EP3631492A1 - Hochfrequenz-erzeugungseinheit - Google Patents
Hochfrequenz-erzeugungseinheitInfo
- Publication number
- EP3631492A1 EP3631492A1 EP18717034.5A EP18717034A EP3631492A1 EP 3631492 A1 EP3631492 A1 EP 3631492A1 EP 18717034 A EP18717034 A EP 18717034A EP 3631492 A1 EP3631492 A1 EP 3631492A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- frequency
- signal
- digital
- clock
- shf
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- 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
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/03—Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
- G01S7/032—Constructional details for solid-state radar subsystems
-
- 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
-
- 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
Definitions
- the invention relates to a high-frequency generating unit for an FMCW radar-based level gauge.
- sensors are used, for example, in level gauges, flowmeters, pressure and temperature measuring devices, pH redox potential measuring devices or
- Conductivity meters are used. They record the corresponding process variables, such as level, flow, pressure, temperature, pH value, redox potential or conductivity in the respective process plant. For influencing
- Process variables are actuators, such as valves or pumps that allow the flow rate of a fluid in a conduit section or the level in a reservoir to be changed.
- actuators such as valves or pumps that allow the flow rate of a fluid in a conduit section or the level in a reservoir to be changed.
- a large number of these field devices are manufactured and sold by Endress + Hauser.
- FMCW Frequency Modulated Continuous Wave
- radar also known as continuous wave radar
- high frequency and radar refer to signals or Electromagnetic waves with frequencies between 0.3 GHz and 300 GHz.
- FMCW-based distance or velocity measurement there are already technically mature solutions for frequencies up to approximately 79 GHz for generating a high-frequency electrical signal by means of corresponding high-frequency generating units
- a transmission / reception antenna whereby the resulting microwave-based transmission signal is generated and radiated, Accordingly, the frequency of the transmission signal is determined by the high-frequency generating unit.
- Suitable high-frequency generating units for generating high-frequency signals for FMCW radar are already known.
- a typical high-frequency generation unit according to the prior art is shown:
- Core of the local high-frequency generating unit is a voltage-controlled high-frequency oscillator (this is usually a VCO, ie a "Voltage Controlled Oscillator” used), which generates a corresponding high-frequency signal whose frequency is variable by the control voltage typical
- VCO Voltage Controlled Oscillator
- Sawtooth-shaped frequency change of the electrical high-frequency signal is impressed by the fact that the oscillator via a feedback circuit, also known as “phase locked loop” or PLL ("Phase Locked Loop”), regulated.
- PLL Phase Locked Loop
- the feedback is realized by the high frequency signal of the
- a control signal is diverted. This is supplied to a phase comparator, which compares the instantaneous phase position with that of a frequency-constant clock signal.
- the frequency of the clock signal is in the range of preferably 10 MHz to 100 MHz and can be generated by means of a corresponding quartz oscillator.
- the phase comparator controls the VCO via an analog DC signal, wherein the voltage value of the DC signal depends on the instantaneous phase position at the inputs of the phase comparator. As the name implies, the frequency of the VCO depends on the voltage at its input.
- Sensitivity with which small or poorly reflecting measurement objects can be detected, especially at long distances, drastically decreases.
- the invention is therefore based on the object, a simple and robust
- a high-frequency generating unit for an FMCW radar-based fill level measuring device which comprises at least the following components: A clock unit configured to generate a clock signal having a predetermined clock frequency;
- a digital switching device clocked by the clock signal (for example as an arbitrary generator or a circuit operating according to direct digital synthesis) which is designed to generate a digital output signal, ie discrete-time and / or discrete-value signal;
- a digital / analogue converter which converts the digital output signal of the digital switching device into an analogue high frequency signal.
- Rear derailleur so that the digital output signal with a variable frequency, in particular a within a predetermined frequency band linearly changing frequency, is generated.
- the digital switching mechanism is preferably designed so that the frequency of the output signal is at most half as high as the clock frequency of
- the digital switching mechanism is also preferably designed so that it generates the digital output signal with a frequency (or in a frequency band) at least 1 GHz, in particular 6 GHz. Even applications at 26 GHz or even 79 GHz, which represent further typical areas for radar-based level measurement, would be conceivable.
- the digital / analogue converter is to be adapted to the digital output signal of the digital switching mechanism (in particular its level and pulse width or frequency range). On the output side, the digital / analog converter is dependent on the further processing of the high-frequency signal in
- the digital / analog converter shall be designed to produce the analog high frequency signal either as a current-based signal or as a voltage-based signal ,
- the high-frequency generating unit additionally comprises a filter which is designed to handle the
- the filter (which is preferably designed as a low-pass or bandpass) at least for the frequency of
- Output signal permeable In particular, if the frequency of the output signal is at most half as high as the clock frequency of the clock signal, the use of a low-pass filter is necessary to smooth the discrete-time output signal of the digital / analog converter.
- a very compact design of the high-frequency generating unit according to the invention can be achieved if at least the clock unit, the digital switching mechanism and the digital / analog converter are constructed in the form of an integrated monolithic circuit.
- the integrated circuit also comprises the clock unit, there is a particularly favorable embodiment variant in that the clock unit is realized as an acoustic surface resonator.
- the reference source it is preferable for the reference source to have a reference frequency which is equal to or corresponds to an integer divisor of the clock frequency.
- an FMCW radar-based level measuring device which is used to measure a level of a filling material located in a container, has
- a high-frequency generation unit according to one of the previously described embodiments,
- a transmitting / receiving antenna which emits the analog high frequency signal as an electromagnetic transmission signal in the direction of the contents and / or the reflected signal after reflection on the surface of the contents receives (a separate transmitting and receiving antenna would also be used), a Control / evaluation unit, which determines the level according to the FMCW method by means of the measured frequency difference between the electromagnetic transmission signal and the reflected signal.
- FIG. 1 shows a general representation of an FMCW radar-based level gauge on a container
- Fig. 2 a characteristic of FMCW radar frequency characteristic of the electrical
- Fig. 3 a high-frequency generation unit for FMCW radar according to the prior art
- FIG. 4 shows a high-frequency generation unit according to the invention.
- FIG. 1 shows a typical arrangement of a fill level measuring device 1 operating according to the FMCW radar principle on a container 2.
- a filling material 3 the level of which L is to be determined by the level gauge 1.
- L the level of which L is to be determined by the level gauge 1.
- Level gauge 1 via an internal control evaluation unit 15 and a
- a corresponding bus system such as "PROFIBUS", "HART” or “Wireless HART” is connected to a higher-level unit 4, for example a process control system, which can be used to communicate information about the operating state of the fill level measuring device 1.
- Information about the fill level L can also be communicated be transmitted to optionally control on the container 2 existing inflows and / or outflows.
- the level gauge 1 is mounted in a known installation height h above the filling material 3 on the container 2.
- the container 2 depending on the application can be up to more than 30 m high.
- the level gauge 1 is arranged on the container 2 so that it emits an electromagnetic transmission signal SHF in the direction of the surface of the filling material 3. After reflection at the Gregut- surface receives the level gauge 1, the reflected signal EHF in
- the difference frequency ie the difference between the instantaneous frequency IHF of the transmission signal SHF and the frequency of the reflected signal EHF currently received by the level measuring device 1
- the difference frequency changes linearly with the distance d to the product surface
- the transmission signal SHF not at a constant frequency fHF but at a frequency fHF that varies with time within a fixed frequency band Af.
- Common frequency bands are in the field of level measurement at 6 GHz, 26 GHz or even at 79 GHz.
- the width of the respective frequency band Af is approximately between 5% and 20% of the absolute frequency.
- Frequency change ie a time linearly increasing frequency implemented (a linearly decreasing frequency change would be equally applicable), wherein the frequency change within the frequency band Af cyclically repeats with a preset repetition rate r.
- a transceiver antenna 13 for example, a horn antenna as shown in FIG.
- a common high-frequency generating unit 1 1 ' according to the prior art is shown in Fig. 3: It is based on a voltage controlled oscillator 1 13 for generating the high-frequency electrical signal SHF. In this case, its oscillation frequency can be adjusted by an applicable DC voltage value Sdc.
- phase comparator within the ramp generator 1 12, wherein the phase comparator the instantaneous phase position with a
- the generation of the clock signal s C iock is effected by means of a clock unit 1 1 1, which is implemented for example as a quartz oscillator, which clocks the ramp generator 1 13 here in a frequency of 10 MHz to 100 MHz.
- a clock unit 1 1 1 which is implemented for example as a quartz oscillator, which clocks the ramp generator 1 13 here in a frequency of 10 MHz to 100 MHz.
- the ramp generator 1 12 is also the frequency fHF or the
- This control signal Sf can cause the frequency change, for example, by changing the divider values of the frequency divider in the ramp generator 112.
- the high-frequency electrical signal SHF via a transmitting / receiving switch 12 of the transmitting / receiving antenna 13 of the
- Level meter 1 is supplied to emit for purposes of level measurement, the electrical high frequency signal SHF as electromagnetic transmission signal SHF.
- the electromagnetic signal EHF which is reflected by the surface of the filling material 3, is received via the transmitting / receiving antenna 13. Subsequently, the received electromagnetic signal EHF is supplied via the transmitting / receiving switch 12 to a mixer 14 and through the mixer 14 with the electric
- Radio frequency signal SHF for this purpose between the voltage controlled oscillator 1 13 and the transmitting / receiving switch 12, for example by means of a corresponding
- Signal divider to be branched off.
- an intermediate frequency signal ezF is formed as known in FMCW. Due to the sawtooth-shaped frequency change of the electrical high-frequency signal SHF, the so-called difference frequency of the intermediate frequency signal ezF changes approximately linearly to the distance d between the level measuring device 1 and the surface of the filling material 3.
- Intermediate frequency ezF the level L can be determined. This can be achieved, for example, by means of the corresponding designed control / evaluation unit 15 of the level measuring device 1, in particular by processing the
- the high-frequency generating unit 1 V according to the prior art described with reference to FIG. 3 has several characteristics which have a disadvantageous effect especially in the level measurement: In addition to the complex and thus fault-prone circuit construction, a central disadvantage is that the oscillator 1 13 a comparatively high power consumption and a strong noise and a strong temperature dependence. A high power consumption of the
- Level gauge 1 makes it difficult to comply with explosion protection regulations.
- the disadvantageous effect of noise on the distance or level measurement is that the sensitivity with which poorly reflecting contents 3 can be detected, especially at long distances or low level L, drastically decreases. Accordingly, not only the resolution or the
- a high-frequency generating unit 1 1 according to the invention for an FMCW-based level measuring device 1 which has a structure, as shown in Fig. 4:
- the digital switching mechanism 14 serves to generate a digital, periodic output signal Sd and accordingly can be implemented, for example, as an arbitrary generator (also known by the term “Arbitrary Waveform Generator") or a circuit operating according to direct digital synthesis
- the frequency fHF or the sawtooth-shaped frequency change of the high-frequency signal SHF (and thus also the frequency of the transmission signal SHF, which is in the microwave range) is also produced via the digital switching mechanism 14
- the clocking of the digital switching mechanism 1 14 is in turn effected by a separate clock unit 1 1 1.
- the clock unit 1 1 1 The clock unit
- 1 1 1 is here preferably designed to generate the clock signal s c iock with a clock frequency fdock which is at least twice as high as the frequency fHF of the
- the high-frequency generating unit 11 comprises a digital / analog converter 15, which purely optimally inputs the digital output signal Sd of the digital switching mechanism 1 14 into the desired analog high-frequency signal SHF
- the digital / analog converter 1 15 may be designed to output the high-frequency signal SHF either as a voltage-based or as a current-based signal.
- the high-frequency electrical signal SHF can be realized without a voltage-controlled oscillator and with substantially reduced circuit complexity compared with the prior art.
- the setting of a wide frequency band Af and a high repetition rate r is also possible with the aid of the high-frequency generation unit 1 according to the invention, which in turn results in a higher accuracy in the measurement of the fill level L.
- a further advantage of the high-frequency generation unit 1 1 according to the invention is that the entire circuit or at least the clock unit 11, the digital switching unit 114 and the digital / analog converter 15 can potentially be realized in a very compact manner in a single integrated circuit ,
- the clock unit 1 1 1 could also be integrated as an acoustic surface resonator within the monolithic circuit.
- the filter 1 16 it is optionally possible to filter the high-frequency signal SHF by means of a corresponding filter 16, so as to filter out any interference frequencies from the high-frequency signal SHF.
- the filter 1 16 but at least for the Frequency f H F of the output signal SHF be permeable.
- the filter 1 16 can be designed for example as a low-pass or bandpass.
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE102017111820.9A DE102017111820A1 (de) | 2017-05-30 | 2017-05-30 | Hochfrequenz-Erzeugungseinheit |
PCT/EP2018/059128 WO2018219534A1 (de) | 2017-05-30 | 2018-04-10 | Hochfrequenz-erzeugungseinheit |
Publications (1)
Publication Number | Publication Date |
---|---|
EP3631492A1 true EP3631492A1 (de) | 2020-04-08 |
Family
ID=61952719
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP18717034.5A Pending EP3631492A1 (de) | 2017-05-30 | 2018-04-10 | Hochfrequenz-erzeugungseinheit |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP3631492A1 (de) |
DE (1) | DE102017111820A1 (de) |
WO (1) | WO2018219534A1 (de) |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB9903461D0 (en) * | 1999-02-17 | 1999-04-07 | Motherwell Control Systems Lim | Radar gauge |
DE10201310A1 (de) | 2002-01-15 | 2003-07-24 | Siemens Ag | Verfahren und System zur Datenumsetzung |
CN200979438Y (zh) * | 2006-11-28 | 2007-11-21 | 戴奉周 | 一种数字收发的多频连续波雷达液位仪 |
DE102008050329A1 (de) * | 2008-10-10 | 2010-04-15 | Endress + Hauser Gmbh + Co. Kg | Mit Mikrowellen arbeitendes Füllstandsmessgerät |
DE102009032811A1 (de) * | 2009-07-10 | 2011-02-17 | KROHNE Meßtechnik GmbH & Co. KG | Frequenzsynthesizer für ein Füllstandsmessgerät und Füllstandsmessgerät |
US8629799B2 (en) * | 2011-03-30 | 2014-01-14 | Sandia Research Corporation | Surface penetrating radar system and target zone investigation methodology |
KR101238778B1 (ko) * | 2011-10-25 | 2013-03-04 | 주식회사 파나시아 | 직접 디지털 합성기를 이용하여 직선성과 정밀성을 향상시킨 레이더 레벨 측정 시스템 |
JP5773950B2 (ja) * | 2012-06-08 | 2015-09-02 | ムサシノ機器株式会社 | 液位測定装置およびそのvcoキャリブレイション方法 |
DE102013105019A1 (de) | 2013-05-16 | 2015-02-19 | Endress + Hauser Gmbh + Co. Kg | Füllstandsmessung mit verbesserter Entfernungsbestimmmung |
-
2017
- 2017-05-30 DE DE102017111820.9A patent/DE102017111820A1/de not_active Withdrawn
-
2018
- 2018-04-10 EP EP18717034.5A patent/EP3631492A1/de active Pending
- 2018-04-10 WO PCT/EP2018/059128 patent/WO2018219534A1/de active Application Filing
Also Published As
Publication number | Publication date |
---|---|
WO2018219534A1 (de) | 2018-12-06 |
DE102017111820A1 (de) | 2018-12-06 |
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