Core temperature probe and system having same

Abstract

The invention relates to a core temperature probe (1), having a temperature measuring device (3) with at least one temperature sensor (9), and having a signal transmission antenna (2) connected to the temperature measuring device (3) via a coaxial line (4), wherein via the signal transmission antenna (2) an item of temperature information determined by the at least one temperature measuring device (3) can be emitted at a signal transmission frequency which differs from a microwave frequency, wherein the coaxial line (4) has at least one line resonance element (11a, 11b, 12) set to the microwave frequency, and an electrically conductive plate (14a-14d) is provided at at least one boundary face of at least one such line resonance element (11a, 11b), said plate being electrically connected to an inner conductor (5) or an outer conductor (6) of the coaxial line (4). The invention also relates to a microwave cooking appliance having a signal transmission antenna, and to a system. The invention can be particularly advantageously applied to ovens which are configured to interact with a core temperature probe and also have a microwave function.

Description

[0001] 202300988 1 / 34 Core temperature sensor and system therewith The invention relates to a core temperature sensor having at least one temperature sensor and a signal transmission antenna connected to the at least one temperature sensor, wherein temperature information determined by the at least one temperature sensor can be transmitted via the signal transmission antenna at a signal transmission frequency that differs from a microwave frequency, wherein the at least one temperature sensor is connected to the signal transmission antenna via a coaxial line, and wherein the coaxial line has at least one line resonance element tuned to the microwave frequency. The invention also relates to a microwave cooking appliance having a cooking chamber irradiated by microwaves of a predetermined microwave frequency, comprising a signal transmission antenna for transmitting signals at a signal transmission frequency,which differs from the microwave frequency, and a signal path, in particular guided through an oven wall, wherein the signal path is at least partially a coaxial line and the coaxial line has at least one line resonance element tuned to the microwave frequency. The invention further relates to a system with a microwave cooking appliance and at least one such core temperature sensor, wherein the system is configured to wirelessly transmit signals at the signal transmission frequency between the signal transmission antenna of the core temperature sensor and the signal transmission antenna of the microwave cooking appliance. The invention is particularly advantageously applicable to ovens that are configured to work with a core temperature sensor and also have a microwave function. It is known that in ovens that also have a microwave function, the problem arises that microwave energy,which is coupled via a signal transmission antenna of a core temperature sensor, can disrupt the operation of components connected to the signal transmission antenna, such as a temperature sensor, an electrical circuit, etc., or even destroy the components. WO 2017 / 029059 A1 discloses a core temperature sensor. This has at least one temperature sensor and a signal transmission antenna connected thereto, wherein temperature information determined by the at least one temperature sensor can be transmitted via the signal transmission antenna at a signal transmission frequency that differs from a microwave frequency.wherein the at least one temperature sensor is connected to the signal transmission antenna via a coaxial line, and the coaxial line has at least one lambda (λ) / 4 line resonance element tuned to the microwave frequency. Furthermore, a microwave cooking appliance with a cooking chamber irradiated with microwaves is disclosed. The microwave cooking appliance has a signal transmission antenna arranged in the cooking chamber for transmitting signals at a signal transmission frequency that differs from a microwave frequency, and a signal line routed through an oven wall, wherein the signal line is at least partially a coaxial line.which has at least one lambda / 4-line resonance element tuned to the microwave frequency. A system comprising this can wirelessly transmit signals at the signal transmission frequency between the signal transmission antenna of the core temperature sensor and the signal transmission antenna of the microwave cooking appliance. EP 1757862 B1 discloses an oven for cooking food, comprising: a cooking chamber accessible through an oven door, means configured to generate and emit microwaves for propagation in the cooking chamber, control means configured to process signals received from external sources and to control the microwave generation and emission means for operation depending on the signals received from the external sources, a movable temperature probe configured to be inserted into the food arranged inside the cooking chamber of the oven,and which is provided with a plurality of temperature sensors distributed at predetermined distances from one another along the movable probe, the sensors being electrically connected to the control means for supplying them with the signals from the external sources, the control means being configured to receive the temperature control signal coming from a predetermined one of the sensors and to modify the operation of the microwave generation and emission means when it has been determined that the temperature control signal has reached a predetermined value, the control means being configured to receive and compare the signals relating to the temperatures detected by the sensors, identify the signal corresponding to the highest temperature, and select and use it as the current temperature control signal to be compared with the predetermined temperature value.to modify the operating mode of the microwave generation and emission means accordingly. The problem of unwanted coupling of microwaves into electrical circuits is not addressed. EP 2163823 A1 relates to a cooking process sensor for a cooking appliance for cooking food, which has a tip that can be inserted at least partially into the food, a handle, and at least one temperature sensor, wherein the output data of at least a first temperature sensor can be used to adjust at least one microwave source of the cooking appliance.and the first temperature sensor is surrounded by a microwave-absorbing material; and a cooking appliance with such a cooking process sensor. However, such shielding for the signal transmission antenna is of little practical use. DE 2935282 A1 discloses a temperature measuring device for wirelessly monitoring the temperature of an object with a passively excitable temperature sensor and a transmitter / receiver unit for externally exciting electromagnetic waves as information carriers for the respective temperature of the object. A throttle arrangement is disclosed to prevent microwave signals from penetrating the interior of the temperature sensor. The location and structure of the throttle arrangement are not further explained. The object of the present invention is to at least partially overcome the disadvantages of the prior art and, in particular, to provide a compact, robust, and inexpensive option.To protect components of a core temperature sensor particularly effectively from microwave signals radiated into a cooking chamber of a microwave cooking appliance and coupled in via a signal transmission antenna. This object is achieved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims. The object is achieved by a core temperature sensor comprising at least one temperature measuring device with at least one temperature sensor and a signal transmission antenna connected to the temperature measuring device via a coaxial line, wherein temperature information determined by the at least one temperature measuring device can be transmitted via the signal transmission antenna at a (data) signal transmission frequency that differs from a microwave frequency.wherein the coaxial line has at least one line resonance element tuned to the microwave frequency, and at least one interface of at least one such line resonance element has an electrically conductive plate that is electrically connected either to an inner conductor or to an outer conductor of the coaxial line. The electrically conductive plate creates at least one additional contact point in the path of the microwaves along the coaxial line in a space-saving, robust, and cost-effective manner. Due to the resulting impedance jump, it is particularly effectively prevented that microwave signals from the outside are transmitted via the signal transmission antenna to electrical and / or electronic components of the core temperature sensor, such as temperature sensors, integrated circuits, resistors, coils,Capacitances, etc. can get into the core temperature probe. This makes the core temperature probe, or rather its interior, particularly resistant to microwave interference. This, in turn, enables not only passive, but especially active signal processing and generation in the core temperature probe, without causing significant signal interference or even damage or destruction to circuits. Since the core temperature probe can also be used in cooking appliances without a microwave function, but with or without a steam function, for example, the user advantageously does not need to pay attention to which core temperature probe is used in which appliance. The core temperature probe can also be referred to as a food thermometer or temperature probe. In particular, it can have a skewer- or needle-shaped section ("measuring section") on the front, with which it is inserted into the food to be monitored.and a handle adjoining the measuring section at the rear. The at least one temperature sensor can be arranged in the measuring section. In the case of multiple temperature sensors, these can be arranged in a row in the longitudinal direction in the measuring section. The measuring section can, in particular, have a hollow cylindrical sleeve (e.g., made of metal or ceramic, in particular stainless steel) that is closed at the front and in which the at least one temperature sensor is housed. The core temperature sensor can generally be configured to transmit at least one ("temperature") signal via the coaxial cable to the signal transmission antenna for wireless transmission at the signal frequency.wherein the temperature signal comprises at least one piece of temperature information determined by means of the at least one temperature sensor and optionally processed by the associated temperature measuring device. In general, data signals can also be received on the signal frequency via the signal transmission antenna, so that in a further development it can be designed as a combined transmitting / receiving antenna. The signal transmission antenna can be located in the handle or protrude from the handle. Due to its signal transmission antenna, the core temperature sensor is wireless or configured for wireless signal transmission. This offers the advantage that a user can insert it into the food on a countertop and only then place the food in the cooking appliance. Radio signal transmission has the advantage that openings in the oven for cable connections and the associated disadvantages such as microwave leakage radiation, steam escape,The escape of hot air, oxidation of contact transitions, etc. must be avoided. Frequently used microwave frequencies are in a range between 2.4 GHz and 2.5 GHz, e.g., 2.45 GHz. However, it is also known to use microwave frequencies in a range between 902 MHz and 928 MHz. The fact that the coaxial cable has at least one line resonance element tuned to the microwave frequency means, in particular, that the line resonance element is specifically tuned to a specific microwave frequency or a specific microwave frequency band, and the core temperature sensor is thus intended for use in microwave devices that use microwaves at this frequency. Frequently used signal frequencies are in a range between 433.05 MHz and 434.79 MHz. This ISM band advantageously allows data and information transmission with widely available and inexpensive data transmission components. However, other frequency bands such as those between 13.553 MHz and 13.567 MHz, 26.957 MHz and 27.283 MHz, 40.66 MHz and 40.70 MHz, 863 MHz and 870 MHz, and 902 MHz to 928 MHz (if not used for microwaves) can also be used. Other bands for signal frequencies are also usable, although possibly with regulatory barriers if they are not freely usable frequencies from ISM bands. As is generally known, the coaxial cable hasan inner conductor and an outer conductor. The volume between the inner conductor and the outer conductor consists, as is usual for coaxial cables, of an electrically non-conductive or insulating material or contains such a material. The material can be solid or gaseous. If the volume is filled with a solid or consists of a solid, the solid can be present as a solid and can then also be referred to as an "insulator body." The use of an insulator body is particularly advantageous for providing a resonant line section with a high dielectric conductivity or relative permittivity. The insulator body can be a compact insulator body in the sense that it has little or no porosity. In a further development, the insulator body can be a prefabricated component. The microwaves as well as the data signals run along the coaxial line. It is a further development,that the coaxial cable has an inner conductor formed from a piece of wire and an outer conductor formed from an electrically conductive sleeve, in particular a metal sleeve, wherein the metal sleeve also represents the sleeve of the measuring section, at least in part. In particular, the outer conductor has the shape of a cylindrical tube with a defined inner diameter. The piece of wire runs, in particular, parallel to and centrally in the metal sleeve and has a defined diameter. The piece of wire can have a circular cross-section. The piece of wire can be a copper wire, for example. The piece of wire can be continued as the signal transmission antenna, so that one section of a wire can form the signal transmission antenna and another section of the wire can form the wire section of the coaxial cable. The outer conductor, in particular in the form of a metal sleeve, is advantageously made of stainless steel,because it is robust and inexpensive. 202300988 7 / 34 The line resonance element tuned to the microwave frequency corresponds in particular to a section of the coaxial line with a defined length along the coaxial line tuned to the microwave frequency or wavelength of the microwaves. A transition of the relative permittivity ε occurs at at least one end point or at least one boundary surface of the line resonance element. r of the material present between the inner conductor and the outer conductor to a neighboring material with a different relative permittivity ε r , so that in interaction with the length of the line resonance element, a respective impedance jump occurs there. In other words, a line resonance element borders on its interfaces to neighboring sections of the coaxial line with different relative permittivity ε for the microwaves. r, especially to neighboring line resonance elements. The line resonance element creates a deliberate mismatch, resulting in impedance jumps at the interfaces (also referred to as "junctions"), through which a significant portion of the microwaves are reflected back. The reflectivity tends to be higher, the greater the difference in the relative permittivities ε rat the interface. A section of the coaxial line that has the line resonance element can also be referred to as a resonance line or resonance line section. Line resonance element and resonance line section can be used synonymously as long as the context does not indicate otherwise. It is a development that the volume between the inner conductor and outer conductor is hollow cylindrical, with the inner conductor running particularly centrally through this volume. The interfaces then correspond to the base areas of the hollow cylinder. It is a particularly effective development that the outer surface of the tubular volume extends to the outer conductor, and if this is not possible, as close as possible to the outer conductor. It is a particularly effective development that the inner surface of the volume extends to the inner conductor, and if this is not possible, as close as possible to the inner conductor.Thus, in a further development, the distance or gap can be only a few tenths of a millimeter. It is a further development that the electrically non-conductive volume consists of or is filled with technical ceramic, or at least contains ceramic. Ceramic has the advantage of high thermal, mechanical, and chemical resistance. Furthermore, a ceramic body with a highly electrically insulating ceramic material can be used. Possible technical ceramics can be, for example, aluminum oxide, Al2O3, with a typical relative permittivity ε. r between 6 and 15 or zirconium dioxide, ZrO2, with a typical relative permittivity ε rbetween 20 and 40. Alternatively, glass or glass-ceramic can be used as the material. A ceramic-filled resonant line can also be referred to as a "ceramic line," etc. In the further development with an insulator body between the inner and outer conductors, very small tolerances should advantageously be maintained. The gaps to the inner and outer conductors should advantageously be reduced to a minimum. Microwaves coupled in via the signal transmission antenna are at least partially reflected at the interface of the insulator body facing the signal transmission antenna, since the insulator body causes an impedance jump there due to the transition from, for example, air to the material of the insulator body.A portion of the microwaves that is not reflected there, but continues along the coaxial line along the insulator body, will experience another impedance jump at the interface of this insulator body facing away from the signal transmission antenna and will therefore be at least partially reflected back to the signal transmission antenna. Radio signals, on the other hand, are transmitted with almost no loss. A further development is that the electrically non-conductive volume between the inner conductor and outer conductor of at least one line resonance element is made of air (ε). r= 1). This is particularly advantageous for providing a line resonance element or a resonant line section with a low dielectric conductivity or relative permittivity. The use of air in particular enables a particularly inexpensive and simple construction. An air-filled resonant line can also be referred to as an "air line." The fact that the coaxial line has at least one line resonance element tuned to the microwave frequency can include the coaxial line having exactly one line resonance element tuned to the microwave frequency, or the coaxial line having several line resonance elements arranged in series along the direction of extension of the coaxial line. It is a design for strong attenuation orFiltering the microwaves along the coaxial line, an advantageous development is that the series-connected line resonance elements alternately have a high dielectric constant and a low dielectric constant, because this results in particularly high impedance jumps. For example, a glass or ceramic line, an air line, and another glass or ceramic line can be arranged in this order. However, rows with several solid-filled, adjacently arranged resonance lines can also be used, as long as the relative permittivities differ significantly. For example, two adjacently arranged resonance lines can be equipped with respective insulator bodies with significantly different relative permittivities, e.g., as two ceramic lines with ε. r = 6 or ε r= 40. The plate is in particular perpendicular to the inner conductor, i.e. its normal vector is aligned parallel to the inner conductor or its main surface is aligned perpendicular to the inner conductor. In one development, the electrically conductive plate is designed in the form of a perforated disk. In particular, the plate can rest with one of its base surfaces on a base surface of a hollow cylindrical body of a line resonance element adjacent along the coaxial line. In particular, the electrically conductive plate can completely cover the base surface of the hollow cylindrical body. In one embodiment, the electrically conductive plate is a metal plate. This is particularly cost-effective and advantageously has high electrical conductivity. The metal can be, for example, copper, silver, brass, aluminum, or an alloy thereof, etc.Alternatively, the electrically conductive plate can be a ceramic plate made of highly electrically conductive ceramic. One embodiment is that the thickness of the plate is less than 10%, in particular less than 5%, especially less than 2% of a microwave wavelength. The thickness can also be referred to as "thickness" or, with reference to the propagation direction of the microwaves, as "length." Since the length of the plate or the corresponding coaxial "plate line" is small compared to the microwave wavelength, advantageously no impedance transformation needs to be considered, but only the impedance jump that results between the different coaxial line impedances. The real impedance of the plate can thus be used directly to determine the reflection factor at the joints between a plate and at least one adjacent line resonance element.This significantly simplifies the design of the coaxial line. One embodiment provides that at least one line resonance element is a lambda (λ) / 2 line resonance element. Its length, taking into account its relative permittivity, corresponds to half a wavelength of the microwave radiation, or a multiple thereof. The lambda / 2 line resonance element can generally have a length of λ / 2 or generally of λ / 2 + n ^ λ / 2 with n = 0, 1, 2, 3, ... One embodiment provides that at least one line resonance element is a lambda / 4 line resonance element. Its length, taking into account its relative permittivity, corresponds to a quarter wavelength of the microwave radiation. The lambda / 4 line resonance element can generally have a length of λ / 4 or generally of λ / 4 + n ^ λ / 2 with n = 0, 1, 2, 3, …If there are multiple line resonance elements, in one embodiment, all line resonance elements can be lambda / 4 line resonance elements. In another embodiment, all line resonance elements can be lambda / 2 line resonance elements. In general, however, if there are multiple line resonance elements, their type, number, and series arrangement are fundamentally arbitrary, and for example, at least one lambda / 4 line resonance element can be present together with at least one lambda / 2 line resonance element. The number of line resonance elements can depend, for example, on the desired reflectivity, the achievable quality, and the desired compactness of the structure. For example, a series of three lambda / 4 line resonance elements or a series of one lambda / 4 line resonance element and one lambda / 2 line resonance element can be used.The latter development, in particular, is particularly advantageous because it achieves a high filtering effect, in particular a filtering effect as high as three lambda / 4 line resonance elements, but requires less manufacturing and assembly effort and enables a shorter overall length of the line resonance elements. In one embodiment, the coaxial line has an inner conductor formed from a piece of wire and an outer conductor formed from a metal sleeve, and at least one line resonance element has a hollow-cylindrical insulator body, in particular a ceramic body, mounted on the inner conductor and extending radially almost to the outer conductor. Such an arrangement is particularly robust and inexpensive to implement and easy to install. In addition, the insulator body can be particularly compact and geometrically particularly simple.It is a design that the material of the insulator body has a dielectric constant ε. rbetween 6 and 40, which advantageously enables high impedance jumps. Another advantage is that a short material body can be achieved using inexpensive materials. One embodiment is that the material of the insulator body has a thermal conductivity κ of at least 20 W / (m ^ K), whereby the insulator body can then advantageously serve as an effective thermal bridge between the inner conductor and the outer conductor. This in turn enables effective heat dissipation of the microwave energy converted into heat in this line resonance element to the outer conductor, which is at least partially at the temperature of the food being cooked. Aluminum oxide, for example, is suitable as a material for the insulator body. One embodiment is that the coaxial line has two spaced-apart line resonance elements made of ceramic or glass, which have an air gap between them designed as a resonance line.This design can advantageously be implemented compactly and strongly attenuates microwaves. This configuration can also be expressed as the coaxial cable having two spaced-apart line resonance elements with insulator bodies made of ceramic or glass, which are separated from each other by an air-filled line resonance element or air line, or which have an air gap between them designed as a resonance line. In general, the insulator bodies themselves or the sections of the coaxial line that generate a line resonance can be referred to or regarded as line resonance elements. In a further development, the core temperature sensor has a substrate that is connected to the inner conductor, and on the substrate, a free-running conductor track is electrically connected to the inner conductor, which has a free length along its length of lambda / 4 (so-called "λ / 4 stub").The λ / 4 stub is open (in particular unconnected and thus idle) and creates an idle circuit at its free end, which is transformed into a short circuit at the contact point. This advantageously allows further backreflection of microwave signals at the substrate. The fact that the λ / 4 stub has a corrugated profile advantageously results in a particularly compact design, which is short in the longitudinal direction of the core temperature sensor. The corrugated profile can, for example, be sinusoidal or meander-shaped. The λ / 4 stub can also have a curved, rolled-up profile. The substrate can, for example, be made of ceramic or a circuit board material such as FR4 or polyimide. The substrate can, for example, be clamped, crimped and / or soldered to the inner conductor at a corresponding contact or contact point.In addition to the λ / 4 stub, at least one further ("connecting") conductor track leads from the contact on the substrate, which leads to the temperature measuring device and is electrically connected to the inner conductor via the contact. The conductor tracks can be copper conductor tracks, for example. The recess can be filled with metal, in particular copper. The inner conductor, in particular if in the form of a piece of wire, can be pressed into the recess and soldered there and to the conductor track(s). However, the contact of the inner conductor to the substrate can also be achieved in other ways, e.g., without a recess, for example, by simple soldering. An advantageous development for achieving a particularly compact design is for the λ / 4 stub to be arranged on a side of the substrate facing away from the side on which the at least one temperature sensor is arranged.The temperature measuring device, in particular its at least one temperature sensor, can be electrically connected, for example, to the inner conductor where the RF short circuit is located on the conductor track. The temperature measuring device, in particular its at least one temperature sensor, can form a common node with the inner conductor. In one development, the temperature measuring device has at least one temperature sensor applied to the substrate. In one development, the temperature measuring device additionally has one or more components applied to the substrate, which, for example, process the measurement signal generated by the at least one temperature sensor, for example, digitize it, filter it, etc. Alternatively, the at least one temperature sensor and / or at least one component can be connected to the substrate via at least one electrical line.It is a further development that the temperature measuring device is a passive temperature measuring device, i.e., in particular, receives energy for its operation from an externally generated query signal. Such a temperature measuring device can be constructed particularly robustly and inexpensively. It is a further development that the temperature measuring device is a surface acoustic wave (SAW) temperature measuring device. The at least one temperature sensor is then an SAW temperature sensor, and the substrate is advantageously a ceramic substrate. Further optional components can include, for example, an SAW filter. The use of an SAW temperature sensor—in particular together with a ceramic substrate—has the advantage that the temperature measuring device is highly temperature-resistant (e.g., up to over 200°C) and robust. The SAW temperature measuring device makes it possible, in particular, to form a passive, remotely readable temperature sensor, e.g.in the manner of a radio-readable transponder. In a further development, the temperature measuring device is an electrically operated (non-SAW) temperature measuring device. It can comprise at least one electrically operated temperature sensor, such as an NTC element or a thermocouple, such as a Pt or PtRh thermocouple. The temperature measuring device can additionally have one or more electrical and / or electronic components which, for example, process the measurement signal generated by the at least one temperature sensor, for example digitize it, filter it, format it, etc. The substrate here can also be a ceramic substrate or an FR4 substrate. The electrically operated temperature measuring device can be a passive temperature measuring device. In principle, the temperature measuring device can be an active orAn actively operable temperature measuring device can be an electrical energy storage device and at least one electrical or electronic component that can be supplied from the energy storage device, and which is, in particular, independently capable of generating at least one temperature signal. Such components can, for example, comprise at least one microcontroller, amplifier, filter, resistor, capacitor, inductor, and / or bipolar transistor or field-effect transistor, etc. The actively operable circuit enables, in particular, active signal processing and generation in the core temperature sensor.The principle of active signal processing and enhanced information transmission through digital data processing, for example, by a microcontroller, has the advantage that, on the one hand, a wealth of information can be exchanged bidirectionally, but, on the other hand, adaptation or improvement is possible through software updates during the production phase or, in special cases, even during the product's lifetime at the customer's site. The electrical energy storage device can be a rechargeable battery, a non-rechargeable battery, a supercapacitor, etc. The energy storage device can be arranged on or next to the substrate. It is also possible to use a temperature measuring device with SAW elements and non-SAW elements together. A further development is that at least some of the components are available as SMD components, which enables particularly simple assembly.In one embodiment, at least one microwave filter constructed from conventional electrical or electronic components is arranged on the substrate. This utilizes the fact that the incoming microwave energy is already so low that it no longer damages the conventional components. The microwave filter is permeable to the signal transmission frequencies, e.g., in the 433 MHz range. In one embodiment, the microwave filter is a passive microwave filter. The microwave filter can be a single-stage or multi-stage microwave filter. In one embodiment, the microwave filter is a low-pass filter if the signal transmission frequency is lower than the microwave frequency. This is particularly easy to implement, especially if its components are present as discrete SMD components.The low-pass filter can be designed, for example, as an LC low-pass filter, RL low-pass filter, RC low-pass filter, RCL low-pass filter, SAW filter, etc. 202300988 15 / 34 The microwave filter is located in particular between the inner conductor and the remaining circuit (for example the temperature measuring device with the at least one temperature sensor and optionally the active circuit) on the substrate in order to advantageously further protect the remaining circuit from microwaves. In one embodiment, the antenna is designed such that its reflection attenuation at microwave frequency is low, i.e., the antenna is adapted such that it absorbs as little microwave power as possible. This adaptation can be achieved, depending on the mechanical design of the antenna, by appropriately adjusting the length, diameter, and / or antenna shape. These parameters, in turn, determine the impedance that the antenna "sees" at the input of the microwave filter.It is an embodiment that the core temperature sensor or its outer conductor, in particular sleeve, is completely or partially filled, in particular cast or foamed, with at least one electrically non-conductive or insulating filler, which has a significantly lower expansion coefficient α than air, but at least approximately the same relative permittivity as air (ε. r ≈1). This is based on the observation that rapid temperature changes can lead to damage due to the expansion behavior of air trapped in the core temperature sensor (e.g. in the area of ​​the air duct and / or the substrate), for example microcracks, breaking of a seal at the end of the stainless steel sleeve at the first electrically conductive plate serving as the end plate, etc. Furthermore, the filler should have a suitable thermal conductivity λ WWith regard to the air line, the air volume is replaced by a volume of filler, which may be a solid after curing, in particular a porous solid. The filler can be, for example, a pourable and then curing filler or a curing foam. The fact that the core temperature sensor or the outer conductor is completely or partially filled with the at least one filler means that a volume in the core temperature sensor or outer conductor that would otherwise be filled with air is now filled with the filler. An "at least approximately equal relative permittivity" as air for the at least one filler can in particular include its relative permittivity being in the range 1 < ε r < 3 202300988 16 / 34, especially in the range 2 < ε r < 3, since for ε r > 2 there are considerably more suitable materials than for ε r< 2. It is an embodiment that the at least one filler has at least two fillers which differ at least in their thermal conductivity λ Wclearly distinguish, wherein the outer conductor, in particular the sleeve, is filled with one of the fillers in sections along the longitudinal extent of the outer conductor, and in the case of two fillers, in sections with one or the other filler. This offers the advantage that, depending on the components located in the respective section, a specially adapted thermal conductivity can be set, for example along the longitudinal extent and / or to the outer conductor. For example, in the area of ​​the temperature sensors, a higher thermal conductivity from the at least one temperature sensor to the outer conductor is advantageous so that the at least one temperature sensor can react more quickly and precisely to the ambient temperature or changes therein.A higher thermal conductivity can also be advantageous in the area of ​​the air duct to enable more effective cooling, as microwave radiation power should still be dissipated here to reduce the filter's own heating. In the remaining sections of the substrate (outside of the at least one temperature sensor), however, a lower thermal conductivity of the filler can be advantageous to prevent the temperature sensors from thermally influencing each other, e.g., to prevent a thermal short circuit between the temperature sensors on the rear side. In other words, the temperature sensors should couple well to the local sleeve temperature, but not be located in a common rear "isothermal" heat pool. This is particularly advantageous when different temperature zones can be measured in the food being cooked, either because this allows for the implementation of additional cooking information (e.g.via a temperature gradient in the food), or because it can be used to detect incorrect insertion, for example. For example, in the case of a chicken, the tip of the core temperature probe may already be in its hollow abdominal cavity, which is why the temperature information from the probe tip is incorrect because it indicates the ambient temperature rather than the meat temperature. 202300988 17 / 34 A further development is that the signal transmission antenna is embedded in filler or surrounded by filler. Two properties in particular can be important for the filler: firstly, a noticeably higher permittivity than air (e.g. with ε. r≥ 6) so that the dimensions of the antenna can be smaller than with air filling. On the other hand, the probability of electrical breakdown should be minimized by using a filler with low ionizability or good electrical insulation properties. The specific design can be determined, for example, experimentally or through simulations. The signal transmission antenna and the filler can, for example, be housed in an electrically non-conductive sleeve, e.g., made of plastic, of the core temperature sensor. The filler can be present as a single-piece body.The object is also achieved by a microwave cooking appliance with a cooking chamber that can be irradiated by microwaves of a predetermined microwave frequency, comprising a signal transmission antenna for transmitting signals at a signal transmission frequency that differs from the microwave frequency, and a signal path that is guided, in particular, through an oven wall, wherein the signal path is at least partially a coaxial line and wherein the coaxial line has at least one line resonance element or a resonance line section tuned to the microwave frequency. The coaxial line of the microwave cooking appliance can be designed analogously to the coaxial line of the microwave cooking appliance described in WO 2017 / 029059 A1, in particular can be further developed analogously to the coaxial line of the core temperature sensor described above.A microwave cooking appliance with such a coaxial cable designed as an antenna feed line offers the same advantages as the coaxial cable of the core temperature sensor. It is a further development that the microwave cooking appliance is a household appliance, in particular a kitchen appliance. It is a further development that the microwave cooking appliance is a standalone microwave appliance. It is a further development that the microwave cooking appliance is a combined microwave / oven appliance, e.g., an oven with an integrated microwave function. The cooking appliance can also have a steam cooking function. The microwave cooking appliance can have a magnetron or a semiconductor-based microwave generator to generate the microwaves.202300988 18 / 34 The object is further achieved by a system comprising a microwave cooking appliance as described above and at least one core temperature sensor as described above, wherein the system is configured to wirelessly transmit signals at the signal transmission frequency between the signal transmission antenna of the core temperature sensor and the signal transmission antenna of the microwave cooking appliance. The system can be designed analogously to the core temperature sensor and / or to the microwave cooking appliance, and vice versa, and results in the same advantages. In a further development, the system can be operated as follows: A food to be cooked in a cooking chamber of the microwave cooking appliance, e.g. a piece of meat, is to be monitored for its core temperature so that the microwave cooking appliance can control a cooking operation based on the core temperature.For example, the microwave cooking appliance can end cooking when a predetermined core temperature is reached or when the temperature remains above a certain core temperature for a predetermined period. The microwave cooking appliance is, for example, an oven with additional microwave functionality, so that the food can be treated alternately or simultaneously by electrical oven heating elements such as a convection heater, a top heat element, a bottom heat element, etc., and by microwaves. To monitor the core temperature, the core temperature probe with its needle-shaped section, which contains several temperature sensors arranged in series, is inserted into the food. A rear handle of the core temperature probe is located outside the food. The core temperature probe can be remotely interrogated wirelessly (particularly via radio) by the microwave cooking appliance.For this purpose, the microwave cooking appliance has a signal transmission antenna located at least partially within the cooking chamber, by means of which an excitation radio signal (e.g., in the 433 MHz frequency band) can be emitted into the cooking chamber. The excitation radio signal can, for example, be emitted whenever the microwave cooking appliance requires temperature information for operation, e.g., including the core temperature values ​​measurable or detectable by the temperature sensors. 202300988 19 / 34 The excitation radio signal is received by a signal transmission antenna of the core temperature sensor, which is tuned to the transmission frequency of approximately 433 MHz. The received excitation radio signal is forwarded via the coaxial cable to, for example, a passively excitable SAW temperature measuring device. The OFW temperature measuring device comprises, for example, a substrate, e.g. made of ceramic or FR4, on the surface of which at least one OFW temperature sensor is present.The SAW temperature sensors can be understood as part of the SAW temperature measuring device. The excitation radio signal passively stimulates the at least one SAW temperature sensor to generate an information signal containing the requested core temperature values ​​and transmit it to the signal transmission antenna. The information signal is radiated into the cooking chamber by the signal transmission antenna of the core temperature sensor (also in the 433 MHz ISM frequency band) and received by the signal transmission antenna of the microwave cooking appliance. The received information signal is transmitted via a coaxial cable through a cooking chamber wall to a receiving circuit, which processes the information signal for use by the cooking appliance. Alternatively, a passive non-SAW temperature measuring device or an active temperature measuring device can be used.For this purpose, the cooking appliance can, for example, have an independent evaluation circuit which is connected, for example, to a central control device. Alternatively, the central control device can have the function of an evaluation circuit. The microwave cooking appliance can, in particular, have a combined radio transmitting / receiving circuit for generating the excitation radio signal and for processing the information signal. This can, for example, be connected to a central control device of the microwave cooking appliance. Although the signal transmission antennas of the core temperature sensor and the microwave cooking appliance are tuned to the 433 MHz ISM frequency band and specifically designed for poor coupling in the microwave frequency range (e.g. 2.45 GHz), the high power of the microwaves of up to approx.1000 W, such a strong coupling of microwave signals into the signal transmission antennas can occur that structures connected to the signal transmission antennas are damaged 202300988 20 / 34 or even completely destroyed. In order to render these coupled microwave signals practically harmless, a coaxial cable as described above is provided. The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more easily understood in connection with the following schematic description of an exemplary embodiment, which is explained in more detail in connection with the drawings. Fig. 1 shows a sectional view in plan view of a not-to-scale sketch of a core temperature sensor according to several possible exemplary embodiments. Fig.Figure 1 shows a sectional view in plan view of a core temperature sensor 1 with a signal transmission antenna 2, a temperature measuring device in the exemplary form of an OFW temperature measuring device 3, and a coaxial line 4 connecting the signal transmission antenna 2 and the OFW temperature measuring device 3. The signal transmission antenna 2 is designed as a helical antenna made of copper wire, which merges into a straight inner conductor 5 of the coaxial line 4, made of copper wire. The signal transmission antenna 2 and the inner conductor 5 can be made integrally from a single piece of wire. The outer conductor 6 of the coaxial line 4 here consists, for example, of a hollow cylindrical stainless steel sleeve 7, which extends - if necessary with a change in its cross-sectional shape - lengthwise over the OFW temperature measuring device 3 and beyond to its tip, by means of which it can be plugged into a power source.The stainless steel sleeve 7 can also be described as needle-shaped. A handle is present, but not shown. The stainless steel sleeve 7 can also have an elliptical or rectangular cross-section. The SAW temperature measuring device 3 has a ceramic or FR4 substrate 8, on the top of which one or more SAW temperature sensors 9 are arranged. In particular, the SAW temperature sensors 9 can be soldered to the substrate 8. The SAW temperature sensors 9 can be SMD components. The inner conductor 5 is inserted at the end into a slot-shaped recess 10 of the substrate 8, for example, and can be pressed or soldered there. The SAW temperature sensors 9 are electrically connected to the inner conductor 5 via conductor tracks (not shown) applied to the substrate 8 202300988 21 / 34. The stainless steel sleeve 7 also serves as a shield and prevents the OFW temperature measuring device 3 from being directly irradiated by radio and microwave radiation.At least the section of the stainless steel sleeve 7 that encompasses the SAW temperature sensors 9 can also be referred to as the measuring section. The SAW temperature measuring device 3 can be excited via a radio excitation signal in the 433 MHz ISM band. The radio excitation signal is coupled via the signal transmission antenna 2 designed for this purpose and transmitted with low loss or even virtually no loss through the coaxial line 4 to the SAW temperature measuring device 3. The radio excitation signal excites the SAW temperature sensors 9 to generate a modified radio signal as the temperature signal, which is transmitted via the coaxial line 4 back to the signal transmission antenna 2 and radiated by it. The modified radio signal contains (temperature) information that has been determined by means of the at least one SAW temperature sensor 9.The core temperature sensor 1 is typically inserted so deeply into the food that at least one SAW temperature sensor 9 is inserted into the food and consequently measures a temperature value that corresponds to the core temperature of the food with sufficient accuracy. To prevent microwave signals or microwave energy coupled in via the signal transmission antenna 2 from damaging or destroying the SAW temperature measuring device 3, the signal transmission antenna 2 can be designed such that its reflection attenuation at microwave frequency is as low as possible, so that it absorbs as little microwave power as possible. A signal transmission antenna 2 designed in this way can also be regarded as an optional "first" filter stage F1 with regard to microwave irradiation. For the same purpose, a filter element 5 is provided between the signal transmission antenna 2 and the SAW temperature measuring device 3 orThe substrate 8 of the filter element includes a "second" filter stage F2 with at least one line resonance element, here: with two line resonance elements adapted to the microwave frequency to be filtered in the form of hollow cylindrical ceramic tubes 11a and 11b arranged in series along the inner conductor 5 at a distance from each other. For this purpose, the wire-shaped inner conductor 5 is guided through the inner cavity of the ceramic tubes 11a and 11b. Ideally, the ceramic tubes 11a and 11b each radially completely fill the space between the inner conductor 5 and the outer conductor 6, thus reaching up to the outer conductor 6. If only an annular gap application is possible, the gaps between the outer conductor 6 and the ceramic tubes 11a and 11b, as well as between the inner conductor 5 and the ceramic tubes 11a and 11b, should be as small as possible. The ceramic material can, for example, have a dielectric constant ε. r between 6 and 40 (e.g. out of 10) and for example from aluminum oxide Al2O3(εr typically from 6 to 15) or zirconium dioxide ZrO2(ε r typically from 20 to 40). The ceramic tubes 11a and 11b each have a length of one quarter of the wavelength λ Ker of the microwave radiation to be filtered in the ceramic material, e.g., approximately 10 mm, and are therefore designed as lambda / 4 line resonance elements. The two ceramic tubes 11a and 11b are spaced apart along the inner conductor 5 by a distance of λ Luft / 4 (with λ Luft the wavelength of the microwave radiation in air) to each other, e.g., of approximately 30 mm. This creates a so-called air line 12 for the microwaves of length λ on the coaxial line 4 between the ceramic tubes 11a and 11b. Luft / 4. The air line 12 acts as a λ / 4 line resonance or a λ / 4 line resonance element. The second filter stage F2 thus has three series-connected λ / 4 line resonance elements 11a, 12, 11b, which alternately have a high dielectric constant (ceramic) and a low dielectric constant (air). In a particularly simple embodiment without components 14a to 14d, at the section of the coaxial line 4 serving as the second filter stage F2, a first transition from air to the ceramic tube 11a is present on the antenna-side end face of the ceramic tube 11a, starting from the signal transmission antenna 2. This transition, at which an impedance jump occurs, corresponds to an RF open circuit for the microwaves. At the end face of the ceramic tube 11a facing away from the signal transmission antenna 2, an RF short circuit is generated by an impedance jump at the ceramic-air transition.Analogous to the first ceramic tube 11a, an RF open circuit for the microwaves is present on the coaxial line 4, where – starting from the signal transmission antenna 2 – a first transition from air to the ceramic tube 11b is present (namely at the antenna-side end of the ceramic tube 11b). An RF short circuit can also be generated by the ceramic-to-air transition on the end of the ceramic tube 11b facing away from the signal transmission antenna 2. Consequently, an impedance conversion for the microwave signals is effected at each end of the two ceramic tubes 11a, 11b, due to which the microwave signals are noticeably reflected back to the signal transmission antenna 2. The design of the air line 12 between the two ceramic tubes 11a and 11b as a λ / 4 open-circuit line can result in a particularly effective impedance conversion.The RF open circuit occurs in particular when a significant change in the impedance of the coaxial line 4 causes a reflection of a forward wave. The reflected, returning wave is superimposed on the forward wave. Depending on the viewing point of the superposition on the coaxial line 4, cancellations or peaks can occur depending on the phase position. One case with a particularly strong reflection is the λ / 4 line, where reflection at one end (corresponding to an open circuit) of the λ / 4 line results in complete cancellation at the input of the λ / 4 line, i.e. an open circuit is transformed into a short circuit. In the case of a short circuit at one end of the line, the opposite is true. The capacitances and inductances of the coaxial line 4 determine the impedance of the λ / 4 line and thus the size of the reflection factor. The points where an impedance jump occurs can also be called "shock points".Alternatively, one, two, or all three of the line resonance elements 11a, 12, 11b can be designed as a lambda / 2 line resonance element. A "third" filter stage F3 can be provided by a conductor track 13, for example made of copper, applied to the substrate 8—in particular on the back side. The conductor track 13 and the SAW temperature sensors 9 are arranged, in particular, on different flat sides of the substrate 8. The conductor track 13 adjoins the, for example, slot-shaped recess 10 of the substrate 8 and is therefore connected to the end of the inner conductor 5 there. To further block or filter the microwave signals, the conductor track 13 is designed as a λ / 4 open-circuit line or "λ / 4 stub." For this purpose, it has a length of λ / 4 of the microwave to be filtered, which depends on the permittivity of the substrate 8.In addition, its substrate-side end is open (i.e., not electrically connected), thus transforming an open circuit into a short circuit to the input of the 202300988 24 / 34 coaxial line 4. To create space on the substrate 8, the open conductor track 13 has a corrugated or wave-like, in particular meandering, course in the direction of extension. A "fourth" filter stage F4 can be provided by the SAW temperature measuring device 3, in addition to the SAW temperature sensors 9, also having at least one microwave filter F4 constructed from conventional components (not shown). This can, in particular, be designed as a low-pass filter. This takes advantage of the fact that the microwave energy arriving at the substrate 8 is so low that it no longer damages the conventional components.The individual filter stages F1 to F4 withstand high microwave power without being destroyed, as well as the high ambient temperatures that occur in an oven. In an embodiment that attenuates microwaves particularly well or filters them particularly effectively, thin metal plates 14a to 14d rest on the base surfaces of the ceramic tubes 11a and 11b, which serve as interfaces. The metal plates 14a to 14d can be made of copper, brass, aluminum, etc., for example. A diameter D. pl of the metal plates 14a to 14d radially to the direction of extension of the inner conductor 5 advantageously corresponds to the inner diameter D H of the outer conductor 6 and / or the diameter of the corresponding interface, here e.g. D pl = 3.6 mm. The thickness L Pl of the metal plates 14a to 14d along the inner conductor 5 is significantly smaller than the wavelength of the microwaves to be filtered, here e.g. L Pl = 1.5 mm. The thickness LPlcan also be referred to as "thickness" or, with reference to the propagation direction of the microwaves, as "length." In one variant, the metal plates 14a to 14d are electrically connected to the inner conductor 5, but then not to the outer conductor 6. The gap or radial distance between the metal plates 14a to 14d and the outer conductor 6 is small, for example, only a few tenths of a millimeter. In an alternative variant, at least one of the metal plates 14a to 14d is electrically connected only to the outer conductor 6 and has an annular gap to the inner conductor 5, for example, if the metal plate 14a also serves as the termination of the outer conductor 6 to the antenna 2. With the metal plates 14a to 14d 202300988 25 / 34, further joints for the microwave are added on the flat sides of the metal plates 14a to 14d.This can be illustrated by an example by considering the individual line sections 14a, 11a, 14b, 12, 14c, 11b, and 14d as separate coaxial lines and calculating the impedances of these coaxial lines. It is assumed that the inner diameter of the stainless steel sleeve 7 serving as the outer conductor 6 is D. H = 4 mm. The diameter D I of the inner conductor 5 is D I = 1.5 mm. The real impedance R Luft the coaxial air line 12 is calculated as: 5 8.85 Ω The real impedance R Keram the coaxial ceramic line 11a or 11b with a relative permittivity of ε r = 29 is calculated as: 1 0.93 Ω The output impedance Z A,λ / 4 of a λ / 4 line can be calculated from the line impedance Z L,λ / 4 and the input impedance Z E,λ / 4 according to Z A,λ / 4 = Z 2 L,λ / 4 / Z E,λ / 4For the output impedance of a ^ / 2 line, however, Z A,λ / 2 = Z E,λ / 2 . For a ^ / 4 line, the output impedance Z A,λ / 4 depending on the input impedance Z E,λ / 4 the line and the line impedance of the ^ / 4 line Z L,λ / 4 . In a ^ / 2 line, however, the input impedance Z E,λ / 2 and the output impedance Z A,λ / 2 of the line have the same value. This means that the following physical quantities are decisive for the effectiveness of these two line transformers as microwave filters: Basically, for a λ / 4 line, the length L L,λ / 4 of the line corresponds to λ / 4, i.e., a quarter of the wavelength of the microwaves, depending on the propagation speed of the electromagnetic wave on the line. The output impedance Z A,λ / 4 depends on the input impedance Z E,λ / 4 the line and the impedance 202300988 26 / 34 Z L,λ / 4of the line itself. On the other hand, for a λ / 2 line, the length of the line L L,λ / 2 of the line corresponds to λ / 2, i.e., half the wavelength of the microwaves, and depends on the propagation speed of the electromagnetic wave on the line. The output impedance Z A,λ / 2 is equal to the input impedance Z E,λ / 2 of the cable. If the diameter of the metal plates 14a to 14d is, for example, D Pl = 3.6 mm and their thickness or length L Pl = 1.5 mm, the real impedance R Pl the corresponding coaxial "platelet line" to: 6 .32 Ω Since the length L Pl small compared to the wavelength of the microwave of e.g. λ MW≈ 122 mm at a frequency of 2.45 GHz, no impedance transformation is taken into account, but only the impedance jump that results between the different coaxial line impedances. Thus, the real impedance R can be used directly to determine the reflection coefficient at the joints between the ceramic line and the plate line, and between the plate line and the air line. PlThe entire coaxial filter string F2 is composed of the various line components. Firstly, there are impedance jumps in the microwave filter function caused by impedance transformers in the form of the 1 / 4 and / or 1 / 2 air and ceramic lines 11a, 11b, 12. Additionally, there are impedance jumps on the metal plates 14a to 14d. All four filter stages F1 to F4 together can achieve, for example, an attenuation of 60 dB to 80 dB at a microwave frequency of 2.45 GHz. In contrast, the data signal at a frequency of 433 MHz is only attenuated by 1 dB to 10 dB. In the event of rapid temperature changes, the expansion behavior of the air enclosed in the core temperature sensor 1 can lead to damage, for example through 202300988 27 / 34 microcracks, breaking of the seal at the end of the stainless steel sleeve 7 on the end plate 14a, etc.Therefore, it may be advantageous to completely or partially fill or foam the core temperature sensor 1 with a filler FS1, FS2 that has a significantly lower coefficient of thermal expansion than air. The filler FS1, FS2 should also have a low relative permittivity ε. r Especially in the area of ​​the air line 12, a relative permittivity ε rclose to 1 (similar to air) is advantageous. For example, foamed fillers FS1, FS2 could be used that can withstand the temperature range in use (e.g., up to 300 °C). The signal transmission antenna 2 can also be embedded in a filler (not shown). This filler fulfills the following criteria in particular: first, it has a noticeably higher permittivity than air (= easily polarizable material), which ensures that the dimensions of the antenna can be smaller than with air filling. Second, the probability of electrical breakdown should be kept low by a filler with low ionizability (= electrical insulator). For the specific design, a suitable combination of properties can be found, for example, experimentally or through simulations. In addition, the filler should have a suitable thermal conductivity λ WIn the area of ​​the temperature sensors 9, a higher thermal conductivity between the stainless steel sleeve 7 and the temperature sensor 9 is advantageous, so that the temperature sensors 9 can thermally couple better to the ambient temperature and can therefore react more quickly and precisely to the ambient temperature or changes therein. A higher thermal conductivity is also advantageous in the area of ​​the air duct 12 in order to be able to cool there more effectively, since the microwave irradiation power still has to be dissipated here in order to reduce the filter's own heating. In the remaining area of ​​the substrate 8, a lower thermal conductivity of the filler can be advantageous in order to prevent the temperature sensors 9 from influencing one another, ie to prevent a thermal short circuit, for example on the back, between the temperature sensors 9.In other words, the temperature sensors 9 should couple well to the local sleeve temperature, but not be located in a common rear "isothermal" heat pool. This is particularly advantageous when different temperature zones can be measured in the food, either because this provides additional cooking information (e.g., via a temperature gradient in the food), or because it can be used to detect, for example, incorrect insertion. For example, in a chicken, the tip of the core temperature probe 1 could already be in the hollow abdominal cavity, which is why the temperature information from the probe tip is incorrect, since it indicates the ambient temperature, not the meat temperature.These different requirements for the thermal conductivity of the filler material can be met by using two different filler materials FS1 and FS2 with at least different thermal conductivities, for example a first filler material FS1 with a relatively low thermal conductivity and a second filler material FS2 with a relatively high thermal conductivity. In sections along the sleeve 7 or the inner conductor 5 where low thermal conductivity is advantageous, e.g. on the substrate 8 in the area of ​​the fourth filter stage FS4, the core temperature sensor 1 is filled with the first filler material FS1. Analogously, in sections where high thermal conductivity is advantageous, e.g. comprising the temperature sensors 9 and in the area of ​​the air line 12, the core temperature sensor 1 is filled with the second filler material FS2.The core temperature sensor 1 equipped with the metal plates 14a to 14d results in a greater attenuation of the power level at the respective microwave frequency than the core temperature sensor 1 without the metal plates 14a to 14d, while at the same time providing very little attenuation of the power level at the signal frequency. This effect is amplified by the matched signal transmission antenna 2. Of course, the present invention is not limited to the described embodiments. Thus, in an alternative, a series of only one of the lambda / 4 line resonance elements 11a, 11b and the lambda / 2 line resonance element 12 can be used. In general, "a", "an", etc., can be understood as a singular or a plural, in particular in the sense of "at least one" or "one or more", etc., as long as this is not explicitly excluded, e.g., by the expression "exactly one", etc.Also 202300988 29 / 34 a numerical value can include exactly the specified number as well as a usual tolerance range, as long as this is not explicitly excluded.

[0002] 202300988 30 / 34 List of reference symbols 1 Core temperature sensor 2 Signal transmission antenna 3 (SAW) temperature measuring device 4 Coaxial cable 5 Inner conductor 6 Outer conductor 7 Stainless steel sleeve 8 Ceramic substrate 9 (SAW) temperature sensor 10 Recess 11a Ceramic tube 11b Ceramic tube 12 Air line 13 Conductor track 14a-14d Metal plate D H Inner diameter of the stainless steel sleeve D Pl Diameter of the metal plates L Pl Thickness or length of the metal plates

Claims

202300988 31 / 34 Patent claims 1. Core temperature sensor (1), comprising a temperature measuring device (3) with at least one temperature sensor (9) and a signal transmission antenna (2) connected to the temperature measuring device (3) via a coaxial line (4), wherein temperature information determined by the at least one temperature measuring device (3) can be transmitted via the signal transmission antenna (2) at a signal transmission frequency that differs from a microwave frequency, wherein ^ the coaxial line (4) has at least one line resonance element (11a, 11b, 12) tuned to the microwave frequency and ^ an electrically conductive plate (14a - 14d) is present on at least one boundary surface of at least one such line resonance element (11a, 11b), which plate is electrically connected to an inner conductor (5) or an outer conductor (6) of the coaxial line (4) is. 2.Core temperature sensor (1) according to claim 1, wherein the electrically conductive plate (14a-14d) is a metal plate.

3. Core temperature sensor (1) according to one of the preceding claims, wherein a thickness of the plate (14a-14d) is less than 2% of a wavelength of the microwave.

4. Core temperature sensor (1) according to one of the preceding claims, wherein at least one line resonance element (11a, 11b, 12) is a lambda / 2 line resonance element.

5. Core temperature sensor (1) according to one of the preceding claims, wherein at least one line resonance element (11a, 11b, 12) is a lambda / 4 line resonance element.

6. Core temperature sensor (1) according to claim 5, characterized in that the coaxial line (4) has two spaced-apart line resonance elements (11a, 11b). 202300988 32 / 34 made of ceramic or glass, which have an air gap (12) formed as a resonance line between them.

7. Core temperature sensor (1) according to one of the preceding claims, characterized in that ^ the coaxial line (4) has an inner conductor (5) formed from a piece of wire and an outer conductor (6) formed from a metal sleeve, and ^ at least one line resonance element (11a, 11b) is designed as a hollow cylindrical insulator body pulled onto the inner conductor (5) and extending radially to the outer conductor (6).

8. Core temperature sensor (1) according to claim 7, characterized in that the material of the insulator body (11a, 11b) has a dielectric constant ε rbetween 6 and 40, in particular made of ceramic.

9. Core temperature sensor (1) according to one of the preceding claims, wherein ^ the core temperature sensor (1) has a substrate (8) which is connected to the inner conductor (5), ^ on the substrate (8) there is a free-running conductor track (13) which is electrically connected to the inner conductor (5) and has a free length of lambda / 4, and ^ the free-running conductor track (13) has a wavy, in particular meandering, or rolled-up course.

10. Core temperature sensor (1) according to one of the preceding claims, wherein the signal transmission antenna (2) is designed such that its reflection attenuation at microwave frequency is low. 11.Core temperature sensor (1) according to one of the preceding claims, wherein the core temperature sensor (1) is completely or partially filled, in particular cast, with at least one filler (FS1, FS2) which has a significantly lower coefficient of thermal expansion than air, but an at least approximately equal relative permittivity. 202300988 33 / 34 12. Core temperature sensor (1) according to one of the preceding claims, wherein the core temperature sensor (1) is completely or partially filled with at least one electrically non-conductive or insulating filler (FS1, FS2) which has a significantly lower expansion coefficient than air, but has at least approximately the same relative permittivity as air.

13. Core temperature sensor (1) according to claim 12, wherein the at least one filler comprises at least two fillers (FS1, FS2) which differ at least in their thermal conductivity λ Wclearly distinguish, wherein the outer conductor (6) is filled with one of the fillers (FS1, FS2) in sections along its longitudinal extent.

14. Core temperature sensor (1) according to one of the preceding claims, wherein the signal transmission antenna (2) is surrounded by filler that has a noticeably higher permittivity than air.

15. System comprising a microwave cooking appliance and at least one core temperature sensor (1) according to one of the preceding claims, wherein the system is configured to wirelessly transmit signals at the signal transmission frequency between the signal transmission antenna (2) of the core temperature sensor (1) and a signal transmission antenna of the microwave cooking appliance.

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