Pressure sensor

Abstract

Having a pressure sensor (10a, 10d, 10e, 10f, 10g, 10h): - a sensor body (12) with a deformable membrane (14) arranged such that two sides (20, 22) of the membrane (14) can be subjected to different pressures in order to deform the membrane (14), - a phase measurement unit (16, 16a, 16e, 16f, 16g, 16h) arranged opposite the membrane (14), which is formed as follows: -- to generate a periodic electrical signal with a constant frequency, -- to send the signal as high-frequency radiation (30) to the membrane (14), -- to receive high-frequency radiation (32) reflected at the membrane (14), and -- to determine a phase difference between emitted radiation (30) and reflected radiation (32), - a beam focusing unit (34) for focusing the radiation (30, 32), -- which has a dielectric lens (36), -- wherein the beam focusing unit (34) is connected to the phase measurement unit (16, 16e, 16f, 16g, 16h), or -- wherein an intermediate layer (38) is provided between the phase measuring unit (16a) and the beam focusing unit (34), and - a pressure determination unit (18) which is designed to determine a pressure acting on the membrane (14) on the basis of the phase difference.

Description

[0001] The invention relates to a pressure sensor with a deformable membrane. In particular, the invention relates to a pressure sensor in which the pressure acting on the membrane is determined based on the deformation of the membrane using a phase difference measurement.

[0002] Strain gauge pressure sensors are well known. The mechanical deformation of the strain gauge caused by pressure can be converted into an electrical signal. Strain gauges are typically made of metal or a semiconductor material. Pressure measurement by strain gauge pressure sensors is based on a change in the resistance of the strain gauge material caused by mechanical deformation. Other pressure sensors use changes in inductance or capacitance to measure pressure.

[0003] EP 1 772 718 A2 and US 7 299 700 B2 show a pressure sensor that uses a microwave radar sensor to measure the distance of the microwave radar sensor to a membrane and to generate therefrom an electrical signal containing information regarding the pressure acting on the membrane.

[0004] DE 10 2013 107 963 A1 describes a pressure sensor that uses a resonator arranged in the measuring chamber, which is excited by a transmitter / receiver unit. The deformation caused by the measuring pressure causes the resonator's natural frequency to change. The measuring pressure of the medium is determined from the change in the natural frequency.

[0005] DE 10 2009 009 384 A1 describes the detection of pressure fluctuations in a hot medium, e.g., in a gas turbine combustion chamber. A flexible element is used that is deflected from a resting position when the pressure of the medium fluctuates. The flexible element is irradiated with an electromagnetic millimeter-wave signal emitted by a transmitter and reflects the electromagnetic signal. The phase position of the emitted signal is then compared with the phase position of the reflected signal. The result of the phase comparison allows the deflection of the flexible element to be detected, and from this, the pressure fluctuation to be determined.

[0006] US 3,973,259 A describes a device for measuring vibrations in turbines and similar objects. Electromagnetic signals are directed from a transmitter toward the object, and the reflected signals are picked up by a receiver. The transmitted and received signals are continuously compared to generate a signal representing the phase relationship between them. This signal is used to calibrate the device, which also includes a device for intermittent frequency modulation of the transmitter oscillator. The frequency of the oscillator is automatically controlled so that the center frequency of the transmitted signal reaches a value at which the phase difference between the transmitted and received signals is equal to n × 180°, where n is an integer. Between calibration periods, the signal representing the phase relationship is used as an indicator of the turbine vibrations.

[0007] DE 297 09 926 U1 describes a system for detecting water levels, particularly for groundwater level measurements in gauges and boreholes. A microwave and / or radar wave measuring attachment can be attached to the opening of a sealable gauge tube of this system.

[0008] The aim of the invention is to create a simple and cost-effective pressure sensor that enables more accurate pressure measurement.

[0009] This goal is achieved by a pressure sensor comprising a sensor body with a deformable membrane, a phase measuring unit, and a pressure determination unit. The membrane is arranged such that two sides of the membrane can be subjected to different pressures in order to deform the membrane. The phase measuring unit is arranged opposite the membrane. The phase measuring unit is designed to generate a periodic electrical signal with a constant frequency, transmit the signal as high-frequency radiation to the membrane, receive high-frequency radiation reflected by the membrane, and determine a phase difference between the transmitted radiation and the reflected radiation. The pressure determination unit is designed to determine a pressure acting on the membrane based on the phase difference.

[0010] A spatially separated arrangement of the diaphragm and phase measurement unit allows the pressure sensor to be used in harsh environments, such as high temperatures, without damaging the temperature-sensitive electronic components of the phase measurement unit. The pressure sensor can therefore be used, for example, in a heater, a turbine, or other systems that consume solid, liquid, or gaseous fuels such as natural gas, gasoline, diesel, coal, or oil. The pressure sensor can also be used in sensitive applications, such as in the chemical industry or in medical applications.

[0011] The inventors have recognized that known pressure sensors that operate according to the radar principle have disadvantages. For example, Doppler radar cannot be used for pressure measurement because it can only measure speeds and not distances. Furthermore, determining pressure based on a phase difference is more accurate than a pressure measurement performed with pulse radars. Compared to pressure sensors based on frequency-modulated radars, the pressure sensor according to the invention enables a simpler design, since frequency-modulated radars require a precisely linear frequency ramp to achieve the required accuracy, which necessitates a complex design. Furthermore, pressure sensors based on frequency-modulated radars require a much larger bandwidth than the pressure sensor according to the invention to be able to measure at the required close range.

[0012] The phase measuring unit is designed to determine the phase difference between transmitted radiation and reflected radiation. For this purpose, the phase measuring unit can be designed to compare a phase position of the transmitted radiation with a phase position of the reflected radiation. The phase measuring unit provides the phase difference to the pressure determining unit. The pressure determining unit is designed to determine a pressure acting on the membrane based on the phase difference of the radiation. The pressure sensor can have a memory. The memory can be part of the pressure determining unit or the pressure determining unit can be connected to the memory. The memory is designed to store data. The data can contain phase differences that correspond to certain pressures, such that an associated pressure can be determined from a phase difference.The data stored in the memory can be determined in a calibration process, e.g. by measuring the pressure with another pressure sensor and correlating the measured pressure with the phase difference measured with the phase measuring unit. Alternatively, an external pressure with a known pressure can be applied to the pressure sensor and a phase difference can be assigned to this by measurement. Thus, the pressure can be determined by determining the phase difference of the radiation. Alternatively or additionally, the pressure determination unit or the memory can be designed to provide a pressure measuring function that makes it possible to determine pressure as a function of the phase difference. Coefficients of the pressure measuring function can be determined in a calibration process, for example, using regression analysis, machine learning or another method.Such a pressure measurement function makes it possible to determine the pressure based on a phase difference between the transmitted radiation and the reflected radiation.

[0013] The phase measuring unit is designed to generate the transmitted radiation based on a periodic electrical signal. The phase measuring unit can be designed to generate a received electrical signal based on the received reflected radiation and to determine the phase difference between the periodic electrical signal and the received electrical signal. Since the electrical signal and the received electrical signal have an identical frequency, a difference signal between the two signals is zero except for the phase difference. Therefore, the pressure can be determined via the phase difference. The pressure causes a deformation of the membrane, which bulges, thereby changing the distance between the phase measuring unit and the membrane.The change in distance leads to a change in the phase position of the radiation, since the travel time of the radiation from the phase measurement unit to the membrane and from the membrane back to the phase measurement unit depends on the distance between the phase measurement unit and the membrane. Therefore, the change in distance also leads to a change in the phase difference of the radiation.

[0014] The diaphragm is arranged in such a way that it defines a measuring chamber in which a predefined reference pressure, for example atmospheric pressure of approximately 1 bar, or a pressure to be measured, prevails. The diaphragm can be arranged on the sensor body in such a way that the diaphragm forms part of an outer side of the sensor body. The pressure sensor can therefore be easily manufactured in a flush design. Alternatively, the diaphragm can also be arranged inside the sensor body. In this case, one or more openings are provided in the sensor body so that the diaphragm can be deformed by pressure acting through the opening or openings into the sensor body.

[0015] The pressure sensor can have a pressure line that is arranged and designed such that the pressure line can carry a first pressure to one side of the diaphragm while a second pressure acts on the other side of the diaphragm. This makes it easy to produce a differential pressure sensor. The pressure sensor can also have multiple pressure lines, for example two, that are arranged such that the pressure lines carry a first pressure to one side of the diaphragm and a second pressure to the other side of the diaphragm. Alternatively, the pressure sensor can also have two or more diaphragms, where, for example, two diaphragms are arranged on the sensor body in such a way that a different pressure can act on each diaphragm and thus a differential pressure between the pressures acting on the diaphragms can be determined.

[0016] When measuring pressure, a distinction must be made between absolute pressure, relative pressure and differential pressure. Absolute pressure measures the absolute pressure acting on the diaphragm against a vacuum. Relative pressure measures the pressure acting on the diaphragm relative to a reference pressure supplied to the measuring chamber. The reference pressure supplied to the measuring chamber can, for example, be atmospheric pressure, which is supplied via a pressure line or which is provided through an opening in the housing of the pressure sensor. Differential pressure measures a pressure difference between a first pressure and a second pressure. The differential pressure can be a pressure difference between a first pressure acting on one side of the diaphragm and a second pressure acting on the other side of the diaphragm, or a pressure difference between a pressure acting on a first diaphragm and a pressure acting on a second diaphragm.

[0017] The phase measuring unit can be arranged at a predefined distance from the membrane in the undeformed state.

[0018] When pressure is applied to the membrane, the membrane deforms, changing the distance of a membrane surface from the phase measurement unit. Due to the pressure-dependent deformation of the membrane, the phase of the reflected radiation is shifted relative to the transmitted radiation as a function of distance and can be used to measure the pressure acting on the membrane.

[0019] The operating principle of the pressure sensor according to the invention is based on the pressure-dependent deformation of the membrane, whereby the membrane surface bulges toward the phase measuring unit, thus reducing the distance between the membrane and the phase measuring unit. The reflection conditions of the radiation at the membrane depend on the pressure acting on the membrane. The radiation is at least partially reflected by the membrane and received by the phase measuring unit.

[0020] Parts of the phase measurement unit can be arranged opposite the membrane in such a way that one part of the phase measurement unit, for example, a transmitting antenna, transmits the signal to the membrane as high-frequency radiation, while another part of the phase measurement unit, for example, a receiving antenna, receives the high-frequency radiation reflected by the membrane. The transmitting antenna can also additionally serve as a receiving antenna.

[0021] The pressure sensor can have a beam condenser for condensing the radiation. The beam condenser can be arranged such that the beam condenser focuses the radiation emitted by the phase measurement unit onto the membrane and focuses the radiation reflected by the membrane onto the phase measurement unit. The beam condenser is designed to condense the high-frequency radiation. The beam condenser enables a focused propagation of the high-frequency radiation, thus further improving the accuracy of the pressure measurement.

[0022] The beam focusing unit can be positioned at a predefined distance from the membrane, between the phase measurement unit and the membrane. This predefined distance is relative to the membrane in an undeformed state. Since a phase difference measurement is used to determine the deformation, the deflection of the membrane must be within the unambiguous range of the wavelength of the high-frequency radiation. The wavelength λ in air is determined from the frequency f of the radiation and the speed of light. c:λ=cf. In a medium other than air or vacuum, a correspondingly shorter wavelength results, since the speed of light is lower in other media. The wavelength in air, for example, is approximately 1 mm at a radiation frequency of 300 GHz. This results in a phase unambiguousness range of 1 mm. The phase unambiguousness range is limited because points with the same phase repeat outside and an unambiguous measurement outside the unambiguousness range is not possible. Preferably, the predefined distance of the beam focusing unit to the membrane is selected such that the distance is less than or equal to the first unambiguousness range; i.e., in the case of radiation with a frequency of 300 GHz, the predefined distance is preferably less than or equal to 1 mm. Alternatively, the distance of the beam focusing unit to the membrane can be greater than the first unambiguousness range.In this case, however, the maximum deformation of the membrane must be less than or equal to a certain unambiguous range to ensure the unambiguousness of the measured phase position. For example, for radiation with a frequency of 300 GHz, the membrane can be positioned within a certain unambiguous range between 1 mm and 2 mm.

[0023] The predefined distance between the beam condenser and the diaphragm can be dimensioned such that the predefined distance corresponds to a maximum deformation of the diaphragm. In this case, the diaphragm will only bulge inward to the point where the surfaces of the diaphragm and the beam condenser touch. This allows the diaphragm to be held in place at overpressure, thus preventing a potential rupture of the diaphragm, thus increasing the safety of the pressure sensor. Furthermore, it allows for the production of a compact pressure sensor, as the available space can be optimally utilized.

[0024] The beamforming unit can be arranged at a fixed distance from the phase measurement unit or connected to the phase measurement unit. When pressure is applied to the membrane, the membrane deforms, changing the distance of a surface of the membrane to the beamforming unit and thus also to the phase measurement unit. Due to the pressure-dependent deformation of the membrane, the phase of the reflected radiation is shifted relative to the transmitted radiation as a function of the distance and can be used to measure the pressure acting on the membrane.

[0025] The beam condenser may comprise a dielectric lens, a dielectric waveguide, or a dielectric lens and a dielectric waveguide. The beam condenser may also comprise multiple dielectric lenses, or multiple dielectric lenses and a dielectric waveguide.

[0026] A dielectric lens arranged between the phase measuring unit and the membrane makes it possible to refract high-frequency radiation emitted by the phase measuring unit in such a way that it is bundled, and radiation reflected back from the membrane onto the phase measuring unit is bundled onto the phase measuring unit. The dielectric lens can, for example, be a rotationally symmetric lens, in particular a dielectric lens as known, for example, from DE 10 2014 200 272 A1. The dielectric lens can comprise silicon, a plastic material, and / or another dielectric material. The dielectric lens can therefore comprise silicon, a plastic material, or silicon and a plastic material. The plastic material preferably has good transmission properties for the frequency used, which can, for example, be in the range between 10 GHz and 1 THz. The dielectric constant of the plastic material can, for example, be between 2.5 and 12.The dielectric constant indicates the permeability of a material to electric fields, such as high-frequency radiation, and is frequency-dependent. The dielectric constant, or relative permittivity, is defined as: εr=εε0 with ε the permittivity and ε0=8.854⋅10−12AsVm the permittivity of the vacuum, ie for vacuum ε r = 1. The dielectric lens can also be made of silicon or plastic material.

[0027] At least part of an inner surface of the sensor body can comprise a radiation-attenuating material. The radiation-attenuating material allows for the attenuation of unwanted reflected radiation and increases measurement accuracy. Radiation-attenuating materials can be, for example, carbon-containing layers or foams.

[0028] The side of the membrane opposite the phase measurement unit may comprise a radiation-attenuating material extending around a center of the side of the membrane opposite the phase measurement unit. The side of the membrane opposite the phase measurement unit is the side that reflects the radiation emitted by the phase measurement unit. The center of the side of the membrane opposite the phase measurement unit may, for example, be circular and occupy part of the side of the membrane opposite the phase measurement unit. The center may, for example, comprise 10%, 20%, 30%, 40%, or 50% of the side of the membrane opposite the phase measurement unit. In the case of a circular center, the radiation-attenuating material extends annularly around the center and comprises, for example, 90%, 80%, 70%, 60%, or 50% of the side of the membrane opposite the phase measurement unit.

[0029] The measuring chamber of the pressure sensor is preferably located between the diaphragm and the phase measurement unit. The measuring chamber can contain a radiation-attenuating fluid, such as oil. This allows unwanted reflected radiation to be attenuated in the measuring chamber and increases measurement accuracy. Due to the oil, the effective relative dielectric constant can be greater than one, which allows the wavelength to be reduced and the measurement accuracy to be further improved. The oil can, for example, contain or be silicone oil.

[0030] The phase measuring unit can be designed to generate the periodic electrical signal with a constant frequency in the terahertz range or with a wavelength in the millimeter wave range. The phase measuring unit can be designed to generate the periodic electrical signal with a constant frequency between 10 GHz and 1 THz, for example between 100 GHz and 1 THz or between 100 GHz and 300 GHz. The phase measuring unit can, for example, be designed to generate the periodic electrical signal with a constant frequency of 24.125 GHz, 61.25 GHz, 122.5 GHz and / or 245 GHz. With a higher frequency, the wavelength of the radiation generated based on the electrical signal becomes smaller and thus the phase shift per changed distance becomes larger, since the wavelength λ of the radiation is related to the frequency f of the radiation via the relationship λ=cf where c is the speed of light. A higher frequency therefore allows for more accurate pressure measurement. Furthermore, the use of high-frequency radiation with a frequency in the range between 10 GHz and 1 THz, and especially between 100 GHz and 1 THz, enables the production of a compact pressure sensor, since electronic components, such as waveguides, can be very small.

[0031] The phase measurement unit may comprise an antenna, an oscillator, and a radio-frequency amplifier, or a combination of these electronic components. The antenna is configured to transmit and / or receive the radio-frequency radiation, i.e., the antenna is configured to transmit radio-frequency radiation, receive radio-frequency radiation, or transmit and receive radio-frequency radiation. The oscillator has a frequency-stabilized frequency and is configured to generate the periodic electrical signal. The radio-frequency amplifier processes electrical signals such that output signals from the radio-frequency amplifier are larger than input signals.

[0032] Preferably, if the phase measuring unit has only one antenna, the phase measuring unit comprises a coupler for transmitting the periodic electrical signal to the antenna and for transmitting electrical signals received by the antenna away from the antenna. The coupler enables signals to be transmitted and received via a single antenna.

[0033] The phase measurement unit may also comprise multiple antennas, for example, two antennas, for transmitting and / or receiving the radio-frequency radiation, i.e., for transmitting, receiving, or both transmitting and receiving the radio-frequency radiation. In this case, one of the antennas may be provided for transmitting the radio-frequency radiation and the other for receiving the radio-frequency radiation.

[0034] The oscillator can provide the periodic electrical signal at a constant frequency. The high-frequency amplifier can amplify the electrical signal, and the antenna can transmit the electrical signal as high-frequency radiation to the membrane. The beamforming unit can focus the radiation. The membrane reflects at least a portion of the focused radiation, so that the reflected radiation strikes the beamforming unit, which focuses the reflected radiation onto the antenna of the phase-measuring unit. If the phase-measuring unit has only one antenna, this is the same antenna that was used to transmit the radiation. If the phase-measuring unit has multiple antennas, for example, two antennas, the beamforming unit is preferably arranged and configured to focus the reflected radiation onto the antenna for receiving the radiation.The antenna can receive the reflected radiation and generate a received electrical signal, which can be compared with the periodic electrical signal provided by the oscillator to determine the phase difference. From the phase difference of the radiation, the pressure acting on the membrane can be determined using the pressure determination unit.

[0035] The pressure sensor can include a frequency stabilizer to stabilize the oscillator frequency. The frequency stabilizer can be included in the phase measurement unit. The frequency stabilizer allows the frequency to be kept stable, thus increasing measurement accuracy. The frequency stabilizer can, for example, be a phase-locked loop (PLL). The phase-locked loop can, for example, use a quartz oscillator as a reference. A phase-locked loop is easy to manufacture and enables high frequency stability.

[0036] The phase measurement unit may include a mixer. The mixer may be configured to determine the phase difference. The mixer enables mixing of the periodic electrical signal and the received electrical signal. The mixer processes the periodic electrical signal and the received electrical signal by generating electrical signals with the difference frequency and the sum frequency. The pressure sensor may include a bandpass filter to suppress the electrical signal with the sum frequency, so that only the electrical signal with the difference frequency is further processed for pressure measurement in the pressure determination unit. In this case, the electrical signal with the difference frequency has a difference frequency of 0 Hz.

[0037] The phase measurement unit can include a low-noise amplifier. The low-noise amplifier can be located between the antenna and the mixer or between the coupler and the mixer. The low-noise amplifier makes it possible to increase the sensitivity of the pressure sensor.

[0038] The phase measurement unit can be made of silicon, for example, a silicon chip. This allows the phase measurement unit to be manufactured using silicon chip technology. Alternatively, the phase measurement unit or part of the phase measurement unit can also be made of another material, for example, GaAs or other materials used in semiconductor and / or chip technology.

[0039] Electronic components of the phase measurement unit, such as the oscillator, the antenna, the mixer, the high-frequency amplifier, the frequency stabilizer, a waveguide, or several of these, can be arranged on a single chip or circuit board, or on various interconnected chips and / or circuit boards. Additionally, the pressure determination unit can also be arranged on a single chip with the phase measurement unit or a portion of the electronic components of the phase measurement unit. The electronic components of the phase measurement unit and pressure determination unit can be temperature-sensitive and can operate at temperatures in the range between -40°C and 150°C, for example, between -40°C and 125°C or between -40°C and 85°C.

[0040] The phase measuring unit can be connected to the beam focusing unit. The phase measuring unit can, for example, be glued, clamped, hooked, or connected to the beam focusing unit in some other way using a fastening means. Alternatively, an intermediate layer can be provided between the phase measuring unit and the beam focusing unit. The intermediate layer serves to hold the phase measuring unit, particularly when the phase measuring unit is arranged on a chip, for holding the chip or the chip in the housing. The intermediate layer enables improved heat dissipation of the chip's waste heat to the environment. The intermediate layer can comprise silicon, another material, or a combination of several materials that enable good heat dissipation and absorb as little radiation as possible.The intermediate layer is preferably made of high-resistance silicon, as silicon has good heat dissipation and also good radiation transmission. The material of the intermediate layer has a high specific resistance of at least 50 Ωcm. The intermediate layer can, for example, have a specific electrical resistance between 50 Ωcm and 10 kΩcm. The intermediate layer can, for example, be formed from a material with a specific electrical resistance between 50 Ωcm and 10 kΩcm, between 50 Ωcm and 5 kΩcm, or between 50 Ωcm and 1000 Ωcm. A high specific electrical resistance reduces the attenuation of the radiation because there are fewer defects in the material. The intermediate layer can, for example, have a thickness of 200 μm to 750 μm. A thinner intermediate layer reduces the attenuation of the radiation, but also the stability of the intermediate layer and heat dissipation, so the intermediate layer must have a minimum thickness.

[0041] In one embodiment of the pressure sensor, the phase measuring unit has a six-port. The phase measuring unit can have two inputs for signals, four outputs for signals, and four power meters. The four power meters can be arranged in a six-port structure for detecting static wave patterns. The four power meters can also be connected to one another via a waveguide in a reflectometer structure for detecting static wave patterns. The first input can, for example, be supplied with the periodic electrical signal and the second input with the received electrical signal. The four power meters are preferably arranged along a waveguide at a distance of one-quarter of the wavelength of the radiation, so that static wave patterns are formed that can be measured by the four power meters.Since the phase position of the received electrical signal depends on the distance between the phase measuring unit and the membrane, the resulting static wave pattern is also a function of the distance between the phase measuring unit and the membrane and thus a measure of the pressure acting on the membrane. The six-port structure enables the six-port method, which is based on the principle of superposition of the periodic electrical signal and the received electrical signal at the locations of the four power meters. The six-port reflectometer structure and the corresponding six-port method are described, for example, in B. Lämmle et al.: "A 122 GHz Multiprobe Reflectometer for Dielectric Sensor Readout in SiGe BiCMOS Technology, 2011 IEEE Compound Semiconductor Integrated Circuit Symposium and A. Kölpin et al.: "The Six-Port in Modern Society", IEEE microwave magazine, 12 / 2010.

[0042] The pressure sensor may include one or more analog-to-digital converters to convert analog signals into digital signals. The pressure sensor may include a processor. The processor may be part of the pressure determination unit. The processor may be configured to process digital signals.

[0043] The membrane can be made of metal, such as stainless steel. This makes it possible to create a durable membrane that can be used even in harsh conditions, such as high temperatures up to 1000°C.

[0044] The sensor body may include damping material. The damping material may be arranged to attenuate radiation, thus reducing reflections of the radiation from a surface, such as a wall of the sensor body. This allows for increased measurement accuracy and reliability.

[0045] The invention further relates to a sensor device comprising a pressure sensor according to one of claims 1 to 17 or another embodiment of the pressure sensor and a temperature sensor. The sensor device makes it possible to determine both pressure and temperature. The measured values ​​for pressure and temperature can be used, for example, to calibrate the pressure sensor over the temperature range.

[0046] The invention further relates to a sensor device for differential pressure measurement. The sensor device comprises two pressure sensors according to one of claims 1 to 17 or another embodiment of the pressure sensor. The sensor device is designed to determine a differential pressure from the pressures measured by the two pressure sensors. This makes it possible to easily manufacture a differential pressure sensor that can determine differential pressures.

[0047] Furthermore, the invention relates to a method for operating a pressure sensor according to one of claims 1 to 17 or another embodiment of the pressure sensor. The method comprises the steps: - Generating a periodic electrical signal with a constant frequency, - Sending the signal as high-frequency radiation to the membrane, - Receiving high-frequency radiation reflected from the membrane, - Determining a phase difference between transmitted radiation and reflected radiation and - Determining a pressure acting on the membrane based on the phase difference.

[0048] The steps can run continuously and in parallel. The step of determining the pressure acting on the membrane can also be performed based on temperature.

[0049] The invention will now be explained in more detail with reference to exemplary embodiments schematically illustrated in the figures. The figures show: Fig. 1 a schematic representation of a first embodiment of a pressure sensor not claimed in this combination of features; Fig. 2 a schematic representation of a second embodiment of a pressure sensor according to the invention; Fig. 3 a schematic representation of a third embodiment of a pressure sensor for differential pressure measurement according to the invention; Fig. 4 is a schematic representation of a fourth embodiment of a pressure sensor with two antennas according to the invention; Fig. 5 is a schematic representation of a fifth embodiment of a pressure sensor with an antenna according to the invention; Fig. 6 is a schematic representation of a sixth embodiment of a pressure sensor according to the invention; Fig. 7 is a schematic representation of a seventh embodiment of a pressure sensor according to the invention; Fig. 8 a schematic representation of an embodiment of a sensor device according to the invention with a pressure sensor and a temperature sensor; Fig. 9 an embodiment of a method according to the invention for operating a pressure sensor in the form of a flow chart.

[0050] In Fig. Figure 1 shows a schematic representation of a first embodiment of a pressure sensor 10 for the purpose of explaining exemplary embodiments of the invention, and thus not claimed here. The pressure sensor 10 has a sensor body 12 in which a membrane 14, a phase measuring unit 16, and a pressure determination unit 18 are arranged.

[0051] The membrane 14 is a deformable membrane whose outer side 20 is connected to a pressure to be measured, supplied via an inlet 26, and whose inner side 22 is connected to a reference pressure prevailing in a measuring chamber 24 formed by the membrane 14 and the sensor body 12. In this exemplary embodiment, the pressure acting on the outer side 20 is the pressure to be measured. In other exemplary embodiments, the pressure acting on the inner side 22 can also be the pressure to be measured. A reference pressure prevails in the measuring chamber 24, which in this exemplary embodiment corresponds to the atmospheric pressure of 1 bar. For this purpose, in this exemplary embodiment, the atmospheric pressure is ensured via a line to the outside into the environment (not shown in the illustration plane). In further exemplary embodiments, a reference pressure other than atmospheric pressure can also prevail in the measuring chamber.The sensor body can, for example, be formed by a pressure-tight housing that surrounds at least the measuring chamber in a pressure-tight manner, so that the reference pressure in the measuring chamber is fixed, for example by adding a predetermined amount of gas to the volume of the measuring chamber. The reference pressure can also be very low, for example by extracting gas from the measuring chamber. For this purpose, a line for adding and extracting gas into and from the measuring chamber can be provided, or the pressure-tight housing can be manufactured with a predetermined reference pressure in the measuring chamber. The line for adding and extracting gas can also be used to adapt the reference pressure to the pressure to be measured.This makes it possible to measure very high pressures. For example, if the pressure to be measured deforms the diaphragm to such an extent that it touches the phase measurement unit at a first reference pressure, the reference pressure can be increased so that the diaphragm is deformed less, allowing a measurement of the pressure to be measured. If the pressure to be measured and the reference pressure are the same, the diaphragm is not deformed. In this case, if the reference pressure is known, the pressure to be measured corresponds to the reference pressure.

[0052] The pressure to be measured acts on the sensor body 12 and the outer side 20 of the diaphragm 14 via the inlet 26. The diaphragm 14 deforms when the pressure to be measured and the reference pressure are different. For example, the diaphragm 14 bulges inwards into the measuring chamber 24 when the pressure to be measured is higher than the reference pressure. In this exemplary embodiment, the diaphragm 14 is a thin metal foil with a thickness of 200 µm. In other exemplary embodiments, the metal foil can also have a thickness between 100 µm and 400 µm. In this exemplary embodiment, the metal foil is made of stainless steel. In other exemplary embodiments, the diaphragm can also consist of or comprise other materials, in particular metals, which enable elastic deformation of the diaphragm, i.e. a deformation during which the diaphragm returns to its original shape when the pressure to be measured and the reference pressure are the same.

[0053] The membrane 14 is located in an undeformed state at a predefined distance 28 from the phase measuring unit 16. If the membrane 14 bulges inward, the distance between a surface of the membrane 14 and a surface of the phase measuring unit 16, as well as a radiation-emitting and radiation-receiving electronic component of the phase measuring unit 16, changes. The radiation-emitting and radiation-receiving electronic component of the phase measuring unit 16 is an antenna (not shown) in this exemplary embodiment. In this exemplary embodiment, the predefined distance 28 between the phase measuring unit 16 and the membrane 14 is dimensioned such that the predefined distance 28 corresponds to a maximum deformation of the membrane 14, i.e., the membrane 14 bulges inward at most to the extent that the surfaces of the membrane 14 and the phase measuring unit 16 touch.In this embodiment, the predefined distance 28 is selected so that it is less than or equal to a wavelength corresponding to the frequency of the radiation.

[0054] The change in distance between the surface of the membrane 14 and the phase measuring unit 16 can be used to measure the pressure acting on the membrane 14. For this purpose, the phase measuring unit 16 transmits a high-frequency radiation 30 to the membrane 14. The transmitted radiation 30 is at least partially reflected by the membrane 14. The reflected radiation 32 propagates from the membrane 14 to the phase measuring unit 16.

[0055] Radiations 30 and 32 have a constant frequency in the frequency range between 100 GHz and 300 GHz. For example, radiation can be used in a free industrial, scientific, and medical band, the so-called Industrial, Scientific, and Medical (ISM) band, such as in the frequency range between 122 GHz and 123 GHz, for example, 122.5 GHz, or between 244 GHz and 246 GHz, for example, 245 GHz. Alternatively, radiation in the millimeter-wave range or the terahertz range can be used, for example, in the frequency range between 10 GHz and 1 THz or 100 GHz and 1 THz.

[0056] The antenna of the phase measuring unit 16 transmits the radiation 30 and receives the reflected radiation 32 (not shown). In other embodiments, the phase measuring unit can also have multiple antennas. The phase measuring unit 16 generates the radiation 30 based on a periodic electrical signal with a constant frequency and generates a received electrical signal from the received reflected radiation 32. Since the distance between the surface of the membrane 14 and the phase measuring unit 16 changes with changing pressure acting on the membrane 14 to be measured, and the phase difference of the radiations 30 and 32 depends on this distance, the phase difference of the radiations 30 and 32 can be used to determine the pressure acting on the membrane 14 to be measured.In this exemplary embodiment, the phase measuring unit 16 provides a phase difference between the periodic electrical signal and the received electrical signal to the pressure determination unit 18, which determines a pressure to be measured acting on the membrane 14 based on the phase difference. A phase difference that changes depending on the distance between the membrane 14 and the phase measuring unit 16 results from the difference in the phase position between the periodic electrical signal and the received electrical signal, wherein the phase position of the reflected radiation 32 and thus that of the received electrical signal depends on the distance between the membrane 14 and the phase measuring unit 16.

[0057] In this exemplary embodiment, the measuring chamber 24 is coated with a radiation-attenuating material. In other exemplary embodiments, at least a portion of the inner surface of the sensor body, in particular the measuring chamber, can comprise a radiation-attenuating material and, in particular, can be lined with the radiation-attenuating material to prevent disruptive reflections in the measuring chamber. The radiation-attenuating material can, for example, be a carbon-containing layer or a carbon-containing foam. In this exemplary embodiment, a circular center of the inner side 22 of the membrane 14 is further coated with radiation-attenuating material. In this case, the circular center occupies 20% of the surface area of ​​the inner side 22 of the membrane 24. Instead of a coating, in other exemplary embodiments, the membrane 14 can comprise a radiation-attenuating material. Furthermore, the center can also have a different shape, for example, a square shape.The center can also occupy a different surface of the inner side of the membrane, for example, 10%, 30%, 40%, or 50% of the surface of the inner side of the membrane. In other embodiments, the inner side 22 of the membrane 14 is not coated. In other embodiments, the measuring chamber can also be filled with a radiation-attenuating liquid, such as oil. The oil can be, for example, a silicone oil. This makes it possible to attenuate unwanted reflected radiation and increase measurement accuracy.

[0058] The pressure determination unit 18 has a memory containing a table with measured phase differences as a function of the pressure to be measured, so that the pressure to be measured acting on the membrane 14 can be determined from a phase difference. Alternatively, the pressure determination unit 18 can also be connected to a memory (not shown). The table can be created in a calibration process in which the phase difference is measured for various known pressures. The calibration process can also take temperature into account. A temperature sensor can be used for this purpose, which can, for example, also be built into the pressure sensor or connected to the pressure sensor (not shown). If a measured phase difference lies between two table values, the pressure to be measured can be interpolated from the table values.Alternatively or additionally, a phase-difference-dependent pressure measurement function can be determined during the calibration process using regression analysis, machine learning, or other methods, with which a pressure to be measured acting on the membrane 14 can be determined. The pressure measurement function can also be temperature-dependent, i.e., in this case, phase differences can depend on temperature and pressure.

[0059] In Fig. 2 shows a second embodiment of a pressure sensor 10a according to the invention in a schematic representation.

[0060] The pressure sensor 10a has a sensor body 12 with a membrane 14, a beam bundling unit 34 with a dielectric lens 36, an intermediate layer 38, a phase measuring unit 16a integrated on a sensor chip 40, a first circuit board 42, a second circuit board 44 and a pressure determination unit 18.

[0061] In this exemplary embodiment, the membrane 14 forms an outer side of the sensor body 12, so that the membrane 14 and sensor body 12 enclose a measuring chamber 24, and the membrane 14 has an outer side 20 facing the environment and an inner side 22 facing the measuring chamber 24. In other exemplary embodiments, the sensor body 12 can have an external thread so that the pressure sensor can be screwed into a pressure vessel in which the pressure is to be measured. A reference pressure prevails in the measuring chamber 24. In this exemplary embodiment, an atmospheric pressure of 1 bar prevails in the measuring chamber 24. In other exemplary embodiments, the measuring chamber can have an opening to the outside to atmospheric pressure or a line that supplies the measuring chamber with atmospheric pressure to ensure the reference pressure. In this exemplary embodiment, the measuring chamber 24 is closed off by the intermediate layer 38, which connects the dielectric lens 36 to the phase measuring unit 16a.

[0062] In this embodiment, the intermediate layer 38 is made of high-resistance silicon and has a thickness of 500 µm. In other embodiments, the intermediate layer 38 can also have a thickness between 200 µm and 750 µm. The intermediate layer 38 has a specific electrical resistance of 1000 Ωcm. In other embodiments, the intermediate layer 38 can also have a specific electrical resistance between 50 Ωcm and 10 kΩcm, for example, between 50 Ωcm and 5 kΩcm or between 50 Ωcm and 1000 Ωcm.

[0063] Another outer side of the sensor body 12 is formed by a cover 46, which contains a connector 48. A cable 50 is connected to the connector 48 to connect the phase measuring unit 16a to the pressure determination unit 18 and a power source (not shown). In this exemplary embodiment, the pressure determination unit 18 has a processor that can perform calculations. The pressure determination unit can alternatively be, for example, a computer, server, or cloud service. Alternatively, instead of a connector 48, a transmitting / receiving unit or antenna for a wireless connection can be provided, for example, for a WiFi connection, Bluetooth connection, or another wireless connection for data transmission. In a further exemplary embodiment, a battery can also be housed in the sensor body so that the sensor body can be used independently of an external power source.In this case, measured phase differences can be transmitted wirelessly to the pressure determination unit.

[0064] The dielectric lens 36 is arranged separated from the membrane 14 by a predefined distance 52, which in this embodiment is dimensioned to correspond to the maximum deformation of the membrane 14. In Fig. 2, the membrane 14 is in an undeformed state. If the pressure to be measured acting on the outer side 20 of the membrane 14 is higher than the reference pressure acting on the inner side 22 of the membrane 14 in the measuring chamber 24, the membrane 14 bulges inward into the measuring chamber 24, thereby reducing the distance between the membrane 14 and the dielectric lens 36.

[0065] The phase measurement unit 16a has an oscillator with a frequency stabilizer in the form of a phase-locked loop, a transmitting antenna, a receiving antenna, a high-frequency amplifier, and a phase difference determination unit for determining a phase difference, which are connected to one another via waveguides (not shown). The aforementioned electronic components are arranged on the sensor chip 40 in this exemplary embodiment. In an alternative exemplary embodiment, the sensor chip contains further electronic components. Alternatively, the sensor chip can also have fewer electronic components. The oscillator can generate a stable periodic electrical signal with a constant frequency, which can be transmitted via the transmitting antenna as high-frequency radiation 30 to the membrane 14 and provided to the phase difference determination unit as a periodic electrical signal.The periodic electrical signal is amplified by the radio frequency amplifier before being transmitted via the transmitting antenna.

[0066] The dielectric lens 36 is arranged between the phase measuring unit 16a and the membrane 14, so that the radiation 30 transmitted from the transmitting antenna of the phase measuring unit 16a to the membrane 14 is focused onto a center of the membrane 14. Reflected radiation 32 is focused by the dielectric lens 36 onto the receiving antenna of the phase measuring unit 16a. The receiving antenna receives the reflected radiation 32 and generates a received electrical signal, which it provides to the phase difference determination unit.

[0067] The phase difference determination unit processes the received electrical signal taking into account the transmitted periodic electrical signal. The phase position of the received electrical signal is compared with the phase position of the transmitted periodic electrical signal. The pressure to be measured acting on the membrane 14 can then be determined, as described for the first embodiment of the pressure sensor 10, based on the phase difference between the periodic electrical signal and the received electrical signal. For this purpose, the phase measurement unit 16 transmits a processed electrical signal, i.e., the processed electrical signal containing the phase difference, via the connection 48 and the cable 50 to the processor of the pressure determination unit 18. In addition, the temperature is measured by a temperature sensor and transmitted as an electrical temperature signal to the pressure determination unit 18 (not shown).The pressure determination unit contains a memory with a table of pressures as a function of phase difference and temperature, so that the processor of the pressure determination unit 18 can determine the pressure to be measured acting on the membrane by determining the table value of the pressure to be measured, which corresponds to the measured phase difference at the measured temperature. Alternatively, the memory can also be arranged on the sensor chip 40 or arranged on the first circuit board 42 or second circuit board 44 and connected to the sensor chip 40 (not shown). In this case, a processor can also be part of the phase measurement unit 16a.

[0068] The first circuit board 42, together with the intermediate layer 38, serves as a holder for the sensor chip 40. The first circuit board 42 contains a quartz oscillator that supplies the phase-locked loop of the phase measurement unit 16a with a stable reference frequency. The sensor chip 40 is electrically connected to the circuit board 42 via bonding wires. In other embodiments, the sensor chip 40 can be electrically connected to the circuit board 42 via other connections. Alternatively, another high-quality reference oscillator can be used instead of the quartz oscillator. In further embodiments, the first circuit board contains an analog-to-digital converter.

[0069] The second circuit board 44 contains electronic components for data transmission via the connector 48.

[0070] In an alternative embodiment, the electronic components of the phase measurement unit 16a, except for the antennas, can also be distributed across the first and second circuit boards (not shown). In a further alternative embodiment, a reflector can be arranged behind the sensor chip to amplify the transmitted radiation by reflecting it toward the membrane. The phase position of the transmitted signal and the received signal is determined from an average over time.

[0071] In further embodiments, the pressure sensor, for example, a portion of an inner surface of the sensor body or the center of the inner surface of the membrane, can comprise a radiation-attenuating material. Furthermore, the measuring chamber can be filled with a radiation-attenuating liquid. This makes it possible to attenuate unwanted reflected radiation and increase measurement accuracy.

[0072] In Fig. 3 shows a schematic representation of a third embodiment of a pressure sensor 10d according to the invention. In contrast to the Fig. 1 and Fig. 2, the pressure sensor 10d has, in addition to the inlet 26, a second inlet 58 that can supply the pressure sensor 10d with a second pressure to be measured. The pressure sensor 10d includes a pressure barrier 59 arranged in the sensor body 12 between the diaphragm 14 and the phase measuring unit 16 such that the phase measuring unit 16 and the pressure determination unit 18 are not directly exposed to the pressure entering the pressure sensor 10d via the inlet 58. This makes it possible to prevent damage to the phase measuring unit 16 and the pressure determination unit 18 due to high pressures.

[0073] The pressure sensor 10d is suitable for differential pressure measurements. For this purpose, side 20 of the membrane 14 is supplied with a first pressure via inlet 26, and side 22 of the membrane 14 is supplied with a second pressure via inlet 58. The inlets 26 and 58 can each be connected to a pressure line for this purpose. At different first and second pressures, the membrane 14 bulges, thus changing the distance between the surface of the membrane 14 and the phase measuring unit 16. The phase measuring unit 16 determines a phase difference between the periodic electrical signal and the received electrical signal. The differential pressure can then be determined by the pressure determination unit 18 based on the phase difference, as described for the previous embodiments.

[0074] In other embodiments, a temperature sensor may be arranged to measure the temperature and the pressure determination unit 18 may determine the pressure to be measured based on the phase difference and the temperature.

[0075] In Fig. 4 shows a fourth embodiment of a pressure sensor 10e according to the invention in a schematic representation.

[0076] The pressure sensor 10e has a sensor body 12, a diaphragm 14, a beam condenser unit 34 with a dielectric lens 36, a phase measuring unit 16e, a quartz oscillator 60, and a pressure determination unit 18. In this embodiment, the sensor body 12 and the diaphragm 14 enclose a measuring chamber 24 having a reference pressure corresponding to atmospheric pressure, such that an outer side of the diaphragm 14 is connected to a pressure to be measured and an inner side of the diaphragm 14 is connected to the reference pressure. In this embodiment, the measuring chamber 24 has a line 61 that connects the measuring chamber 24 to the atmospheric pressure. The dielectric lens 36 is adhesively bonded to the phase measuring unit 16e in this embodiment.

[0077] The phase measuring unit 16e is connected to the quartz oscillator 60, which supplies the phase measuring unit 16e with a reference frequency. Furthermore, the phase measuring unit 16e is connected to the pressure determination unit 18 via a cable 50.

[0078] The phase measuring unit 16e contains a phase-frequency comparator 62, an oscillator 64, and a frequency divider 66, which form a frequency stabilizer in the form of a phase-locked loop 68, as well as a radio-frequency amplifier 70, a transmitting antenna 72, a receiving antenna 74, a mixer 76, and an analog-to-digital converter (AD converter) 78. In this embodiment, the phase measuring unit 16e operates according to the mixer principle. In other embodiments, the mixer can be implemented as a quadrature mixer.

[0079] Oscillator 64 is connected via high-frequency amplifier 70 to transmitting antenna 72 and to mixer 76, which is also connected to receiving antenna 74. The output of mixer 76 is connected to pressure determination unit 18 via AD converter 78 and cable 50. In other embodiments, the AD converter is not part of the phase measurement unit, but rather part of the pressure determination unit or is arranged between the phase measurement unit and the pressure determination unit. AD converter 78 converts analog signals into digital signals so that a processor of pressure determination unit 18 can process the signals containing the phase difference coming from phase measurement unit 16.

[0080] The function of the pressure sensor 10e of the fourth embodiment is described below.

[0081] Oscillator 64 is stabilized by phase-locked loop 68, generating a periodic electrical signal with a constant frequency. For this purpose, oscillator 64, together with frequency divider 66 and phase-frequency comparator 62, forms phase-locked loop 68. Phase-frequency comparator 62 compares the oscillator frequency of phase-locked loop 68 with the reference frequency supplied by quartz oscillator 60. The reference frequency is typically between 10 MHz and several hundred MHz. This so-called phase-locked loop (PLL) arrangement makes it possible to maintain the oscillator frequency very precisely at a constant value. In this embodiment, oscillator 64 provides a constant frequency of 245 GHz. In other embodiments, the oscillator can be combined with a frequency doubler or frequency multiplier to achieve the high frequency.Alternatively, the oscillator 64 can also generate a frequency of 24.125 GHz, 61.25 GHz, 122.5 GHz, or another frequency in the range between 10 GHz and 1 THz, for example a frequency in the range between 100 GHz and 1 THz or 100 GHz and 300 GHz.

[0082] The periodic electrical signal generated by oscillator 64 is split into two paths. One portion is passed via high-frequency amplifier 70 to transmitting antenna 72, and another portion is passed to mixer 76. Transmitting antenna 72 transmits the electrical signal in the form of high-frequency radiation 30 to diaphragm 14. High-frequency radiation 30 is focused by dielectric lens 36 and impinges on diaphragm 14, which partially reflects the radiation. Reflected radiation 32 is focused by dielectric lens 36 onto receiving antenna 74. Receiving antenna 74 receives reflected radiation 32 and generates a received electrical signal, which it provides to mixer 76. Mixer 76 thus receives two signals of the same frequency: the periodic electrical signal generated by oscillator 64 and the received electrical signal generated by receiving antenna 74 based on reflected radiation 32.The mixer 76 mixes the electrical signals and the mixed product is an electrical signal with the difference frequency and an electrical signal with the sum frequency, i.e. in this case an electrical signal with twice the frequency. The signal with twice the frequency is filtered out by the mixer because the mixer strongly attenuates this very high frequency. Since the frequencies of the mixed electrical signals are the same, their difference frequency is zero. This therefore results in only a DC voltage component, which depends on a phase position between the electrical signal and the received electrical signal. The phase position of the received electrical signal depends on the distance between the membrane 14 and the phase measuring unit 16e, in particular the distance between the membrane 14 and the antennas 72 and 74. The distance, in turn, depends on the pressure.Therefore, the DC voltage signal generated by the mixer 76 can be used to determine the pressure to be measured acting on the membrane 14. For this purpose, the DC voltage signal is converted into a digital signal via an AD converter 78 and further processed accordingly in the pressure determination unit 18 by the processor of the pressure determination unit 18. In this exemplary embodiment, the DC voltage signal is supplied to the pressure determination unit 18 via the cable 50. The pressure determination unit 18 determines the pressure to be measured using a table as described for the first exemplary embodiment of the pressure sensor 10. Alternatively, the pressure determination unit 18 can also use a pressure measurement function that depends on the phase difference. Furthermore, the pressure determination unit 18 can also be designed to take the temperature into account when determining the pressure to be measured, which can be provided, for example, by a temperature sensor.Alternatively, the pressure sensor can also be used at a constant temperature. In this case, no temperature measurement is used to determine the pressure to be measured.

[0083] In Fig. Figure 5 shows a schematic representation of a fifth embodiment of a pressure sensor 10f according to the invention. The phase measuring unit 16f of the pressure sensor 10f also operates according to the mixer principle. The fifth embodiment of the pressure sensor 10f is essentially identical to the fourth embodiment of the pressure sensor 10e and differs only in that the transmitting antenna 72 and receiving antenna 74 of the phase measuring unit 16e are replaced by an antenna 80 and a coupler 82 of the phase measuring unit 16f.

[0084] The coupler 82 passes the electrical signals amplified by the radio frequency amplifier 70 to the antenna 80 and the electrical signals received by the antenna 80 to the mixer 76. In an alternative embodiment, a low-noise amplifier is arranged between the coupler and the mixer (not shown).

[0085] In Fig. 6 and Fig. Figure 7 shows a sixth exemplary embodiment of a pressure sensor 10g according to the invention and a seventh exemplary embodiment of a pressure sensor 10h according to the invention, each in a schematic representation. Pressure sensor 10g operates on the basis of a six-port structure 84 that uses power couplers. The operation of pressure sensors 10g and 10h is analogous and is explained below.

[0086] The pressure sensor 10g operates according to the six-port principle, and the pressure sensor 10h operates according to the reflectometer principle, which is a special case of the six-port principle. The reflectometer principle is described, for example, in B. Lämmle et al.: "A 122 GHz Multiprobe Reflectometer for Dielectric Sensor Readout in SiGe BiCMOS Technology, 2011 IEEE Compound Semiconductor Integrated Circuit Symposium," and the six-port principle is described in A. Kölpin et al.: "The Six-Port in Modern Society," IEEE microwave magazine, 12 / 2010. The six-port arrangement 84 consists of a network of power couplers. The reflectometer arrangement 86 essentially consists of a series of waveguide sections 92, 92a, and 92b.

[0087] The pressure sensor 10g has a sensor body 12, a membrane 14, a beam condenser unit 34 with a dielectric lens 36, a phase measuring unit 16g, a quartz oscillator 60, and a pressure determination unit 18. In this embodiment, the sensor body 12 and the membrane 14 enclose a measuring chamber 24 having a reference pressure, such that an outer side of the membrane 14 is connected to a pressure to be measured and an inner side of the membrane 14 is connected to the reference pressure. The reference pressure in this case is atmospheric pressure, which is supplied via line 61. In this embodiment, the dielectric lens 36 is glued directly to the phase measuring unit 16g. In other embodiments, the dielectric lens can be glued to an intermediate layer attached to the phase measuring unit.

[0088] The phase measuring unit 16g is connected to the quartz oscillator 60, which supplies the phase measuring unit 16g with a reference frequency. Furthermore, the phase measuring unit 16g is connected to the pressure determination unit 18 via cable 50. In other embodiments, the pressure determination unit can also be arranged together with the phase measuring unit on a common chip.

[0089] The phase measuring unit 16g contains a phase-frequency comparator 62, an oscillator 64 and a frequency divider 66, which form a frequency stabilizer in the form of a phase-locked loop 68, a six-port arrangement 84, an antenna 80, four power meters 88, 88a, 88b and 88c and four AD converters 90, 90a, 90b, 90c.

[0090] The phase measurement unit 16h of the pressure sensor 10h is similar to the phase measurement unit 16g. However, the phase measurement unit 16h has an optional high-frequency amplifier in the form of an impedance converter 70a, and the six-port array 84 is replaced with the reflectometer array 86. The four power meters 88, 88a, 88b, and 88c are connected to each other via the three waveguide sections 92, 92a, and 92b.

[0091] The phase measurement unit 16h is designed in the form of a sensor chip with a reflectometer structure, i.e., a structure with two inputs 94, 94a and four outputs 96, 96a, 96b, and 96c. The sensor chip has a first input 94, into which a periodic electrical signal with a constant frequency is fed from the frequency-stabilized oscillator 64. Furthermore, an electrical signal received from the antenna 80, which is generated based on reflected radiation, is fed via a second input 94a.

[0092] The reflectometer method is based on the principle of superposition of the two electrical signals at four points on the waveguide 87 of the reflectometer arrangement 86. For this purpose, the length of the waveguide sections 92, 92a, and 92b is each a quarter of the wavelength of the signals. The wavelength λ of the signals is related to the frequency f of the signals via the relationship λ=cfεr where c is the speed of light and ε r the relative dielectric constant of the surrounding medium. At each junction of the waveguide sections 92, 92a, 92b, one of the power meters 88, 88a, 88b, 88c is arranged, each capable of measuring power. The power meters 88, 88a, 88b, 88c send the signal they generate to a respective one of the AD converters 90, 90a, 90b, 90c, which can send the digital signals via an output 96, 96a, 96b, and 96c via cable 50 to the pressure determination unit 18 for further processing.

[0093] The operation of the pressure sensor 10h with phase measurement unit 16h in the form of a sensor chip with a reflectometer structure is described below. Alternatively, the six-port structure can also be arranged in a different configuration, for example, with power couplers as in the case of the phase measurement unit 16g.

[0094] Oscillator 64, embedded in phase-locked loop 68, generates a periodic electrical signal with a constant frequency of 245 GHz. Alternatively, oscillator 64 can also generate a frequency of 24.125 GHz, 61.25 GHz, or 122.5 GHz, for example, or another frequency in the range between 10 GHz and 1 THz, for example, a frequency in the range between 100 GHz and 1 THz or between 100 GHz and 300 GHz.

[0095] The periodic electrical signal travels from the oscillator 64 via the waveguide 87 of the reflectometer arrangement 86 and the waveguide sections 92, 92a, 92b to the antenna 80. The antenna 80 transmits the periodic electrical signal in the form of high-frequency radiation to the membrane 14. The high-frequency radiation is focused by the dielectric lens 36 and impinges on the membrane 14. The membrane 14 reflects the radiation at least partially. The reflected radiation is focused by the dielectric lens 36 onto the antenna 80. The antenna 80 generates a received electrical signal based on the reflected radiation, which travels through the waveguide 87 and is added to the periodic electrical signal at the four junctions of the waveguide sections 92, 92a, and 92b along the waveguide 87. This results in a static wave pattern that is measured via the four power meters 88, 88a, 88b and 88c (“sampled line” method).

[0096] Since the phase position of the received electrical signal depends on the distance of the antenna 80 from the membrane 14, the resulting static wave pattern is also a function of the distance of the antenna 80 from the membrane 14. The resulting static wave patterns can be used to determine the pressure to be measured acting on the membrane 14.

[0097] The DC voltage signals at the power meters can be converted into digital signals via the AD converters 90, 90a, 90b, 90c and further processed in the pressure determination unit 18. For this purpose, the pressure determination unit 18 has a processor and a memory with a table containing corresponding values ​​of the pressures to be measured as a function of the measured values ​​of the standing wave patterns, taking temperature into account, so that the pressure acting on the membrane to be measured can be determined in a similar manner as described for the first embodiment of the pressure sensor 10. Measured values ​​for the temperature can be supplied separately to the pressure determination unit 18 (not shown).

[0098] Alternatively, in addition to the phase measurement unit 16h, the sensor chip can have the pressure determination unit 18 with a processor and memory, which contains a table with measured static wave patterns as a function of the pressure to be measured, so that the pressure to be measured acting on the membrane 14 can be determined from the measured static wave pattern. The table can be created in a calibration process in which the respective static wave pattern is measured for various known pressures. If measured values ​​for the static wave pattern lie between table values, a pressure to be measured can be interpolated. Alternatively or additionally, a pressure measurement function dependent on the static wave pattern can be determined in the calibration process using regression analysis, machine learning, or other methods, with which a pressure to be measured acting on the membrane 14 can be determined.

[0099] Fig. 8 shows a schematic representation of an embodiment of a sensor device 100 according to the invention with a pressure sensor 10 and a temperature sensor 102.

[0100] The sensor device 100 allows both pressure and temperature to be determined. In this exemplary embodiment of the sensor device 100, the measured values ​​for pressure and temperature are used to calibrate the pressure sensor 10, taking temperature into account. Alternatively, a separate temperature sensor can also be used to measure the temperature during the calibration process.

[0101] In an alternative embodiment, the temperature sensor 102 can also be replaced by a second pressure sensor (not shown). A different pressure can be supplied to the respective inlets of the pressure sensors, and the sensor device can be used for differential pressure measurement.

[0102] Fig. Figure 9 shows an embodiment of a method according to the invention for operating a pressure sensor in the form of a flowchart. The method can be used to operate one of the embodiments of the pressure sensor 10, 10a, 10d, 10e, 10f, 10g, or 10h.

[0103] In step 200, a periodic electrical signal with a constant frequency is generated. In step 210, the periodic electrical signal is transmitted as high-frequency radiation to the membrane. There, the radiation is at least partially reflected. In step 220, the high-frequency radiation reflected by the membrane is received. The received reflected high-frequency radiation is converted into a received electrical signal and fed to a phase measuring unit. In step 230, a phase difference between the transmitted radiation and the reflected radiation is determined. For this purpose, the phase position of the periodic electrical signal and the received electrical signal is compared. The phase difference is fed to a pressure determination unit. In step 240, a pressure acting on the membrane is determined based on the phase difference.This is done, as described for pressure sensor 10, using a table of phase-difference correlated pressures. Alternatively, a pressure measurement function can also be used. In this embodiment, temperature is not taken into account, since the method for operating the pressure sensor is intended for use at a constant temperature. In other embodiments, temperature may be taken into account.

Claims

[1] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) comprising: - a sensor body (12) with a deformable membrane (14) arranged such that two sides (20, 22) of the membrane (14) can be subjected to different pressures in order to deform the membrane (14), - a phase measuring unit (16, 16a, 16e, 16f, 16g, 16h) arranged opposite the membrane (14), which is designed: -- to generate a periodic electrical signal with a constant frequency, -- to send the signal as high-frequency radiation (30) to the membrane (14), -- to receive high-frequency radiation (32) reflected at the membrane (14), and -- to determine a phase difference between transmitted radiation (30) and reflected radiation (32), - a beam bundling unit (34) for bundling the radiation (30, 32), -- which has a dielectric lens (36), -- wherein the beam bundling unit (34) is connected to the phase measuring unit (16, 16e, 16f, 16g, 16h), or -- wherein an intermediate layer (38) is provided between the phase measuring unit (16a) and the beam bundling unit (34), and - a pressure determination unit (18) which is designed to determine a pressure acting on the membrane (14) on the basis of the phase difference. [2] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to claim 1, wherein the beam bundling unit (34) is arranged such that the beam bundling unit (34) bundles the radiation (30) transmitted by the phase measuring unit (16, 16a, 16e, 16f, 16g, 16h) onto the membrane (14) and bundles the radiation (32) reflected by the membrane (14) onto the phase measuring unit (16, 16a, 16e, 16f, 16g, 16h). [3] Pressure sensor (10a, 10d) according to claim 2, wherein the beam bundling unit (34) is arranged at a predefined distance (52) from the membrane (14), between the phase measuring unit (16, 16a) and the membrane (14). [4] Pressure sensor (10a, 10d) according to claim 3, wherein the predefined distance (52) between the beam bundling unit (34) and the membrane (14) is dimensioned such that the predefined distance (52) corresponds to a maximum deformation of the membrane (14). [5] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to one of claims 1 to 4, wherein the beam bundling unit (34) additionally comprises a dielectric waveguide. [6] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to claim 1, wherein the dielectric lens (36) comprises silicon and / or a plastic material having a dielectric constant between 2.5 and 12. [7] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to one of claims 1 to 6, wherein at least a part of an inner surface of the sensor body (12) comprises a radiation-attenuating material. [8] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to one of claims 1 to 7, wherein the side (22) of the membrane (14) arranged opposite the phase measuring unit (16, 16a, 16e, 16f, 16g, 16h) comprises a radiation-attenuating material extending around a center of the side (22) of the membrane (14) arranged opposite the phase measuring unit (16, 16a, 16e, 16f, 16g, 16h). [9] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to one of claims 1 to 8, wherein the pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) has a measuring chamber (24) which is arranged between the membrane (14) and the phase measuring unit (16, 16a, 16e, 16f, 16g, 16h) and which has a radiation-attenuating liquid in order to attenuate unwanted reflected radiation and to increase the measuring accuracy. [10] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to one of claims 1 to 9, wherein the phase measuring unit (16, 16a, 16e, 16f, 16g, 16h) is designed to generate a received electrical signal based on the received reflected radiation (32) and to determine the phase difference between the periodic electrical signal and the received electrical signal. [11] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to one of claims 1 to 10, wherein the phase measuring unit (16, 16a, 16e, 16f, 16g, 16h) is designed to generate the periodic electrical signal with a constant frequency in the terahertz range or with a constant wavelength in the millimeter wave range. [12] Pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to one of claims 1 to 11, which has a memory which contains phase differences which correspond to certain pressures, so that an associated pressure can be determined from a phase difference, or which contains a pressure measuring function which is designed to determine the pressure acting on the membrane (14) as a function of the phase difference. [13] Pressure sensor (10e, 10f, 10g, 10h) according to one of claims 1 to 12, wherein the phase measuring unit (16e, 16f, 16g, 16h) comprises: - an antenna (72, 74, 80) for transmitting and / or receiving the radiation (30, 32), - an oscillator (64) having a frequency-stabilized frequency for generating the periodic electrical signal, and - a high-frequency amplifier (70, 70a). [14] Pressure sensor (10e, 10f, 10g, 10h) according to claim 13, wherein the phase measuring unit (16e, 16f, 16g, 16h) comprises a frequency stabilizer (68) for stabilizing the frequency of the oscillator (64). [15] Pressure sensor (10e, 10f) according to claim 13 or 14, wherein the phase measuring unit (16e, 16f) comprises a mixer (76) for determining the phase difference. [16] Pressure sensor (10g) according to one of claims 1 to 14, wherein the phase measuring unit (16g) has two inputs (94, 94a) for signals, four outputs (96, 96a, 96b, 96c) for signals and four power meters (88, 88a, 88b, 88c), and wherein the four power meters (88, 88a, 88b, 88c) are arranged in a six-port structure for detecting static wave patterns. [17] Pressure sensor (10h) according to one of claims 1 to 14, wherein the phase measuring unit (16h) has two inputs (94, 94a) for signals, four outputs (96, 96a, 96b, 96c) for signals and four power meters (88, 88a, 88b, 88c), and wherein the four power meters (88, 88a, 88b, 88c) are connected to one another via a waveguide (87) in a reflectometer structure for detecting static wave patterns. [18] Sensor device (100) comprising a pressure sensor (10a, 10d, 10e, 10f, 10g, 10h) according to one of claims 1 to 17 and a temperature sensor (102).

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