CN110568215A - Radar meter and measuring method thereof - Google Patents
Radar meter and measuring method thereof Download PDFInfo
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- CN110568215A CN110568215A CN201910938331.2A CN201910938331A CN110568215A CN 110568215 A CN110568215 A CN 110568215A CN 201910938331 A CN201910938331 A CN 201910938331A CN 110568215 A CN110568215 A CN 110568215A
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01F23/284—Electromagnetic waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
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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
- 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
- G01S13/88—Radar or analogous systems specially adapted for specific applications
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Abstract
a radar flowmeter and a measuring method thereof. The invention transmits electromagnetic wave signals to the water surface through the radar main body arranged with a plurality of antenna array elements, receives the electromagnetic wave signals reflected by the water surface, processes the electromagnetic wave signals reflected by the water surface and received by the radar main body by the signal processing unit, and calculates the water flow speed and the water level height according to the transmitted and received electromagnetic wave signals. Therefore, the radar flow meter independently arranged on one side of the water body can be used for simultaneously obtaining the flow speed and the water level of the water body, and compared with the existing mode, the radar flow meter has the characteristics of convenience in installation, small limitation on an installation angle, simple installation structure, lower overall cost and capability of being used in various conventional and unconventional environments.
Description
Technical Field
the invention relates to the technical field of microwave measurement, in particular to a radar flow meter and a measurement method thereof.
Background
The existing radar water flow meter can only measure the flow velocity of water flow or the height of water surface independently usually, and the measuring device with a plurality of different energy supplies is needed to be arranged for detecting the flow velocity and the water amount of a water body simultaneously, so the cost is higher.
In addition, conventional radar for measuring water level is generally mounted on a cross bar, which is generally horizontally fixed on a bridge of a river or fixed at one end by a vertical column deeply buried at the bank of the river. During measurement, the cross bar arranged on the water flow meter needs to be horizontally extended above the river surface, so that radar beams emitted by a radar in the water flow meter are vertically irradiated to the horizontal plane. The mounting structure is easy to encounter various environmental restrictions in actual use, influences the mounting effect of the measuring device, even cannot mount the measuring device, and cannot realize automatic water state detection. Especially, in the river course do not have the bridge or river course slope special circumstances such as too big, because the stand can't be fixed when the river course slope is too big, and the whippletree that originally is used for fixed measuring device can't be connected to again and realize the installation on the outrigger, consequently, can only measure through artifical mode under this kind of circumstances usually. The manual approach is costly and measurement errors are large.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the radar flow meter and the measurement method thereof. The invention specifically adopts the following technical scheme.
first, in order to achieve the above object, there is provided a radar flow meter including: the radar main body is provided with a plurality of antenna array elements arranged on the front side and used for transmitting electromagnetic wave signals to the water surface and receiving the electromagnetic wave signals reflected by the water surface; the back side of the metal diaphragm is provided with the metal diaphragm, and the metal diaphragm is grounded to provide a reference signal. And the signal processing unit is opposite to the radar main body, is arranged on the other side of the metal partition plate, and is used for outputting a driving signal to the radar main body according to a set time interval to drive the radar main body to emit an electromagnetic wave signal to the water surface, processing the electromagnetic wave signal reflected by the water surface, and calculating the water flow speed and the water level height according to the emitted and received electromagnetic wave signal. And a signal isolation cover which surrounds the signal processing unit, is arranged on the other side of the metal partition plate relative to the radar main body, and isolates electromagnetic wave interference signals outside the signal processing unit. And the mounting fixing seat is connected and fixed on the back side of the radar main body and fixes the radar main body above the water surface.
optionally, in the radar flow meter, the radar main body includes: the dielectric plate is provided with a lead through hole penetrating through the front side surface and the back side surface at the center, the lead through hole is used as the center, the front side surface of the dielectric plate is provided with a center feeder line in a direction parallel to the width direction of the dielectric plate, and a plurality of long feeder lines are symmetrically arranged on the front side surface of the dielectric plate perpendicular to the center feeder line. The antenna array elements comprise a plurality of antenna array elements which are uniformly arranged on the front side surface of the dielectric plate along the long feeder line, and the length of each antenna array element is equal to that of each antenna array elementThe width of each antenna element isWherein λ represents an operating wavelength of the radar body,effective dielectric constantC0Indicating the speed of light, frRepresents the operating frequency of the radar body, epsilonrdenotes the dielectric constant of the dielectric plate, and d denotes the thickness of the dielectric plate. And the metal partition plate is attached to the back surface of the dielectric plate and is a grounded metal plate, and a gap is formed in the center of the metal plate for the lead to pass through the lead through hole without contacting with the metal plate.
Optionally, in the radar flow meter, the position on the long feeder line close to each antenna element, and the connection position on the central feeder line close to each long feeder line is also respectively provided with a 1/4 impedance transformation structure, each 1/4 impedance transformation structure respectively comprises at least one step with the length of 1/4 of the working wavelength lambda of the radar main body, the 1/4 impedance transformation structure is arranged along the long feeder line or the central feeder line, the width of the step is designed according to the requirement of 100 ohm matching, so that the Chebyshev polynomial coefficient is adopted to carry out excitation current distribution on each antenna array element through each 1/4 impedance transformation structure, the radiation intensity of each side lobe in the lobe pattern of the whole radar main body is within a set range, and, wherein a beam range of the radar body in the water velocity direction is greater than a beam range perpendicular to the water velocity direction.
optionally, in the radar flow meter, the radar body is made of a Rogers4350B plate material, the thickness of the radar body is 0.254mm, and the dielectric constant is epsilonr＝3.66。
Optionally, in the radar flow meter, there are 1 radar main body, where the radar main body transmits an electromagnetic wave signal with a frequency f to a water surface, and all the radar main bodies receive the electromagnetic wave signal reflected by the water surface at the same time;
The signal processing unit comprises an analog-to-digital conversion module, the electromagnetic wave signals received by each radar main body and the local oscillation signals of the radar flow meter are subjected to frequency mixing, the difference frequency between the transmitting frequency f and the received electromagnetic wave signals is obtained by taking down-conversion signals after frequency mixing, the difference frequency signals are converted by the analog-to-digital conversion module to respectively obtain mutually orthogonal I/Q data, the signal processing unit performs time domain to frequency domain conversion on the mutually orthogonal I/Q data to obtain frequency variation delta f, and therefore the frequency variation delta f is obtained through calculation: distance between reflection points of the radar main body to the water surfacewherein K represents a frequency change slope; carrying out time domain-frequency domain transformation on the data at the same position of the multiple frequency change slope to obtain the target Doppler frequency fdCalculating and obtaining the speed of the reflection point of the water surface moving to the radar main bodyWherein f iszIndicating the frequency of the local oscillator signalRate; according to the phase difference between the electromagnetic wave signals received between the antenna elements in the radar main bodyCalculating a target angle theta of a reflection point of the water surface, wherein lambda represents the working wavelength of the radar main body, and d represents the distance between each antenna array element
Meanwhile, in order to achieve the above object, the present invention further provides a measurement method of a radar flow meter, which is used for the radar flow meter, and the measurement steps include: the first step is as follows: obtaining an included angle (alpha + theta) between the measuring point of the radar flow meter and the height direction of the radar main body, and obtaining an included angle beta between the measuring point of the radar flow meter and the direction vertical to the water flow; secondly, driving a radar main body in the radar flow meter to emit an electromagnetic wave signal with the frequency f to the water surface; thirdly, controlling all radar main bodies in the radar flow meter to simultaneously receive electromagnetic wave signals reflected by the water surface; fourthly, mixing the electromagnetic wave signals received by each radar main body with local oscillation signals of the radar flow meter, obtaining difference frequency between transmitting frequency f and the received electromagnetic wave signals by using down-conversion signals after mixing, and respectively obtaining orthogonal I/Q data after the difference frequency signals are converted by the analog-to-digital conversion module; fifthly, converting the mutually orthogonal I/Q data from time domain to frequency domain to obtain frequency variation delta f, thereby obtaining by calculation: distance between reflection points of the radar main body to the water surfaceWherein K represents a frequency change slope; sixthly, performing time domain-frequency domain transformation on the data at the same position of the multiple frequency change slope to obtain the target Doppler frequency fdcalculating and obtaining the speed of the reflection point of the water surface moving to the radar main bodyWherein f iszRepresenting the frequency of the local oscillator signal; according to each antenna in the radar main bodyPhase difference between electromagnetic wave signals received between array elementsand calculating a target angle theta of a reflection point of the water surface, wherein lambda represents the working wavelength of the radar main body, and d represents the distance between the antenna array elements to respectively perform analog-to-digital conversion on the electromagnetic wave signals received by the radar main bodies, so as to respectively obtain mutually orthogonal I/Q data corresponding to the radar main bodies.
optionally, in the measurement method of the radar flow meter, the number of the radar main bodies is 1, each radar main body includes a plurality of antenna array elements, and each antenna array element is manufactured by the following steps: step 101, calculating the length of each antenna array element in the radar main bodyEach of the antenna elements has a width ofWherein λ represents an operating wavelength of the radar body,C0indicating the speed of light, frRepresents the operating frequency of the radar body, epsilonrRepresents the dielectric constant of the dielectric plate, d represents the thickness of the dielectric plate; 102, arranging a lead through hole penetrating through the front side surface and the back side surface of the dielectric plate at the center of the dielectric plate; 103, taking the wire via hole as a center, arranging a center feeder on the front side surface of the dielectric slab in parallel to the width direction of the dielectric slab, uniformly and symmetrically arranging a plurality of rows of long feeders in parallel to each other on the front side surface of the dielectric slab in a direction perpendicular to the direction of the center feeder, uniformly arranging the antenna array elements on the front side surface of the dielectric slab along the long feeders, and processing the front side surface of the dielectric slab according to the structure; 104, arranging a metal plate as a metal separator on the back surface attached to the dielectric plate, wherein the metal separator is grounded and at leastReaching the area of the dielectric plate; and 105, a lead penetrates through the lead through hole, one end of the lead is connected with the central feeder line and/or the long feeder line near the lead through hole, and the other end of the lead is led into the signal isolation cover to be connected with the signal processing unit.
Optionally, in the measurement method of the radar flow meter, a gap is further provided between the center of the metal plate and the wire via hole, and the wire passes through the wire via hole and does not electrically contact the metal plate.
optionally, in the measuring method of the radar flow meter, in step 103, in the structure processed on the front side surface of the dielectric slab, positions on the long feeder line close to the antenna array elements and connection positions on the center feeder line close to the long feeder lines, 1/4 impedance transformation structures are respectively provided, each of the 1/4 impedance transformation structures respectively includes at least one step having a length of 1/4 of an operating wavelength λ of the radar main body, the 1/4 impedance transformation structures are provided along the long feeder line or the center feeder line, a width of the step is designed according to a requirement of 100 ohm matching, so that when excitation current distribution is performed on each antenna array element through each 1/4 impedance transformation structure by using a chebyshev polynomial coefficient, radiation intensity of each side lobe in a lobe diagram of the radar main body is within 10dB, and wherein a beam range of the radar body in the water velocity direction is larger than a beam range perpendicular to the water velocity direction
advantageous effects
The invention transmits electromagnetic wave signals to the water surface through the radar main body arranged with a plurality of antenna array elements, receives the electromagnetic wave signals reflected by the water surface, processes the electromagnetic wave signals reflected by the water surface and received by the radar main body by the signal processing unit, and calculates the water flow speed and the water level height according to the transmitted and received electromagnetic wave signals. Therefore, the radar flow meter independently arranged on one side of the water body can be used for simultaneously obtaining the flow speed and the water level of the water body, and compared with the existing mode, the radar flow meter has the characteristics of convenience in installation, small limitation on an installation angle, simple installation structure, lower overall cost and capability of being used in various conventional and unconventional environments.
particularly, in order to accurately obtain electromagnetic wave signals reflected by a water surface and correctly process the signals so as to improve the measurement accuracy, on one hand, the two radar main bodies are arranged, the electromagnetic wave signals are transmitted by one radar main body, the reflected signals are simultaneously received by the two radar main bodies, the reflected signals and local oscillator signals are subjected to down-conversion and then sampled so as to obtain two paths of orthogonal IQ data, and the signal processing unit respectively calculates two paths of relatively independent signals so as to improve the operation accuracy. On the other hand, the invention also provides a signal isolation cover for the signal processing unit arranged at the back of the radar main body, so that the electromagnetic wave signals of the radar main body or external signals are prevented from interfering the normal operation of the signal processing unit.
In the calculation process, the signal processing unit obtains the frequency variation delta f by calculating the electromagnetic wave reflected by the water surface and processing the electromagnetic wave, and calculates the distance L between the radar main body and the reflection point of the water surface according to the relationship of the frequency variationBAComparing the electromagnetic wave reflected from the water surface with the emission frequency to obtain the target Doppler frequency fdand calculating the speed V of the reflection point of the water surface moving to the radar main body (1) according to the speed VBAAnd according to the phase difference between the electromagnetic wave signals received between the antenna elements in the radar main bodyAnd calculating a target angle theta of the reflection point of the water surface. The method has the advantages of simple operation process and high water flow data calculation speed, and can realize accurate measurement through a single radar main body.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic illustration of the measurement mode of the radar flow meter of the present invention;
FIG. 2 is an exploded view of the overall structure of the radar flow meter of the present invention;
FIG. 3 is a schematic diagram of a radar body structure in the radar flow meter of the present invention;
fig. 4 is a schematic diagram of an antenna element and its connection with a long feed line in the radar body of the present invention;
FIG. 5 is a schematic diagram of a portion of a long feed line and corresponding antenna elements to which a center feed line is connected in a radar body of the present invention;
FIG. 6 is a lobe pattern of a radar body structure in the radar flow meter of the present invention;
FIG. 7 is a schematic diagram of the connection between the signal isolation cup and other circuit components in the radar flow meter of the present invention.
In the figure, 1 denotes a radar main body; 2 denotes a long feeder; 21 denotes a center feeder; 22 denotes a wire via; 3 denotes a dielectric plate; 4 represents a metal separator; 5, a mounting fixed seat; 6, supporting rods; 7 denotes a signal processing unit; and 8 denotes a signal isolation cover.
Detailed Description
in order to make the purpose and technical solution of the embodiments of the present invention clearer, the technical solution of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Fig. 1 is a radar flow meter according to the present invention, which is arranged on a pillar at the side of a water body, and comprises:
The radar main body 1 is provided with a plurality of antenna array elements arranged on the front side and used for transmitting electromagnetic wave signals to the water surface and receiving the electromagnetic wave signals reflected by the water surface; a metal partition plate 4 is arranged on the back side of the metal partition plate, and the metal partition plate 4 is grounded to provide a reference level signal;
a signal processing unit 7, which is opposite to the radar main body 1, is arranged on the other side of the metal partition plate 4, is electrically connected with the radar main body 1, and is used for outputting a driving signal to the radar main body 1 according to a set time interval to drive the radar main body 1 to emit an electromagnetic wave signal to the water surface, processing the electromagnetic wave signal reflected by the water surface, and calculating the water flow speed and the water level height according to the emitted and received electromagnetic wave signal;
The signal isolation cover 8 is a metal cover shell matched with the circuit structure of the signal processing unit, the signal isolation cover 8 surrounds the signal processing unit, is arranged on the other side of the metal partition plate 4 relative to the radar main body 1, and isolates electromagnetic wave interference signals outside the signal processing unit; referring to fig. 2 and 7, the edge of the signal isolation cover 8 is connected to a PCB board disposed in the signal processing unit 7 by a bolt, and in order to further reduce interference, a grounded copper wire is further disposed at a position on the PCB board in fig. 7 corresponding to the side wall of the signal isolation cover 8, so that the signal isolation cover 8 obtains a grounded reference level, and interference of external or radar main body 1 signals to each circuit component in the signal processing unit therein can be effectively reduced;
each structure is further fixed to the supporting structure beside the water surface through the mounting fixing seat 5. Here, the support structure for mounting the radar flow meter may be simply provided as a pillar on the water surface side, a tree beside the water surface, or a bridge building on the water surface, or the like. The specific form and the fixed position of the radar main body are not limited as long as the radar main body 1 in the water meter can be adjusted to enable the microwave signal emitted by the radar main body to be directed to the water surface.
In one implementation, referring to fig. 3, the radar main body 1 includes:
The dielectric plate 3 is made of Rogers4350B plates with the thickness of 0.254mm, a lead through hole 22 penetrating through the front side surface and the back side surface of the dielectric plate is formed in the center of the dielectric plate 3, a central feeder 21 is arranged on the front side surface of the dielectric plate 3 in parallel to the width direction of the dielectric plate by taking the lead through hole 22 as the center, and a plurality of long feeders 2 are symmetrically arranged on the front side surface of the dielectric plate 3 perpendicular to the central feeder 21;
A plurality of antenna elements shown in fig. 4 are uniformly arranged on the front side surface of the dielectric plate 3 along the long feeder 2, and the length of each antenna element is equal to that of each antenna elementThe width of each antenna element isWherein λ represents an operating wavelength of the radar main body 1, C0Indicating the speed of light, frRepresents the operating frequency, ∈ of the radar body 1rDenotes the dielectric constant of the dielectric plate 3, d denotes the thickness of the dielectric plate;
and the metal partition plate 4 is attached to the back surface of the dielectric plate 3 and is a grounded metal plate, and a gap is formed in the center of the metal plate for a lead to pass through the lead through hole 22 without contacting with the metal plate.
Referring to fig. 4 and 5, on the dielectric plate, positions of the long feeder lines 2 close to the antenna array elements and connection positions of the center feeder line 21 close to the long feeder lines 2 are further provided with 1/4 impedance transformation structures respectively, each 1/4 impedance transformation structure includes at least one step with a length of 1/4 of an operating wavelength λ of the radar main body 1, the 1/4 impedance transformation structures are arranged along the long feeder lines 2 or the center feeder line 21, and widths of the steps are designed according to a requirement of 100 ohm matching, so that when excitation current distribution is performed on each antenna array element through each 1/4 impedance transformation structure by using a chebyshev polynomial coefficient, radiation intensities of side lobes in a lobe diagram of the radar main body 1 are all within a set range, and a beam range of the radar main body 1 in the water flow velocity direction is larger than that in a direction perpendicular to the water flow velocity direction The beam range of (a).
The radar main body 1 adopts a micro-strip array antenna mode, a structure of one-transmitting and two-receiving is adopted, transmitted electromagnetic waves are transmitted through the river surface and received by two receiving antennas, orthogonal I/Q data are obtained after analog-to-digital sampling, and the flow velocity and water level information of river water are obtained through a signal processing circuit. The same array structure is adopted for transmitting and receiving, the array structure adopts a plurality of antenna array elements to form a multi-row and multi-column array structure, and all the antenna array elements adopt the same structure and size and are connected through feed wires. As shown in the figure, the antenna has an array structure consisting of 4 rows of 14 oscillators, the arrays of each row are parallel to each other, and each array element is arranged at equal intervals. The middle part of the center feeder is a conductor through hole of the antenna, and the array elements and the conductors on the two sides of the center feeder are in a symmetrical structure. The front surface of the dielectric plate is provided with an antenna radiator, the back surface of the dielectric plate is grounded, and the feed power distribution network is further optimized through electromagnetic simulation software on the basis of design, so that the energy distribution of the oscillator achieves a better side lobe suppression effect. The high-frequency material Rogers4350B adopted by the antenna has extremely low dielectric constant and dielectric loss and the performance of small change of electrical performance with frequency, so that the antenna has extremely excellent performance and extremely small loss. The thickness of the copper foil is 1 OZ.
The antenna element shown in FIG. 4 has a frequency of 24G, a dielectric constant of 3.66-3.7 and a plate thickness of 0.254 mm. Wherein the content of the first and second substances,
wherein, C0indicating the speed of light, frRepresents the operating frequency, ∈ of the radar body 1rThe dielectric constant of the dielectric plate 3 is shown, and d is the thickness of the dielectric plate.
after the approximate size of the array element is calculated according to the formula, the antenna is optimized by using electromagnetic simulation software such as HFSS and ADS, and the antenna has better performance when the unit size L is 3.7mm and the unit size W is 2.9 mm.
the oscillator and the feed wire impedance are designed according to 100 ohms, the Chebyshev polynomial coefficient is adopted to distribute exciting current to the array unit, and the current distribution is realized through a 1/4 impedance converter, so that each side lobe of the array antenna can be controlled at the same level, and better side lobe suppression is obtained.
The radar main body 1 composed of the oscillator and the feeder line is manufactured and obtained according to the following steps after the step 101 corresponding to the design and calculation:
102, arranging a lead through hole 22 penetrating through the front side surface and the back side surface of the dielectric plate 3 at the center of the dielectric plate;
103, taking the wire via hole 22 as a center, arranging a center feeder 21 on the front side surface of the dielectric plate 3 in parallel to the width direction of the dielectric plate, uniformly and symmetrically arranging a plurality of rows of long feeders 2 in parallel to each other on the front side surface of the dielectric plate 3 in a direction perpendicular to the direction of the center feeder 21, uniformly arranging the antenna array elements on the front side surface of the dielectric plate 3 along the long feeders 2, and processing the front side surface of the dielectric plate 3 according to the structure;
104, arranging a metal plate as a metal partition plate 4 attached to the back surface of the dielectric plate 3, wherein the metal partition plate 4 is grounded and at least reaches the area of the dielectric plate 3;
And 105, a lead is led through the lead via hole 22, one end of the lead is connected with the central feeder 21 and/or the long feeder 2 near the lead via hole 22, and the other end of the lead is led into the signal isolation cover 8 to be connected with the signal processing unit 7.
A gap is further formed between the central position of the metal plate and the wire through hole 22, and the wire passes through the wire through hole 22 and does not electrically contact with the metal plate.
In the partial structure shown in fig. 5, the structure comprises an array composed of 14 units in the horizontal direction, the left and right structures are symmetrical, and the same array elements and feeder line structures are provided. The antenna array comprises a long feeder line 2, a central feeder line 21 and 1/4 impedance transformation structures, wherein the positions, close to the antenna array elements, on the long feeder line 2 and the connecting positions, close to the long feeder lines 2, on the central feeder line 21 are respectively provided with 1/4 impedance transformation structures, each 1/4 impedance transformation structure respectively comprises at least one step with the length being 1/4 of the working wavelength lambda of a radar main body 1, and the 1/4 impedance transformation structures are arranged along the long feeder line 2 or the central feeder line 21 so that the array elements are matched with the width of the step to realize 100-ohm impedance matching. When current distribution calculation is performed by using Chebyshev polynomial coefficients and then impedance matching and current distribution are performed by using a 1/4 impedance converter, the radiation intensity of each side lobe in the lobe pattern of the whole radar body 1 is within 10dB, and the beam range of the radar body 1 in the water flow velocity direction is larger than that in the direction perpendicular to the water flow velocity direction. Since each of the 7 unit oscillators in the symmetrical structure has a different current division ratio, their equivalent impedance transformers also have different sizes, respectively. The initial values were calculated theoretically and then optimized by HFSS to give the optimum dimensions in the structure shown in FIG. 5, as given in the following table (unit: mm)
TABLE 1 Radar Main body 1 size
| A1 | A2 | A3 | A4 | A5 | A6 | A7 | B1 | B2 | B3 |
| 1.38 | 0.93 | 0.25 | 1.12 | 0.6 | 0.87 | 0.6 | 0.54 | 0.255 | 0.64 |
| B4 | B5 | B6 | B7 | B8 | B9 | B10 | B11 | B12 | B13 |
| 0.44 | 0.53 | 0.3 | 0.43 | 0.19 | 0.34 | 0.1 | 0.34 | 0.1 | 0.19 |
| W | L | ||||||||
| 3.6 | 2.9 |
The lobe parameters of the antenna obtained with this structure are shown with reference to figure 6. At a 24.125G frequency point, the antenna gain is about 25dB, a dotted line is an H-plane directional diagram, the 3dB width of an H plane is about 11 degrees, the first secondary lobe level is about-17 dB, the 3dB width of an E plane is 7 degrees, the first secondary lobe level is about-21 dB, the radiation intensity of each side lobe in the whole lobe diagram of the radar main body 1 is within 10dB, and the design requirement is met.
Therefore, the angle of the radar wave beam is adjusted by the mounting fixing seat 5, and the radar wave beam is supported to be mounted on the bank and can irradiate the area of the river surface. The wave beam of the radar main body 1 is set to be wider up and down along the water flow direction and narrower left and right perpendicular to the water flow direction in the propagation direction, so that the energy of electromagnetic waves can be concentrated in a long and narrow elliptical cone along the water flow direction as much as possible while the application requirements of the system are met, the power of the system can be effectively reduced, and meanwhile, the Doppler frequency shift component in the water flow direction can be easily and accurately obtained. When the system is installed, the surface of the radar is aligned to the upstream or downstream position of the cross section of the river at the current position of the radar, and the radar beam is preferably controlled to fall on the central position of the river surface, so that the radar beam and the river flow direction and the radar beam and the river level have certain included angles, and the system can exert the best performance within the range of 30-60 degrees.
in this implementation, the same radar body 1 transmits an electromagnetic wave signal with frequency f to the water surface, and the radar body 1 simultaneously receives the water surfaceReflected electromagnetic wave signals; the electromagnetic wave signals pass through an analog-to-digital conversion module included in the signal processing unit, the electromagnetic wave signals received by each radar main body 1 and the local oscillator signals of the radar flow meter are subjected to frequency mixing, the difference frequency between the transmitting frequency f and the received electromagnetic wave signals is obtained by taking down-conversion signals after frequency mixing, the difference frequency signals are converted by the analog-to-digital conversion module to respectively obtain orthogonal I/Q data, and the signal processing unit performs time domain to frequency domain conversion on the orthogonal I/Q data to obtain the frequency variation of down-conversion, namely, the frequency difference, Δ f, so that the frequency variation is obtained by calculation: the distance between the radar main body 1 and the reflection point of the water surface in the AB directionWherein K represents a frequency change slope; performing time domain-frequency domain transformation on the data at the same position of the multiple frequency change slope, namely the data at the same sampling position in the continuous multiple emission period, namely the data at the same position (slope ramp) of the multiple frequency change slope curve, to obtain the Doppler frequency of the target and obtain the Doppler frequency f of the targetdor acquiring the frequency corresponding to the data at the same position of the frequency change slope for multiple times, namely the target Doppler frequency; calculating to obtain the moving speed of the reflection point of the water surface to the radar main body 1Wherein f iszRepresenting the frequency of the local oscillator signal; according to the phase difference between the electromagnetic wave signals received between the plurality of antenna elements in the radar main body 1and calculating a target angle theta of a reflection point of the water surface, wherein lambda represents the working wavelength of the radar main body 1, and d represents the distance between the antenna array elements.
The beam of the radar microwave signal is a narrow beam in the horizontal direction perpendicular to the water flow, but a wide beam in the vertical direction of the horizontal plane. For a measured water surface target, it can be consideredThe targets are all distributed on the water surface along the propagation direction of the radar and are distributed along a straight line. The reflected wave of the target is received by a receiving antenna, the data collected by an analog-to-digital converter is subjected to fast Fourier transform to obtain frequency domain data of the target B, and the frequency domain data is passedDetermining the distance L of the target B from the radar AABThe received data between two antenna array elements includes phase information of wave beam propagation, the angle theta of the target relative to the connection line of the radar and the wave beam center can be obtained by carrying out wave beam synthesis on the corresponding data, the installation angle alpha of the radar is the included angle between the radar wave beam center and the vertical direction, the initial installation is determined, the height of the radar relative to the horizontal plane is H in the initial calibration, and when the height of the water surface changes, the current height H 'from the radar to the water surface can be calculated according to the measured distance and angle of the target B'
H′＝LAB·cos(α+θ)
relative change height of water level:
ΔH＝H′-H＝LAB·cos(α+θ)-H
The signal processing unit used in the above calculation process can also perform the calculation of the water flow speed in parallel or backward direction while measuring the water level change. In the calculation process of the water flow velocity, referring to fig. 1, D is the projection of the radar a on the river reference plane, β is the included angle between the projection of the radar center beam on the river surface and the cross section of the river, when the river has a velocity V, the river has a velocity component in the beam propagation direction AB between the radar and the detection target, so that the echo received by the radar has a frequency variation f compared with the transmitted waveformdI.e. the Doppler frequency, according to the amount of change f in the frequencydcalculating the speed V of the river flow in the BA directionBA＝(c0·fdL _ AB)/(f. H. tan (. alpha. + θ). sin. beta.). The component of the river flow velocity V in the BD direction is:
VBD＝V·cos(90°-β)
the component of the river flow velocity in the direction BA is:
VBA＝VBD·cos(90°-α-θ)
The flow rate of the river water can be obtained as follows:
Therefore, the invention can obtain the speed of the water flow simultaneously by the method of oblique measurementAnd height H' ═ L of liquid surfaceABCos (. alpha. + Theta). Wherein the content of the first and second substances,c0Is the speed of light, (alpha + theta) is the angle between the measuring point of the water surface and the height direction of the radar main body 1, beta is the angle between the measuring point of the water surface and the direction vertical to the water flow, fzis the radar local oscillator signal frequency. The invention can be realized by a single radar scheme, other modules are not required to be additionally arranged, the radar is not required to vertically irradiate the horizontal plane, and the direction of water flow is not required to be rightly opposite. The installation is convenient, the angle is arbitrary, simple structure, low cost can be used to various conventional and unconventional environment. The design has no special requirements on installation, has a simple structure, and can be applied to various required application occasions. This design utilizes single radar to realize velocity of flow and water level measurement between them, and the function of two unifications lets the system architecture can be light reasonable more.
The above are merely embodiments of the present invention, which are described in detail and with particularity, and therefore should not be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the spirit of the present invention, and these changes and modifications are within the scope of the present invention.
Claims (9)
1. A radar flow meter, comprising:
The radar device comprises a radar main body (1), a plurality of antenna array elements are arranged on the front side of the radar main body, and the radar main body is used for transmitting electromagnetic wave signals to the water surface and receiving the electromagnetic wave signals reflected by the water surface; a metal partition plate (4) is arranged on the back side of the device, and the metal partition plate (4) is grounded to provide a reference signal;
the signal processing unit (7) is opposite to the radar main body (1), arranged on the other side of the metal partition plate (4), electrically connected with the radar main body (1), and used for outputting a driving signal to the radar main body (1) according to a set time interval to drive the radar main body (1) to emit an electromagnetic wave signal to the water surface, processing the electromagnetic wave signal reflected by the water surface, and calculating the water flow speed and the water level height according to the emitted and received electromagnetic wave signal;
a signal isolation cover (8) which surrounds the signal processing unit, is arranged on the other side of the metal partition plate (4) relative to the radar main body (1), and isolates electromagnetic wave interference signals outside the signal processing unit;
And the mounting fixing seat (5) is connected and fixed on the back side of the radar main body (1) and fixes the radar main body (1), the signal processing unit (7) and the signal isolation cover (8) above the water surface.
2. A radar flow meter according to claim 1, characterised in that the radar body (1) comprises:
The dielectric plate (3) is provided with a lead through hole (22) penetrating through the front side surface and the back side surface at the center, the lead through hole (22) is taken as the center, the front side surface of the dielectric plate (3) is provided with a central feeder line (21) in a direction parallel to the width direction of the dielectric plate, and a plurality of long feeder lines (2) are also symmetrically arranged on the front side surface of the dielectric plate (3) in a manner of being vertical to the central feeder line (21);
The antenna array elements comprise a plurality of antenna array elements which are uniformly arranged on the front side surface of the dielectric plate (3) along the long feeder (2), and the length of each antenna array element is equal to that of each antenna array elementThe width of each antenna element isWherein λ represents an operating wavelength of the radar body (1),Effective dielectric constantC0Indicating the speed of light, frrepresents the operating frequency ∈ of the radar body (1)rRepresents the dielectric constant of the dielectric plate (3), d represents the thickness of the dielectric plate;
And the metal partition plate (4) is attached to the back surface of the dielectric plate (3) and is a grounded metal plate, and a gap is formed in the center of the metal plate for a lead to pass through the lead through hole (22) without contacting with the metal plate.
3. a radar flow meter according to claim 2, wherein the positions of the long feeder lines (2) close to the antenna elements and the connection positions of the center feeder lines (21) close to the long feeder lines (2) are respectively provided with 1/4 impedance transformation structures, each 1/4 impedance transformation structure comprises at least one step with the length of 1/4 of the working wavelength λ of the radar main body (1), the 1/4 impedance transformation structures are arranged along the long feeder lines (2) or the center feeder lines (21), the width of the step is designed according to the requirement of 100 ohm matching, so that when the antenna elements are excited to be distributed by the 1/4 impedance transformation structures by using chebyshev polynomial coefficients, the radiation intensity of each side lobe in the whole lobe diagram of the radar main body (1) is within a set range, and wherein the beam range of the radar body (1) in the water velocity direction is larger than the beam range perpendicular to the water velocity direction.
4. a radar flow meter according to claims 1-3, characterised in that the radar body (1) is made of a sheet material such as Rogers4350B, having a thickness of 0.254mm and a dielectric constant er＝3.66。
5. A radar flow meter according to claims 1-4, characterised in that the number of radar bodies (1) is 1, wherein electromagnetic wave signals with frequency f are transmitted from the same radar body (1) to the water surface, and electromagnetic wave signals reflected from the water surface are received simultaneously by all radar bodies (1);
The signal processing unit comprises an analog-to-digital conversion module, the electromagnetic wave signals received by each radar main body (1) and the local oscillator signals of the radar flow meter are subjected to frequency mixing, the difference frequency between the transmitting frequency f and the received electromagnetic wave signals is obtained by the down-conversion signals after frequency mixing, the difference frequency signals are converted by the analog-to-digital conversion module to respectively obtain mutually orthogonal I/Q data, the signal processing unit performs time domain to frequency domain conversion on the mutually orthogonal I/Q data to obtain frequency variation delta f, and therefore the frequency variation delta f is obtained through calculation: the distance between the radar body (1) and the reflection point of the water surfaceWherein K represents a frequency change slope; carrying out time domain-frequency domain transformation on the data at the same position of the multiple frequency change slope to obtain the target Doppler frequency fdCalculating and obtaining the moving speed of the reflection point of the water surface to the radar main body (1)Wherein f iszRepresenting the frequency of the local oscillator signal; according to the phase difference between the electromagnetic wave signals received between the antenna elements in the radar main body (1)And calculating a target angle theta of a reflection point of the water surface, wherein lambda represents the working wavelength of the radar main body (1), and d represents the distance between the antenna array elements.
6. a measuring method of a radar flow meter, which is used for the radar flow meter according to claims 1 to 5, characterized in that the method comprises the steps of:
The first step is as follows: obtaining an included angle (alpha + theta) between the measuring point of the radar flow meter and the height direction of the radar main body (1), and obtaining an included angle beta between the measuring point of the radar flow meter and the direction vertical to the water flow;
Secondly, driving a radar main body (1) in the radar flow meter to emit an electromagnetic wave signal with the frequency f to the water surface;
Thirdly, controlling all radar main bodies (1) in the radar flow meter to simultaneously receive electromagnetic wave signals reflected by the water surface;
Fourthly, mixing the electromagnetic wave signals received by each radar main body (1) with local oscillation signals of the radar flow meter, taking down-conversion signals after mixing to obtain difference frequency between transmitting frequency f and the received electromagnetic wave signals, and respectively obtaining orthogonal I/Q data after the difference frequency signals are converted by the analog-to-digital conversion module;
Fifthly, converting the mutually orthogonal I/Q data from time domain to frequency domain to obtain frequency variation delta f, thereby obtaining by calculation: the distance between the radar body (1) and the reflection point of the water surfaceWherein K represents a frequency change slope;
Sixthly, acquiring data at the same position of the multiple frequency change slope to perform time domain-frequency domain transformation to acquire target Doppler frequency fdCalculating and obtaining the moving speed of the reflection point of the water surface to the radar main body (1)wherein f iszRepresenting the frequency of the local oscillator signal; according to the phase difference between the electromagnetic wave signals received between the antenna elements in the radar main body (1)Calculating a target angle theta of a reflection point of the water surface, where lambda represents a working wave of the radar body (1)And d represents the distance between the antenna array elements to respectively perform analog-to-digital conversion on the electromagnetic wave signals received by the radar main bodies (1) so as to respectively obtain mutually orthogonal I/Q data corresponding to the radar main bodies (1).
7. the method for measuring a radar flow meter according to claim 6, wherein the number of the radar bodies (1) is 1, and the radar bodies (1) are respectively manufactured by the following steps:
Step 101, calculating the length of each antenna array element in the radar main body (1)Each of the antenna elements has a width ofWherein λ represents an operating wavelength of the radar body (1),C0Indicating the speed of light, frRepresents the operating frequency ∈ of the radar body (1)rRepresents the dielectric constant of the dielectric plate (3), d represents the thickness of the dielectric plate;
102, arranging a lead through hole (22) penetrating through the front side surface and the back side surface of the dielectric plate (3) at the center of the dielectric plate;
103, taking the wire via hole (22) as a center, arranging a center feeder (21) on the front side surface of the dielectric plate (3) in a direction parallel to the width direction of the dielectric plate, uniformly and symmetrically arranging a plurality of rows of long feeders (2) parallel to each other on the front side surface of the dielectric plate (3) in a direction perpendicular to the center feeder (21), uniformly arranging the antenna array elements on the front side surface of the dielectric plate (3) along the long feeders (2), and processing the front side surface of the dielectric plate (3) according to the structure;
104, arranging a metal plate as a metal partition plate (4) attached to the back surface of the dielectric plate (3), wherein the metal partition plate (4) is grounded and at least reaches the area of the dielectric plate (3);
And 105, a lead passes through the lead through hole (22), one end of the lead is connected with the central feeder (21) and/or the long feeder (2) near the lead through hole (22), and the other end of the lead is led into the signal isolation cover (8) to be connected with the signal processing unit (7).
8. The measurement method of the radar water meter according to claims 1 to 7, wherein a gap is further provided between a central position of the metal plate and the wire passing hole (22), and the wire passes through the wire passing hole (22) without electrically contacting the metal plate.
9. The method for measuring a radar flow meter according to claims 1-7, wherein in the step 103, in the structure processed on the front side surface of the dielectric plate (3), 1/4 impedance transformation structures are respectively provided at positions on the long feeder lines (2) close to the antenna array elements and at connecting positions on the center feeder line (21) close to the long feeder lines (2), each 1/4 impedance transformation structure comprises at least one step with a length of 1/4 of the operating wavelength λ of the radar main body (1), the 1/4 impedance transformation structures are arranged along the long feeder lines (2) or the center feeder line (21), the width of the step is designed according to the requirement of 100 ohm matching, so that excitation current distribution is performed on each antenna array element through each 1/4 impedance transformation structure by using Chebyshev polynomial coefficient, the radiation intensity of each side lobe in the lobe pattern of the whole radar body (1) is within 10dB, and the beam range of the radar body (1) along the water flow speed direction is larger than that perpendicular to the water flow speed direction.
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