WO2004068081A1 - Bottom reflector for a radar-based level gauge - Google Patents
Bottom reflector for a radar-based level gauge Download PDFInfo
- Publication number
- WO2004068081A1 WO2004068081A1 PCT/SE2004/000110 SE2004000110W WO2004068081A1 WO 2004068081 A1 WO2004068081 A1 WO 2004068081A1 SE 2004000110 W SE2004000110 W SE 2004000110W WO 2004068081 A1 WO2004068081 A1 WO 2004068081A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- bottom reflector
- microwave signal
- reflector
- liquid
- tank
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/14—Reflecting surfaces; Equivalent structures
- H01Q15/22—Reflecting surfaces; Equivalent structures functioning also as polarisation filter
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
- H01Q15/0026—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective said selective devices having a stacked geometry or having multiple layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/006—Selective devices having photonic band gap materials or materials of which the material properties are frequency dependent, e.g. perforated substrates, high-impedance surfaces
- H01Q15/008—Selective devices having photonic band gap materials or materials of which the material properties are frequency dependent, e.g. perforated substrates, high-impedance surfaces said selective devices having Sievenpipers' mushroom elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/14—Reflecting surfaces; Equivalent structures
Definitions
- the first and second reflection coefficients are advantageously so-called in-polarization reflection coefficients.
- in-polarization reflection coefficient is meant the ratio of the microwave signal (i.e. amplitude thereof) in a specified polarization state as reflected at the surface of the bottom reflector and the incident microwave signal (i.e. the amplitude thereof), where the specified polarization state is given by the polarization of the microwave signal as reflected at the surface of the fluid.
- a structure 16 which can be an inclined plate, a conical surface, a piece of radar absorbing material etc.
- a bottom reflector comprising a grid structure arranged within the pipe 13.
- the pipe 13 is in this case arranged to support a microwave propagating in the H mode with the direction of the electric field essentially as indicated by arrow 22.
- the grid structure consists of a plurality of conductive preferably metallic ribbons 23 with a separation slightly below ⁇ /2 causing the propagating to be cut-off when the liquid level is below the grid structure .
- the spacing may be 14 mm and the ribbons 23 may have a height of 28 mm, which thus corresponds to a distance of ⁇ m /2 in the waveguide formed by the ribbons, where ⁇ m is the wavelength of the microwave signal in the liquid (i.e.
- the microwaves as transmitted through the bottom reflector may be deflected or absorbed.
- Fig. 2d is illustrated a 45° degree metal reflector 27 mounted below a bottom reflector 15 in the pipe 13.
- the reflector is by means of a support structure 28 attached to the pipe 13 or to the bottom of the tank (not illustrated) .
- deflector Depending on the shape of the tank a similar deflection reflector (here named deflector) may be used with all bottom reflector embodiments of the present invention.
- the angle can be very different from 45° and obstacles of very different shape can also be used to spread out the radar wave to prevent it from entering the pipe 13 again.
- a conical part attached to the bottom or to the pipe is another usable deflector embodiment. Such part is indicated by reference numeral 16 in Fig. 1.
- a suitably shaped member 29 of attenuating material such as e.g. a member of carbon filled PTFE, arranged at the bottom of the tank below the bottom reflector 15 in the pipe 13 to obtain a low reflection at the bottom.
- the member 29 is shown by dashed lines to indicate that the actual shape may be very different from the box-like shape as illustrated.
- the member may be shaped as a standard anechoic absorber.
- Fig. 2e shows the bottom reflector 15 mounted in the pipe 13
- the bottom reflector may alternatively be integrated with the deflecting or absorbing member 29.
- Such bottom reflector design will give a true reflection from the bottom of the tank, rather than from a lower portion of the pipe 13.
- Some of the bottom reflectors described here are quite small (one or two ⁇ /2 dipoles), which obviously will make such integration simple and straightforward.
- Figs. 3a-e illustrate various bottom reflectors based on the principle of resonant structures .
- Each bottom reflector comprises a resonant structure including e.g. a number of dipoles tuned to be resonant in dry condition to give a distinct reflex when the tank is empty. As the resonant structure is immersed in the liquid the dipoles are tuned out of resonance and the reflection decreases considerably.
- a bottom reflector comprising two stacked dipoles 32.
- the two dipoles 32 are tuned to give maximum reflection approximately when the dielectric constant of the surrounding medium is very close to 1 (i.e. air or gas) while the vertical distance between them is chosen to be close to a quarter of a wavelength ( ⁇ m /4) in a typical liquid, which may have a dielectric constant of 2.1.
- the dipoles 32 are attached to a vertical support pin 33, which may be of metal or a dielectric. If the vertical support pin 33 is of metal the complete structure 32, 33 can be stamped out of the same piece of plate (as being indicated in Fig. 3a).
- the structure 32, 33 is attached to some support 34 on or above the bottom.
- the dipole length may typically be slightly below 14-15 mm at 10 GHz.
- Fig. 3b a bottom reflector including an element with dual crossed dipoles 32, 35 to achieve a polarisation independent function. Except of the dipoles 32 indicated in Fig. 3a, two crossed dipoles of the same length 35 are provided. The crossed dipoles are preferably not connected and Fig. 2c indicates a mounting on a dielectric pin 33.
- the transversal electrical field is low in the middle.
- This case can be covered by using a number of resonant structures, typically like the one shown in Fig. 3a.
- Fig. 3d is shown such embodiment in the pipe 13. With two to four resonant structures located according to the field pattern of the mode of the microwave signal, a mode specific reflection can be obtained.
- the Fig. 3d embodiment is particularly suitable for use with a microwave signal in H 01 propagation mode.
- Another manner of obtaining the resonant structure for the H 01 mode is to locate a ring 37 in the middle of the pip 13 like the arrangement in Fig. 3e.
- the ring 37 has a resonance when it under dry conditions is one wavelength in circumference (or an integer number of wavelengths ) .
- This embodiment is applicable also for microwaves propagating in other modes than H 01 .
- the ring shape will for instance make the reflection polarisation independent and may be used as an alternative to the crossed dipole embodiment.
- this dipole combination gives a reflection similar to an oil surface in dry condition and a considerably lower under immersed condition. More than two dipoles can be stacked to give a more wideband suppression of the radar echo in immersed condition and other resonant structures than dipoles can be used.
- Figs. 4a-b illustrate various bottom reflectors based on a principle related to dielectric radar radomes .
- Another suitable geometry to achieve a similar inho ogeneous behaviour is a plate made of horizontally arranged dielectric bars or pins .
- Fig. 4c is a reflection diagram for partially filled dielectric plate, i.e. the plate illustrated in Fig. 4a, over a typical frequency range.
- the dielectric plate is in this example a PTFE plate perforated to 50%, i.e. half the volume is PTFE and half is empty.
- the average dielectric constant is the average of that of PTFE and air (gas) and under immersed conditions the average dielectric constant is the average of that of PTFE and the liquid.
- immersed condition the thickness is very close ⁇ ra /2 in the middle of the band reducing the reflection considerable but under dry conditions a certain reflection is desired which is achieved as the effective electrical thickness deviate significantly from ⁇ m /2.
- portions of the dielectric material can be made of attenuating material (such as carbon loaded PTFE), which makes both the reflection and transmission lower.
- Figs. 5a-c illustrate various bottom reflectors based on the principle of polarization turning structures.
- Figs. 5a-b is shown a reflector known as twist reflector in antenna engineering, see The handbook of antenna design , Volumes 1 and 2, editors A.W. Rudge et al., Peter Peregrinus Ltd, 1986, pages 184-185, and Antenna Engineering Handbook, Third edition, editor R.C. Johnson, McGraw-Hill, Inc., 1993, pages 17-28 — 17-29, the text passages of which being hereby incorporated by reference.
- the incoming field can be thought of as a superposition of two fields directed -45° and +45° as compared to the field lines 53.
- One of this fields is parallel to the ridges 52 and will be reflected from the top of the ridges 52 and the other polarisation will approximate not be influenced by the ridges 52, but will be reflected from the reflector structure as exposed between the ridges 52.
- Due to the height of the ridges 52 of ⁇ m /4, a relative phase shift of 2x90° 180° will be introduced, which in turn will twist the electric field 54 of the reflected microwaves 90° relative to the electric field 53 of the incoming microwaves. This behaviour is similar to the function of the standard twist reflector in antenna engineering.
- the dielectric constant of the material filling the space between the ridges will be different depending on weather it is liquid or air/gas. Once the tank is empty the twist function will be only partial and it will be possible to obtain reflections from the reflector 51.
- the reflector is very thin, and may thus be arranged very close to the bottom of the tank allowing level gauging to be performed closer to the bottom.
- the microwave signal as used in the level gauging in the above identified embodiment 5 has a specified polarization state and that the first and second reflection coefficients as described above and as found in the appended patent claims are given for that specified polarization state.
- the effect of rotating the polarization of a linearly polarized microwave signal at 0 reflection in the liquid is equivalent to decreasing the reflection coefficient for the microwave signal in its specified polarization state.
- _5 directed dipoles 55. Further, the dipoles 55 in Fig. 5c are single and not stacked.
- a suitable design of the reflector of Fig. 5c provides for a very small reflection in the incoming waveguide mode when the reflector is immersed in the liquid, and substantially stronger reflection in the incoming waveguide mode when the reflector is in air or gas .
- the reflection in the incoming waveguide mode may be very strong, i.e. nearly total reflection, (if the plate 55 is of metal) or may be comparable to a reflection from an oil surface (if the plate 55 is of a suitable attenuating material).
- attenuation material can be included in anyone of the polarisation turning embodiments to adjust the reflection in dry condition.
- the waveguide portion 64 can easily be designed to give a low reflection as long as the waveguide is filled with liquid of fairly well known properties (including a range of hydrocarbons).
- the distance from the tank bottom 60 and the end of the pipe 13 can be made very short.
- the funnel 61 and waveguide can be attached to the tank bottom 60 or to the pipe 13.
- the waveguide 62 is narrow to restrict propagation to one mode when the waveguide 62 is immersed in the liquid, the propagation will be cut-off in dry condition and the empty tank will have a reflection at the bottom of the funnel 61.
- the radar level gauge 11 is mounted at the top of the tank 12 with a main direction 77 of the antenna beam 76, which is close to vertical to be capable of receiving the reflex from the liquid surface 71.
- the dotted lines 76 indicate the width of the antenna beam.
- a bottom reflector 72 is mounted close to the bottom on support members 73.
- the bottom reflector 72 can be similar to Fig. 2a but it has to be much larger.
- An approximate area of ⁇ * [ square root(h ⁇ )] 2 /4 is active in the reflection, where h is the distance from the level gauge 11 to the bottom reflector 72, so the bottom reflector should have an area covering at least an essential portion of the active reflection area.
- the bottom reflector 72 has a structure like the one in Fig. 2a it will not accumulate any water or sludge, which is advantageous.
- the bottom reflector 72 may have a smaller size. If the phase shift of the transmission through the bottom reflector 72 is controlled so that the portion of the bottom or water reflection passing through the bottom reflector 72 will cancel the portion of the reflection going outside of the bottom reflector 72.
- the support pins 73 should be as low as possible with regard to the expected water level. It shall be appreciated by the man skilled in the art that the principles of bottom reflection as described with reference to Figs. 2-5 also are applicable for a level gauge, which is arranged for transmission and • reception of microwaves, which are not guided by any pipe .
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2005518787A JP4130459B2 (en) | 2003-01-29 | 2004-01-28 | Bottom reflector for radar level gauge |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/353,836 | 2003-01-29 | ||
SE0300222-7 | 2003-01-29 | ||
SE0300222A SE0300222D0 (en) | 2003-01-29 | 2003-01-29 | Bottom reflector for a radar-based level gauge |
US10/353,836 US6795015B2 (en) | 2003-01-29 | 2003-01-29 | Bottom reflector for a radar-based level gauge |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/223,355 Continuation-In-Part US20060064721A1 (en) | 2004-03-10 | 2005-09-09 | Method and apparatus for implementing a synchronized electronic program guide application |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2004068081A1 true WO2004068081A1 (en) | 2004-08-12 |
Family
ID=32829156
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE2004/000110 WO2004068081A1 (en) | 2003-01-29 | 2004-01-28 | Bottom reflector for a radar-based level gauge |
Country Status (3)
Country | Link |
---|---|
JP (1) | JP4130459B2 (en) |
KR (1) | KR100724682B1 (en) |
WO (1) | WO2004068081A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2005031284A2 (en) * | 2003-09-23 | 2005-04-07 | Endress+Hauser Gmbh+Co. Kg | Arrangement for measuring the filling level in a tank equipped with a sounding pipe |
NO20100519A1 (en) * | 2010-04-12 | 2011-10-13 | Kongsberg Maritime As | Method and apparatus for measuring the density of a liquid |
WO2012004122A1 (en) * | 2010-07-09 | 2012-01-12 | Rosemount Tank Radar Ab | Radar level gauge system with bottom reflector and bottom reflector |
EP3014254A4 (en) * | 2013-06-28 | 2017-05-17 | Sensors & Software Inc. | System and method for measurement of material property using variable reflector |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
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NO323548B1 (en) * | 2005-10-28 | 2007-06-11 | Kongsberg Maritime As | Niva Templates |
DE102008027969B4 (en) * | 2008-06-12 | 2017-11-02 | Hella Kgaa Hueck & Co. | Device for detecting a level with a damping cup |
EP2796902B1 (en) * | 2013-04-23 | 2017-06-14 | Spinner GmbH | Millimeter Wave Scanning Imaging System |
CN103398756A (en) * | 2013-08-13 | 2013-11-20 | 中钢集团马鞍山矿山研究院有限公司 | Real-time online detecting device of liquid level of storage tank in emulsion explosive production |
JP5932746B2 (en) * | 2013-09-25 | 2016-06-08 | ムサシノ機器株式会社 | Media boundary position measurement system |
US9506796B2 (en) * | 2014-10-10 | 2016-11-29 | Rosemount Tank Radar Ab | FMCW based guided wave radar level gauge |
US10234321B2 (en) * | 2016-07-07 | 2019-03-19 | Rosemount Tank Radar Ab | Radar level gauge system with single propagation mode feed-through |
JP6822388B2 (en) * | 2017-12-12 | 2021-01-27 | 日本製鉄株式会社 | Level measuring device |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1123939A (en) * | 1965-12-15 | 1968-08-14 | Commissariat Energie Atomique | Ultrasonic apparatus for measuring the position of a liquid level |
US4805453A (en) * | 1982-10-14 | 1989-02-21 | Gilbarco, Inc. | Tank sonic gauging system and methods |
US4847623A (en) * | 1986-02-19 | 1989-07-11 | Idea, Inc. | Radar tank gauge |
US5969666A (en) * | 1997-06-06 | 1999-10-19 | Endress + Hauser GmbH +Co. | Radar-based method of measuring the level of a material in a container |
WO2001029523A1 (en) * | 1999-10-21 | 2001-04-26 | Saab Marine Electronics Ab | Apparatus for measuring the level in a container |
-
2004
- 2004-01-28 WO PCT/SE2004/000110 patent/WO2004068081A1/en active Application Filing
- 2004-01-28 KR KR1020057014010A patent/KR100724682B1/en active IP Right Grant
- 2004-01-28 JP JP2005518787A patent/JP4130459B2/en not_active Expired - Fee Related
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1123939A (en) * | 1965-12-15 | 1968-08-14 | Commissariat Energie Atomique | Ultrasonic apparatus for measuring the position of a liquid level |
US4805453A (en) * | 1982-10-14 | 1989-02-21 | Gilbarco, Inc. | Tank sonic gauging system and methods |
US4847623A (en) * | 1986-02-19 | 1989-07-11 | Idea, Inc. | Radar tank gauge |
US5969666A (en) * | 1997-06-06 | 1999-10-19 | Endress + Hauser GmbH +Co. | Radar-based method of measuring the level of a material in a container |
WO2001029523A1 (en) * | 1999-10-21 | 2001-04-26 | Saab Marine Electronics Ab | Apparatus for measuring the level in a container |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2005031284A2 (en) * | 2003-09-23 | 2005-04-07 | Endress+Hauser Gmbh+Co. Kg | Arrangement for measuring the filling level in a tank equipped with a sounding pipe |
WO2005031284A3 (en) * | 2003-09-23 | 2005-06-23 | Endress & Hauser Gmbh & Co Kg | Arrangement for measuring the filling level in a tank equipped with a sounding pipe |
NO20100519A1 (en) * | 2010-04-12 | 2011-10-13 | Kongsberg Maritime As | Method and apparatus for measuring the density of a liquid |
NO331262B1 (en) * | 2010-04-12 | 2011-11-14 | Kongsberg Maritime As | Method and apparatus for measuring the density of a liquid |
WO2012004122A1 (en) * | 2010-07-09 | 2012-01-12 | Rosemount Tank Radar Ab | Radar level gauge system with bottom reflector and bottom reflector |
US8350752B2 (en) | 2010-07-09 | 2013-01-08 | Rosemount Tank Radar Ab | Radar level gauge system with bottom reflector and bottom reflector |
EP3014254A4 (en) * | 2013-06-28 | 2017-05-17 | Sensors & Software Inc. | System and method for measurement of material property using variable reflector |
US10247680B2 (en) | 2013-06-28 | 2019-04-02 | Sensors & Software Inc. | System and method for measurement of material property using variable reflector |
US10527560B2 (en) | 2013-06-28 | 2020-01-07 | Sensors & Software Inc. | System and method for measurement of material property using variable reflector |
Also Published As
Publication number | Publication date |
---|---|
JP4130459B2 (en) | 2008-08-06 |
KR20050090466A (en) | 2005-09-13 |
KR100724682B1 (en) | 2007-06-04 |
JP2006515068A (en) | 2006-05-18 |
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