T is time, T is transmission time difference, R is the reflectivity of a target to be measured, G () is a time domain characteristic function of a frequency domain interference signal after inverse Fourier transform, and phi is a microwave signal phase angle.
Further, step (2) performs complete sampling of the signal in the frequency domain for a whole period at a sampling interval 1/3 which is lower than the period of the interference fringe in the frequency domain, and the sampling interval is not 0.
The utility model discloses an adopt broadband microwave frequency domain interference technique, overcome the tradition based on in the microwave wavelength of space time domain microwave range finding technique, factor such as electronic components response rate and oscilloscope bandwidth to the restriction of measuring range and precision. Adopt this patent to interfere principle range finding technique based on microwave frequency domain and can utilize current components and parts can realize that long range high accuracy absolute distance measures, the utility model discloses the device has simple structure, the range is long, advantage that the precision is high.
Drawings
FIG. 1 is a microwave frequency domain interference-based absolute distance measuring device according to example 1;
FIG. 2 is a diagram showing an absolute distance measuring apparatus according to embodiment 2 based on microwave frequency domain interference;
FIG. 3 is a frequency domain interference spectrum obtained by the absolute distance measurement method based on microwave frequency domain interference in example 1;
FIG. 4 shows the results of measurements of absolute distance measurements repeated 100 times in the method of example 1;
in the figure, 101, an ASE light source 102, a narrow-band filter 103, a photoelectric detector 104, a microwave power divider 105, a microwave transmitting antenna 106, a microwave receiving antenna 107, an adjustable attenuator 108, a microwave power combiner 109, a spectrum analyzer 110, a signal processing module 111, a target 104 'to be measured, a microwave circulator 105' and a microwave transmitting and receiving antenna.
Detailed Description
The present invention will be explained in further detail with reference to the drawings and examples.
The utility model provides a microwave frequency domain interference specifically indicates that two bundles of broadband microwave signals that have the correlation pass through frequency spectrograph mixing detection, because its different frequency components interfere the stack separately, finally forms the phenomenon of obvious interference fringe in the frequency domain.
As shown in fig. 1, an absolute distance measuring device based on microwave frequency domain interference includes three functional modules, which are a broadband microwave radiation source module, a frequency domain interference module, and a signal processing module 110, wherein the broadband microwave radiation source module is composed of an ASE light source 101, a narrow-band filter 102, and a photodetector 103, and the connection relationship is as follows: the output end of the ASE light source 101 is connected with the input end of the narrow-band filter 102 through an optical fiber, the output end of the ASE light source is connected with the optical input end of the photoelectric detector 103 through an optical fiber, and the broadband microwave signal generated by the photoelectric detector 103 is output from the electrical output end of the photoelectric detector through a cable.
Further, the frequency domain interference module is composed of a microwave power divider 104, a microwave transmitting antenna 105, a microwave receiving antenna 106, an adjustable attenuator 107, a microwave power combiner 108, and a spectrum analyzer 109, wherein the output end of the photodetector 103 is connected to the input end of the microwave power divider 104 through a cable, 2 output ends of the microwave power divider 104 are respectively connected to the adjustable attenuator 107 and the input end of the microwave transmitting antenna 105 through cables, the output ends of the adjustable attenuator 107 and the microwave receiving antenna 106 are respectively connected to 2 input ends of the microwave power combiner 108 through cables, and the output end of the microwave power combiner 108 is connected to the spectrum analyzer 109 through a cable.
Further, the frequency domain interference module is composed of a microwave circulator 104 ', a microwave transceiving antenna 105 ' and a spectrum analyzer 109, wherein the output end of the photodetector 103 is connected to the port 1 of the microwave circulator 104 ' through a cable, and the ports 2 and 3 of the microwave circulator 104 ' are respectively connected to the microwave transceiving antenna 105 ' and the spectrum analyzer 109 through cables. Further, the signal processing module 110 is composed of a microcomputer.
The utility model also discloses an absolute distance measuring method of absolute distance measuring device based on this microwave frequency domain is interfered, this method includes following step:
s1: generating a broadband microwave signal based on a broadband microwave radiation source module, and entering a frequency domain interference module;
s2: based on frequency domain interference module, the broadband microwave signal is divided into two beams, and one beam is used as reference wave Eref(t) emitting the other beam to the target and receiving the reflected signal as signal wave Epr(t); mixing a reference wave and a signal wave, interfering, and completely sampling in a frequency domain according to the Nyquist theorem on the basis of a signal period to obtain a frequency domain interference signal I (f, T);
s3: based on the signal processing module, the frequency domain interference signal I (f,t) inverse Fourier transform to obtain a transmission time difference T, the transmission time difference T being determined by a functional relationship between the absolute distance S and the transmission time difference T
The absolute distance S can be obtained by calculation, wherein c is the speed of light, n is the refractive index of the transmission medium, and T satisfies the formula:
the specific derivation process of the transmission time difference T is as follows:
two beams of broadband microwave signals E participating in interference are arrangedref(t) and Epr(t) are each independently
Eref(t)＝E0(t)exp(i2πf0t) (1)
Wherein E (t) is a complex function, t is time, i is an imaginary unit, E0(t) is amplitude intensity, f0T is a certain reference frequency in the time domain, the transmission time difference of two microwave signals,
is the initial phase of the phase,
is Epr(t) and Eref(t) amplitude ratio of (F) to (t)]The fourier transform of equations (1), (2) by the translational and phase-shifting properties of the fourier transform is shown below:
F[Eref(t)]＝F[E0(t)exp(i2πf0t)＝E0(f-f0) (3)
according to Parserval's theorem, the intensity distribution of the time domain interference field is equivalent to that of the frequency domain interference field, so that the frequency domain interference field spectral intensity distribution function can be analyzed by using the frequency domain interference theory, and the frequency domain interference field spectral intensity distribution function can be obtained by the following two formulas (3) and (4):
and (3) obtaining a frequency domain interference field spectral intensity distribution function by squaring the formula (5), wherein the function is as follows:
the intensity distribution of the frequency domain interference field is obtained from the formula (6) and not only the amplitude intensity ratio R and the phase angle of the two microwave signals
It is also related to the time frequency f and the transmission time difference T, which is the period of the interference signal. Rewriting the formula (6) as follows:
wherein I (f, T) is a spectral intensity distribution function of the domain interference field, R is the reflectivity of the target body to be measured, I0(f) For the broadband microwave spectrum distribution function, the formula (7) is developed to obtain:
let F [1(F) ] -g (t), the phase shift property of the inverse fourier transform be expressed as
F-1[I(f)eiTf]＝G(t+T) (9)
By using the phase shift property of inverse Fourier transform, the inverse Fourier transform of formula (9) can be obtained
In the formula, F [ I (F, T) ] is an inverse Fourier transform function of a frequency domain interference field spectral intensity distribution function, I (F, T) is the frequency domain interference field spectral intensity distribution function, F is microwave frequency, T is time, T is transmission time difference, R is the reflectivity of a target to be measured, G () is a time domain characteristic function of a frequency domain interference signal after inverse Fourier transform, and phi is a microwave signal phase angle;
as can be seen from the expression (10), after the inverse Fourier transform is performed on the frequency domain interference intensity distribution spectrum, the expression comprises three characteristic frequencies T, T + T and T-T. Wherein t is time, and the value of t is equal to the distribution function I of the broadband microwave spectrum0(f) A characteristic value in the time domain. Due to I0(f) A quasi-gaussian distribution, whose eigenvalues are substantially 0 in the time domain, i.e., t is 0. Therefore, the characteristic frequency value obtained by the inverse fourier transform is the transmission time difference T.
Again, the relationship between the absolute distance S and the transmission time difference T is as follows:
where c is the speed of light, and n is the refractive index of the transmission medium, absolute distance information can be obtained by combining expressions (10) and (11).
According to the analysis, the absolute distance measurement based on the microwave frequency domain interference only needs to obtain a frequency domain interference spectrum in a broadband range, and the absolute distance information of the target body to be measured can be simply calculated by obtaining the transmission time difference through inverse Fourier transform.
For example, according to equation (11), when the measurement distances are 1m and 100m, the periods of the interference signals in the frequency domain are 0.15GHz and 1.5MHz, respectively. According to the Nyquist sampling law, in order to realize complete sampling of the signals, the sampling intervals of the frequency spectrograph are required to be set to be respectively lower than 60MHz and 0.6MHz, which can be easily realized by any commercial frequency spectrograph at present without using a high-bandwidth oscilloscope to collect high-frequency signals.
Because the measurement precision is independent of the selected microwave wavelength range and the response rate of electronic components and depends on the precision of inverse Fourier transform, under the condition that the signal-to-noise ratio is enough, the calculation length of the inverse Fourier transform reaches 226On the order of magnitude (about 6 μm), measurement accuracy on the order of microns can be achieved, which is also easily achievable by computers at present. Therefore, the utility model discloses absolute distance measurement technique based on microwave frequency domain interference has overcome the realistic engineering factor of restriction prior art measuring range and precision in principle, under the realizable prerequisite of engineering, utilizes current commercial components and parts can realize long-range high accuracy absolute distance measurement.
Further, the step (2) performs complete sampling of the signal in the frequency domain for a whole period at 1/3 which is lower than the period of the interference fringe in the frequency domain, wherein the sampling interval cannot be 0. The sampling interval is determined by the measuring distance, the frequency domain interference period is smaller as the distance is farther, and the sampling interval is less than one third of the frequency domain interference period.
The utility model discloses an utilize microwave frequency domain to interfere the principle and build absolute distance measuring device and method, and then realize the absolute distance measurement of long range, micron order precision. And simultaneously, the utility model discloses simple structure, the simple operation can effectual reduction microwave range finding technique to experimental facilities performance and application environment's requirement, and this has the impetus to the practical application in fields such as scientific research production to the non-contact absolute distance measurement based on the microwave section.
Example 1
In the present embodiment, the absolute distance measurement based on microwave frequency domain interference is performed by the absolute distance measurement apparatus shown in fig. 1, in the apparatus, the frequency domain interference module may be composed 109 as shown in fig. 1 by a microwave power divider 104, a microwave transmitting antenna 105, a microwave receiving antenna 106, an adjustable attenuator 107, a microwave power combiner 108, and a spectrum analyzer, wherein broadband microwaves are connected to the input end of the microwave power divider 104 through a cable, 2 output ends of the broadband microwaves are respectively connected to the input ends of the adjustable attenuator 107 and the microwave transmitting antenna 105 through cables, the output ends of the adjustable attenuator 107 and the microwave receiving antenna 106 are respectively connected to 2 input ends of the microwave power combiner 108 through cables, and the output end of the adjustable attenuator 107 and the output end of the microwave receiving antenna 106 are connected to the spectrum analyzer 109 through cables.
The method for measuring the absolute distance based on the microwave frequency domain interference by using the device of the embodiment specifically comprises the following steps:
s1: an ASE light source 101 is filtered by a narrow linewidth filter 102 of 0.8nm and then injected into a photoelectric detector 103 with the bandwidth of 20GHz, and broadband microwave radiation with the bandwidth of 0-20GHz is generated through an optical beat effect.
S2: dividing the generated broadband microwave into two beams by a microwave power divider 104, wherein one beam enters an adjustable attenuator 107 and is used as a reference wave after being attenuated properly; the other beam is transmitted to the target body 111 to be measured through the microwave transmitting antenna 105, and enters the microwave receiving antenna 106 after being reflected, and the other beam is a signal wave because the other beam contains distance information. The reference wave and the signal wave are combined into a beam by the microwave power combiner 108, and then enter the spectrum analyzer 109 for detection to form a frequency domain interference spectrum.
S3: the computer 110 performs inverse fourier transform on the generated frequency domain interference spectrum to obtain a transmission time difference, and then calculates to obtain absolute distance information.
When the target body to be measured is a metal plate and the distance to be measured is about 1.8m, the frequency domain interference spectrum obtained in the experiment by using the technical scheme is shown in the attached figure 3. The uncertainty of the device class A was found to be 3.8 μm (confidence interval 95.5%) by calculation, as shown in FIG. 4, after 100 measurements on the target. The absolute distance measurement was 1.852156. + -. 0.0000038m (confidence interval 95.5%). To sum up, can see, the utility model discloses based on the microwave frequency domain interference principle, built the microwave absolute distance measuring device of simple structure compactness, realized the absolute distance measurement of long range, micron order precision.
Example 2
The present embodiment is based on the device shown in fig. 2 to perform absolute distance measurement based on microwave frequency domain interference, and compared with embodiment 1, the present embodiment 2 is different in that the frequency domain interference module may further include a microwave circulator 104 ', a microwave transceiver antenna 105', and a spectrum analyzer 109 (as shown in fig. 2), and the connection relationship is that broadband microwaves are connected to 1 port of the microwave circulator 104 'through a cable, and 2 and 3 ports of the module are connected to the microwave transceiver antenna 105' and the spectrum analyzer 109 through cables, respectively.
The method for measuring the absolute distance based on the microwave frequency domain interference by using the device of the embodiment specifically comprises the following steps:
s1: an ASE light source 101 is filtered by a narrow linewidth filter 102 of 0.8nm and then injected into a photoelectric detector 103 with the bandwidth of 20GHz, and broadband microwave radiation with the bandwidth of 0-20GHz is generated through an optical beat effect.
S2: the generated broadband microwaves are injected into a port 1 of the microwave circulator 104 ', are output to the microwave transceiving antenna 105' through a port 2, are transmitted to the target body 111 to be measured, are also received by the microwave transceiving antenna 105 'after being reflected, are input through the port 2 of the microwave circulator 104', and are finally output from the port 3 as signal waves. Meanwhile, since the isolation between the 1 port and the 3 port of the microwave circulator 104' is only 20dB, a part of the microwave signal will directly leak from the 1 port to the 3 port for output, i.e. it can be used as a reference wave. After the reference wave and the signal wave pass through the 3 ports of the microwave circulator 104' and are combined into a beam, the beam enters the spectrum analyzer 109 to form a frequency domain interference spectrum.
S3: the computer 110 performs inverse fourier transform on the generated frequency domain interference spectrum to obtain a transmission time difference, and then calculates to obtain absolute distance information.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.
Claims (4)
1. The absolute distance measuring device based on microwave frequency domain interference is characterized by comprising a broadband microwave radiation source module, a frequency domain interference module and a signal processing module (110), wherein the broadband microwave radiation source module consists of an ASE light source (101), a narrow-band filter (102) and a photoelectric detector (103), and the connection relation is as follows: the output end of the ASE light source (101) is connected with the input end of the narrow-band filter (102), the output end of the narrow-band filter (102) is connected with the light input end of the photoelectric detector (103), and the broadband microwave signal generated by the photoelectric detector (103) is output from the output end of the photoelectric detector (103) through a cable.
2. The microwave frequency domain interference-based absolute distance measuring device according to claim 1, wherein the frequency domain interference module is composed of a microwave power divider (104), a microwave transmitting antenna (105), a microwave receiving antenna (106), an adjustable attenuator (107), a microwave power combiner (108), and a spectrum analyzer (109), wherein the output end of the photodetector (103) is connected to the input end of the microwave power divider (104), 2 output ends of the microwave power divider (104) are respectively connected to the adjustable attenuator (107) and the input end of the microwave transmitting antenna (105), the output ends of the adjustable attenuator (107) and the microwave receiving antenna (106) are respectively connected to two input ends of the microwave power combiner (108), and the output end of the microwave power combiner (108) is connected to the spectrum analyzer (109) through a cable.
3. The microwave-based absolute distance measurement device based on interference in frequency domain is characterized in that the frequency domain interference module is composed of a microwave circulator (104 '), a microwave transceiving antenna (105 ') and a spectrum analyzer (109), wherein the output end of the photodetector (103) is connected to the port 1 of the microwave circulator (104 '), and the ports 2 and 3 of the microwave circulator (104 ') are respectively connected to the microwave transceiving antenna (105 ') and the spectrum analyzer (109).
4. The microwave frequency-domain interference based absolute distance measuring device according to claim 1, wherein the signal processing module (110) is a microcomputer.
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| CN112859060B (en) * | 2021-01-26 | 2024-09-03 | 中国工程物理研究院流体物理研究所 | Absolute distance measuring device and method based on microwave frequency domain interference |
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