Classifications

• • 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
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q1/00—Details of selecting apparatus or arrangements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P5/00—Coupling devices of the waveguide type
  • H01P5/08—Coupling devices of the waveguide type for linking dissimilar lines or devices
  • H01P5/10—Coupling devices of the waveguide type for linking dissimilar lines or devices for coupling balanced lines or devices with unbalanced lines or devices
  • H01P5/103—Hollow-waveguide/coaxial-line transitions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
  • H01Q19/06—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using refracting or diffracting devices, e.g. lens
  • H01Q19/08—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using refracting or diffracting devices, e.g. lens for modifying the radiation pattern of a radiating horn in which it is located

Definitions

• the invention relates to a device for transmitting high-frequency signals with a signal generation unit, a signal line, a radiating element and a waveguide, which is closed in an end region by a rear wall, the signal generating unit generating the high-frequency signals, the signal line transmitting the high-frequency signals to the radiating end Guide element of the waveguide, and wherein the radiating element protrudes into the waveguide.
• a device of the type described above is used, for example, in measuring devices which determine the filling level of a filling material in a container over the running time of high-frequency measuring signals.
• Runtime procedures take advantage of the physical law, according to which the running distance is equal to the product of the running time and the speed of propagation.
• the running distance corresponds to twice the distance between the antenna and the surface of the product.
• the useful echo signal i.e. the signal reflected on the surface of the filling material, and its transit time are determined on the basis of the so-called echo function or on the basis of the digitized envelope curve, the envelope curve representing the amplitudes of the echo signals as a function of the distance 'antenna - surface of the filling material'.
• the level itself then results from the difference between the known distance of the antenna from the bottom of the container and the distance of the surface of the medium to the antenna determined by the measurement.
• Usual methods for determining the distance over the transit time of electromagnetic signals are the pulse radar method and the frequency modulation continuous wave radar method (FMCW method).
• pulse radar method short microwave pulses are sent periodically.
• FMCW method a continuous microwave is transmitted, which is periodically linearly frequency-modulated, for example according to a sawtooth function.
• the frequency of the received echo signal has a frequency difference compared to the frequency that the transmission signal has at the time of reception, which depends on the transit time of the echo signal.
• the frequency difference between the transmitted signal and the received signal which can be obtained by mixing both signals and evaluating the Fourier spectrum of the mixed signal, thus corresponds to the distance of the reflector, for example the surface of the filling material, from the antenna.
• the amplitudes of the spectral lines of the frequency spectrum obtained by Fourier transformation correspond to the echo amplitudes, so that the Fourier spectrum represents the echo function.
• the propagation of the high-frequency measurement signals follows the physical laws of the propagation of electromagnetic waves in the signal line and in the waveguide.
• the signal line is usually a coax line.
• the high-frequency measurement signals are conducted from the inner conductor of the coaxial cable to the radiating element of the waveguide via a coupling.
• the waveguide is designed either as a rectangular waveguide or as a round waveguide, antennas with a circular cross section preferably being used in the area of the fill level measurement, since they are used for installation in e.g. B. the neck of a container (tank, silo, etc.) are more suitable than waveguides with a rectangular cross-section.
• the transverse electromagnetic mode In a coaxial line, the transverse electromagnetic mode (TEM mode) ideally spreads without dispersion. This TEM mode is therefore particularly well suited for the transport of wave packets or electromagnetic waves that have a certain bandwidth. Wave packets that spread in TEM mode are therefore not widened; a linearity deviation is largely avoided in the case of linear frequency-modulated microwaves.
• a mode is preferably used for the directed transmission of electromagnetic waves by means of an antenna, the radiation characteristics of which have a pronounced forward lobe.
• This is the characteristic of the transverse-electrical basic mode, TE U - mode, which can be propagated in circular waveguides.
• the corresponding basic mode is the JE ] () mode.
• the range of ambiguity for a rectangular waveguide that is, the range in which only the basic mode can propagate
• the range of ambiguity for a circular waveguide is relatively narrow.
• the probability that undesired higher modes are excited in addition to the basic mode when broadband signals are coupled in is therefore much greater in the case of a round waveguide than in the case of a rectangular waveguide.
• An undesirable consequence of the formation of different modes is the so-called ringing.
• the ringing is caused by the fact that the individual modes that can propagate in a waveguide have different propagation speeds. This is shown by the fact that the transmit pulse does not drop abruptly, but slowly loses amplitude. This ringing edge can cover the echo signal in the measuring range or overlap with the echo signal in such a way that relatively large errors can occur when determining the measured value.
• the invention is based on the object of proposing a device for emitting high-frequency measurement signals, which is characterized by an optimized radiation characteristic.
• the radiating element is arranged at an angle to the rear wall of the waveguide or to a plane of the waveguide parallel to the rear wall.
• the radiating element that is to say the excitation pin, must be arranged parallel to the rear wall of the waveguide.
• the radiating element is guided through the rear wall of the waveguide.
• An alternative embodiment of the device according to the invention provides that the radiating element is guided through the side wall of the waveguide.
• the amount of the angle between the radiating element and the rear wall of the waveguide or a plane parallel to the rear wall is greater than 4 °.
• the radiating element can be, for example, a transmission wire.
• a transmission mushroom is preferably arranged in the region of the free end of the transmission wire.
• a conductor structure which is arranged on a circuit board can be used as the radiating element, the radiating structure being arranged on the circuit board at an angle to the rear wall of the waveguide or to a plane parallel to the rear wall of the waveguide.
• the waveguide leads to a horn, rod or parabolic antenna.
• the radiation characteristic of the device can be further optimized.
• an advantageous embodiment of the device according to the invention provides that a dielectric material at least fills the interior of the waveguide in the area of the transmission wire.
• a recess be provided in the dielectric material into which the transmission wire protrudes.
• the dielectric material is, for example, polytetrafluoroethylene (PTFE) or aluminum trioxide (Al 2 0 3 ).
• the device according to the invention is preferably part of a fill level measuring device.
• the use of the device according to the invention is by no means restricted to this use.
• the device can be used in any devices that work with high-frequency measurement signals.
• the device 1 shows a schematic representation of the device 1 according to the invention, which is integrated in a rod antenna 15.
• the device 1 according to the invention consists of the signal generating unit 2, the signal line 3 and the radiating element 4, which is arranged in the waveguide 5, here a circular waveguide.
• the radiating element 4 is a transmission wire.
• the radiating element 4 does not run parallel to the rear wall 6 of the waveguide 5 or to a plane parallel to the rear wall 6 of the waveguide 5, but is arranged at a certain angle to the rear wall 6 or to the plane parallel to the rear wall 6.
• High-frequency measurement signals are generated in the signal generation unit 2 and coupled to the radiating element 4 via the signal line 3, which is usually a coaxial cable.
• the rod antenna 15, via which the high-frequency measurement signals are emitted or via which the reflected echo signals are received, consists of a circular waveguide 5 in the case shown.
• An end region of the rod-shaped dielectric material 18 is positioned in the interior of the circular waveguide 5.
• an opening 7 is provided, in which the bushing 9 is locked. via which the measurement signals are routed from the signal line 3 to the radiating element 4.
• the radiating element 4 is arranged in a corresponding recess 14 in the rod-shaped dielectric material 18.
• FIG. 2 shows a schematic representation of the device 1 according to the invention, which is integrated in a horn antenna 16. While the radiation characteristic in the rod antenna 15 shown in FIG. 1 is optimized by the rod-shaped dielectric material 18, the optimization in the horn antenna 15 is supported by the horn-shaped element 11, which adjoins the free end of the waveguide 5 in the radiation direction. The dielectric material 10 placed in the waveguide 5 is also used to improve the directional characteristic of the horn antenna 16 and is also taped in the radiation direction.
• FIG. 3 shows a schematic illustration of a fill level measuring device 29 according to the invention, which is fastened in an opening 24 of the cover 22 of a container 21.
• the fill level measuring device 29 is a horn antenna 16, in which the device 1 according to the invention is used.
• high-frequency measurement signals generated by the transmission unit 25 are emitted in the direction of the surface of the filling material 23 via the horn antenna 16.
• the echo signals reflected on the surface of the filling material 23 are detected by the receiving unit 26.
• the control / evaluation unit determines the filling level of the filling material 23 in the container 21 on the basis of the difference in transit time between the measurement signals and the echo signals.

Landscapes

• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• General Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Fluid Mechanics (AREA)
• Computer Networks & Wireless Communication (AREA)
• Engineering & Computer Science (AREA)
• Waveguide Aerials (AREA)
• Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
• Aerials With Secondary Devices (AREA)
• Waveguide Switches, Polarizers, And Phase Shifters (AREA)
• Luminescent Compositions (AREA)
• Nuclear Medicine (AREA)
• Investigating Or Analysing Biological Materials (AREA)
• Transmitters (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2000
  • 2000-12-22 DE DE10064812A patent/DE10064812A1/de not_active Withdrawn
• 2001
  • 2001-07-16 US US09/905,183 patent/US6549174B2/en not_active Expired - Fee Related
  • 2001-11-17 KR KR1020037008355A patent/KR100584058B1/ko not_active IP Right Cessation
  • 2001-11-17 CN CNB018211291A patent/CN100432637C/zh not_active Expired - Fee Related
  • 2001-11-17 EA EA200300721A patent/EA005259B1/ru not_active IP Right Cessation
  • 2001-11-17 WO PCT/EP2001/013301 patent/WO2002052888A2/de active IP Right Grant
  • 2001-11-17 AU AU2002218303A patent/AU2002218303A1/en not_active Abandoned
  • 2001-11-17 EP EP01271983A patent/EP1377801A2/de not_active Ceased
  • 2001-11-17 CA CA002432692A patent/CA2432692A1/en not_active Abandoned
  • 2001-11-17 JP JP2002553860A patent/JP2004535693A/ja active Pending

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