Measuring apparatus and method for measuring electromagnetic waves

- Patent application The present invention relates to the technical field of measurement technology.

State of the art

radar technology

Radar (radio detection and ranging) is the name for various locating methods and devices. This technology is based on electromagnetic waves in the radio frequency range. A radar device usually includes three components: a radar antenna, a radar transmitter and a radar receiver. The radar antenna is used to align the transmitted impulse^ and is used to d^detcmg-the-lmisuisanswers·'......~.........

used. The radar transmitter sends eiiren etekuumdgneLisLHenimpcris7'&er receiver------------------waits for the signal response, which occurs on an object as an echo of the impulse.

For example, the distance to the object can be deduced from the elapsed time. The frequencies used range from 30 MHz to 300 GHz [rad]. With the latest radar technology, an accuracy of less than one micrometer is currently possible [see].

A distinction must be made between pulse radar and continuous wave radar, with the former calculating the distance from the signal propagation time. The continuous wave radar transmits a permanent pulse width modulated signal and calculates the distance from the frequency shift between the outgoing signal and the incoming response signal.

-1Hermetic seal

In the technical sense, hermetic sealing means an almost tight, ideally absolutely tight, closure. This can, for example, prevent an exchange of air or water [Wiki],

With regard to the sensor technology, a seal against water or other liquids is primarily desired. If water penetrates into a sensor, the functionality is usually no longer given. One way to hermetically seal is to fill or encapsulate sensors with gel so there are no voids [Mic][Brown], Many applications are temperature and pressure sensors. (Temperature: Omega RTD Sensor [Omega], Krohne, Sauermann Wika [Dir], Pressure: Kavlico High Pressure Sensor [Kav]) Regarding radar technology, there is a patent from Hitachi in which the cavities in the radar are filled with resin [ Tosh03]. The Fraunhofer Society for the Promotion of Applied Research registered a patent for a hermetically sealed module unit with integrated antennas [Fra]. The lock (apparently) serves to protect the internal components, possibly with cavities.

Other hermetically sealed antennas:

US Pat. 6243040B1; Hermetic package with external path antenna and associated method [Corey]

US Pat. 6236366B1; Hermetically sealed semiconductor module composed of semiconductor integrated circuit and antenna element [Yama]

EU Pat. 1357395B1; Radar Sensor [Tosh07]

US Pat. 7180440B2; Integrated circuit for a radar device in a hermetically sealed housing comprising a patch antenna formed from a bent component from sheet metal [Sch]

These approaches of hermetic sealing serve primarily to protect the components, in particular to protect against water.

-2Drift Compensation

Patent US 4435712 presents a radar with drift compensation. (A comparison with the measurement of a known length measurement is achieved.) [Kipp]

Other radar systems that include drift compensation:

US Pat. 4106020; FM-CW radar ranging system [John]

CA Pat. 2483971; US Pat. 7209072B2; Method for drift compensation with radar measurements with the aid of reference radar signals [Brau]

EP no. 1065518; High Resolution Synthetic Aperture Radar System [Runge]

Oscillator Clock Drift Compensation on Bistatic interferometric SAR [On]

The examples of radar technology in connection with drift compensation listed here all use a comparison measurement whose distance is known.

In US Pat. 7180440 B2, the term hermetic sealing is used for the spatial separation of a radar antenna and a calculation unit. The modules are still exposed to environmental influences, only the mutual influence is reduced.

In EP Pat. 1357395 Bl, the radar antenna and the calculation unit are also spatially separated from each other. The effect of the hermetic seal is enhanced by the encapsulation of the electrical components with resin. This makes it more difficult to condition the atmosphere/material surrounding the components.

-3Description of the invention

The invention includes a measuring device which is suitable for the low-interference and precise measurement of distances using electromagnetic waves, is hermetically sealed and is equipped with drift compensation. A radar unit, in particular, is used to transmit and measure the electromagnetic waves.

Radar units that work, for example, according to the FM-CW principle (frequency modulated continuous wave, continuous wave radar) are subject to environmental influences, for example air temperature, air pressure and humidity, as well as aging of the components, which have an influence on the measurement result. The deviations have a particular impact on measurement processes that require high quality.

In the present invention, the hermetic sealing is intended to prevent, for example, the exchange of gas, in particular the air surrounding the components, and the penetration of radiation into the module housing, in particular infrared rays for heat transfer. For example, the seals between the housing front panel and the housing body, and between the housing body and the housing cover, can be used to seal the housing. Another possible use of the hermetic seal is, for example, to create a (partial) vacuum inside the housing so that little or no heat convection between the modules is possible. In another embodiment, the inner cavity could be filled with an inert gas atmosphere, which impedes heat transfer between the modules and/or facilitates heat removal therefrom.

A (partial) vacuum is in particular any gas pressure which is less than 1 atm.

Another way to use the hermetic seal is in over-pressurization. An overpressure is regularly greater than 1 atm.

The present embodiment of a radar unit consists of a transmitter and receiver, which are designed as a transceiver unit, for electromagnetic waves according to the FM-CW principle, in particular for waves in the radio frequency range. The radar unit is equipped with a calculation unit (microcontroller, single-board computer, etc.)

-4connected. The radar unit includes an oscillator for radio wave generation and reception LU102493 in the radio frequency range.

The advantages of the hermetic seal are that the atmosphere, which immediately surrounds the calculation unit and the radar front end, is not in direct exchange with the environment surrounding the measuring device the measurement and calculation components can be kept more constant.

The calculation unit records physical measured values ​​from at least one detection unit, for example another sensor. The recorded physical variable can be the temperature, for example, which affects the functionality of the radar unit. A temperature sensor records the temperature in the module housing and passes it on to the calculation unit.

Due to the hermetic sealing of the housing, the temperature measured in this way is particularly accurate and precise. In particular, the temperature measured in this way corresponds to the temperature of the radar unit in a particularly good approximation.

A further measurement of the direct temperature of the calculation unit can also take place, for example, via the temperature sensor integrated in most processors.

In one embodiment, a physical quantity sensor can be applied, where the physical quantity is the pressure in the cavity of the measuring instrument. A pressure sensor measures the pressure of the air or another gas inside the module housing and forwards the measured value to the calculation unit.

In one embodiment, the calculation unit or the detection unit can measure the current oscillator frequency of the radar unit, for example using a sensor, or determine it on the basis of a measurement and use it to calculate the drift compensation. These physical parameters change over time and therefore have a variable influence on the measurement. By taking these physical parameters into account, the drift compensation function can always adapt the measurement signal to the current status and thus achieve an optimal measurement result.

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In one example, the current temperature is used. However, it can also be measured and updated at regular time intervals and, for example, stored in the calculation unit. For example, this occurs once per millisecond, once per second, or once per minute, or at any other temporal sampling rate.

For example, at least one circulation unit, in particular a rotor, propeller and/or fan, is used to record the temperature from the calculation unit. This ensures that the air or another gas circulates and thus ensures that the temperature inside the module housing is evenly distributed. This makes the drift compensation even more precise.

An additional circulation unit, if necessary, can be used to remove heat from the radar unit.

The circulation units are connected to the calculation unit, for example, and can be controlled by it, in particular also according to the values ​​recorded by the temperature sensor.

In another example, the circulation unit always runs at a constant speed (or a nearly constant speed, deviations less than 5%). This is particularly beneficial for a convection process that is as constant as possible. This allows the temperature in the housing to be as uniform as possible.

The heat removal by convection from the surface is one of the cheapest options and, in addition to the application, also ensures an even distribution and thus a more accurate measurement of the temperature.

The housing of the measuring device can reduce heat transport. For this purpose, it can have a material, for example, which is suitable for preventing the effect of electromagnetic radiation in the infrared range on the measuring device, in particular for absorbing and/or reflecting electromagnetic radiation in the infrared range or in the range of thermal radiation, but not or only rarely to

-6transmit. For example, less than 90%, 95%, 98%, or 99% of the incident LU102493 radiation is transmitted. In another example, less than 90%, 95%, 98%, or 99% of the incident radiation is absorbed. In a further example, these two properties can also be present simultaneously, ie in combination. Temperature fluctuations and their effect on the measurements can be reduced by this constructive measure. The selection of suitable material for the housing represents a passive and thus energy-saving possibility for temperature control, especially the temperature inside the measuring device. By shielding the infrared radiation, the influence of temperature fluctuations in the environment on the measuring and calculation units inside the measuring instrument is reduced more precise MeaStïr geb11 lüe ei aims werd&rikÖ7n lern' — - —

The material used for the housing of the measuring device, in particular the material of the cover plate, is set up in such a way that it transmits electromagnetic radiation in the radio frequency range, i.e. it has a low dielectric constant, in particular a dielectric constant or dielectric constant close to 1.

The housing of the measuring device is made of a material that includes a ceramic and/or PTFE and/or metal. The metal or ceramic case includes a hole for the transmission of electromagnetic waves in the radio frequency range. This hole is covered or sealed with a material that includes PTFE and/or ceramics. Sealing the housing with a material that allows transmission of electromagnetic radiation in the radio frequency range maintains the hermetic sealing of the housing. In addition to the advantages of a constant atmosphere inside the measuring instrument, there are other advantages, for example the possibility of using the measuring instrument in a dirty and/or dusty environment, whereby the interior of the measuring instrument is not affected.

For example, a capacitor, in particular a polymer capacitor, can be used to detect physical parameters, in particular to detect the temperature inside the housing of the measuring device. So that's a reliable LU102493

Possibility of temperature measurement given. However, the polymer capacitor is only an example.

It can also be measured redundantly, in particular in combination with measurement technologies/sensor technologies of different types. This again increases the measurement accuracy.

The individual sensor technologies have advantages. For example, a thermocouple reacts quite quickly, so it is not very sluggish. On the other hand, a variable resistance sensor is typically extremely accurate but introduces some inertia/response time.

A further or different physical parameter to be recorded can be, for example, the air humidity. This measures the air humidity, in particular the relative air humidity, inside the housing of the measuring device and sends the values ​​to the calculation unit. The composition of the air or another gas that surrounds the calculation unit and the radar sensor inside the measuring device has an influence on the electromagnetic waves, in particular on the electromagnetic waves in the radio frequency range of the radar sensor front end. These influences can be compensated for by recording by a moisture sensor and calculating the compensation by the calculation unit.

A further or different physical parameter to be recorded for the drift compensation can be, for example, the pressure, in particular the pressure of the air or another gas inside the housing. The pressure of the air or another gas that surrounds the calculation unit and the radar sensor inside the measuring device has an influence on the electromagnetic waves, in particular on the electromagnetic waves in the radio frequency range of the radar sensor front end. These influences can be compensated by means of recording by a pressure sensor and calculation of the compensation by the calculation unit.

-8The consideration of multiple physical parameters has synergistic effects. LU102493

For example, the measurement inaccuracy is reduced again by recording and taking into account several physical parameters, for example pressure, temperature AND humidity together or quasi simultaneously, and not just linearly, but more.

This can be achieved, for example, by detecting and taking into account and detecting pressure and temperature.

This can be achieved, for example, by detecting and taking into account and detecting humidity and temperature.

This can be achieved, for example, by detecting and taking into account and detecting pressure and humidity.

This can be achieved, for example, by detecting and taking into account and detecting pressure, temperature and humidity.

The calculation unit, which is located inside the housing, is responsible for evaluating the radar sensor measurement signal. In addition, it calculates the compensation for signal drifts. This makes it easy for the user to use the measuring device, since the signals do not have to be processed further.

The calculation unit can be digital or analog or provided as a combination of digital and analog technology. In particular, the compensation can be done digitally or by analog circuits.

For example, the calculation unit records the physical values, in particular the air or gas pressure inside the housing, the temperature inside the housing and/or the calculation unit or the oscillation and/or natural frequency of the oscillator of the radar unit and/or the humidity. One or more of these physical measured values ​​can be used to calculate the drift compensation of the radar measured values. As a result, the radar measuring device can be highly accurate, regardless of its age, its physical environmental values ​​or its internal physical values. For the calculation, a Schwing

-9 and/or natural frequency of the oscillator of the radar unit and an environmental value, in particular LU102493 an ambient temperature and an oscillation and/or natural frequency of the sensor or

Receiver are recorded. By calculating the compensation from two or more influencing variables instead of one influencing variable, a higher accuracy of the measurement signal is achieved. An exact calculation of the measurement signal is possible thanks to modern computer technology.

For the compensation, the calculation unit can, for example, be able to extrapolate the time profile of the temperature. It is therefore possible to make predictions about the temperature development. This makes the drift compensation even more accurate and the measured values ​​more precise. This means that computing resources can also be used sparingly and distributed optimally in terms of time.

In one embodiment, sensors can also be attached to the outside of the measuring device. The sensors can measure either the temperature and/or the radiation. A prediction about the temperature development inside the housing can be made on the basis of the temperature and/or the radiation incident on the housing.

In one embodiment, a circulation unit for heat transport or heat removal is used at the radar front end, which circulates the air or other gas over a temperature sensor. This enables a reliable measurement of the temperature and/or an improved circulation of the air or other gas inside the housing. Alternative arrangements can consist, for example, in that the fan is positioned between the radar sensor front end and the temperature sensor, or in that the fan is positioned behind the radar sensor front end and the temperature sensor, seen in the gas flow direction. In principle, the gas heated by the radar sensor front end should flow over the temperature sensor. This achieves effective overflow of the sensors and thus good temperature detection.

-10LU102493

In one embodiment, at least one further fan, propeller or rotor is used for the heat removal from the calculation unit, which in one example can be different from the circulation unit. The air or gas flow of the heat removal assumes an angle of between 30° and 150° or 45° and 135° or 60° and 120° or 80° and 100° relative to the air or gas flow of the circulation. This arrangement achieves a high degree of turbulence and thus a high degree of mixing of the heat flow and the circulation flow and thus a uniform distribution of the temperature of the atmosphere inside the measuring device.

According to the invention, a method for measuring distances while compensating for a signal drift is also provided.

According to one embodiment, the method for measuring distances while compensating for a signal drift with the present measuring device comprises the following steps:

1. The detection of at least one physical parameter in the housing of the measuring device, which is a temperature, in particular an ambient temperature, and/or a pressure and/or humidity and/or a current frequency of an oscillator, in particular an oscillator of a sensor or receiver for electromagnetic waves , can be.

2. Calculation of the compensation and/or compensation function of a measurement error based on the environmental values ​​recorded in step 1.

3. Receiving a single in the form of an electromagnetic wave in the radio frequency range.

4. Compensation of the measurement error of the signal received in step 3 using the compensation and/or compensation function calculated in step 2.

For a temperature equalization inside the housing of the measuring device, for example, with a movable element, a circulation flow of air or a

-11LU102493 other gas. The movable element can in particular be a rotor, propeller or fan.

According to the invention, for example, a measured signal strength can also be compensated for in addition to a distance. Several variables, such as distance and signal strength, can also be compensated for simultaneously.

It can be compensated on the basis of a temperature, another parameter or also several parameters simultaneously, for example including a temperature.

All combinatorial possibilities of measured values ​​to be compensated on the one hand and physical parameters on the basis of which compensation is carried out can be used within the scope of an embodiment of the present invention.

In a radar application, for example, a signal strength can be proportional to a surface of one or more objects facing the sensor and/or receiver. For example, this signal strength correlates with a size or quantity of one or more measured objects.

For specific measurement and compensation examples and exemplary compensation data, reference is made to the descriptions of the figures.

The features which are disclosed in the present document in connection with the device can in any case also be used in connection with the method. This also applies vice versa, and also for drift-compensated measurement data and programs for computers according to the invention.

-12LU102493

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Description of the figures

1 shows the overall view of an embodiment of the measuring device. The housing body 11 is closed off at the back by the housing cover 12 and at the front by the housing front panel 1 . The recess in the housing front panel 1 is closed by the cover panel 3. The cover plate 3 is designed for the electromagnetic waves in the radio frequency range of the radar unit, here the radar sensor front end 4 in FIGS. 2 and 3 . The housing front panel 1, the housing body 11 and the housing cover 12 are designed to absorb electromagnetic waves in the infrared range.

2 shows an exploded drawing of an embodiment of the measuring device. The seals 2 allow the housing to be hermetically sealed. The radar sensor front end 4, which contains the transmitter and receiver, is arranged behind the cover plate 3. The air or gas around it is moved by a circulating unit, referred to herein as a fan 8. Additional fans 8 are located above the calculation unit 9. The fans 8, the radar sensor front end 4, by means of a connecting cable, radar sensor front end 6, and the temperature sensor 5, by means of a connecting cable, temperature sensor 7, are connected to the calculation unit 9.

3 shows an embodiment of the electronic components as a unit. In this case, the calculation unit 9 is mounted directly on the radar sensor front end 4 . A fan 8 lets the air or the gas flow over the radar sensor interface 4 over a temperature sensor 5 which is also connected to the calculation unit 9 . The network and power supply cable 10 leads from the calculation unit out of the housing through the housing cover 12 . in figure 4 the fan 8 is arranged between the radar sensor front end 4 and the temperature sensor, so that the

Radar sensor front end 4 attracted air flow is blown onto the temperature sensor 5. In FIG. 5 the temperature sensor 5 is arranged between the fan 8 and the radar sensor front end 4 . The air flow drawn in by the fan 8 is first drawn over the radar sensor front end 4 and then over the temperature sensor 5 .

-14In Fig. 6 the temperature profile during a test case can be seen. The measured LU102493 distances are shown in Fig. 7. A connection can be clearly seen since the uncompensated curve is similar to the temperature curve, whereas the compensated curve is not influenced by the temperature change thanks to the use of the present invention. The measured value decreases with decreasing temperature. This compensated reading, a distance, is shown in Fig. 8th plotted and shown over time.

A similar temperature influence can be seen in FIG. 9, where the measured signal intensity is shown compensated and uncompensated over time. Thereby, by virtue of the present invention, the intensity in the compensated state behaves essentially independently of the temperature, whereas the uncompensated one shows a strong influence. With decreasing temperature inside the measuring device, the measured uncompensated signal intensity increases significantly.

The invention thus enables access to significantly more accurate measured values, which correspond to the measured variables to be measured that are actually present in reality and are significantly more accurate and independent of the internal conditions of the measuring device.

The measurement curves shown in Figures 6-9 show real measurement results from actually performed test series.

-15Bibliography

[Brau] CA Pat. 2483971; US Pat. 7209072B2; Method for drift compensation with radar measurements with the aid of reference radar signals;

https://patentimages.storage.googleapis.com/fl/f9/d6/df775305c4e85e/CA2483971C.pdf;

https://patentimages.storage.googleapis.com/15/3d/5e/8683997265fecb/US7209072.pdf

[Brown] US Pat. 5454270; hermetically sealed pressure sensor and method thereof;

https://patentimages.storage.googleapis.com/d8/4e/77/eaf7e6c4444677/US5454270.pdf

[Corey]US Pat. 6243040B1; Hermetic package with external patch antenna and associated method;

https://patentimages.storage.googleapis.com/e8/0e/8f/2258409b362808/US6243040.pdf

[Dir] Waterproof temperature sensor;

https://www.directindustry.com/industrial-manufacturer/waterproof-temperature-sensor231651.html

[On] Ocillator Clock Drift Compensation in Bistatic Interferometric SAR; Eineder, Michael; 2003; DOI: 10.1109/IGARSS.2003.1294140

[Fra] DE Pat. 10 2018 205 670 A1; Hermetically sealed module unit with integrated antennas;

https://patentimages.storage.googleapis.com/90/b8/69/100387077e59d4/DE10201820567 OAl.pdf

[John] US Pat. 4106020; FM-CW radar ranging system;

https://patentimages.storage.googleapis.com/45/5f/d0/blleed7cl0ad5c/US4106020.pdf

[Kav] P5000 Hermetically Sealed High Pressure Sensor;

http://www.konkurel.ru/kavlico/pdf/P5000_Kavlico.pdf

-16[Kipp] US Pat. 4435712A; FM-CW radar ranging system with signal drift compensation; LU102493 https://patentimages.storage.googleapis.com/68/71/92/f04819f231891d/US4435712.pdf

[Mic] HermeSeal - Hermetically Sealed Infrared Components by Micro-Hybrid;

https://www.sensortest.de/ausstellerbereich/upload/mnpdf/en/Product presentation_HermeSeal_EN_14.pdf

[Omega] Flexible Sealed PFA RTD Sensors;

https://br.omega.com/omegaFiles/temperature/pdf/HSRTD.pdf

[rad] https://www.radartutorial.eu/07.waves/Frequenz-%20und%20Wellenbereiche.de.html

[Runge] EU Pat. 1065518A2; High resolution synthetic aperture radar system;

https://patentimages.storage.googleapis.com/e2/26/bl/854a3d9de60844/EP1065518A2.pd f

[Sch] US Pat. 7180440B2; Integrated circuit for a radar device in a hermetically sealed housing comprising a path antenna formed from a bent component from sheet metal;

https://patentimages.storage.googleapis.com/29/da/87/27bl7af8cl5a28/US7180440.pdf

[See] Dissertation: FMCW radar signal processing for high accuracy ranging; Scherr, Steffen; 2016

[Tosh03] EU Pat. 1357395A1; Miniaturized and hermetically sealed radar sensor for millimeter wave signals;

https://patentimages.storage.googleapis.com/83/13/c8/101a04f6c5b4e0/EP1357395Al.pdf

[Tosh07] EU Pat. 1357395B1; radar sensor;

https://patentimages.storage.googleapis.com/d9/bd/8b/a05afl3ddl6357/EP1357395Bl.pdf

[Wiki] https://de.wikipedia.org/wiki/Hermetischer_Verschluß

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[Yama] US Pat. 6236366B1; Hermetically sealed semiconductor module composed of semiconductor integrated circuit and antenna element;

https://patentimages.storage.googleapis.com/d9/32/64/92768e3e2f2d3f/US6236366.pdf

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Reference List

1. housing front panel

2. seal (2x)

3. Cover plate (ceramic/PTFE)

4. radar sensor frontend

5. temperature sensor

6. Connection cable radar sensor front end

7. Connection cable temperature sensor

8th. Fan

9. calculation unit

10 Network and power supply cables

11. case body

12. housing cover