CN108801398A - A kind of 120GHz frequency modulated continuous wave radars level meter and distance measuring method - Google Patents
A kind of 120GHz frequency modulated continuous wave radars level meter and distance measuring method Download PDFInfo
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- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
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Abstract
The invention discloses a kind of 120GHz frequency modulated continuous wave radars level meter and distance measuring method, radar levelmeter includes FM module, intermediate-freuqncy signal conditioning and sampling module, echo signal processing module, threshold curve generation module and Power estimation module；Wherein, FM module is configurable for generating the difference frequency orthogonal signalling IF_Q of the difference frequency in-phase signal IF_I and TX and RX of transmission frequency TX and receives frequency RX；Intermediate-freuqncy signal improves and sampling module is configurable for respectively handling to generate intermediate frequency quadrature signal IF_I', IF_Q' after digitizing difference frequency in-phase signal IF_I and difference frequency orthogonal signalling IF_Q successively；Echo signal processing module is configurable for intermediate frequency quadrature signal IF_I', IF_Q' being converted into spectrum curve from time-domain signal；Threshold curve generation module is configurable for, according to the spectrum curve of above-mentioned generation, being dynamically generated threshold curve, to obtain multiple echoes.The present invention has many advantages, such as that measurement blind area is small, precision is high.
Description
Technical field
The present invention relates to a kind of level meters, particularly, are related to a kind of 120GHz frequency modulated continuous wave radars level meter.
Background technology
Industrial stokehold, factory automation implementation process in, the height of material position can be carried out reliable and stable
It measures very crucial.Radar levelmeter rapid proliferation due to the characteristics of its is non-contact, it is accurate to measure, easy maintenance.
Radar levelmeter is divided into two kinds of pulse radar material level meter and frequency modulation radar body place meter：
One is pulse radar material level meters, and target range is calculated by the time difference between measurement transmitting-receiving microwave pulse, when
When target range only has several meters, the time difference for sending microwave pulse and reflected microwave pulse only has several nanoseconds, it is necessary to pass through the time
Expansion technique is extended to after grade the time difference of nanosecond and can measure.Time expansion technique needs slightly different
Tranmitting data register frequency and sample clock frequency, the two clock frequencies need very high resolution ratio, accuracy and the linearity, with
And highly stable Time -based Control.But temperature drift can make the device parameters of the frequency generating units of pulse radar change,
The accuracy of measurement of pulse radar is caused to reduce.Meanwhile time expansion technique also makes the measurement period of pulse radar become larger, and measures
Speed reduces.The transmission pulse width of pulse radar determines the precision of measurement, and pulse width is smaller, and precision is higher.It is limited
System, the precision of pulse radar also can only achieve ± 3mm ~ ± 10mm.
Another kind is fmcw radar level meter, compares pulse radar, and fmcw radar, which has, measures fast and stable, and accuracy is high
The characteristics of.CW with frequency modulation (FMCW) radar continuously transmits the microwave of frequency linearity variation, connects simultaneously within a frequency modulation period
The microwave of reflection is received, the space length between radar and target leads to currently transmitted microwave frequency and the microwave frequency of reflection
Between there are one difference on the frequency（Intermediate-freuqncy signal, IF）, this intermediate-freuqncy signal can be obtained by by mixing.Intermediate-freuqncy signal is filtered again
Wave sampling, FFT operations, obtain its frequency, and conversion obtains corresponding target range.
The frequency of radar is higher, and wavelength is shorter, and required antenna size is smaller, and field angle is also smaller, is more suitable for canister
The measurement of body and fine-powder also has blind area small, feature with high accuracy.It is public according to the calculating of the distance resolution of fmcw radar
Formula：C/2B, modulating bandwidth B is bigger, and the resolution ratio of distance is higher.
Currently marketed frequency modulated(FM) radar, frequency are generally 24GHz ~ 26GHz or 78GHz ~ 80GHz, modulating bandwidth highest
For 1GHz, it is unfavorable for the measurement of small tank body, the requirement of small blind area, high-acruracy survey is not achieved.
Invention content
In view of this, the first purpose of the invention is to provide a kind of 120GHz frequency modulated continuous wave radars level meter, have
The advantages that measurement blind area is small, precision is high.
To achieve the goals above, the technical scheme is that：
A kind of 120GHz frequency modulated continuous wave radars level meter, including the conditioning of FM module, intermediate-freuqncy signal and sampling module, echo letter
Number processing module, threshold curve generation module and Power estimation module；Wherein,
The FM module is configurable for generating the difference frequency in-phase signal IF_I of transmission frequency TX and receives frequency RX, and
The difference frequency orthogonal signalling IF_Q of TX and RX；Wherein, transmission frequency TX, receives frequency RX value be 120GHz ~ 130GHz.
Intermediate-freuqncy signal conditioning and sampling module be configurable for respectively to difference frequency in-phase signal IF_I and difference frequency just
It hands over signal IF_Q to be amplified successively, after low-pass filtering, analog-to-digital conversion process, generates the intermediate frequency quadrature signal IF_ after digitlization
I',IF_Q'；
The echo signal processing module is configurable for converting by complex fast Fourier, by intermediate frequency quadrature signal IF_
I', IF_Q' are converted into spectrum curve from time-domain signal, according to the spectrum curve of above-mentioned generation, are dynamically generated threshold curve, with
Multiple echoes are obtained, echo is assessed further according to the energy size of echo；Wherein, the maximum echo of energy is as target echo, and
Determine that the peak position of target echo is the corresponding target frequency point of target range.
Preferably, the FM module includes phaselocked loop, loop filter, voltage controlled oscillator, 32 times of frequency dividers, 90 ° of shiftings
Phase device, 2 frequency multipliers, the first power amplifier, the second power amplifier, low-noise amplifier, the first frequency mixer, the second mixing
Device, transmission antenna and reception antenna；Wherein, the phaselocked loop, loop filter, voltage controlled oscillator, 2 frequency multipliers, the first power
Amplifier is sequentially connected electrically；The another way output end of the input terminal connection voltage controlled oscillator of 32 times of frequency dividers, output end connect
Connect the input terminal of phaselocked loop；The input terminal of another way output the second power amplifier of termination of 2 frequency multiplier, second work(
The output end of rate amplifier is separately connected the input terminal of the first frequency mixer, 90 ° of phase shifters；The another way of first frequency mixer is defeated
Enter the output end of end connection low-noise amplifier, the input terminal of the low-noise amplifier connects reception antenna；Described second is mixed
The two-way input terminal of frequency device is separately connected the output end of 90 ° of phase shifters, low-noise amplifier.
Preferably, the echo signal processing module is additionally configured to quasi- to the wave crest progress curve of above-mentioned target echo
It closes, obtains matched curve, and determine that the peak of matched curve is the corresponding target frequency point of target range.
Preferably, the echo signal processing module is realized using the digital signal processor of high speed, and configured with extension
External static memory.
Preferably, the intermediate-freuqncy signal conditioning and sampling module include：
The first processing branch being made of sequentially connected third power amplifier, the first low-pass filter, the first analog-digital converter
Road；And
The second processing branch being made of sequentially connected 4th power amplifier, the second low-pass filter, the second analog-digital converter
Road；
Wherein, first processing branch, second processing branch respectively to difference frequency in-phase signal IF_I and difference frequency orthogonal signalling IF_Q into
Row processing.
Second object of the present invention is to provide a kind of distance measuring method based on radar levelmeter, small with measurement blind area,
The advantages that precision is high.
To achieve the goals above, the technical scheme is that：
A kind of distance measuring method based on radar levelmeter, including：
The difference frequency orthogonal signalling of the difference frequency in-phase signal IF_I and TX and RX of S01, generation transmission frequency TX and receives frequency RX
IF_Q；Wherein, transmission frequency TX, receives frequency RX value be 120GHz ~ 130GHz；
S02, difference frequency in-phase signal IF_I and difference frequency orthogonal signalling IF_Q are amplified successively respectively, low-pass filtering, modulus turn
After changing processing, intermediate frequency quadrature signal IF_I', IF_Q' after digitlization are generated；
S03, it is converted by complex fast Fourier, intermediate frequency quadrature signal IF_I', IF_Q' is converted into frequency spectrum from time-domain signal
Curve；
S04, according to the spectrum curve of above-mentioned generation, threshold curve is dynamically generated, to obtain multiple echoes；
S05, echo is assessed according to the energy size of echo, the wherein maximum echo of energy determines target as target echo
The peak position of echo is the corresponding target frequency point of target range；
S06, above-mentioned target frequency point, calculating the distance between target and radar levelmeter are utilized；Wherein, distance value is equal to target
Frequency point index value is multiplied by measurement accuracy Sacc.
Preferably, the calculation formula of the measurement accuracy Sacc is, wherein Sacc：Measurement accuracy；
Fs:Sample frequency；T：Frequency modulated time；C:The light velocity；Nfft:FFT operations are counted；B：Modulating bandwidth.
Preferably, further include：Spectrum curve is refined by the way of zero padding.
Preferably, further include：
It is carried out curve fitting to the wave crest of above-mentioned target echo using wave crest approximating method, obtains matched curve, and determined quasi-
The peak for closing curve is the corresponding target frequency point of target range.
Preferably, the specific generation method of above-mentioned threshold curve includes：
S041, first with the first filter width moving average filter is carried out to spectrum curve, obtain it is smooth after curve；
S042, with the second filter width moving average filter is carried out to spectrum curve again, obtains another smoothed curve, this is smooth
Curve is combined with the smoothed curve that S041 steps generate, and obtains required threshold curve；
Wherein, the first filter width is more than the second filter width.
The technology of the present invention effect major embodiment is in the following areas：By using 120GHz Terahertz frequency ranges, up to 10GHz's
Modulating bandwidth is used in combination the echo signal processing algorithm that high-speed dsp is realized, solves frequency modulation radar body place meter in existing market
Blind area is big, precision is low, is not suitable for the problems such as canister bulk measurement.
Description of the drawings
Fig. 1 is the structure chart of FM module in embodiment；
Fig. 2 is the structure chart of intermediate-freuqncy signal conditioning and sampling module in embodiment；
Fig. 3 is the structure chart of echo signal processing module in embodiment；
Fig. 4 is that threshold curve schematic diagram is generated in embodiment；
Fig. 5 is embodiment medium wave peak matched curve schematic diagram.
Specific implementation mode
Below in conjunction with attached drawing, the specific implementation mode of the present invention is described in further detail, so that technical solution of the present invention is more
It should be readily appreciated that and grasp.
Embodiment one,
Present embodiments provide a kind of 120GHz frequency modulated continuous wave radars level meter, including the conditioning of FM module, intermediate-freuqncy signal and
Sampling module, echo signal processing module, threshold curve generation module and Power estimation module.
Referring to Fig.1, FM module includes phaselocked loop 1, loop filter（LF）2, voltage controlled oscillator（VCO）4,32 times of frequency dividings
6,90 ° of phase shifters 15 of device, 2 frequency multipliers 8, the first power amplifier 10a, the second power amplifier 10b, low-noise amplifier
（LNA）13, the first frequency mixer 14a, the second frequency mixer 14b, transmission antenna 11 and reception antenna 12；Wherein, phaselocked loop 1, loop
Filter（LF）2, voltage controlled oscillator（VCO）4,2 frequency multipliers 8, the first power amplifier 10a are sequentially connected electrically；32 times of frequency dividers 6
Input terminal connect voltage controlled oscillator（VCO）4 another way output end, output end connect the input terminal of phaselocked loop 1；2 frequency multipliers 8
The second power amplifier 10b of another way output termination input terminal, the output end of the second power amplifier 10b is separately connected the
The input terminal of one frequency mixer 14a, 90 ° of phase shifters 15；The another way input terminal of first frequency mixer 14a connects low-noise amplifier
（LNA）13 output end, low-noise amplifier（LNA）13 input terminal connects reception antenna 12；The two-way of second frequency mixer is defeated
Enter end and is separately connected 90 ° of phase shifters 15, low-noise amplifiers（LNA）13 output end.
The operation principle of FM module is：Phaselocked loop（PLL）1 was set as within a frequency modulation period, linear convergent rate
The frequency of 1.875GHz ~ 2.03125GHz.When frequency modulation, the pulse current of phaselocked loop output passes through loop filter（LF）2, it generates
The voltage 3 of linear increase, linear voltage controls voltage controlled oscillator again（VCO）4 generate the frequency of oscillation 5 of linear change, from 60GHz
To 65GHz.Frequency of oscillation 5 divides two-way, all the way after 32 times of frequency dividers 6, generates the frequency 7 of 1.875GHz ~ 2.03125GHz,
Feed back input is to phaselocked loop 1；Another way passes through 2 frequency multipliers 8, the output frequency 9 of 120GHz ~ 130GHz is generated, using first
Power amplifier 10a obtains final transmission signal TX, is sent by transmission antenna 11.
Reception antenna 12 receives the frequency signal RX of 120GHz ~ 130GHz, by low-noise amplifier（LNA）13 amplifications
Afterwards, the first frequency mixer 14a is inputted.The another way input of first frequency mixer 14a is that frequency 9 is put by the second power amplifier 10b
Transmission frequency TX after big.After mixed, the same phase of difference frequency of the first frequency mixer 14a outputs transmission frequency TX and receives frequency RX
Signal IF_I.The another way of second power amplifier 10b exports after 90 ° of 15 phase shifts of phase shifter, generates and transmission frequency TX
Orthogonal signal, this signal input the second frequency mixer 14b and are mixed with signal RX is received, output TX letters orthogonal with the difference frequency of RX
Number IF_Q.
As it can be seen that the frequency for sending and receiving is from 120GHz linear change to 130GHz, bandwidth B is up to 10GHz, by formula C/
2B calculates its distance resolution and can reach 1.5 centimetres.
With reference to Fig. 2, intermediate-freuqncy signal conditioning and sampling module include by sequentially connected third power amplifier 17a, first
The first processing branch that low-pass filter 18a, the first analog-digital converter 19a are constituted；And by sequentially connected 4th power amplification
The second processing branch that device 17b, the second low-pass filter 18b, the second analog-digital converter 19b are constituted.
Intermediate-freuqncy signal improves and the operation principle of sampling module is：Intermediate frequency quadrature signal IF_I, IF_Q pass through third respectively
Power amplifier 17a, the 4th power amplifier 17b amplifications, then it is input to the first low-pass filter 18a, the second low-pass filter
18b is filtered, and is then sampled with the first analog-digital converter 19a, the second analog-digital converter 19b, after being digitized
Intermediate frequency quadrature signal IF_I', IF_Q'.
With reference to Fig. 3, echo signal processing module 20 is realized using the digital signal processor of high speed.Echo signal processing mould
Block 20 handles if sampling signal.Intermediate frequency quadrature signal IF_I', IF_Q' after digitlization is by plural number quickly Fu
Leaf transformation（FFT）After 21, spectrum curve 22 is converted into from time-domain signal.
The frequency resolution of spectrum curve 22 is sample frequency Fs divided by FFT points N, and frequency resolution is higher, is corresponded to
Range measurement accuracy it is higher.The calculation formula of the measurement accuracy of frequency modulated(FM) radar is（Sacc：Precision；
Fs:Sample frequency；T：Frequency modulated time；C:The light velocity；Nfft:FFT operations are counted；B：Modulating bandwidth）.Within a frequency modulation period,
The points of sampling are limited, in order to improve frequency resolution, the mode of zero padding can be used to refine frequency spectrum, but the point of zero padding
Number is more, and the execution time of FFT and required memory space just consume bigger.Therefore, the Digital Signal Processing of high speed is used
Device, and it is aided with the external static memory of extension, avoid this disadvantage so that the FFT points after zero padding can reach 60,000
Point, greatly improves measurement accuracy, and when measuring range is 50 meters, measurement accuracy can reach ± 0.76mm.
Noise suppression module 23 is averaged to multiple spectrum curve 22, inhibits random noise, improves signal-to-noise ratio, obtains
Spectrum curve 25, as shown in Figure 4.
Threshold curve generation module 24 is dynamically generated threshold curve according to spectrum curve 25, as shown in Figure 4.In Fig. 4,
There are one the echoes 26 very close to transmitted wave for spectrum curve 25.First spectrum curve 25 is slided with the first filter width W2
Dynamic average filter, the curve 27 after obtaining smoothly, it can be seen that curve 27 cannot be differentiated effectively and cut transmitted wave and echo, so
Moving average filter is carried out to spectrum curve 25 with smaller second filter width W1 again, obtains smoothed curve 28, smoothed curve
28 are combined with smoothed curve 27, obtain final threshold curve 29.This threshold curve 29 can be effectively partitioned into close to hair
The echo of ejected wave reduces the blind area of measurement.Spectrum curve 25 can be cut into multiple echoes by threshold curve 29, wherein there is ranging
The echo of target also has the echo of fixed obstacle.
Power estimation module 30 assesses echo according to the energy size of echo, and the maximum echo of energy is as target echo
31.Under normal circumstances, the peak position of target echo is the corresponding frequency point of target range, if measuring distance of target is particulate matter,
Or surface irregularity, there are angle of rest (repose) etc., the wave crest of target echo that can broaden, have sawtooth, there is no apparent peaks, at this moment use
Wave crest is fitted function 32 to carry out curve fitting, and finds the peak of wave crest.
Fig. 5 is the schematic diagram of wave crest fitting function 32.Irregular wave crest 33 passes through curve matching, obtains matched curve
34, the peak 35 of matched curve 34, as the corresponding frequency point of target range, index value W3.It is obtained after wave crest fitting
Wave crest can reflect the average case of target level, improve accuracy.The index value W3 of target frequency point is counted by distance
Module 36 is calculated, the distance between target and radar levelmeter can be obtained, distance value is multiplied by survey equal to target frequency point index value W3
Accuracy of measurement Sacc.
Embodiment two,
The present embodiment provides a kind of distance measuring method based on radar levelmeter on the basis of embodiment one, and this method includes：
The difference frequency orthogonal signalling of the difference frequency in-phase signal IF_I and TX and RX of S01, generation transmission frequency TX and receives frequency RX
IF_Q；Wherein, transmission frequency TX, receives frequency RX value be 120GHz ~ 130GHz；
S02, difference frequency in-phase signal IF_I and difference frequency orthogonal signalling IF_Q are amplified successively respectively, low-pass filtering, modulus turn
After changing processing, intermediate frequency quadrature signal IF_I', IF_Q' after digitlization are generated；
S03, it is converted by complex fast Fourier, intermediate frequency quadrature signal IF_I', IF_Q' is converted into frequency spectrum from time-domain signal
Curve；
S04, according to the spectrum curve of above-mentioned generation, threshold curve is dynamically generated, to obtain multiple echoes；
S05, echo is assessed according to the energy size of echo, the wherein maximum echo of energy determines target as target echo
The peak position of echo is the corresponding target frequency point of target range；
S06, above-mentioned target frequency point, calculating the distance between target and radar levelmeter are utilized；Wherein, distance value is equal to target
Frequency point index value is multiplied by measurement accuracy Sacc.
In above-mentioned steps, the calculation formula of measurement accuracy Sacc is, wherein Sacc：Measure essence
Degree；Fs:Sample frequency；T：Frequency modulated time；C:The light velocity；Nfft:FFT operations are counted；B：Modulating bandwidth.
In step S03, also spectrum curve is refined by the way of zero padding.
As further improvement of this embodiment, in above-mentioned steps, also utilize wave crest approximating method to above-mentioned target
The wave crest of echo carries out curve fitting, and obtains matched curve, and determines that the peak of matched curve is the corresponding mesh of target range
Mark frequency point.
In addition, the specific generation method of above-mentioned threshold curve includes：
S041, first with the first filter width moving average filter is carried out to spectrum curve, obtain it is smooth after curve；
S042, with the second filter width moving average filter is carried out to spectrum curve again, obtains another smoothed curve, this is smooth
Curve is combined with the smoothed curve obtained in S041 steps, obtains required threshold curve；
Wherein, the first filter width is more than the second filter width.
Certainly, the representative instance of the above only present invention, in addition to this, the present invention can also have other a variety of specific implementations
Mode, all technical solutions formed using equivalent substitution or equivalent transformation, is all fallen within the scope of protection of present invention.
Claims (10)
1. a kind of 120GHz frequency modulated continuous wave radars level meter, characterized in that including FM module, intermediate-freuqncy signal conditioning and sampling
Module and echo signal processing module；Wherein,
The FM module is configurable for generating the difference frequency in-phase signal IF_I of transmission frequency TX and receives frequency RX, and
The difference frequency orthogonal signalling IF_Q of TX and RX；Wherein, transmission frequency TX, receives frequency RX value be 120GHz ~ 130GHz；
The intermediate-freuqncy signal conditioning and sampling module are configurable for respectively to difference frequency in-phase signal IF_I and the orthogonal letter of difference frequency
Number IF_Q is amplified, successively after low-pass filtering, analog-to-digital conversion process, generate the intermediate frequency quadrature signal IF_I' after digitlization,
IF_Q'；
The echo signal processing module is configurable for converting by complex fast Fourier, by intermediate frequency quadrature signal IF_
I', IF_Q' are converted into spectrum curve from time-domain signal, according to the spectrum curve of above-mentioned generation, are dynamically generated threshold curve, with
Multiple echoes are obtained, echo is assessed further according to the energy size of echo；Wherein, the maximum echo of energy is as target echo, and
Determine that the peak position of target echo is the corresponding target frequency point of target range.
2. a kind of 120GHz frequency modulated continuous wave radars level meter as described in claim 1, characterized in that the FM module packet
Include phaselocked loop, loop filter, voltage controlled oscillator, 32 times of frequency dividers, 90 ° of phase shifters, 2 frequency multipliers, the first power amplifier,
Two power amplifiers, low-noise amplifier, the first frequency mixer, the second frequency mixer, transmission antenna and reception antenna；Wherein, described
Phaselocked loop, loop filter, voltage controlled oscillator, 2 frequency multipliers, the first power amplifier are sequentially connected electrically；32 times of frequency dividers
Input terminal connection voltage controlled oscillator another way output end, output end connect phaselocked loop input terminal；2 frequency multiplier it is another
The input terminal of the second power amplifier of output termination, the output end of second power amplifier are separately connected the first mixing all the way
The input terminal of device, 90 ° of phase shifters；The output end of the another way input terminal connection low-noise amplifier of first frequency mixer, institute
State the input terminal connection reception antenna of low-noise amplifier；The two-way input terminal of second frequency mixer is separately connected 90 ° of phase shifts
The output end of device, low-noise amplifier.
3. a kind of 120GHz frequency modulated continuous wave radars level meter as described in claim 1, characterized in that at the echo-signal
Reason module is additionally configured to carry out curve fitting to the wave crest of above-mentioned target echo, obtains matched curve, and determines that fitting is bent
The peak of line is the corresponding target frequency point of target range.
4. a kind of 120GHz frequency modulated continuous wave radars level meter as described in claim 1 or 3, characterized in that the echo letter
Number processing module realized using the digital signal processor of high speed, and configured with the external static memory of extension.
5. a kind of 120GHz frequency modulated continuous wave radars level meter as described in claim 1, characterized in that the intermediate-freuqncy signal tune
Reason and sampling module include：
The first processing branch being made of sequentially connected third power amplifier, the first low-pass filter, the first analog-digital converter
Road；And
The second processing branch being made of sequentially connected 4th power amplifier, the second low-pass filter, the second analog-digital converter
Road；
Wherein, first processing branch, second processing branch respectively to difference frequency in-phase signal IF_I and difference frequency orthogonal signalling IF_Q into
Row processing.
6. a kind of distance measuring method based on radar levelmeter, characterized in that including：
The difference frequency orthogonal signalling of the difference frequency in-phase signal IF_I and TX and RX of S01, generation transmission frequency TX and receives frequency RX
IF_Q；Wherein, transmission frequency TX, receives frequency RX value be 120GHz ~ 130GHz；
S02, difference frequency in-phase signal IF_I and difference frequency orthogonal signalling IF_Q are amplified successively respectively, low-pass filtering, modulus turn
After changing processing, intermediate frequency quadrature signal IF_I', IF_Q' after digitlization are generated；
S03, it is converted by complex fast Fourier, intermediate frequency quadrature signal IF_I', IF_Q' is converted into frequency spectrum from time-domain signal
Curve；
S04, according to the spectrum curve of above-mentioned generation, threshold curve is dynamically generated, to obtain multiple echoes；
S05, echo is assessed according to the energy size of echo, the wherein maximum echo of energy determines target as target echo
The peak position of echo is the corresponding target frequency point of target range；
S06, above-mentioned target frequency point, calculating the distance between target and radar levelmeter are utilized；Wherein, distance value is equal to target
The index value of frequency point is multiplied by measurement accuracy Sacc.
7. distance measuring method as claimed in claim 6, characterized in that the calculation formula of the measurement accuracy Sacc is, wherein Sacc：Measurement accuracy；Fs:Sample frequency；T：Frequency modulated time；C:The light velocity；Nfft:FFT operations
Points；B：Modulating bandwidth.
8. distance measuring method as claimed in claim 6, characterized in that further include：Spectrum curve is carried out by the way of zero padding
Refinement.
9. distance measuring method as claimed in claim 6, characterized in that further include：
It is carried out curve fitting to the wave crest of above-mentioned target echo using wave crest approximating method, obtains matched curve, and determined quasi-
The peak for closing curve is the corresponding target frequency point of target range.
10. distance measuring method as claimed in claim 6, characterized in that the specific generation method of above-mentioned threshold curve includes：
S041, first with the first filter width moving average filter is carried out to spectrum curve, obtain it is smooth after curve；
S042, with the second filter width moving average filter is carried out to spectrum curve again, obtains another smoothed curve, this is smooth
Curve is combined with the smoothed curve that S041 steps generate, and obtains required threshold curve；
Wherein, the first filter width is more than the second filter width.
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| CN115166708B (en) * | 2022-09-06 | 2022-12-30 | 比业电子（北京）有限公司 | Judgment method, device and equipment for target recognition in sensor blind area |
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| CN116500609B (en) * | 2023-05-16 | 2023-11-21 | 北京锐达仪表有限公司 | Composite microwave radar measurement system for detecting blanking state and material level fluctuation state |
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